Physicists Debate Hawking’s Idea That the Universe Had No Beginning | Hacker News Reader

Physicists Debate Hawking’s Idea That the Universe Had No Beginning

quantamagazine.org

249 points_Microft284 comments

This seems different than the concept of infinite time, where prior to the big band there was something the collapsed into a ball of energy and maybe someday our universe will collapse back again (which has lost merit since we've seen matter in the universe isn't slowing down in spreading apart, but accelerating .. meaning in a few trillion years, atoms may be so far apart that light can't reach anything .. the eventual heat death of the Universe).

In the shuttlecock example, there is an assumption the shuttlecock is the Universe and there is nothing outside to observe the object. Same with "What's south of the south pole." It ignores the stars and galaxies past Earth itself.

There is also a theory there could be many other big bangs and universes next to our own, but they are all accelerating away from each other. We can't see the one next to ours because it's expanding itself, as is ours, and all these are moving away from each other. Imagine a room of beach balls and they're all just inflating, but also moving away from each other at the rate they're inflating. In you're inside one, it's not only impossible to see another one, but because of the speed-of-light speed limits, it's impossible to travel to another one or even provide/disprove it exists.

There are a lot of questions about what, if anything, is outside the observable universe. Are we sitting in a ball on some gigantic alien's coffee table?

In terms of expansion we have little data to extrapolate thousands of times the current age of the universe. The reasons behind said expansion are unknown making extrapolation have meaningless error bars.

Current estimates for heat death are vastly beyond a few trillion years. With another universe possibly randomly showing, though the odds of that depend on the unknowable size of this universe.

> what, if anything, is outside the observable universe

The answer is similar to the time. Remember, in cosmology there's no really separate space and time, there's only space-time.

So when you're looking at the edge of the observable universe, you really looking back in time. So the answer to the question "what is outside" is the same as "what was before".

Or, in simpler words, the question is meaningless, as there's no space to talk about "outside". Not sure the last phrase is correct, as I've just talked about separate space from time.

If you are restricted to the typical 3 dimensions of movement (and 1 through which we are non-optionally traveling) - you should either get to a physical boundary, or you end up in a loop, right? I mean, you won't travel so far you end up in Tuesday.

Sorta.

We are in this thing called space-time.

It came out of the Big Bang (we think).

There is a finite amount of it (about 45 GLY in radius, maybe).

You can only ever see about 14GLY of it due to some speed limits.

You can't get to an edge or boundary of space-time because it's not 3-D, it's curved in this really weird way.

There are a lot of holes in space-time that we're still thinking a lot about.

For some reason, the space-time is getting bigger and bigger, we think this is related to all that stuff in space-time, but we're really not sure.

Most of the stuff in it is not the same stuff as you are made of; most of the stuff seems to fall up, while the stuff you're made of falls down.

There is a lot more stuff that falls down than just the stuff you are made of.

There is a still a lot of things to learn about all of this, we're not really all that close to understanding it.

> You can't get to an edge or boundary of space-time because it's not 3-D, it's curved in this really weird way.

Can you elaborate? I was under the impression that the curvature is essentially zero and that the universe is open.

Best described here: https://www.livescience.com/33646-universe-edge.html

We use a Robertson-Walker (RW) metric to describe the universe at the largest scales because it does the job well. There are several components to the (vacuum) RW metric, and two are relevant to your question.

Let's take a planar ("equatorial") slice of the expanding universe at a given time. In that slice let's put two test objects that aren't interacting with each other in any way: the gravitational attraction is effectively zero, and there are no electromagnetic or other interactions between them. They also don't decay or radiate. In the flat Minkowski spacetime of Special Relativity these test objects would follow completely parallel worldlines eternally (to the infinite past or the infinite future): the spatial distances are the same in every slice.

One parameter of the RW metric controls the spatial distance between these test objects in the immediately preceeding and immediately following slices. That is the expansion function. In an expanding or contracting RW universe, these objects are spatially closer together in one immediately neighbouring slice and farther apart in the other. In the expanding case, the spatial distances are greater in each slice into the future, and smaller in each slice into the past. "Unslicing", if these objects could (without disturbing their trajectories) measure their distances using RADAR signals, the RADAR distances would always increase into the arbitrary future. Flat spacetimes do not expand: expansion is a manifestation of spacetime curvature.

Another parameter controls whether each slice is spatially flat. If a slice is spatially curved in an expanding RW spacetime, then optical distortions change the observed size of distant objects with the expansion. In practice, this would be encoded as a distance-dependency in the brightness-angle-redshift relationship observed in distant galaxies. This isn't required by current observations made in ultra-deep-field studies, so the universe cannot depart from spatial flatness by more than a tiny amount.

The third relevant parameter is the extent of each slice. In principle every slice can be spatially infinite, no matter where in the past or future the slice is, and that is what accords with observation. However, slices could be merely finite but very large, and there might be a function relating each slice's extent to its past-predecessor or future-successor. A "closed" universe is one in which [a] the spatial curvature discussed above is positive, [b] the slices are finite but very large, and [c] there is no boundary because the slice "wraps" around spherically or toroidally or in some other fashion, and [d] the expansion function decays into a contraction function. Any non-closed universe is "open" to some extent.

This is "punned" with the non-vacuum modelling of the Friedmann-Lemaître-Robertson-Walker expanding universe with various types of matter as a fluid "dust" embedded within the vacuum RW spacetime, wherein the matter in a non-closed RW universe in the sense of the previous paragraph is dense enough that it will eventually collapse. Our two test objects above would still have always-increasing RADAR distances while all the mutually-attracting charged matter that started around them collapses into ever denser structures.

Indeed, in the FLRW model the "dust" motes are galaxy clusters, which individually collapse in a Schwarzschild-like metric (typically one uses a Lemaître-Tolman-Bondi metric, since Schwarzschild is eternal, and LTB is a collapsing dust). However, at the galaxy-cluster scales they're like our idealized test objects: they don't interact much -- after clustered galaxies form they don't really push distant ones around with their emitted radiation, and clusters are far enough apart that the mutual gravitational attraction is basically zero. Coarsely, their RADAR distances always increase into the future. (More finely, clustered galaxies orbit around inside their clusters, so some galaxies (and bits of spinning galaxies) are moving away a bit faster and some slower than expansion carries them. This is the "peculiar motion" of galaxies, and star clusters within galaxies.)

So: spacetime curvature is large, because galaxy clusters were much closer together in the past. Spatial curvature is zero or close to it, because spiral galaxies have roughly the same basic shapes to them (not squashed or stretched) at all redshifts. The universe is open in the sense that in general widely separated galaxy clusters are not at any risk of recollapsing into each other: it is only peculiar motions of galaxy clusters that cause cluster-cluster collisions, like the Bullet Cluster. (Oh, would that such collisions were commonplace: it would provide lots of useful data! But most galaxy clusters are "Eulerian": they have an unexciting view of practically all other galaxy clusters receding from them exactly according to the expansion parameter of the Robertson-Walker metric.)

Mange takk :)

The hot big bang is an event in spacetime. It does not generate the manifold itself, although the geometry of the manifold necessarily reflects it, especially near the event itself.

There is no evidence to support finiteness of spacetime; there is no reason why there aren't events in the infinite future. The only reason to suspect there are no events in the infinite past is a classical picture of a gravitational singularity in the finite past, but we good reason to believe that quantum gravity will become important in the finite past, and that quantum effects prevent the singularity from forming. However, we do not have a trustworthy theory of quantum gravity with which to assess a number of ideas about how one might test predictions about the even more distant past.

Light-years are a measure of spatial distance; in spacetime we must use an interval for several reasons, including that different observers will disagree about the amount of time it takes a pulse of light at A to reach B; the distance will vary depending on where in spacetime observers are, and the geometry of the spacetime. In order to be generally covariant, intervals must be tensors. We can write the interval tensor in a linear form as \Delta s^2 = x^{\mu}x_{\mu} where \mu is an index of spacetime dimensions runnning 0, 1, ... depending on how many of them there are, x is a displacement four-vector (covariant with \mu below, contravariant with \mu above), and the whole right-hand-side is a Minkowski inner product. The interval itself is s^2; it is not the square root of this quantity.

If we discard general covariance by fixing flat polar coordinates on one observer, we gain the ability to discuss light-years (as measured at some point in time at the spatial origin in that coordinate basis) but invite mistakes in relating those units to physical systems. One runs into this a lot on hackernews, where someone inevitably resurrects the objection that e.g. a binary black hole merger detected at LIGO today akshually happened billions of years ago, and in the process makes a complete hash of the metric tensor.

Unfortunately, this is what is happening in your line about the time-dependent Earth-fixed Hubble radius and the line immediately after that. The metric, as you say in the very next line after that, is very far from that of flat spacetime, and light-years become tricky in general curved spacetime.

As said above, there may be an early boundary to the spacetime: there might not be an infinite past. Not all singularity-abolishing ideas involving quantum gravity require the extension of spacetime beyond the hottest densest phase of the universe, and not all extensions must be infinite. There may be a future boundary to the spacetime, but evidence is that the true metric (which we do not fully know; we only approximate it with an expanding Robertson-Walker metric in the standard model of cosmology) extends into the infinite future barring possible quantum gravity effects at extremely low energies.

> most of the stuff seems to fall up

No. Dark energy is not "stuff": stuff dilutes away with the expansion, and locally tends to slosh about in response to gravitation. Evidence supports the assertion that dark energy is a (physicists') choice of how to represent a linear element in the spacetime interval between any pair of mutually-distant events. That element is \Lambda, the cosmological constant.

As far as we can tell the gravitational interaction is only attractive for all "stuff"; the dilution only manifests when the gravitational interaction is extremely weak. The attractive interaction in the Friedman-Lemaître-Robertson-Walker model in the standard cosmology is represented as a pressure in a fluid dust of gravitating matter; it is calculationally convenient to represent the cosmological constant as a constant isotropic tension. However, the convenience comes with similar risk of misunderstandings, like with using light-years to talk about the intervals between two events separated by cosmological distances.

> a lot more stuff that falls down than just the stuff you are made of

One of the features of galactic halos is that they do not "fall down" towards the central parts of the galaxies they enclose. Ordinary matter collides or scatters electromagnetically or through the weak nuclear force, and and such scatterings radiate away momentum as photons, neutrinos, or other particles. The reduction in momentum allows the remaining matter to fall inward. The matter in the halo does not produce photons, and does not seem to produce neutrinos, so is effectively unable to fall inwards (except by dynamical friction, which is an extremely slow process for sparse gasses or dusts of small-mass particles).

Additionally, we cannot be certain that dark matter -- if it interacts non-gravitationally -- does not form bound states with ordinary matter such as the atomic nuclei inside our bodies. One could compare this to the "hot dark matter" neutrinos that are in your body at any given moment thanks to nuclear interactions (for example, in beta decays in the potassium in your blood). ("hot" because neutrinos generally move at speeds close to that of light; "cold dark matter", found in halos, moves much more slowly).

> There is still a lot of things to learn about all of this

Yes, you're right here.

> we're not really all that close to understanding it

But here I think you are wrong, if your use of "we" is meant to include working physical cosmologists.

Tying those two together, I'd happily recommend practically any of these https://en.wikipedia.org/wiki/Physical_cosmology#Textbooks

Thank you for your comments, they're continually a joy to read.

> and not all extensions must be infinite

any examples?

> any examples?

Sean Carroll has an excellent "zoo" of ideas in a set of slides at https://www.slideshare.net/seanmcarroll/what-we-dont-know-ab... where he gives a reasonable overview of a number of ideas including those which have an earliest time (even if it is far earlier than the hot big bang), and those which do not.

Indeed, a couple of the slides touch on Hawking's idea in the article at the top: discussing or debating that particular model (and "choosing sides") is not especially new.

The references [in square brackets] on each of the slides are mostly easy enough to find via your favourite search engine.

What does it mean for a pair of events to be mutually distant?

Roughly, here I meant far enough away for the metric expansion of space to generate significant observables. If the cosmological redshift is not evident, then the pair of events are not "mutually distant" enough.

In the "mutually distant enough" case, if the expansion is similar to that measured in our universe, then a RADAR pulse sent out by object A to object B would not return to object A before, say, about half of a sample of iron-60 at A had undergone beta decay (half-life 2.6 million years), all assuming that A and B are both moving slowly compared to the speed of light. The returning pulse will be at a significantly longer wavelength than the outgoing pulse. By contrast, a RADAR pulse that returns before half of a sample of carbon-11 has decayed by positron emission (half-life about 20 minutes), the returning pulse will be at pretty much exactly the same wavelength as the outgoing pulse. Here object A and object B move very slowly compared to the speed of light: the redshift is cosmological rather than special-relativistic.

It works for neutrinos too, which have the advantage of always moving slower than the speed of light due to their small but nonzero invariant mass. In SI units, neutrino wavelengths vary from tiny fractions of a meter to several metres. We can measure these to an extent by looking for radiation from nuclear recoil reactions: shorter-wavelength means higher momentum and thus more and stronger recoil reactions. The less famous counterpart to the cosmic microwave background -- the https://en.wikipedia.org/wiki/Cosmic_neutrino_background -- is practically undetectable in this way.

I say advantage because lightlike intervals are always zero by definition (that's why they're also called "null" intervals), so one has to use an affine parametrization of the interval to or otherwise fix coordinates and units to compare how far apart in spacetime events connected by RADAR signals are. The intervals of events connected by neutrino beams ("nadar?") are timelike, and so we can more straightforwardly consider the contribution of the cosmological constant to the (nonzero) magnitude of the interval \Delta s^2. But neutrinos are still ultra-relativistic -- simultaneously emitted neutrinos and photons (say, from extragalactic supernovae) are detected practically simultaneously by instruments on and around Earth. (In practice, such simultaneously-emitted neutrinos can win races to our detectors because the universe is generally more transparent to them than to the photons emitted from the same event: the relative opacity slows down the latter).

I'm of the impression that "the universe is getting bigger and bigger" is the other side of the coin from "space time is curved in this really weird way". Also, I'm under the impression that a curved spacetime doesn't contradict the notion of 3D space or 4D spacetime. As I understand it, a flat spacetime is one in which space neither expands nor contracts, and convex or concave spacetime refer to space that either expands or contracts (I forget which is which). Based on observations that things are getting farther apart (or perhaps that they are accelerating away from each other?), we think spacetime has a curve.

I'm sure I'm misunderstanding something; hopefully someone can jump in and correct me.

The observable universe is a growing sphere around earth or where ever you happen to observe it. So to answer the question "what's outside" we just need to wait for the light to reach us.

Obviously "outside the observable universe" must be outside of that sphere? Just because stars we see now are not still at that position doesn't make the question meaningless. The answer could be that outside the sphere, right now, there are most likely more stars, planets and gas.

it’s actually a shrinking sphere. as the expansion accelerates, more space moves out of view.

> So to answer the question "what's outside" we just need to wait for the light to reach us.

unless what is outside is moving away faster than light (which I think it is), then it will never reach us (from my very basic layman understanding of how much space is being created as the universe expand. The reason why it can move away faster than light is that objects cannot move faster than light, but if space in the universe between two points is being created than the speed of light limit doesn't apply (for some reason I don't understand, but as people much smarter than I do understand, I will go with them)

Wikipedia's 'Timeline of the Far Future' is a great article on the posibilities of our universe's fate [0]. Of note are the entries near the end of the list.

Year 10^(10^(50)) : Estimated time for a Boltzmann brain to appear in the vacuum via a spontaneous entropy decrease [1]

Year 10^(10^(120)) : High estimate for the time for the universe to reach its final energy state, even in the presence of a false vacuum.

Year 10^(10^(10^(56))) : Around this vast timeframe, quantum tunnelling in any isolated patch of the vacuum could generate, via inflation, new Big Bangs giving birth to new universes. Because the total number of ways in which all the subatomic particles in the observable universe can be combined is 10^(10^(115)) a number which, when multiplied by 10^(10^(10^(56))), disappears into the rounding error, this is also the time required for a quantum-tunnelled and quantum fluctuation-generated Big Bang to produce a new universe identical to our own, assuming that every new universe contained at least the same number of subatomic particles and obeyed laws of physics within the range predicted by string theory.

Suffice to say, our understanding of physics and the universe is still in an infant state when it comes to predictions of the universe's future. Much more funding is needed :P

[0] https://en.wikipedia.org/wiki/Timeline_of_the_far_future

[1] https://en.wikipedia.org/wiki/Boltzmann_brain

This kind of discussion always reminds me of the Asimov story "The Last Question"

https://www.multivax.com/last_question.html

https://urbigenous.net/library/nine_billion_names_of_god.htm...

http://www.eastoftheweb.com/short-stories/UBooks/TheyMade.sh...

Another one of a similar theme: you may have seen: http://galactanet.com/oneoff/theegg_mod.html

Thanks. This was an amazing read.

That was a great read. Asimov was always so far ahead of his time.

Reading this, I am again reminded that technological progress is sometimes way slower than people think. Think about how the folks in the 50s/60s envisioned the time around 2000s, flying cars etc. I think the same might happen to autonomous delivery, general AI and the like.

I wouldn't necessarily say slower, but rather different. The folks in the 50s/60s couldn't imagine how something called the Internet would change the world.

An excellently illustrated version of "The Last Question":

https://imgur.com/gallery/9KWrH

I’ve never seen the animated version. That is incredibly well done. The way it takes scrolling into account is brilliant.

Brilliant! Thank you

Boltzmann brains may not occur after all [0], which is reassuring [2]. See De Sitter Space Without Dynamical Quantum Fluctuations [1].

[0] http://www.preposterousuniverse.com/blog/2014/05/05/squelchi...

[1] https://arxiv.org/abs/1405.0298

[2] https://arxiv.org/abs/1702.00850

Oh man, all that is decidely out of my realm of expertise. Is there a TL;DR on why BBs are not possible?

Essentially in that paper Carroll argues that the dilution away of the matter means that incoming radiation at a point p in the far future when there are billlllions of light-years of empty space around p is so redshifted that it makes no difference to the massive particle at p, even if by random chance a whole mess of incoming radiation arrives all at once.

The counter-concern is that in a truly infinite universe, enough ultra-infrared energy arrives at p that (with more realistic matter) pair-production occurs in such a way that bound states (nuclei, atoms, molecules, brains-with-memories) start forming.

Infinity is hard to cope with, and Carroll likes playing with those.

Boltzmann Brains are infinitesimally unlikely in the really foreseeable future of our universe, but if we jump from foreseeable (say, trillions of years) to infinite, all sorts of weird stuff can happen. Including your brain in a jar, convinced that it is not in a jar but living (after being conventionally born) in a universe full of other humans and cats and stars and galaxies.

What annoys Carroll is that small fluctuations are much more probable than large fluctuations, and a brain-in-a-jar-with-false-memories requires a much much much much (insert several more "much" here) much smaller fluctuation than a real universe with a hot big bang and structure formation and evolution of primates who walk around staring at smartphones.

This doesn't make sense to me. Maybe I'm misunderstanding. The Universe a BB appears in doesn't have to follow the same rules as the Universe that brain is hallucinating. I don't see how the properties of our Universe give any information on whether Boltzman Brains are possible.

I think you're probably agreeing with Carroll's argument about cognitive instability.

Our universe, assuming we aren't hallucinating or falsely remembering our experiences in it, likely allows for Boltzmann brains that hallucinate or falsely remember a universe like ours, and also those that hallucinate or have false memories about universes very different from ours. I can't even guess at the probability distribution of false experiences of one type complex universe versus another type of complex universe, but hallucinating any universe well is a lot less probable than a lump of Boltzmann grey matter that does not have any memories of experiences (false or otherwise) at all, because a thinking, remembering brain (Boltzmann or not) has a much lower Boltzmann entropy than a non-thinking, non-remembering brain.

> I don't see how the properties of our Universe give any information on whether Boltzman Brains are possible

It's just fluctuation theory combined with two things: a cold and nearly uniform photon "gas" in the far far future assuming expansion continues, and the ability of overdensities of even IR photons to combine into more complicated bound states of matter. The cosmic microwave background exists, and there will also be an even sparser gas of ions that can capture any charged leptons produced if enough CMB photons localize and interact. If forming dense collections of molecules this way seems highly improbable to you, you are on the right track. :-)

The idea is to try to develop a no-go theorem about the early universe being in a high-entropy condition. Fluctuation theory does very well with structure formation, but if it's just fluctuations in an effectively uniform hot gas of matter (in the most general sense) then why do we have a dust of galaxies (at least one of which has real brains) rather a dust of Boltzmann brains? The latter are much much more likely than the former to fluctuate out of a higher-entropy state.

Our past being much lower entropy even at the hottest densest phase of the universe solves some arrow-of-time / manifold-orientability problems as well.

Among other things this motivates attempts to observe the "dark ages" after the CMB formed but before the first starlight, and detailed studies of the fine-grained structure of the relic fields (of which the CMB is one) produced in the early universe. The "noise" in the CMB is expected to be (and frankly appears) at lower entropy than the "noise" in the distribution of matter. But the "noise" in the latter does not appear to produce signs of Boltzmann brains in (or nearby) high-redshift galaxies. (Intriguingly there appears to be quite a lot of singly ionized carbon generating 158 micron fine-structure lines -- ALMA also sees a fair amount of water, HCN, HCO+, SiO and a few other molecular lines at high redshift, and practically everyone thinks it's more reasonable to blame this on the earliest stars being enormous and dying young and very violently, rather than heavier-than-lithium nuclei fluctuating into existence far from what became (proto-)stars. The "Boltzmann brain" argument applies to much simpler things too, including carbon atoms and organic molecules).

[1] is an entertaining argument, but as you know, real brains involve more than a massive free scalar. :D

I do like that balding seems to take about a light-crossing time in the cosmic no-hair in [1]. You'll need some extra patience as you approach fluctuation-free de Sitter, but there's surely infinite patience somewhere in an infinite-dimensional Hilbert space. The trick is how to walk the path from here in that space to there in that space.

I'm not sure [2]'s cognitive instability matters. We do use effective field theory all the time. Heck, even in that paper. We can have useful predictions without having final/total/exact answers.

If the universe reaches a final state at one point, isn’t the implication that this is where all process that defines time ends. If so, how can one speak of things happening “after” that point?

The final state is a kind of thermal death where thermodynamics say that nothing happens anymore. However, thermodynamics is only an effective theory. It is false on tremendously large time scale: after a very very very large time a random fluctuation can bring down the universe entropy to pre-death level and restart a new non-boring universe (for a very short duration compared to the time spent in the thermal death).

To clarify. I wasn’t arguing against there being a possibility of an “after” with new universes from nothing. I was curious about what constitutes “a very very very large time” in a universe without clocks

If I had to choose a favorite article on all of Wikipedia, this would be it. Almost reads like a sci-fi novel of our own personal voyage through the cosmos.

> There is also a theory there could be many other big bangs and universes next to our own, but they are all accelerating away from each other.

I speculate that there is. And I assert that for our universe to be meaningful, it must birth a sentience into life in the fourth dimension. That probably sounds very wishy washy but does anyone get what I mean and agree with me on this? I’ve never told anyone about this postulation before but I doubt that I am alone in thinking this.

Anthony Aguirre at UCSC does research in this area:

https://arxiv.org/pdf/0712.0571.pdf

http://scipp.ucsc.edu/~aguirre/Research.html

Must? Or the universe has no meaning?

That seems to me like you've grabbed on to a mysticism with no foundation.

there is an assumption the shuttlecock is the Universe and there is nothing outside to observe the object.

It's not an assumption, it's explicitly part of the model.

Same with "What's south of the south pole." It ignores the stars and galaxies past Earth itself.

If I say "the latex in this balloon is like the surface of the earth," I'm not so much ignoring the stars & galaxies, they're just not part of the analogy.

Is your point that, for an object to be curved, there must be something for it to curve into? For example, in order for a 2D surface (like the latex in the balloon) to be curved, it necessarily must be in a 3D (or higher) space?

> Is your point that, for an object to be curved, there must be something for it to curve into? For example, in order for a 2D surface (like the latex in the balloon) to be curved, it necessarily must be in a 3D (or higher) space?

Given the context I'm guessing you asked this rhetorically, but if not: it is not true in general that a curved n-dimensional object must be embedded in a n + k-dimensional space. Curvature can be intrinsic.

Could you expand on that statement a little, please.

You can take a curved object in 3D space and project it into 2D space and it remains curved?

In the examples of Gaussian curvature here https://www.maths.ox.ac.uk/about-us/departmental-art/theory/... they only appear to be curved because they're 3D (an arc-section of a sphere, a paraboloid), none of them is 2D. Are the examples just weak?

Wolfram has a curious definition:

>"A curvature such as Gaussian curvature which is detectable to the "inhabitants" of a surface and not just outside observers. An extrinsic curvature, on the other hand, is not detectable to someone who can't study the three-dimensional space surrounding the surface on which he resides." (http://mathworld.wolfram.com/IntrinsicCurvature.html) //

but it doesn't make sense to me. A cylinder has no intrinsic curvature but the curvature is discoverable by travelling in one direction only to return from the other?

A sphere has positive Gaussian curvature everywhere, in 3D. You don't need to view it from 4D to discover this, you can draw a triangle on the surface and note that the interior angles add up to >180 degrees. You can't project it into 2D space and keep the curvature, which is why all maps have distortion.

> matter in the universe isn't slowing down in spreading apart, but accelerating

How come this does not violate the law of conservation of energy which says there's a fixed amount of energy in the universe? For matter to accelerate would require energy right? Where is the energy fueling this universal acceleration coming from? According to Newton's laws, doesn't there also need to be an external actor causing this acceleration? (Sorry if this sounds like a basic question--I don't know much physics besides some required intro courses I took for my CS major).

"How come this does not violate the law that says there's a fixed amount of energy in the universe?"

It may. It is currently not clear if conservation of energy holds at the cosmological scale.

Energy conservation is a consequence of time-translation symmetry (by Noether’s theorem), which is broken in general relativity. Hence, broadly speaking, energy is not conserved in general relativity.

https://www.preposterousuniverse.com/blog/2010/02/22/energy-...

There is no matter being accelerated but space itself is expanding, which is why distant objects may accelerate beyond the speed of light, atleast that is what it looks like.

Wow, that's new to me. My understanding has always been that space is just the absence of matter. The ideally of null/void expanding is strange, to say the least.

Do you have recommendations for any books or resources online that break this down, and explain it in an ELI5 way?

I don't know any good resources/books on the topic, I've learned most of it via the education system with some additional background in internet.

There isn't much of a good analog from daily life, but essentially as you said, the null/void itself is becoming more. Two objects with a certain distance between eachother will find this distance growing even if they are not in relative motion in reality, though from either's perspective, the other is moving away at increasing speeds (due to more space inbetween expanding). Eventually the distance will be large enough that the space created between the two objects will exceed the distance that light could have travelled; the object becomes superluminal, or faster-than-light. This is allowed because it's not actually the object moving but the coordinate system they are in moving. With some luck you can still observe these objects.

>> Are we sitting in a ball on some gigantic alien's coffee table?

sometimes I have the same question but quite opposite. What if there are miniscule worlds right on our coffee table.

Both.

Men in Black and Horton Hears A Who: Both true tales that future generations will understand as visionaries slipping a little reality under the door of our current narrow-minded and backwards prejudices.

Horton Hears a Who

On being given the planetary model of an atom I think it's relatively common to consider that maybe atoms are mini star systems. That was one of my early "aw shucks, someone else had that idea already!?" deflationary moments.

That was exactly the early thought and why the commonly accepted image of an atom with a nucleous and orbiting electrons looks just like a solar system.

Of course that’s not at all what atoms look like or how they behave.

Do you have a source for that?

AIUI Rutherford's model focussed the mass in the nucleus based-on/inspired-by Nagaoka's Saturnian model. Then Bohr's model specifically put electrons in orbit but they were there to explain atomic emission spectra and so needed to move between orbits - not at all like planets.

I think the thought was that electrons orbited a nucleus in a "planetary" way, rather than them being actual nano-scale planets.

Or both...we can simultaneously exist on some aliens coffee table while they simultaneously exist on your coffee table.

There are. Look into a microscope.

And notice that just to discuss these questions, even to start, we make a LOT of assumptions about space, time, dimensions, etc. that as far as we know are particular to our experience. The assumption that these hold outside our universe -- that there is even space out there anything like the space we experience -- is laughable. It's nearly as absurd as assuming that ET has two arms, legs, eyes, and ears and then discussing height, weight, and hair color!

I'm under the impression that with the heat death, such a large vacuum would create the massive quantum states which would lend to a new big bang. Would that not also be infinite time?

Possibly one of the most intriguing ideas I've ever heard is that there is no difference between "true" in the sense of "1+1=2" and "true" in the sense of "polar bears exist". The universe isn't described by the mathematics we have constructed to explain it, it is that mathematics.

In that sense, the question of what happened before our universe is similar to the question of what happened before 1+1=2... sort of a strange thing to ask. Our universe exists because it is a coherent tautology.

Of course, like all metaphysical posturing it's almost certainly impossible to ever know. But I find the elegance of the idea appealing.

Edit: I believe I was thinking of Max Tegmark's mathematical universe hypothesis, but also a little of David Lewis's modal realism:

https://en.wikipedia.org/wiki/Mathematical_universe_hypothes...

https://en.wikipedia.org/wiki/Modal_realism

> like all metaphysical posturing it's almost certainly impossible to ever know

The concept that we can round off infinity and fit it within some tidy scientific experiment shall have seemed quaint by the time we meet the Almighty.

Nevertheless, reverse-engineering reality is our task under the sun, so: best be about it.

Note that this idea -- that the basis of the universe is math itself -- is attributed to the presocratic philosopher Pythagoras.

In the ensuing Platonic worldview, it was understood that the world began with total Oneness. In modern terms, that's treating the entropy of the universe as equal to 1; there is only one state for the entire universe to be in. Then, this increases to twoness, between the something and the nothing. As the something and the nothing interact, that interaction is the threeness; and from the three, the multitude. They then believed that this resulted in the formations of geometry which led to the elements, which they expected to consist of the simplest 3 dimensional shapes. They were pretty much spot on, except they didn't know that the spherical harmonics of atoms are even simpler than the platonic forms.

Not a bad cosmology for 2500 years ago. I think there is still a lot of profound thought to process and consider.

>In modern terms, that's treating the entropy of the universe as equal to 1; there is only one state for the entire universe to be in. Then, this increases to twoness, between the something and the nothing. As the something and the nothing interact, that interaction is the threeness; and from the three, the multitude. They then believed that this resulted in the formations of geometry which led to the elements, which they expected to consist of the simplest 3 dimensional shapes.

>They were pretty much spot on.

Is it me or is that paragraph completely devoid of meaning? Is it actually saying anything? This reads like medieval scholastic philosophy: so far up its own bottom it no longer makes any sense.

I'm curious what you find meaningless about a plausible mathematical origin story for the universe. You don't sense meaning in the idea of "Oneness" or "Twoness", I'm guessing? Oneness is clear, I hope and twoness can be understood as a contrast or gradient (which we know to be necessary for energy flows). I'd be happy to unpack further.

And by saying something, you mean predicting something? One clear prediction (from the Pythagorean Democritus) is that the geometries of atoms would determine their physical properties. Is that meaningful?

I don't know if your comment intends to dismiss all premodern scholarship, but I would guess that there is more depth and meaning than you may have personally encountered.

I'd be happy to share some references or further ideas.

One of the dirty secrets of mathematics is that not all axiomatic systems are equally successful. There is a kind of survivorship bias whereby axiomatic systems that are "interesting" are studied whereas axiomatic systems that are "boring" fall into obscurity.

For example, number theory has an incredibly rich structure that stems from the very simple axioms of peano arithmetic. Linear algebra is another field that has been amazingly fruitful, not just in physics but also in pure mathematics too.

Those axiomatic systems survived infant mortality and grew to become adults, but they are the rare exceptions.

What "the universe is math" really means is that the universe has structure. The universe is not complete randomness, nor is it complete emptiness. The universe has enough structure that we can use increasingly sophisticated mathematics to describe it.

But don't think that the universe embodies all of mathematics. There are vast wastelands of mathematics that people thought up that didn't end up being interesting, even if internally consistent.

What is really happening is the intersection of survivorship bias in pure mathematics with the anthropic principle in physics. We can observe the structure of the universe only because it has structure, and there are certain theories of mathematics that survived because they are not "boring".

Is it a surprise that the "not boring" kinds of mathematics are often the kind required to describe the structure of the universe?

Pure nothingness has no potential for creation. The laws of physics don't invent themselves, so it would seem that true "nothing" never existed. I'm not talking about the quantum soup of the vacuum of space, because that is something.

If we take Hawking's idea that the universe smoothed out to a zero point where there was no time and nothing else, how does that point because laws of physics, gravity, etc? What properties of a zero point (that had no properties) cause it to create an inflationary universe?

Everything breaks down at that point, because trying to use mathematics or physics to explain something that existed before mathematics and physics doesn't work.

Is there a theory that the beginning and the ending of the universe are directly connected to each other? And that time doesn't so much start over and return to the starting point on a circle, so to speak?

The Big Bounce! https://en.wikipedia.org/wiki/Big_Bounce

To me it's more satisfying than the idea of https://en.wikipedia.org/wiki/Heat_death_of_the_universe

I once heard of the hypothesis that once the last proton decays, the universe will once more be completely uniform in every way. With nothing to distinguish any part of the universe from any other part, space becomes meaningless and the universe has once more entered a state of nothingness much like how it was "before" the Big Bang.

So, in a sense, the heat death is not so different from the big bounce.

Unfortunately I did not bother to bookmark what I had read, and can no longer find a name or anything referring to it on the internet.

You and your parent should definitely read Asimov's short story "The last question", if you haven't yet. Just Google for it.

"You and your parent" definitely confused me for a second!

There is a great mini documentary made that tries to answer this question https://m.youtube.com/watch?v=uD4izuDMUQA

Roger Penrose believes in a model he calls Conformal Cyclic Cosmology. He doesn't believe in Cosmic Inflation, and instead proposes that the accelerating expansion of our present universe forms the inflationary period of the next universe. He gets around the second law of thermodynamics by saying that the difference between the two universes is a redefinition of entropy. The mapping between the two different definitions of entropy makes our maximal entropy state look like a minimal entropy state in the new universe.

This reminded me of a pretty good (and robust) debate with some of the world's leading physicists regarding the existence of and quantification of nothing.

2013 Isaac Asimov Memorial Debate: The Existence of Nothing

https://www.youtube.com/watch?v=1OLz6uUuMp8

There was no "before" as time itself was created with the universe.

How was time created, time means changing state, without time there is no change. So in order for a change to happen in the existence of time you'd need a further time dimension; then you're just shifting the problem up the stack.

Creation of time requires a meta-universe of some sort. Though perhaps there's some other way to conceive time not existing further back than a given point that works around creation being something that's done within a temporal dimension.

Although in that case, barring any meta-universe to provide a defintion of time beyond time, time must simply be.

Or not be, but I think we can rule that one out.

It is no different from the question how any other dimension suddenly existed. Time and space are connected.

I have wondered in the past if "time" has varied over the existence of the Universe, like if the first 100,000,000 years relative to our own reckoning was actually more like 100 billion years as time is elastic and changed over some other higher-dimensional axis. Just a musing by a speculator

The problem in your argument is the word 'become'. To 'become', something has to not be so and then later be so- with 'later' implying time on both sides. Hawking's argument is that there is no time on the other side.

My interpretation is that the energy of the universe exists in time and space, evolving across the dimension of time. But it has an edge called 'the beginning'. That's the shape of the beast- a defined edge that we cannot reason outside of.

Edit: At least, I presume your 'because' was meant to be 'become'.

> My interpretation is that the energy of the universe exists in time and space, evolving across the dimension of time. But it has an edge called 'the beginning'.

Actually, Hawking's proposal was that there is no "edge". In his proposal, the 4-D spacetime of the universe has no boundary, just as the 2-D surface of the Earth has no boundary. What we call the "beginning" of the universe is more like the South Pole of the Earth: we pick it out of all the other points because of a particular property we're interested in, but it's not an "edge" any more than any other point is. (Note that this analogy, which Hawking used, is referred to in the article.)

Is the hypothesis still that the limit as time goes to zero still exists as a part of our universe? In your analogy, is the south pole still a point contained on earth or is it just a point you can get arbitrarily close to?

> the limit as time goes to zero

There is no "time" at the "South Pole" point of the universe, or sufficiently close to it. The spacetime geometry in Hawking's model is purely spacelike in that region, not split up into "space" and "time" parts the way it is now. (As I understand the model, the boundary of the "spacelike" region" is at the beginning of inflation.)

> is the south pole still a point contained on earth or is it just a point you can get arbitrarily close to?

It's still contained.

That's really cool. Thanks for the explanations :D

You're welcome!

> Is the hypothesis still that the limit as time goes to zero still exists

Note that in other models of the universe, the ones that have an "initial singularity" which can be thought of as "the limit as time goes to zero", the initial singularity itself is not part of the universe; it can be approached as a limit but never reached. (The reason is that spacetime curvature increases without bound as the singularity is approached, and the equations of GR break down at the singularity.)

One of the nice things about Hawking's model is that it totally avoids this problem; spacetime curvature is finite everywhere and there are no singularities and no points where the equations break down.

> Pure nothingness has no potential for creation.

I disagree, pure nothingness has the largest potential for creation because by virtue of not being there (nor anywhere) it doesn't prevent anything at all from creating itself.

if this sounds strange is because the concept of nothingness is strange.

rather than asking why is there nothing rather than something, I marvel at how we can conceptualize 'nothingness' in such a way that we can even think of these kinds of questions

You're misunderstanding potential.

Potential cannot exist of its own accord. It is secondary to something already actual and only then can it be actualized.

If in the beginning there was truly nothing, and I mean also the absence of any cause that could make things exist, then there is not only nothing to actualize anything since only actual things can actualize, but not even the potential to be actualized.

So no, absolute nothing can not produce nothing and can never yield anything not even in principle.

You're speaking in tautologies. If you define "Nothingness" as "That which is unable to produce anything" and use that to conclude that it is not possible for there to be nothing at the start of the universe, you are begging the question. Your axioms trivially contain your conclusion, but why should we accept those axioms?

As a layman when it comes to physics, I've always had the impression that the nature of existence must be tautological. If the logic doesn't form a circle, then any attempt to explain the cause and effect sequence that resulted in our universe can always be met with a "well why did the first step occur"?

Logic is a human invention. The universe doesn't owe you the ability to explain the entire chain of cause and effect. Not being able to prove your axioms is what differentiates science from religion.

By definition axioms can't be proven but they are assumptions which we take for granted upon which we build science. However, in science, the axioms are such that they can be observed and discarded if we ever find them to be false. This is where it differs from religion.

I think that using logical fallacies to prove your own assumptions likewise discards observation in favor of a totalitarian explanation of everything, which amounts to a religious belief. A key aspect of science is accepting that our understanding is limited and contingent, whereas religion tends to use faith to prove itself.

Agreed.

EDIT: _Mostly agreed_. Religion never proves itself. It just demands that you have faith.

Science doesn’t prove axioms... Gödel already parsed this problem :)

Pure nothingness cant be detected or measured because nothingness isn't there. if it was there it wouldn't be nothingness it would be something.

the more i think about this the more wrong i think you are.

You're assuming that "nothingness" isn't an impediment to creation of something... it may very well be the ultimate barrier to something being created.

We'll probably never know, but at the end of the day until we can devise a way to define and measure "nothingness" we cant setup any experiments (thought or otherwise) to develop theories from/about it.

but nothingness in fact isn't an impediment to creation because nothingness just isn't. it's not an impediment nor a boon nor anything at all.

and how can you concieve of a way to measure "nothingness" when by definition you would be trying to measure that which isn't there to be measured?

have you ever seen zero of anything? how would you measure that?

I agree that conceiving of nothingness is hard and as yet unsolved.

but I fail to see how this is related to your first statement. >but nothingness in fact isn't an impediment to creation because nothingness just isn't.

Again the statement that nothingness isn't an impediment, literally can not be proven. Because of that, you must leave open the potential that pure nothingness might be not only an impediment to creation but it might also be the ultimate impediment to creation of something.

We dont know what the properties of nothingness holds in our universe or how our universe of stuff behaves around nothingness.

> We dont know what the properties of nothingness holds in our universe or how our universe of stuff behaves around nothingness.

nothingness holds no properties.

I think it's more useful to ponder how can we even talk about it to discuss its precise nature. which it doesn't have, so is it kind of recursive? i.e its nature is its 'own' non-self? ugh..

The act of creation requires there to be something there beforehand. You can't create something from nothing, it doesn't make any sense.

I don't understand why would creation require something beforehand, that seems to be transformation or transmutation of some sort.

in any case, nothingness already makes no sense on its own

> What properties of a zero point (that had no properties) cause it to create an inflationary universe?

In Hawking's proposed model, there is no "creation". The 4-D spacetime of the universe just is; it's a 4-dimensional geometric object with no boundary. See my response to mabbo downthread.

> Pure nothingness has no potential for creation

In mathematics, at least, this is not true. For example, a set consisting of the empty set is not empty.

You're confusing formalism with metaphysics.

Emptiness isn't nothingness. Emptiness presupposes something that is empty of something expected to fill it, the absence of something not the total absence of anything. Absolute nothingness isn't empty because there's nothing that can be empty. Nothingness is not a something, but people here seem to be reifying the notion.

Because you can't get rid of the potential to reify.

"Pure nothingness" would be the empty set, not a set with something in it.

Yes, that's their point. Pure nothingness, the empty set, has the potential to create the set containing the empty set, and then the set containing that, sets containing combinations, etc etc.

How does the empty set "create" the set containing the empty set?

By being the contents that make that set exist.

>Everything breaks down at that point, because trying to use mathematics or physics to explain something that existed before mathematics and physics doesn't work.

What is the meaning of this paragraph? Mathematics are not dependent on the existence of any particular universe

The explanation I've found most persuasive is to take a purely philosophical approach: the universe had no beginning and will have no end because those concepts do not apply. The universe is everything. If there was something that "caused" the universe, it would just be part of the universe. If there is something after the universe ends, it would just be part of the universe. There is nothing outside the universe, if there was it would be part of the universe.

Yep. If you're a programmer, think about a "game of life" simulation (or any other simulation).

The answer to "what was there before the first state in my simulation?" is simply: "nothing, within this universe".

That's not an explanation, that's just a relabeling, moving the questions people have from the label "the universe" to the label "the observable universe", but neither answering them, nor making them any less relevant.

The universe is everything. By definition, there can be no evidence for anything outside, before, or after it. Any such evidence would be in the universe. There are no valid questions about it, nor valid answers. Any claims about something outside the universe are neither true nor false—they are completely arbitrary. They have the same intellectual status as God.

I addressed what you said, you just blindly re-iterated your point without any engagement with mine at all.

To spell it out even more clearly, what if "the universe" is larger than the observable universe? In that case, it would still be reasonable to ask where did the observable universe come from? For instance, if we are a simulation, you would place the simulator in "the universe", which as a definition is a fine place to put such a simulator. But it means that questions about our observable universe would then be fair game.

You're trying to shut down thought by simply redefining terms, but even by your own definitions, it doesn't work. It's not a sophisticated or well-thought out position, it's just "I give up entirely, and so should everybody else" dressed up in pretty clothes that are trying to look cool. You're welcome to give up in that way, most people do by default after all, but you've got no grounds to insist that others also give up.

This is precisely the form of argument made by religionists.

I agree.

The problem seems to be the word “Universe”. As soon as you assign a word to a thing, it gains boundaries that separate it from nothing and everything else.

My favorite description of origins of things comes from Spencer G. Brown in Laws of Form.

My own short poem about the origin of things:

First there is none, and so just one. Yet none and one are two. Once there’s two, they share a room, hence there now are three. Remembering the two before, the three completes the five, and on the numbers multiply until they are complete.

And a koan:

The student asks the master, please teach me. The master replies, how can I teach you if I have no tongue with which to speak, and no space within which to exist?

Cosmology is deeply disturbing if you think about it too long. Why should the universe exist? What is a causeless cause? How can something come from nothing? Regardless of the precise mechanisms involved, at some scale, some kind of steady-state cyclic model seems unavoidable --- the whole idea of existence not existing is bizarre and puzzling. The only way out of the causeless effect problem is to nop out of the effect.

That's only disturbing if you believe everything is simple enough that humans could comprehend it straight away. If you accept that some stuff is beyond our understanding, and will be for quite a while yet, everything is much less bothersome. Accept that you are fallible and the universe is fine.

I'm not saying this is easy though.

This is how I view the universe. We make attempts to interpret it and probably never will fully comprehend it. The perceived boundaries of our universe is the edge of our consciousness and what we understand as humans. As we evolve so will our understanding and interpretations.

For me it is more of a humbling feeling than disturbing.

> If you accept that some stuff is beyond our understanding

isn't that just an elaborate way to say 'give up'? I asked religious friends of mine about what god _is_, and the common answer is that it's beyond human understanding.

I don't believe that people should take things on faith, and accept that anything is beyond understanding.

isn't that just an elaborate way to say 'give up'?

Accepting that we don't understand something is a first and very necessary step to even realising there's something to understand. Believing that we have the answer (eg "God made the universe!") is exactly what shuts down scientific inquiry and makes people 'give up'. I'm saying literally the opposite of that - we have to realise there's something to out there to learn in order to try and learn it.

If we accept your logic, then believing gravity to be the answer to "why things fall" would shut down scientific inquiry?

On the contrary, it was belief in the creator that opened up scientific inquiry in the minds of Johannes Kepler etc.

That the universe was not chaotic, but created by a personal being, led them to think there must be some order to it that could be studied.

He only said it was beyond our understanding "for some unknown amount of time", or that it might end up being too complicated/incompatible with our existence.

His comment wasn't at all about giving up, honestly the exact opposite. It was about avoiding/managing the disturbed/dreadful feelings that commonly accompany the thoughts and work in this domain.

To some degree, it is the willingness to "know your place" in human history. No one in ancient Greece could have discovered cosmic background radiation or observed that all galaxies exhibit redshift, which would have provided evidence for the existence of a Big Bang.

Similarly, we have limitations to what we can observe and measure. We strive to continuously make improvements, but we also need to accept that not all questions will be answered within our lifetimes, and unless civilization collapses, schoolchildren will have a more complete understanding of the nature of the universe in 300 years than we do.

There's good reason to believe that humans can understand everything that exists: we're Turning complete, and mathematics admits no higher category of functions than those that a Turing machine can compute. We may not be able to physically compute every function, but we can devise a plan for computing any function, and isn't that tantamount to being able to understand anything in principle?

> the whole idea of existence not existing is bizarre and puzzling

The alternative is that matter has always existed, which is equally bizarre and puzzling, though things make more sense that way.

While everyone else wonders about the nature of time. I wonder about the nature of "sense." What is "sense"? How do some things 'make' sense and others don't? Is "sense" universal? If not, why?

From a probabilistic point of view, we're observing with extreme selection bias: we only see the universe in which we do exist, not all the ones in which we don't, so no matter how incredibly unlikely existence is, from the perspective of existing consciousness it is guaranteed. This means it's possible for consciousness to arise from pure entropy: https://en.wikipedia.org/wiki/Boltzmann_brain.

Related question: how fast does time go in a “pure entropy” situation?

Or, maybe more useful, what happens to time as you asymptotically approach pure entropy? Does it speed up?

If so, it would make a Boltzmann brain inevitable. Or... not an inevitable brain, but an inevitable random low entropy state, right?

> what happens to time as you asymptotically approach pure entropy

Uh, maybe nothing? Depends on how you approach the pure entropy condition, and where the observer is and how it's moving compared to a clock.

Let's consider the measure of entropy in Boltzmann's relation : S = k log W or essentially that the quantity of entropy is the log relationship between the macrostate and the number of possible microstates that can represent that macrostate. A tree is a macrostate. Its individual cells, or the atoms that make those cells, or the quarks that make the nuclei, are examples of ever more micro microstates.

You are pretty low entropy because we can't take a cubic centimetre of one of your bones and swap it with a cubic centimetre around the mitral valve of your heart and expect the same macrostate to persist: you rapidly become a corpse. Empty space is "pure" entropy because we can take a cubic centimetre of vacuum and swap it with a cubic centimetre of vacuum elsewhere, and it will make absolutely no difference to the macrostate. We can swap all of the cubic centimetres of vacuum in an empty spacetime with one another, so the combinations at just that scale that produce the same empty spacetime is enormous. A black hole (assuming no-hair conjecture is true) can be represented by eleven variables, most of which vanish by a suitable choice of coordinates, leaving mass as the dominating item in the macrostate. But that mass can be all hydrogen atoms, or half as many helium atoms, or some arbitrary mix of gas and dust, but those all don't matter to the horizon that defines the black hole. The entropy of the horizon is enormous, because we can't distinguish between an isolated black hole made of nothing but atomic hydrogen to a different isolated black hole of the same mass, charge, and spin made of nothing but molecular hydrogen.

Now let's add a clock somewhere in these vast seas of entropy. How fast does it tick? It depends on who is looking! If we put it into otherwise empty expanding space, someone close to it will see it ticking faster than someone extremely far away from it. The latter, watching for long enough, will see the clock slow, dim, shrink, and ultimately vanish thanks to the metric expansion of space. The former, staying close by the clock, would see it tick at the same rate for an arbitrarily long time. But if we put it close to a black hole, what happens? The close by observer, staying close to it, will see it tick at the same rate for an arbitrarily long time. Observers at greater distance will see it ticking more slowly. If it were to fall into a very large black hole along with the close by observer, there is "no drama": the observer sees the same ticking rate upon them crossing the event horizon together. But the distant observer will see the clock slow, dim, and shrink until it vanishes. (Don't be tempted to think that a black hole is the same as an expanding universe because of this coincidence! We are definitely not inside a black hole, but we are definitely inside an expanding universe. The metrics are very different and lead to different trajectories for things moving through the respective spacetimes, even though the very different spacetimes coincidentally have boundaries that can in some circumstances produce similar observables for a clock near the boundary.)

We can complicate the picture by having the observer move relativistically with respect to the clock, especially if we introduce extreme acceleration.

So the thing about time in a relativistic context: how fast a clock ticks is observer-dependent, and in curved spacetime it's position-dependent too. It's the curvature of spacetime that makes the context relativistic; from the equivalence principle (non-gravitational) acceleration likewise makes the context relativistic.

If we lower the entropy of the vacuum by introducing things like galaxy clusters and cats, these less-entropic things generate curvature. So there are more places for a clock to slow down in a universe that has less entropy, than in a universe which has more entropy. Even in the black hole case, we can add another black hole and now there are two event horizons around which a clock will tick slowly from the perspective of a distant observer. Add more black holes, add more places where the clock could be ticking slowly for this observer. Of course, as you add more black holes, you are generating a more complicated macrostate, so entropy is dropping.

So the answer is: as a universe's entropy increases, there are fewer places for clocks to run slowly.

Even though a uniform gas has very high entropy, it still has less entropy than empty vacuum, and it is also subject to things like brownian motion and other fluctuations in density. Is a Boltzmann brain inevitable in such a gas (in the farrrrrr future of our universe, there may be a sparse gas of ultra-infrared photons with an even sparser gas of black holes and diffuse ordinary matter, and it may be uniform after a verrrry long time) ? No, but we can assign a low probability that the matter will fluctuate into a Boltzmann brain. The problem that obsesses Boltzmann brain cosmologists is that the low probability of a Boltzmann brain with false memories of having grown up in a universe like ours is enormously enormously enormously more likely than the ultra-low entropy of a hot big bang which evolves into a "real" brain with "real" memories of having grown up with cats and computers and so on, with entropy increasing as you get further from the big bang[1].

So does that mean you are a Boltzmann brain with false memories?

- --

[1] The early universe is almost certainly low entropy. If, when it is suuuuuper dense but with tiny variations, we swap some of it at "A" with some of it at "B", the stuff around "A" won't be dense enough to collapse into the galaxy it otherwise would have. Or maybe the stuff at "B" will suddenly be at a critical density to start collapsing gravitationally, leading to star formation and so on. The tiny variations are expected because of quantum behaviour at densities where quantum gravitation is important. Also, of course, it would be weird if the second law of thermodynamics depends on how close to the early universe you are: and that would be the case if the early universe had more entropy than the present universe (which is full of lots of nearly empty space, with a large and growing number of indistinguishable cubic centimetres between galaxy clusters).

Thank you for writing this up! It’s a little above my head, but it helped me see some signposts on the question.

Your point that the random low entropy Big Bang is a super unlikely event interests me.

I think the original thought came to me from Roger Penrose’s Big Bang theory that posits physics is scale free, and in that uniform gas state, something... happens, to allow a Big Bang.

In my (simple) mind it is akin to electron orbital collapse? Like quantum information collapse... the entropy at a certain scale becomes high enough that it Works Like low entropy at the next scale above, and that causes a Big Bang at a larger scale than we have physics for, which also basically erases this universe.

So, there are repeated big bangs but each one at a different scale.

I probably misunderstood him as much as I misunderstood you, but those are the points I am pondering. In practicality I am trying to figure out if these ideas could be used to make a video game engine.

In my current thinking, This would require some “rebalancing of registers” so maybe an as yet unknown quantum field which shifts all the registers so meters become centimeters, information is destroyed, and entropy miraculously drops?

Not sure. :)

This is the so-called 'superultimate question', whose answer defies inquiry: "Why is there something rather than nothing?"

Say we could break any physical rules of our current universe, is there a good theory that would explain how something might have been created out of nothing? i.e. imagine for a second that we're in a simulation and that the current laws of physic are just arbitrary created by a "host". This "host" could have very different physical laws. Could we think of any theory that would explain the creation of something out of nothing in this "host"?

I'm very puzzled as to why the universe even exist.. wouldn't it have been much simpler not to have anything at all? I can only think of one answer: It couldn't have been otherwise. I.e. physically speaking, it had to happen.

Maybe that's how we should approach the problem? Let's try to "create nothing"... maybe we'll realize that it's actually impossible to "have nothing" unless X happens, and maybe we'll figure out that X happening would explain how our universe was created?

Or said in a different way, maybe the universe is actually "nothing", like it always was and will always be. But "nothing" may just be physically impossible so you need "positive" and "negative" things to cancel each other out so that the end result is "0".

I'm not too sure where I'm going with this, but it reminds me of the quote "Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth." So, whatever the theories about big bang, multi-verse, universe expanding/collapsing indefinitely or even God-based theories, all of it comes back to "how did the first thing come out out of nowhere?" People talk about "Singularity", but this is just "kicking the can down the road". Still, by kicking the can I guess we keep learning new things, and maybe someday we will have the technology to answer these questions. Unfortunately, it seems like answering the next frontier seems to be an order of magnitude harder (time-wise and cost-wise) than answering the previous question.

That is the most fundamental question.

Why does anything exist at all?

Conceptually, this question persist across all the big bangs, collapses, multi universes, or any other conception science has made informed conjectures about, doesn't require time, sequences, or cause and effect These are all processes suppose there is some underlying construct / process / force / structure. But nothing, not even the concept of nothing, not even ideas, maths, shadows on a cave wall.

It is unknowable.

Yet, for many specific values of $anything the answer is very much known.

You might be interested in Our Mathematical Universe by Max Tegmark. He tries to argue that, fundamentally, the universe is "just math." In other words (glossing over enormous complexity here) if the basic axioms of math are true, the universe must exist.

I have to admit I didn't fully buy the line of reasoning. But it's very interesting.

> if the basic axioms of math are true

Isn't the problem that you can't prove axioms. We intuitively "know" them to be true but without proof.

You can't use deduction to prove them... but you use induction to show them to be statistically non-violated through experience so far.

UD+ASSA (http://fennetic.net/irc/finney.org/~hal/udassa/) is an extension/refinement of the mathematical universe idea that I find very compelling. It explains why even though "everything mathematically describe-able is real", we personally see and anticipate that some things are more likely than other things, including why physics stays the same instead of spontaneously changing, etc. (One of the original authors of the idea thinks there's issues with it, but I think it's still a very useful idea: https://www.lesswrong.com/posts/zd2DrbHApWypJD2Rz/udt2-and-a...)

Since considering it and the mathematical universe idea, the question of why anything exists at all no longer feels so mysterious. Even if there were somehow an objective universe with nothing in it, as long as the basic concepts of logic still held (which of course they do, they don't depend on the universe), then there would still be logical/mathematical structures that describe entities that see themselves as conscious.

I haven't read it, but that certainly sounds a lot like saying that the map is, in fact, the territory.

There's an interesting philosophical line of thought that distinguishes between things that are necessary and things that are contingent.

A necessary thing must exist; it can't not exist. A contingent thing may exist, or it may not.

In the classical definition of God, he has no beginning or end. He was not created by some other force. He exists necessarily. He just _is_. In fact, many theists describe God using terms such as "being itself" or "pure is-ness". Even the Hebrew name for God -- I AM -- makes references to this. And if God is necessary and uncreated, it gets around the question of, "Well, who created God?"

But I've heard people point out that if you can say that God just is, without having been created, then why not say that the universe just is, without having been created?

I think the answer to that question lies in this distinction between necessary and contingent things.

Theists who have a classical conception of God would argue that God is necessary, but the universe is contingent.

If you're interested in the philosophy behind this, here's an interesting resource: https://plato.stanford.edu/entries/god-necessary-being/

Why is God a necessary thing?

A valid question, and not one that in my opinion (even though I am a theist) that has an argument that is both clear and compelling (look up various Ontological arguments to see the gamut).

I think it is enough to say the following things:

1. The universe clearly exists, but it is also clear that it doesn't have to exist (i.e. the universe is contingent)

2. Therefore, there must be some thing that exists, and exists of necessity, to explain the existence of the universe

3. The existence of necessary truths such as logic and mathematics are not sufficient to explain the existence of the universe, so therefore there must be something else, which could act as both the sufficient and necessary cause of the universe.

We can call this thing God, but by that we don't commit ourselves to any particular religion. At most that gets us the God of deism.

> We can call this thing God, but by that we don't commit ourselves to any particular religion. At most that gets us the God of deism.

Not so. The deist God is more of a Cartesian/Paleyian watchmaker, not the God of the philosophers classically understood. The God of the philosophers is very much in line with the Judeo-Christian God (not everything can be inferred through unaided reason, but much of it can). And God as "I am" ("ehyeh asher ehyeh") is precisely not a thing ipsum esse subsistens, or that who's essence it is to exist, and by which all things are. However, it precedes things and in doing so puts a stop to the infinite regress of having to appeal to still further things to explain the existence of things (which cannot work because we aren't trying to a chain of causes but the cause of their existence in the here and now).

Response to mythrwy:

If existence were a property, then it would follow that things precede their own existence, which it absurd. And as I've written above, things cannot account for their own existence, thus you must posit existence as distinct from the things that are by virtue of it. You must appeal to a causal non-thing to account for things and thus depend on that cause for their own being in the here and now.

> Not so. The deist God is more of a Cartesian/Paleyian watchmaker, not the God of the philosophers classically understood. The God of the philosophers is very much in line with the Judeo-Christian God (not everything can be inferred through unaided reason, but much of it can). And God as "I am" ("ehyeh asher ehyeh") is precisely not a thing ipsum esse subsistens, or that who's essence it is to exist, and by which all things are. However, it precedes things and in doing so puts a stop to the infinite regress of having to appeal to still further things to explain the existence of things (which cannot work because we aren't trying to a chain of causes but the cause of their existence in the here and now).

I'm not sure I follow the distinction you are making. In any case, my point is that this ontological train of reasoning does not get us all the way to specific religious commitments, although we might argue that some religions are more compatible with this line of reasoning than others.

Response to bobthechef:

If nothing can account for its own existence, how then do we come to the concept of God?

If every existence must have a preceding cause, and the thread were followed long enough, ultimately there could be no prime cause unless cause were cyclical, a loop so to speak.

In the case it's not cyclical but linear at some point "cause" ceases to exist and existence is an intrinsic property of the object, ("the thing without cause"). Why then should we suppose that point is some abstract level above the manifest universe? In other words, if we accept "God" (i.e objects can be without cause) then we have accepted that there need not necessarily be a proceeding cause to existence and the universe is as good a starting place as any.

Doesn't point 2 (something exists of necessity) negate point 1 (clear it doesn't have to exist)?

On point 3 I fail to see logical need for external cause. Existence could simply be an intrensic property of the universe.

Besides it just shuffles the "cause" issue up a level. If God can exist "just because he does and always has and is without external cause" so can a universe.

> Doesn't point 2 (something exists of necessity) negate point 1 (clear it doesn't have to exist)?

they are talking about different things. The universe is contingent, but something other than the universe (that is not contingent) is required to explain the existence of the universe.

> On point 3 I fail to see logical need for external cause. Existence could simply be an intrensic property of the universe.

Could the universe have been in a different configuration than it is? More matter, less matter, no matter, etc.? There is no contradiction in those configurations, therefore we must admit that they are possible. That means that the universe needn't be (as it is, or at all). If something could be different than the way it is, then rationally we must suppose there is an explanation for the way it is.

> Besides it just shuffles the "cause" issue up a level. If God can exist "just because he does and always has and is without external cause" so can a universe.

"God" at this point is just a placeholder to the solution of the problem of infinite regress. The universe is not a suitable stopping point for reasons stated above.

I'm not sure that conventional human mathematics lacking the ability to explain something indicates another abstract level of complexity above what we call "the universe".

Also I don't know that infinite regress is necessarily a problem. Cycles most immediately come to mind, aka "loop quantum gravity".

But really I think think both the concept of God and the universe are a perceptual and a definition problem.

Because of our state of being, we can't speak nor understand much outside of the parameters we know. Which leads us to define ideas in ways that probably aren't very accurate and leads to misunderstanding and miscommunication.

That being said, I see no reason to abstract things more than needed.

I won't say I'm necessarily "atheist" because that presupposes I'd understand and could define what it is I don't believe in. By this same reasoning I most certainly am not a theist either.

"Prime cause" just appears a very fallacious argument to me, I guess that's the point. No offense intended.

> I'm not sure that conventional human mathematics lacking the ability to explain something indicates another abstract level of complexity above what we call "the universe".

I just bring up mathematics as an example of something that philosophers have typically categorized as "necessary truth". For example, 1 + 1 = 2 is necessarily true (there is no possible world in which it is not true) and as such requires no additional explanation as to why it's true (aside from just defining terms).

The fact that the earth is populated with living organisms is a contingent fact. That is, it is possible that there be no living organisms on the earth (or, in philosophical parlance, "there are possible worlds in which the earth is not populated with living organisms"). It seems perfectly logical to conclude that if there are living organisms on the earth, but there need not be, then therefore there must be some explanation as to why it is so. Indeed, one might say that the entire enterprise of science is predicated upon the notion that contingent facts have causal explanations.

So when it comes to the question of "why does anything exist at all, rather than nothing?", I think it's fair to question whether we can know the reason, but it likewise seems inescapable that there must be a reason.

> Also I don't know that infinite regress is necessarily a problem. Cycles most immediately come to mind, aka "loop quantum gravity".

Well, I can say that it doesn't look like the universe is headed in some kind of loop (because of accelerated expansion) but that (at best) answers the physical question whether we are in a cycle, not the metaphysical question of why there must be a prime cause. I admit I don't have a good answer for that, but I will certainly think on it. I also don't know enough about loop quantum gravity know how that relates (though I trust it does).

> That being said, I see no reason to abstract things more than needed.

As the saying goes "a theory should be as simple as possible, but no simpler". In this case, I would say that a "prime cause" is the simplest theory available. To posit that the universe exists without cause is too simple, and alternative theories (such as the multiverse theory) are more complex.

> "Prime cause" just appears a very fallacious argument to me, I guess that's the point. No offense intended.

No offense taken! It's always great to hear what parts of my thinking other people find unconvincing. I like knowing how other people think about these kinds of issues.

First, God is not a thing, so let's rephrase that as God is logically and metaphysically necessary.

Consider a person poking a stone around with a staff. The stone moves only insofar as the staff moves it and the staff moves only insofar as the person moves the staff. Thus, the stone moves only insofar as the person moves it. Analogously, the existence of things, here and now and at any moment, must have a cause that is causing it to be here and now or at any moment. The cause of the existence of something here and now must be other than the thing itself because a thing cannot account for its own existence. If a thing could account for its own existence, then it would need to be identical with existence. But if a thing were identical with existence, then only it could exist and nothing but it. Furthermore, no change would be possible because if a thing is its own existence, then any change could only lead from existence to something that isn't existence, i.e., non-existence. So existence precedes things and things exist here and now because it is, like the person pushing the staff, causing them to be.

We call this cause of existence God and if anything exists it necessary follows that there is a foundational cause and that is God.

Only things exist.

You can call it "God", meaning the above is your definition of "God". But I think that is highly misleading because the word "God" is used in the Bible and it speaks about a very specific type of thing, not defined like you define it but as something which created everything in 7 days, spoke to Moses etc.

Using the same term "God" as Bible, Book of Mormon, Koran and other books do but with a different "definition" is highly confusing and misleading. You should call the "cause of existence" simply "Cause of Existence". If you need a shorter way to refer to it a good one would be "CoE", not "God".

Why use the same name as Bible unless you are saying you are talking about the same thing that Bible is, the thing that spoke to Moses?

Following Goedel: God is necessary, because God is defined as the most capable and most good. For the most good, capable of existence, to not exist, is bad. So either God is bad, not capable, or a necessary existent thing.

But binary Truth is so Platonic. I believe there are universes in our multiverse of possible universes where there is an entity that is better than the best entity possible in our universe (no, I do not think that God can bend the laws of Physics and make an immovable object). Also, God is a gradient, since He manifests in people and nature. God as a force of external Good, may be nearly non-existent in times of human war. Nature is more abundant in some places than others.

Finally, more Jungian psychological: It does not matter whether God exists or not exists, what matters is that we keep talking about God. And humans keep modeling the Universe including a God entity. Therefor God is a necessary outcome of human cognitive modeling. We do not have direct access to the physical universe, only to our mental world models, the ontology question becomes irrelevant, what remains is the models. And there, a category error seems plausible: The most capable of Gods, would be capable of evil too, superseding the only-good God. Just like its human modelers are. Just like the old Testament God was good for the chosen people, but evil to the innocent firstborn children of opposing tribes.

Having traversed from being raised vaguely christian, through atheism, back to a form of what I suppose could be called pantheism, I see the truth of the statement but find it difficult to explain without also explaining a mountain of pre-requisites, if only to negotiate terminology for concepts you may already be aware of, so that the actual answer can be conveyed. Never the less, I will make an attempt at simplified statement of it:

God must necessarily exist because you, the thing that sits behind your eyes and experiences the world, exist.

If you feel that this is a naive statement, as you likely do, then it is because we lack sufficient shared context attached to the words. However, I am confident that if you spend enough time thinking about the nature of the world, and of yourself, you will come to the same conclusion, though you may use different words to describe it.

Btw, laws are not actually things. They're descriptions that are reified by some people. What you have are things in the universe that have natures that their natures lead to detectable patterns. A law of physics is just a shorthand way of saying "things of this kind behave in this way". It's very important to understand this instead of assuming the universe is some vacuous collection of natureless things that are governed from the outside by some "laws".

I don't know about why anything exists, but it stands to reason for me at least that if there is a non-zero net energy, without any boundary conditions, then it has to expand. That it expanded and cooled down into its current form is coincidental.

Why there is non-zero energy in the first place is, I'll agree, odd. Your idea of it balancing out some negative energy elsewhere is interesting.. Maybe we're just the positive side of a temporary virtual particle in a higher universe-particle "foam" like the quantum foam.

The word "beginning" is contextualized to the concept of time, and time is an abstraction that exists within the universe. To say that the universe has a beginning is to say that time has a beginning. But that is nonsensical; something only has a beginning if its existence is preceded in time by other existence. The existence of time can't be preceded in time by the existence of something else. For that to have meaning we need some "meta-time". "Meta-time" can only exist in a "meta-universe": a larger, imaginary universe in which we are embedding "our" universe. Well, did that larger one have a beginning, and why would we even consider it a separate universe at all?

The start of the Universe was the start of time. My personal theory is that when matter enters a black hole, some of that matter (in some form) gets snapped out of space-time, emerging at time 0, at 0,0,0 coordinate. With all the black holes over time, all venting into the same space and time, producing lots of matter in a single space at the same start of time, which would create a big bang.

Just a theory, but one I've not fully proved, nor disproved.

Of course this would mean that the future created the past, and a bit of a paradox, but not entirely impossible.

Slightly different but related thought: what if inside of each black hole singularity is another universe? The stuff it collects ends up in this other universe. Which would mean our universe is just "inside" the black hole of another.

Then perhaps the accelerating expansion of spacetime we detect here has something to do with the accelerating accumulation of mass of our "parent" black hole.

That would add an interesting spin upon multiverses. Without a doubt, black holes and understanding them are very much key to many unanswered and unknown questions.

to me it's more rational to think that each black hole is just punching a hole in our 4-d spacetime fabric just like a sharp point can punch through a bag. what the stuff drains into - I have no idea. Perhaps a higher-dimensional space that contains our universe?

The linked 1981 source document "Astrophysical Cosmology" proceedings from the Vatican look's interesting (Hawking's raw talk is at page 575 in the PDF):

http://www.pas.va/content/dam/accademia/pdf/sv48pas.pdf

The preface mentions the academy was from 1603 and Galileo Galilei was a member.

I have very little knowledge of astrophysics, but I thought it would be an interesting idea if the universe constantly recycled itself. That is, every so often it collapsed in on itself and produced another big bang. Theoretically some parts of the universe would have already achieved escape velocity, but the rest of it is gradually gravitating towards some center of mass. Is such a thing even feasible?

A few decades ago, that was widely believed as the most likely state of the universe. However, it's now known that the big bang is essentially still accelerating and this is blamed on an unknown force called "dark energy". It doesn't have much effect within galaxies, but galaxies themselves are blowing away from each other at ridiculous speeds.

Well it's more that space itself is expanding. It doesn't affect small scales because other forces collapse everything back together fast enough to overcome it. If the increase in dark energy is consistent though, eventually it'll be expanding so fast not even our atoms can hold themselves together.

It's definitely an interesting an idea that has been considered before. Hopefully the Wikipedia page on cyclic models can be a starting point of interest to you! https://en.wikipedia.org/wiki/Cyclic_model

Not really, because you again assuming that there's an independent time-line, where a ball of universe expands and collapses.

Our current understanding of the Universe is that _time itself_ "expands and collapses". You cannot talk about time "before", because there was no time "before" the big bang, just as there's no space "outside" the ball, to talk about its boundaries.

Lee Smolin makes an intriguing suggestion with regard to how the universe reproduces in his book "The Life of the Cosmos" -- I can't say I was persuaded, but I think it's worth reading

Not sure if you were somehow subtly referencing this, but...

“There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another theory which states that this has already happened.” ― Douglas Adams

For me the hardest idea to grasp is the concept of “nothing”. It seems to me that is something the human brain cannot possibly comprehend. There is always something as far as our senses are concerned. I guess that’s why the idea of nothingness after we die so such a hard notion to comprehend.

Conversely, even the concept of "everything" is hard to grasp. "Everything" in the sense of an infinite universe where everything is realized infinite times over. It's absolutely bonkers to me.

You have no proof that it's simply nothingness when you die. If this universe has countless beginning points, what makes you consider a single ending point would exist anywhere?

> You have no proof that it's simply nothingness when you die

Do you mean to imply that you have proof to the contrary? Why is there any reason to assume anything else?

Conservation of matter and energy states that energy cannot be created nor destroyed. So what makes some annihilationist version of reality palatable to a true scientist?

By this logic, a building can't be created or destroyed.

I suppose you argue that consciousness is a fundamental aspect of nature, independent of all other things, rather than some emergent property of matter and energy.

If so, it is an extraordinary belief requiring extraordinary evidence.

Absolutely, and no proof that there isn’t. It certainly seems that the idea of an afterlife is appealing since in some ways it is easier to comprehend than “nothing”.

I can momentarily stun myself if I concentrate long enough on the idea of "what if there was just nothing? No universe, no cosmos, no light, no time, no matter. Just nothing." Think about that for a minute or two.

Things would surely be simpler :) also, that is what you will experience after death according to many here...

I have exactly the same thought, to a tee.

It is stunning that this concept emerges as something physical in the form of an event horizon.

'Dark stars' have been around as a concept a lot longer than black holes.

Whenever I see an image like the one in the article of a cone showing the start of the universe it reminds me of something being shot. Or an object with great velocity striking a stationary object. One end is the point of impact and the cone is the debris spraying outward.

What does it even mean to ask “what happened before time”? The question seems nonsensical to me.

You can still have causality.

Can you expand on this? How can you have causality - cause and effect - that's divorced from some sort of flow of time?

If I turn on a very simple computer, then the clock starts at zero. From the computers perspective that's all there is, it doesn't know the cause. From my point of view there absolutely is a case, me pushing a button.

This is not a god argument, there might be natural processes that can trigger such events.

The computer, and the external universe of which it is unaware, still have time.

Total amateur here: how do we know that time did not exist before the beginning of the universe?

Almost-total amateur here: We don't.

We really don't. We don't have any physical evidence of anything from before the big bang (presuming that's what we call the "beginning"). Zero. All we have is people having views on the current situation, trying to apply those views backwards to "before", where they may or may not fit, and saying "I think it's like this".

I don't think this is an accurate analogy. The computer's space-time and your space-time are the same in this analogy. The space-time that our universe exists in would not be the same as the space-time that some extra-universe process would be inside if the big bang theory is accurate. This isn't an analogy for causality without time, this is causality for the creation of our universe if the big bang theory is wrong and space-time didn't expand out of a point some billions of years ago, ie. that our space-time existed "before" the big bang and there were processes outside of our universe that were still inside of the same space-time as ours.

If the computer is simulating a spacetime, they're not the same.

You could - hypothetically - pause the computer, check its state, change a few variables, and the simulation would experience instant modifications.

A slow simulator could take many "real" time units to calculate each in-simulation time frame - and this would be invisible in-simulation.

And so on.

You have a fully causal system, but the simulation is ruled by its own independent emulation of causality.

Of course a computer implies a conscious user. But let's attempt some wild speculation and suggest that a "simulation" could also be a completely natural process - something that happens in a much bigger causal substrate: a kind of causal symmetry breaking, where a subset of possible relationships crystallises out of a bigger set of possibilities and then continues independently, losing some degrees of freedom.

A simple two level topology is the simplest possible model. But "causality physics" could allow all kinds of topologies - nested, circular, fractal, etc.

Although it raises an interesting question, because physics has a lot of issues with time. Just as in the computer example, why could we not imagine that our universe exists inside the space and time of larger superuniverse, and perhaps the phenomena that explain times arrow is easily observable in that universe, but not in ours.

Good point which brings us to a simple explanation. Time zero isn't when the h/w is booted, it's when the software is started. As unpopular as the simulation theory is, many difficult issues can easily be thought about. Except for the rest of the turtles.

Logically, cause and effect precede time. The concept of time integrates your perceptions of cause and effect. We observe various causes and effects require variable amounts of time, we omit the specific amounts of time, thus inductively identifying the abstract concept of time.

Both causality and the "flow" of time are ultimately artifacts due to the fact that a "universe", by definition, is something thay starts out in a highly-ordered state and evolves away from it. The basic laws of physics are time-symmetrical, at least in a practical sense - they do not involve any distinction between "cause" and "effect".

> a "universe", by definition, is something thay starts out in a highly-ordered state and evolves away from it.

I don't think that's "by definition". That's by observation of an example of one.

Our existence is limited to four dimensions, so we perceive things through the scope of time, including cause -> effect.

On the level of higher dimensions, it's difficult for us to perceive how cause -> effect would play out, but it's similar to how you would influence a drawing of a 2D stick figure. You could draw a house next to the stick figure, and that would cause the house to exist, but to the stick figure it would only perceive a single line with a start and finish on 1 dimension.

To that stick figure, cause and effect would be perceived as the two points on the line, though your four dimensional pencil caused it to exist on a different dimensional level.

According to some theories, space and time arise from causality.

https://en.wikipedia.org/wiki/Causal_sets

Causality is just human perception and there's nothing special about time. Let me try to explain this in three ways, going from intuitive/trivial to non-intuitive/mind-blowing:

• You can have causality in space rather than time: e.g. a convolutional image filter at pixel 13 might consider pixels 12, 13, 14 (of which the first two are causal and the last is non-causal, if we consider higher numbers as going "forward")

• You can have non-causal filters in time: e.g. audio compression at time 0:30 might consider not only the portion of audio from 0:00 to 0:30, but also the audio from 0:30 to 2:33. (This doesn't seem that remarkable, because the track has already been recorded, so it's not in "real time".)

• Finally, what we usually think of as intuitive causality in "real time" is simply a question of entropy. We think of a person dying because she was shot by a bullet, but we could also replay the movie backwards and think of all the tissues of a human body coming together in such a way as to propel the bullet backwards at a high velocity - in other words the wound causes the bullet to fly! The only reason we don't think of it this way is because the latter explanation decreases rather than increases entropy. As it turns out, physicists can show that entropy is also the exact reason why we remember the past and not the future. (And if we did remember the future and not the past, we would simply think of the future as the past and vice versa, so things wouldn't feel any different.)

Causality without time makes no sense. Even if you don't have a ticking clock, you can define "time" with a counter and a Lamport clock. Any time you have state, you have time. A timeless universe is hard to grasp.

Time without causality makes no sense. Time is an identification that entities move and change. The entities themselves cause all actions. The nature of those actions is determined by the nature of the entities.

Time is another dimension that we 'perceive'. Hence for our frame of reference, which is bound by time, asking what is outside this frame of reference makes no sense. But frames of references are relative and meant to be broken.

Similarly it is hard to imagine any object that can be purely 2D in nature, because we are biased to perceive the world in 3D. So we think that every object has to be 3D, even the smallest organism, or even atoms. But a 'fake' example of 2D is a tv screen. It gives us an example to imagine 2D. The point I am trying to make is that time is just our perception. To say causality is always tied to time is a bias created by viewing the universe through a 'time' tinted/colored glass.

The point of singularity where gravity is so high that time comes to stand still, but is still present - this is a possibility.

So maybe time just pauses between big bangs and flows at lower density and lower gravitational fields

> The point I am trying to make is that time is just our perception.

So is causality—I'm not really sure what your point is.

Because we are limited by our perceptions of time (and causality as well) doesn't mean we shouldn't wonder what could have been before the start of the universe. Maybe time started when universe started, or maybe time always existed and was super slow or literally paused at singularity - the gravity is so high (way more than the gravity of a super massive black hole) that time had paused. So maybe there was something before the big bang and I don't think 'talking about that makes no sense' should stop us from talking about it :)

I am also confused a tad about the point I wanted to make though, lol. Maybe causality and time is perceived differently in higher or other dimensions that we do not perceive as of now in our human level of evolution. So the assumption of causality exists only due to time being present could be something relative to our perceptions and not true

Time flows in a similar way throughout the universe. It might be slowed down by gravity here and there but it's a similar effect everywhere. With causality but not time, there would be a partial ordering of events that happened at a particular location, but no definite way to connect it to events that happened elsewhere using relativity like we're used to now.

Julian Barbour has what I consider to be a pretty well-reasoned notion a timeless universe composed of a large number of mathematical configuration spaces he calls "nows" -- i.e., it contains many states, but no objective notion of time -- outlined in his pop-sci book "The End of Time" [1999] and his website http://platonia.com/

p.s. for the record, Barbour is no clown, but a serious cat -- he is also the guy that wrote "Absolute or Relative Motion / the Discovery of Dynamics" which is a bedrock treatise on Machian ideas in physics

It's nonsensical to wonder what happened in our universe before it existed, but if our universe has an external superuniverse, it's not illogical to wonder what happened there that caused our universe to exist.

Can we follow this a little further?

Let’s say you and me are little bits of algae which are floating in blob in the ocean off the coast. We are in a larger current which we cannot see. The current is such that we will eventually strike the shore together.

We are in a cluster of material together. It’s not exactly algae, there are a bunch of random gels, some mostly decomposed skin parts. Some very fine grit.

Of course the ocean is constantly mixing everything up, so even though we have been in this blob together for several weeks, that’s not exactly normal.

Well, there millions of blobs like ours, so I guess it’s sort of normal. But there are a quadrillion billion blobs that won’t last the hour. So our blob is, if not abnormal, improbable.

You and I are algae, so we can’t sense much. But we have noticed many events over our lives. Very early in our lives we perceived the day cycle. There are good times to photosynthesize, boy did we feel that. Time. We noticed quite a few bacterial... situations. And geometrically there have been a number of events in our blob. It used to be much bigger, for one thing. We certainly noticed every time a chunk got taken out of the blob and the energy gradients went haywire.

Of course we’re algae so we don’t remember, but we notice.

There is a world outside our blob, but we cannot know it. Sadly, this is physics. There’s not enough atoms in the blob to make a fin, let alone an eye or a brain. So there will be no peering out of the water at the sky. We can sense events within the blob. Outside the blob there may be more going on, but we certainly can’t see it.

There are unexplainable patterns in the blob. Why does it look sheared off on two sides? “We”, meaning our limited algae consciousnesses, didn’t exist during those events so we are just as cut off from our past as we are cut off from the world around us.

And we are barreling now, in a wave towards the shore.

And now we are floating.

And now we are rolling through a wave towards the shore.

And now we are slipping calmly on the surface.

And soon we will crash onto the sand, where we will be consumed by bacteria and insects, and our blob will be no more.

It is inevitable. The first law of algae says: you will be eaten.

But we will not be eaten this minute. And so I ask you: what happened in the blob, before it existed?

Luckily, though we can’t see outside the blob, we can ponder questions like this, because we are hypothetical blobs, and hypothetical blobs have human brains!

We can certainly guess what our bodies were before the blob existed. They were a cloud phosphorous and nitrogen. And presumably there were other plants or bacteria in our proto-blob that produced those nutrients for to become us.

That bit of skin I mentioned was on a dead whale. It was on the ocean floor but it got kicked up to the surface in a storm.

The gels came from jellyfish. And the salty water around us... well, it was salty water.

What shape was all that stuff in? A strange one. But still, we could draw it if we had some art supplies. And fingers. The current that brought in the whale skin could be drawn to an approximation. The bacteria largely came from two identifiable blooms, plus a long tail of about a thousand others, plus an unknowable tail catalog of origins describing the last 0.001% of bacteria in our blob. We couldn’t draw that, but maybe a light watercolor fog around our greater vicinity could represent it.

If I could draw our blob before it existed, it would look like a strange flower. With very long tendrils but also several beautiful simple twisted surfaces.

Now, what about the universe itself?

Science suggests its origins were not nearly so “soft”. Our blob was sort of “assembled” from pre-blob parts. The universe doesn’t appear to have been assembled in a soup that same way. Trend lines suggest it started as a singularity, not an assemblage.

But all physicists will admit we don’t have the technology to peer into those first moments. Like us and our blob, there’s just not the equipment available to look outside the universe to get data, nor was there equipment present to remember things as they happened.

We just don’t know what physics is like in those kind of moments. Is it an assemblage of parts from a larger vicinity? Are there even larger vicinities than our blob?

Or, to put it in terms that you and I would understand: did the universe, at birth, have a bit of whale skin in it? Some dead jellyfish bodies?

We can only speculate. As for me I say: why not?

But I’m just a bit of algae. What do I know.

That was beautiful, thank you.

> if our universe has an external superuniverse

This is also meaningless, scientifically: there is nothing you can measure which is outside the universe. Things like a holographic universe are inherently untestable. I hope we continue looking for testable things, but this speculative path rapidly leads away from science and physics and into "linguistic tricks to confuse humans". It's not even philosophy at that point, it's just arguing over semantics.

There are still ways we can reason about it. If we come up with a model of a super-universe and then find that model says that universes like ours are more likely to exist, then it can be evidence for the super-universe. We could possibly use the model of the super-universe to make predictions about our own universe.

> If we come up with a model of a super-universe and then find that model says that universes like ours are more likely to exist, then it can be evidence for the super-universe.

That's not evidence FOR the superverse, just like we can inherently not rule out the idea of the https://en.wikipedia.org/wiki/Evil_demon deceiving our every perception.

At best, this is untestable philosophy that's fun to debate over drinks. At worst, it's a tedious discussion about the semantics of existence and time.

Don't get me wrong! We could discover interesting things about our universe looking for holes, but there's no indication this problem is tractable.

If the evil demon theory made specific predictions that turned out to be right and weren't predicted by other theories, then it would be a useful theory. It's possible for a theory of a super-universe to do that.

Imagine if we came up with a super-universe theory that said that the super-universe could only spawn sub-universes which followed conservation of energy plus several other laws no one had ever thought to test before (and weren't implied by any other theories), and as we started testing for those other laws, every single one we tested turned out to hold in our universe.

(If that happened, it would be reasonable to look for simpler theories that also predicted those other laws too, but it's possible that the super-universe theory would turn out to be the simplest possible theory that fits. Theories should be judged by the complexity of their rules, not by the number or complexity of things they predict; a simple theory that implies a large ensemble of universes can be better than a more complex theory that implies only our world or what we can see is real.)

> This is also meaningless, scientifically: there is nothing you can measure which is outside the universe. Things like a holographic universe are inherently untestable.

This is incorrect. Are you familiar with the inverse-square law? In 3-dimensional Euclidean space, the rate at which any force decays over a distance is inversely proportional to the square of the distance. This generalizes to n dimensions; but instead of the drop off rate being inversely proportional to the square of the distance, it becomes inversely proportional to the n - 1th power of the distance.

Suppose our universe is a 3-dimensional embedding of a n-dimensional manifold. Every local force we could empirically test would adhere to the inverse-square law, i.e. have drop off over distance k of ~ 1/(k^2). But theoretically speaking we could empirically test the dimensions of the manifold we reside in by identifying which power of distance is proportional to the drop off rate of extremely small forces where the compactified dimension can be detected.

For practical purposes this would require us to increase the precision with which we can empirically test (and reason about) forces at the subatomic level.

you can't measure emotion or moral principles but they certainly exist.

Right, and I think this illustrates well how linguistic this "problem" is.

It's nonsensical to some, but not to others :) never forget the incredible capability of consciousness.

It might be phrased differently. Like this. Is there something more universal than time. Look at spacetime from an outsider's perspective. Suppose it is 2D+1D, then one way time can be represented is as frames where each frame is slightly different. The interesting part is that those consecutive frames have very strong constraints. But what are those constraints? One of them is that energy is conserved. One other might be that it's Markovian: you only need to have the last frame for the next. If there exist (entangled) histories this seems to be wrong. The quest for (moderately) consistent frameworks that all have their own emergent nature of time might be a very fruitful one. It's rather a "beyond" time than a "before" time.

It helps to think of time as change. Time started when the first thing changed. So to say there was no beginning helps by not having to answer what the first change was ot why it did. It's still hard to imagine no first change without an infinite regress. Maybe if you think of it reletivistically as in there wasn't a singular beginning but a beginning area where depending on where you are it could be a beginning but not the beginning.

I don’t thunk my brain could handle no beginning

With all respect, I think we generally live in a human society that has been built around that very constraint.

Curious to know why that is. Would you mind expanding?

Because if we have not beginning, we have no purpose. If we have no purpose, this is all really for nothing. I am not arguing whether it is or not, or whether there is a beginning, but lets look at it this way... You woke up this morning, that was the beginning of this day at night you will rest. Now, lets say there is no memory or record of 'waking up' beginning, we therefor cannot anticipate an end and everything we do now may feel for some less meaningful. I don't really know. I am just expressing my under-educated overthinking take on it.

Countered the downvote because I’m interested in this line of reasoning. Could you expand on that? Why do you think having no memory of “waking up” to existence makes it less meaningful?

I'm reminded of the following quote by Alan Watts from The Way of Zen:

To the Taoist mentality, the aimless, empty life does not suggest anything depressing. On the contrary, it suggests the freedom of clouds and mountain streams; wandering nowhere; of flowers in impenetrable canyons, beautiful for no one to see, and of the ocean surf forever washing the sand, to no end.

Not the parent, but it kind of makes sense: if a network cable has no beginning it definitely has no purpose.

That's actually a great analogy there. I will say I wasn't really vouching for that line of reasoning more than exploring my own thoughts about it and that was one route my mind went. I like to do that with deeper questions from time to time. I guess that with no..."sense of time" or understanding of our beginning we have a less accurate ideal of what our ending may be. However, there is one thing we know for certain is that we do die. At least our bodies do. What happens after that though is to be disclosed. So maybe only what we do between those two points is what matters anyways? And some may view that as if we are going to die anyways, what does it matter?

I like that idea. I think the world is a beautiful place, and I think also that humans can be a beautiful species at the times they come together. What is that one quote? "All that wander are not lost." I believe we can find peace with our existence and mortality and its something we have to remind ourselves of that individually it is not forever, and how it will end in general is not yet perceived.

All of the worst things in human history have happened as a result of mob mentality or 'humans coming together'.

On the contrary, the only times humanity doesn't sap me of the will to live is when I'm dealing with people on an individual basis.

> All that wander are not lost.

I feel like you're misunderstanding that quote as well.

It's supposed to be "Not all who wander are lost" and it refers to loners, wanderers, vagrants and explorers that never settle down and 'plant roots'.

The idea being that there are plenty of people that exist like that and enjoy that way of life. Other people with families and steady jobs tend to look at them as if they are 'lost', without truly understanding what it is to walk the earth.

I think this is a correct line of thought to a point. There is not greater purpose, and if there is, it ought to be unlike any other form of purpose. Since in general purpose is built up -- you do some task for a purpose, and that purpose is a task in some greater purpose.

As far as individual contentment, it seems maybe the truest greater purpose is actually itself: the greatest purpose is to have a greater purpose that your everyday purposes are acting towards. This gives a consistent mechanism I think, but still incomplete, or is it? Its incomplete because the "why" of the greater purpose doesn't seem to emerge from it existing. But this was mentioned at first: the why is for individual contentment, or more technically, for positive consciousness, joy, happiness, love, whatever you want to call it. The sort of existence which when you are it, you don't need or care to ask about a greater purpose, because you can feel..you know, that you're fulfilling it.

I'm not seeing any purpose to humanity as it is.

What purpose are you seeing?

As biological organisms, notions of birth/death are hard wired into the lowest levels of our cerebral kernel which serves as the foundation for every higher level of consciousness. As such, we only have the fundamental architecture to perceive an existence that is (literally) grounded in a small gravity well, with all of our primary circuitry distinctly focused on what is in “front” of both in space and time. As organisms, we cannot directly experience time that preceded our own existence, we can only mentally model that experience through intuition. That works well enough for relating to the existence of other organisms and the physical world we share, but that relatability breaks down quickly at larger space/time scales.

Incidentally, though our individual multicellular existences may follow a birth/death cycle, the molecular information flow (DNA) that transcends our organismal existences may perhaps provide the closest approximation to a model necessary to conceptualize possible relationships between multiple space-times.

(I’m clumsily alluding to the blackhole/whitehole infinitely branching multiverse concept, with DNA playing the part of sub-atomic mass/energy primitives which encode the structure of new unidirectional space-times/universes in an endless phylogeny which ultimately still doesn’t get us anywhere closer to “where did it all begin?” but surely expands the scope of the investigation wide enough to buy us enough time to keep procrastinating... Ok, back to work.)

disclaimer: I only got a B in undergrad physics and have absolutely no clue what I’m talking about.

Of course the Universe can arise from nothing. Especially when you give nothing specific properties beyond ‘not anything.’

I misinterpreted the direct idea of 'Big Bang' at a very young age and thought that the nature of time changed over time, ergo, 'the beginning' could never be achieved (even if you could travel backwards in time), i.e. it's 'infinitely far back' similar to how time changes for traveller/observer as one approaches the speed of light.

Only in any given time frame could one mark 'the start', but that would be a misinterpretation.

So time did have a 'start' but it was 'infinity ago'.

I realized at some point this has nothing really to do with 'Big Bang', but later I've come back to the idea as at least novel!

It's fun to see smart people contemplating alternative things.

> It's fun to see smart people contemplating alternative things.

It certainly is. Most recent theory I heard of whilst staying up too late watching youtube videos, was by Roger Penrose on CCC (Conformal cyclic cosmology) [1]

My very basic understanding of it (probably wrong understanding though) was that the universe is mathmatical, thus mathmatical tricks are valid constructs when understanding the universe. Once the universe has expanded to heat death, it will have infinite size and zero mass which is the same as having 0 size and infinite mass which will cause a big bang and another universal epoch.

I'm probably remembering it all wrong, but as a layman who enjoys watching much smarter people than I contemplate and try to explain these thing, I found the idea very interesting

--------------------------------

[1] https://www.youtube.com/watch?v=FVDJJVoTx7s

or maybe

https://www.youtube.com/watch?v=sM47acQ7pEQ

I really enjoyed "Why Anything? Why This?" by philosopher Derek Parfit.

http://www.sfu.ca/~rpyke/cafe/parfit.pdf

> Just as a shuttlecock has a diameter of zero at its bottom most point

As a lay person this - right from the starting block - is what messes me up. I.e. something that exists cannot logically have a zero diameter part. Anything zero does not exist.

Most related theories have similar kinds of initial premise that you must just accept.

> something that exists cannot logically have a zero diameter part

Do elementary particles exist?

No, only observations of them do ;o)

Elementary particles have size delineated by the forces that act on them.

The concept of a "physical size" has no meaning, since particles don't act upon each other that way.

But the forces do not have a zero size, and that's important.

It's a metaphor. It's not meant to be taken literally.

taken where?

For an eloquent companion piece, I would highly recommend this essay: http://nautil.us/issue/16/nothingness/the-bridge-from-nowher...

Distances between our limited repetitive Universe Origin Debates and meaning describe how our intellectual ecosystem interferes with knowing. That is something, at least.

If it's shaped like a shuttlecock then it will have a nodal center - a causal echo, if you like - in its early phase but some time after the beginning.

Cognitive biases and the vast cultural/religious narratives around cosmogenesis make it next to impossible to reason about the universe in this way.

Am I wrong, or are they arguing on matters of belief rather than evidence?

The word is 'speculation' not 'belief' that that's pretty much what all science is. The evidence usually comes later.

There I was thinking that the scientific method involved falsifiable hypotheses - so how are they going to prove or disprove their respective beliefs? I'm getting string theory flashbacks where half of the physics community is into it, the other half is not, and no-one can prove anything, but they still have a grand old time arguing about it anyway.

The trouble is, unless you have a grand old time arguing vague ideas, you might not find the ideas that can lead to new falsifiable hypotheses.

https://en.wikipedia.org/wiki/Abductive_reasoning

Modern cosmology got kicked off in the 1700s by observations of "nebulae" that showed many of them were collections of stars, and in particular that some were much much much larger and more distant than others. Just before WW I the absorption and emission line structures of the spiral ones were discovered to be strikingly similar except the smaller (in angle) dimmer (in apparent magnitude) ones were squashed into the red.

Just after WW I is when spiral nebulae were identified as anything remotely like our modern understanding of spiral galaxies. 1920: https://en.wikipedia.org/wiki/Great_Debate_(astronomy) [poor Shapeley, so bright and so so wrong on this point] about five years after a working theory of post-Newtonian gravitation was even available, and almost exactly two years after General Relativity aced its first observational test in the solar system. Up to that point even the greatest names in astronomy (even Einstein) believed everything in the sky was within or in a close (~ kiloparsecs) orbit around the Milky Way.

Towards the end of WW II and just after radio astronomy became important, particularly the study of the 21cm hydrogen gas line, which was clearer than the red-squashed lines of visible light passed through prisms, and in particular different limbs of galaxies had different redshifts, proving rotation. Some three decades later, the 21cm redshift difference between the inner and outer parts of a number of galaxies showed that there is non-Newtonian gravitation obviously at work in large galaxies. (Also coincidentally around that time, the cosmic microwave background was discovered, but it was some years before the small anisotropies in it could be studied -- BOOMERaNG and COBE in particular to start with).

The evidence in all these cases arrived in advance of vague ideas, and forced the hunt for tractable explanations for the evidence in its totality, rather than as individual stand-alone pieces. One of the biggest pieces to fit in is of course the highly successful standard model of particle physics, which also was driven by evidence arriving kinda by surprise somewhat concurrently with surprise evidence from cosmological observations.

The result is the "concordance cosmology", \Lambda-CDM, which concords with all the available data (well, or rather it's updated as new data shows up from various observatories and experiments). It's certainly subject to speculation: what's the microscopic description of dark matter? is the cosmological constant actually uniform everywhere in spacetime? is there a non-cosmological-constant term required to match new data for the Hubble flow? These are pretty big questions, but they're forced on us by the in-your-face obviousness of the metric expansion of space, and the peculiar motions of galaxies within clusters, and the outer parts of galaxies around the inner parts. Also, what's going on in "the dark ages"? We have an obvious gap between the surface of last scattering and the first starlight, but the details of the observed first starlight and the cosmic microwave background don't interpolate as well as one would naively expect. And we have so many exabytes of data about the latter (and a lot of data about early galaxies too) that vague ideas die quick deaths: they don't even get a chance to generate new "falsifiable hypotheses", they are generally born inconsistent with some existing data.

The "trick" is abduction: trying to reason out a simple-enough-to-be-useful explanation that fits the known data.

Of course, you can get away with wild speculation and vague ideas in areas where there is little to no data at present. Anything before the electroweak decoupling is anyone's guess, as is anything much more than a trillion years in the future, or far outside the Hubble volume.

"There I was thinking that the scientific method involved falsifiable hypotheses - so how are they going to prove or disprove their respective beliefs?"

????

Scientists think out of the box, they speculate. They talk. They debate, they argue, they get ideas from one another.

Then they get an idea of 'what might work' and possibly form rough experiment to see 'if it makes sense'. Then if things look good, or they figure a few other things out, they might do a more formal experiment in the context of demonstrating the validity of the theory, and possibly try to get it published.

Or, maybe experiments are not possible, or too expensive, so they write their crazy speculations down for others to think about, riff on, and possibly do some experiments later in time.

That's science.

It's a ton of speculation.

I don't understand why you think these things are 'beliefs' and that speculative discussion is not part of the process.

FYI Einstein mostly only ever 'talked and speculated' about stuff.

The mind is not limited by the laws of physics in the sense that it can actually think about unfalsifiable ideas.

Then we work backwards and try to get it done with falsifiability.

Agreed that is where science starts. Speculation leads to generating testable hypotheses and experiments.

Yeah, but this seems trying to avoid the possibility of the universe having a beginning simply because it's unsettling; taking the less likely thought path because it conflicts with beliefs.

I'm not saying that's what it is, that's just what it seems like what's happening here to me.

Perhaps tangential, but: Why is science up for “debate”? We could all offer opinions around the edges of present-day human understanding, but is there any merit to these debates? Feels like a lot of fluff. I wish Feynman were still around.

Science is born out of debate. The only way current “science” came to be is through postulating and testing of those postulates, the testing of which reveals many flaws in theories and then those theories are tossed out. The fact that the truths we see now seem fixed is merely an illusion of the present. In fifty years, 20% of the current theories could seem like garbage compared to what we will have in the future.

I think that's the most interesting part of science - the place where brilliant minds hypothesize and ponder about what may be. Sure it's fluff but we'd no doubt say similar of Einstein prior to his publications in the early 1900s if we were there then.

We live in a world of echo chambers. Where people can't imagine thoughts other than what they've been fed. I think that while this isn't rigorous, it's a healthy thing in moderation.

The article is vague in the topology. No boundary or also infinite?

The article has an image illustrating the no-boundary proposal.

> “Asking what came before the Big Bang is meaningless ... It would be like asking what lies south of the South Pole.”

Isn't Polaris Australis south of the South Pole? Was Hawking imagining an Earth-shaped space that isn't embedded in a larger space?

A stars position can't be defined as being south of somewhere. South exists as a logical construct of our magnetic poles. Once you lose that you have no relative measure to work with. The same is possibly true of time.

But the trouble with the South Pole and Shuttlecock metaphors is that you assume those objects are literally everything; all matter. If you define the Universe as Everything there is (seen and unseen; where what we see is the "Observable Universe") there is no outside location from which to observe it in entirety.

That's where the analogy really breaks down, but I guess it's still a useful thought experiment so long as you realize the limits to the domain.

There can still be an unobservable (to us) universe outside ours.

If you assume the universe started N billion years ago, there is an event horizon expanding at the speed of light that fit this definition of an "observable universe" for us while allowing for an infinite number of equal universes, some of which are partially shared with ours.

Nitpick: North/south exist due to the planet's rotation, not the magnetic poles.

The magnetic poles happen to be near the rotational poles, but that's incidental.

Sorry to be That Guy today :(

The world is just one big "console.assert(false, world)"

Curiously,Indian philosophy also propounds that the universe has neither a beginning nor an end.

I think it might actually be more unique for western philosophy/religion to be building a narrative with a beginning, middle, and end - a lot of other ancient cultures seemed to see things as a cycle - for instance, we see in the Mayans that they saw the world as a series of cycles. It makes sense in early traditions to not have a beginning and end - if there's no track of "progress" in a historical fashion, it would be hard to visualize any sort of long lasting change in the cycle.

Some of our best fictional stories are in cycles. The "Hero's Journey" is often a circle with growth, where you end up where you started from. Every season of The Wire pretty much ends in a circle.

I'm not saying they aren't, and that all narratives conceived in the west require them, but the Abrahamic (and earlier Zoroastrian) religions developed this sense of there being a definite beginning, middle, and end of everything, and that's not a concept universal to many religions.

It was Aristotle's Unmoved Mover being incorporated into Christian Thought around AD 50 via Philo of Alexandria that changed Monotheistic religion of God being the Organizer of All Things from Chaos into the Creator of All Things out of Nothing, Ex Nihilo. Beforehand Monotheistic Religions believed God was a creator but he created out of chaos and imbued the formless with a specific form.

Likewise simultaneously around the time of Aristotle during the time of the Hellenistic Era, The Seleucid Empire arose from the fires of Alexander the Great Empire. The 2nd king in the Seleucid Dynasty decided to make a universal time calendar that just increments again and again past individual rulers and this change the nature of stories tremendously in the empire.

When Time Became Regular and Universal It Changed History https://aeon.co/essays/when-time-became-regular-and-universa...

When Antiochus I Soter in 281, after his father death decided to keep the calendar his father created (and he had already served 10 years as a co-ruler prior from 291 to 281.) And not start over it started the various populations that were opposed to the Seleucid authorities to tell apocalyptic tales of the end of days, not just the end of the ruler / authority but the end of everything. Especially since later Seleucid rulers such as Antiochus IV Epiphanes (175 BC to 164 BC) seem to limit Jewish religious rights, though Historians are not sure if this true (it may have been about taxes and other areas of authority.) Well there was a rebellion in 167 BC and the internal Jewish Warriors succeeded from the Seleucid Empire (The Maccabees Rebellion.) Well the rebellion was successful and they were independent for 130 years (though lots of civil wars for authority) and only in the end succumb to the Romans except the Jewish People saw the Romans at first as liberators for they still feared various Greek / Hellenistic empires and the Jewish People thought he romans were better.

-----

TLDR: Cyclic thinking and Creation from Something / Chaos was actually the norm in monotheism, only during the Hellenistic (Greek Influenced) / Roman Era did this shift to Creation out of Nothing (Ex Nihilo) instead of Creation out of Chaos. But yeah read the article I linked to.

Zoroastrianism had to concept of a universe that starts with nothing and comes to an end as far back as the 6th century BCE.

But I agree, adding a concrete understanding of time really helps to cement the linear narrative.

Agreed with the Zoroastrianism bit, that did occur prior.

I was trying to be simple and concise so I did not mention other strands of monotheism that influenced Judaismm and the Middle East such as the Egyptians / Amun (the Hidden One) or the Persian Zoroastrianism (which pioneered the concept of Angels as winged divine beings that Judaism and Christianity incorporated.) Yadda, yadda, yadda religion and history is complicated but also interesting.

Check out Nasadiya sukta[0] in Rigveda.

https://en.wikipedia.org/wiki/Nasadiya_Sukta

Cool - Is there a similar verse describing the end?

What of Indian philosophy can you cite regarding this? From what I gather, it's seen as cyclic.

I would imagine the OP meant the cycles are never-ending, as opposed to one iteration of the cycle.

Nasadiya sukta[0] in Rigveda ponders about creation of Universe and what existed before that. Last two paragraphs (6 and 7 in wiki) are the hard-hitting ones.

[0]https://en.wikipedia.org/wiki/Nasadiya_Sukta

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