Age of universe at 26.7B years, nearly twice as old as previously believed
phys.org
phys.org
It is my understanding that the density of the universe billions of years ago was radically different from the one we now observe, and since density is intrinsically tied to our perception of space and time, wouldn't it make more sense that time actually stretches infinitely the further back we go, thus nullifying the concept of a beginning?
I guess I'm having a hard time with the idea that space-time could be discontinuous.
that's the context in which physicists are talking
So maybe we can interpret this claim as saying that 25 billion years ago, the universe was kinda similar to what we have now, but 27 billion years ago everything was ultra compressed and gravity didn’t have a significant effect on anything. Or maybe time is like a left-open interval. Finite, but didn’t have a start. I dunno, I’m making stuff up.
However in today’s day and age that way lie no fat grants, adulating television specials, or NYT bestsellers.
At least what we currently spend most of time studying/researching in physics right now. We can hope to expand beyond that given enough time.
There might literally not be enough time to expand beyond that, given how cosmological horizons work. Being part of the system we're trying to observe puts some nasty limits on what we can know, even in principle.
And since we know that gravity affects the rate of flow of time, wouldn’t the rate of time be enormously distorted earlier universe?
I’m not trained in any of this, so hopefully there are greater minds here who can help me understand
So there must have been a time when electromagnetism, the weak and even the strong force just didn't exist. They couldn't. So particles would just have totally ignored those forces.
We don't know if gravity is the same, but ... why wouldn't it. Though of course according to relativity gravity just wouldn't care, but that just raises a lot more questions than it answers.
What does it mean to compare ("faster") a velocity and a frequency (inverse time)?
The issue is that movement and time are fundamental to the universe, yes, in the way relativity describes but also in a totally different unknown way. In some ways particles are "just" things moving relative to one another. Which, for one thing, brings the perspective question (if you accelerated to a "real" speed, would you see a different universe? Because you would disagree with us slowpokes here on earth on what particles exist at least in some cases. But would you see an entirely different universe?)
As I understand it, that’s an approximation for Euclidean space because the area of a sphere is also proportional to the square of the radius in such a space, but it’s not true of non-Euclidean spaces like in GR because the area-radius relation is different.
IIRC, the cosmic microwave background has a gamma factor of about 1100, so the area of that shell is the same as one 1100 times closer or 1/1100^2 times the area as a Euclidean sphere with that radius.
> And since we know that gravity affects the rate of flow of time, wouldn’t the rate of time be enormously distorted earlier universe?
Time did indeed slow down then compared to now, although it’s not entirely obvious to me that this has any physical interpretation when it happens “everywhere”: https://youtu.be/66V4RSmDqYM
Well... yes it is, in the rigorous sense of "time" defined by general relativity. There's no "before" for a singularity. It may not be the whole story, but whatever metaphysical notion defines the "before/beyond/outside/why" that drives the big bang, it's not a place on the "time" axis of spacetime.
Similar to the singularities in black holes - everything up to a stone's throw of the event horizon is pretty well explained by GR, but as far as the horizon itself or the region beyond are concerned, there might be dragons as far as we know.
I don’t think that’s right. If we interpret Big Bang theory as claiming that there is a singularity at a finite distance into the past history of every present event, then GR can’t predict what happened at or prior to that singularity. Whether time “began” then or whether there was “more time on the other side” is a question GR alone cannot answer, not a prediction of GR
[1] https://en.m.wikipedia.org/wiki/Fuzzball_(string_theory)
How does that work for black holes? It seems like there would be a 'before' they formed in the time dimension of our universe, if not within the singularity itself.
> If time effectively halts at T0, then what possible event could occur (outside of time?) to nudge that infinitely large glob off mass into the motion we observe today?
Anthropic principle explains it. If you need a Prime Mover, you can also replace it with Anthropic principle and random chance.
For example if time halts at T0, physics breaks. Using limes when t->0 you get that v-> Infinity (or c). Slower time moves for you, faster you move in space. At that point, if nothing is there to detect it, every massless particle will be effectively everywhere, all at once. Essentially photons can have Infinite energy and just cause a random Big Bang. This is CCC like explanation.
Another answer is Hawking's North of North Pole time problem (from Universe in a Nutshell). If time halts a T0, you can't ask what's before it. It's just logical impossibility. Like what is North of North Pole? Answer is: Question is invalid. Anthropic principle implies there are however many multiple such configuration so you get a parallel or sequential universe solution.
We arise and wonder how exactly Universe exists that support life, even if we can clearly see, it's only supporting life at this moment. Our existence is a grain in the sand of a universe-sized sand clock that will be the Black Hole epoch.
The universe advanced from T0 because it had to, by definition.
If this seems like a weird cop-out, well, that’s a singularity for you.
Yes.
If you assume that all events have causes.
Our understanding of the world (aka science) is largely based on causality, and if things existed without any cause or reason, our understanding of "science" would probably be very different.
(I'm not a physicist, but this is how I understand things.)
Also, no one is "lazily tossing it aside". It comes out of the mathematics that describe the observations:
Say you find that all observations you make are perfectly described by dx/dt = 1/x with current time t1. If you follow the trajectories backwards, you find that the trajectory can not be extended back past some initial time t0 at which x(t0) = 0 as the equation becomes singular then. You are now at time t1-t0 from the initial singularity. That is the age of the universe since the big bang. Now the trajectory as it approaches t0 has some unusual properties, it moves infinitely fast, etc... These might lead you to postulate that unknown physics will actually invalidate your law as you approach t0. But there is nothing logically or epistemically _wrong_ with the law you have. The finiteness of time flows out of a causal empirical induction argument. It is not introduced ad hoc to avoid some difficulty, it just is how we find nature to be at the most conservative interpretation of the evidence.
You stop at the uncaused first cause or the unmoved mover, of course.
Think of it like a particle decaying - at some point it just happens with no trigger or internal mechanism, and now you suddenly have the decay products wizzing about with some energy and momentum that they just start with.
There is no reason to assume that everything has a cause. It is perfectly logically consistent to have things without cause in the universe.
The big bang could not create universe from nothing, it could only spread matter from a singularity into ever expanding universe (time-space).
is it even possible, to have entirety of universe matter and energy in a single point?
We don't know anything at all about the physics of infinitely small spacetimes, because we don't have a fundamental physics of spacetime at all.
GR is a descriptive approximation of the behaviour of spacetime, but says nothing about the fundamentals that generate that behaviour.
There are proposals for time stretching infinitely back, but we have almost no way of testing them.
Which is to say that there exist respected papers that outline this scenario in great detail, but there’s precious little observable evidence of a previous universal cycle.
If time/space-time existed before the BigBang is probably an unanswerable question (unless we are within a 4d black hole and we can listen to waves that perturbed the matter before the formation of our universe).
Why? Any sign of another Big Bang going from some other point somewhere else would indicate that "our" Big Bang might not have been the first one. It is harder to prove absence though.
Because if inflation is also correct we lost every causal connection with whatever was there before, or is so diluted that we might not be able to detect.
Another possibility could be that at the time of the BigBang the energy density was so high that everything was unified, and so when forces actually separated they "tabula rasa" anything that occupied the bubble of space-time we expanded into.
However, it could also be that the fluctuations we see in the CMB are due to perturbations of what happened before. But that possible clue is better explained by comic inflation expanding quantum fluctuations at an incredible speed that disconnected them.
That's why I said it's (probably) unanswerable. I also hope I am wrong though.
[1] https://en.wikipedia.org/wiki/Penrose%E2%80%93Hawking_singul...
Of course, people do speculate. I seem to recall some level of anisotropy in the cosmic microwave background that was a bit more than expected purely from quantum vacuum fluctuations in the pre-inflationary early universe and at least one physicist musing that it might be a perturbation from some other universe that has since lost causal connection. This, of course, makes no testable predictions, can't be falsified, isn't really science, but human intellectual curiosity goes beyond science.
There's no more events to happen, and more so, no ability for more events to happen.
Thats still likely an artifact of our models though, and that when you do to something like that, that new events start happening again
I’ll search for it but PBS Space time has some wonderful intuition building visualizations and explanations in some of their parts on models for the beginning of the universe. If I can find the ones I’m thinking of I’ll edit later, but regardless I find their background material on “wtf” re: physics can be helpful.
I believe it could be 'turtles all the way down' as the phrase goes. Maybe our Universe started by a collision of two or more other Universes and we got this mess called the Big Bang. This doesn't explain how those other Universes started though.
But then as mere humans, we can't conceptually grasp Infinity itself. This is not some failing of ours, it's actually convenient to not imagine infinity, as it would drive us mad. The minute you include the Infinity Symbol (∞) in a math equation, all logic starts to cease and get very wobbly.
Once upon a time I watched PBS Nova program about string theory. I remember they talked about something along these lines. It's been almost two decades since I saw it so memory is rusty. But it was something along the lines of universes existing in these big "planes" (they visualized them like these big floating membranes) that would vibrate and occasionally smack into each other. When one of these collisions would occur, there was the potential for a new plane to be formed from that collision.
Like you said, that could potentially explain where new universes come from, but not how the other "turtles" got there in the first place.
It all goes back to thermodynamics and the probabilistic understanding that entropy 'always' increases. But if entropy always increases then by reason, it must have started off at small minuscule point sometime in the past. But if energy/mass are constant, how could it have gotten to the low entropy in the first place? Given enough time, a 'once-in-a-gazillion' event actually happened. At a fundamental level, it's all mathematical guesswork.
Why not? Tons of things are, for example, entropy. I have a crackpot idea that the Big Bang itself was just an "entropy population inversion." The big bang is literally just the moment where the discontinuity occurs.
The universe will keep expanding until entropy reaches a maximum -- the "Big Freeze." Once maximum entropy is reached -- wherein all atoms in the universe are totally dispersed, everything is the same distance from everything else, and the universe is a totally uniform field -- one could say that is very orderly indeed, i.e. the theoretical minimum entropy.
I imagine that all of the matter in the universe being perfectly dispersed would quite neatly "fill" the universe. So who's to say such a situation isn't infinitely dense?
Much like the moment just before the Big Bang.
This idea goes all the way back to Plato and his Parmenidean-inspired rejection of the Pythagorean notion of the Monad as being at the centre of the universe as the Number One implies certain properties like perfection, unity, etc., and we see none of those properties in our existence. This led Plato to argue that the One existed separately from our reality, which was just an imperfect copy associated with the idea of an indefinite Dyad.
So it wasn't just that the universe was a densely packed packed ball of all the stuff we see today and it somehow spilled out or burst forward, what existed before was a monad, and all the stuff we see including space-time, the elements, and more were created at the time of the Big Bang.
Also, everything is waves
There's a 'most northern' point on the earth, and the surface is arguably continuous.
So it seems fine to have an 'earliest' point in time and still have continuous space-time.
This was Hawking's point of view. One way of thinking about special relativity is that time is at right-angles to space, and everything travels at the same 'proper' speed (c) through this 4d spacetime, just in different directions (hence why "fast" objects experience "time dilation": their 4d heading is pointed largely in a space direction, so they don't progress much in the time direction). This extends to general relativity, which describes how these directions "bend" into each other. For example, the reason objects fall due to gravity can be described as spacetime curving such that "future" points slightly "downwards" (and hence slightly less in the usual time direction; which, again, causes time dilation).
AFAIK Hawking's idea was that the curvature at the big bang was so high, that "past" is pointing completely in a spatial direction; and hence there's no such thing as "earlier" anymore. Similar to how "north" near the north pole is at right-angles to "north" at the equator.
It’s even more puzzling than that. Our current model features a period of time called the inflationary epoch which lasted between 10^-36 and 10^-33 or so seconds after the Big Bang, in which the universe expanded by a factor of at least 10^26 along each linear direction [1].
This is unfathomably rapid expansion. It makes sense mathematically but not at all intuitively. It’s totally bizarre and weird and I don’t have even close to the level of background needed to challenge it!
Matt from PBS space time covered this here.
They probably are. See Planck length.
If something preceded the big bang, it cannot be observed (by our current reckoning). Similar to things farther than cT away... Unobservable; unknowable.
There's nothing inelegant about it. C is the conversion factor between space and time.
In the paragraph above, you assume time is a primitive concept, but it is really an emergent phenomenon. The passing of time, moving by some amount of (the plank-scale limit of) spacetime interval, can happen only across connected configurations.
Think about evolution in spacetime as a combinatorial game, there can be positions where causal links are not possible, or even empty games.
The best analogous I can think of arises in the field of surreal numbers https://en.wikipedia.org/wiki/Surreal_number, with their built-in concept of generations.
Our upvote tendencies incentivize drastic tones, so it's effectively what we ask for, and what we get as a result.
"It's me, hi, I'm the problem, it's me"
A theory is the highest possible idea here, "just" a theory makes no sense
That said, this theory may or may not be better than the other theories regarding the age of the universe.
Sure it does. A theory that has little explanatory power due to the lack of available evidence can, in the diminutive sense of "just", be called "just a theory" where the understood context is comparative to a theory with a high level of explanatory power and perhaps a general consensus among experts in the field.
Even something that's just a theory is not to be confused with "mere" conjecture, and somewhere way down in the hierarchy have "pure poppycock". Though even pure poppycock on occasion rises up through the ranks, much to the embarrassment (often post-mortem) of those who pooh-poohed it previously. Of course "pooh-poohed" is not a generally accepted scientific term, I use it here as a mere colloquialism. I'm sure (though not certain) that people already understand that and wouldn't bother being pedantic about it.
It doesn't make sense to use it this way given the context of the discussion, though, that's my point.
It doesn't make it pointless but one has to treat it for what it is. It was like String theory, it was all well and good but without a meaningful experiment to test it - it could only go so far.
Particularly I remember when he presented the age of the universe.
The age was estimated with something like plus minus 10 billion years. The teacher made a big deal about how incredible this was. When I first heard that number it sounded beyond imprecise. But he explained: Now we actual had a ballpark figure. Before we didn’t know if it was thousands or quintillions of years, so plus minus 10 billions was really good and ground breaking.
With that in mind, this kinda seems like a minor adjustment.
> Zwicky's tired light theory proposes that the redshift of light from distant galaxies is due to the gradual loss of energy by photons over vast cosmic distances. However, it was seen to conflict with observations. Yet Gupta found that "by allowing this theory to coexist with the expanding universe, it becomes possible to reinterpret the redshift as a hybrid phenomenon, rather than purely due to expansion."
(context for that theory...)
https://en.wikipedia.org/wiki/Tired_light
> The concept was first proposed in 1929 by Fritz Zwicky, who suggested that if photons lost energy over time through collisions with other particles in a regular way, the more distant objects would appear redder than more nearby ones. ... Despite periodic re-examination of the concept, tired light has not been supported by observational tests and remains a fringe topic in astrophysics.
https://en.wikipedia.org/wiki/Non-standard_cosmology#Tired_l...
> Tired light theories challenge the common interpretation of Hubble's Law as a sign the universe is expanding. It was proposed by Fritz Zwicky in 1929. The basic proposal amounted to light losing energy ("getting tired") due to the distance it traveled rather than any metric expansion or physical recession of sources from observers. A traditional explanation of this effect was to attribute a dynamical friction to photons; the photons' gravitational interactions with stars and other material will progressively reduce their momentum, thus producing a redshift. Other proposals for explaining how photons could lose energy included the scattering of light by intervening material in a process similar to observed interstellar reddening. However, all these processes would also tend to blur images of distant objects, and no such blurring has been detected.
> Traditional tired light has been found incompatible with the observed time dilation that is associated with the cosmological redshift. This idea is mostly remembered as a falsified alternative explanation for Hubble's law in most astronomy or cosmology discussions.
https://www.newscientist.com/article/2380881-time-appears-to... (paywalled)
https://www.sciencealert.com/time-appears-to-have-run-5-time...
https://www.advancedsciencenews.com/time-ran-slowly-in-the-e...
> Scientists have confirmed that just 1.5 billion years after the Big Bang, time ran five times slower than it does today, 13.8 billion years later. Though scientists have long been aware that conditions just after Big Bang were radically different than those in the cosmos we see around us today, the discovery shows that time is relative in regards to the age of the Universe, too, just like Einstein predicted.
The referenced paper: https://www.nature.com/articles/s41550-023-02029-2
[1] https://en.wikipedia.org/wiki/Conformal_cyclic_cosmology?use...
Not credible. Tired light doesn't preserve the density of photons in blackbody radiation; the CMBR has density precisely that of blackbody radiation.
https://arxiv.org/pdf/2201.11667.pdf
Here's one of Gupta's papers.
"While tired light (TL) models have been shown to comply with the JWST angular galaxy size data, they cannot satisfactorily explain isotropy of the cosmic microwave background (CMB) observations or fit the supernovae distance modulus vs. redshift data well. We have developed hybrid models that include the tired light concept in the expanding universe."
https://arxiv.org/search/?query=Gupta%2C+Rajendra&searchtype...
and honestly I don't hate it. And his institution (byline at the link at the very top is "by Bernard Rizk, University of Ottawa"; turns out he's a Media Relations Officer there [1]; great journalism, phys.org) hyping an adjunct's paper is novel.
[1] This really fascinates me. https://duckduckgo.com/?q=bernard+rizk+university+of+ottawa&... Good stuff, phys.org.
"We have attempted to permit concurrent variation of c, G, h, and k in our cosmological, astrophysical and astrometric studies: G~c^3~h^3~k^{3/2}." Concurrent. Concurrent. So great, what's the time relationship?
"Let's assume that the coupling constants evolve with the expansion ... as follows: Speed of light: c = c_af_c(a)" Each constant gets the today CODATA value multiplied by some unknown function of a (the scale factor) on that value.
Ok, cool, so what are the functions? [Spoiler: they could just be everywhen 1. Spoiler: that's what he concludes. Spoiler: you can stop here, really.]
Before going into the functions, he first considers supernovae without seeing the functions.
"commoving distance". Commoving. Co-mmoving? Com-moving?
Ok, this is a draft. I will make a typo or two in this commment just out of solidarity.
Draft? Oh, it's in MPLA! With the typo. https://www.worldscientific.com/doi/pdf/10.1142/S02177323225... (just below eqn (1) on the fourth page). <sarcasm> Good catch, editors and reviewer two! </sarcasm> I DO NOT FEEL BAD ABOUT KICKING THEM. Booooooo! Partial refund to the author and/or his institution.
Eqn 2-4, Some of the functions on the constants are determined by an unknown function on c.
Eqn 5 repeats the relation I quote at the top.
"As pointed out by John Hunter (personal communication) the above can be represetned in terms of the variation of the length dimension of each constant ... if a quantity Q has a length dimension of n, it's f_Q(a) = f(a)^n". [bookmark1] Ok, so generalize and put some meat on the "concurrently".
I don't have any idea who John Hunter is. Is it https://www.thespaceshow.com/guest/dr.-john-hunter ?
Hey, fascinating, reviewer two has caused the entire paragraph in the preprint (at link you supplied) to not be in the published version (p. 5 just before the start of section 3). John Hunter is also not in the published Acknowledgments section.
John Hunter you have been Yezhoved! <https://en.wikipedia.org/wiki/Nikolai_Yezhov#Legacy> (photo at right).
Some words about measurement of mass, and aha, "the Kibble balance test mas m is proportional to h/c^2. Then using equation (5) m \propto f(a)^0 resulting in \dot{m} / m = 0."
4. Discussion
"if we do not permit one of the coupling constants to vary, the others are naturally constrained not to vary" more on that in that paragraph.
This result, which I do not think section 2 proves, is actually pretty important. If it were proved, and also the assertion at [bookmark1] were proved, it would kill off adaptations of current theories which put a function on any constant with a length dimension, which is commonly done [bookmark2 below].
"The approach we have taken is rather phenomenological". Well, yes. Ra-ther.
"A more appropriate and satisfying research would involve writing an action for the interrelated constants represented as fields and derive the relationshop between <constants> with the scale factor a". Right, which is how everyone actually does it. For example DSR <https://en.wikipedia.org/wiki/Doubly_special_relativity>, SME <https://en.wikipedia.org/wiki/Standard-Model_Extension>. Nice to know that Dannenberg has talked Gupta into looking at approaches like that. Pretty sure such things are taught out of his department; if not, he could just drive a couple hours down Autoroute 50 and choose a language.
"... it is not an easy task and we have initiated collaboration for this challenging work."
Great.
Now, he does mention Dirac but not as often as you do in the comments on this article; Dirac proposed varying G for reasons. Gupta argues you can't vary just G, so he disagrees with Dirac.
As to tired light, which was mentioned in this thread, this paper doesn't say much about it. Back to §4's idea about actually writing down an action and deriving the relationship between the constants and the scale factor. In this paper, the relationship is not put forth. At best the author admits the studies of the international prototype kilogram aren't good evidence (and went the wrong direction, "We expected this tiny mass loss could possibly be accounted for using the interrelatinoship among the constants. We have shown this is not possible ..." and his tiny amount of supernova data can be explained by "alternative models". Nice. The standard model is alternative.
Spoiler, the byline at phys.org is a media relations officer at Gupta's own university. I bet they talked before the MRO the magic "push PR to phys.org" button.
The MRO, Bernard Rizk, does this a lot it seems:
https://duckduckgo.com/?q=rizk+ottawa+site%3Aphys.org&ia=web
Which means that the result goes from "We don't really have any idea" to "We don't really have any idea, times two". I suppose you could think of that as a big update to your prior, but it's no change at all to your confidence, which still runs from (0, 1).
Which it almost certainly isn't.
I'd assume that if they wanted to spread out, they'd probably have the ability (like we do) to scout out a solar system before sending a ship. Maybe our 8 planets don't have anything of value for the species looking.
If you look at what we know about the history of the earth's atmosphere it went through a phase of high sulfur dioxide, then carbon dioxide, then oxygen rich, then what we have today. A very large portion of that was controlled by the specific life that evolved here. It's almost a fluke that we have an oxygen rich atmosphere. There are so many adaptations that could have happened to deal with the various stages of our atmosphere.
All we know is it's possible for intelligent life to evolve under these specific circumstances. What we don't know is if these are the only circumstances or if these circumstances are particularly common.
What is carbon/oxygen/water life is the only type of life capable of developing intelligence? What if that circumstances that lead to a carbon/oxygen/water rich environment only happen once in a galaxy? And what about the other elements? What if something like iron is, in fact, super rare in the universe on a planet with water/oxygen/carbon. Could you imagine how that might impact the technological growth of an intelligent species? Could you imagine what humanity would look like if the iron age was simply impossible due to a lack of iron?
Intelligence is also a weird evolutionary fluke. Maybe there's life on other planets, but the earth went over a billion years with animals before it finally developed a species with intelligence. Whose to say that nat 20 gets rolled often or at all?
Then there's the sad possibility that interstellar civilizations are simply an impossibility. It takes too many 1000s of years to colonize anything and so no species has tried.
There are just so many factors and the likes of the Drake equation seem to just handwave it all away in a neat little broad overgeneralization.
This is fairly recent compared to the age of the universe, and the speeds can be achieved with know (albeit expensive) human technology.
If the aliens had self replicating probes (of the robotic kind, not the organics-in-factories kind), the known rules of physics suggest that a Dyson swarm can be built in less than a century, at which point (0) now you have to ask why there are stars to see, and (1) 0.9c is easy, as is going intergalactic, so such a civilisation can’t have been that recent in half the Council of Giants either.
That we can see stars and that we exist, says that expanding industrial intelligences like us, either never got to this stage, or are filtered in what currently looks like a small gap between here and there.
Misaligned AGI that doesn’t want to expand could be one, so could in-fighting necessarily becoming too easy at the same time as any tech for interstellar expansion.
Personally, I think there’s dozens to hundreds of small-ish (think factors of 0.95-0.10) filters, some ahead, some behind.
The biggest of the past: the relatively thin crust that allows non-catastrophic volcanism, the dual composition of the crust so we have both oceanic and continental plates and the right amount of water to get both massive oceans and not so much as to be a water world, surviving the oxygenation catastrophe, evolution of multicellular life/Cambrian explosion, that the various inorganic carbon sinks and sources are balanced well enough for billion year evolutionary history, that we’re cooperative enough to work together while being competitive enough to develop new tech for “our side” (too little competition and we’d have stopped in c. 1860 tech and communism; too much competition and we’d be at each other’s throats and not be able to sustain global supply chains needed for modern computers).
Arguably the Moon is a big part of many of these things.
My best guess for the future: as we get more tech, it gets easier for individual insane people to blow up important things and/or kill lots of people. AI (never mind AGI/ASI) is just one of many such technologies that make this risk bigger, but even just sufficiently cheap electricity and manufacturing makes it (relatively) simple to use a cyclotron to enrich uranium.
The only way I can see past that is a ridiculous and unpleasant level of surveillance that you need some kind of AI to be able to achieve in the first place, with all the downsides that come with that surveillance, and that’s still the case even if you’re “only using the surveillance AI to find and section dangerously insane people, honest”.
I've been saying this recently. I think EM or similar could potentially take and defend a big area with the massive number of drones he could buy or build companies to produce. And that's without inventing any new tech, just mass producing specialized drones.
That's scary enough, but then imagine some small nation-state you've never thought much about, that has all that manpower and collective wealth, and maybe some ambition...
Tech is able to concentrate a big amount of power into a very small number of hands.
Difficult to do more than guess past filters beyond oxygenation given the sample size of n=1.
Future? All unknown-unknowns. Even if you rule out paper-clipping-AI-gone-wrong scenarios by assuming only weak and narrow AI slightly less than we have today, the mere ability to get a million colonists to Mars, even with just SpaceX's Starship, requires enough space industry to be a direct military threat to Earth.
Big Filter should leave space debris.
Generally it’s used as a proof of absence: if they existed we would see them, we don’t see them so they don’t exist.
> Big Filter should leave space debris.
What would you expect such debris to look like? Everything I can imagine looks like dust, very quickly.
They should at least be strong enough to withstand an asteroid hit, and those don't just disintegrate into space dust quickly.
Space Junk is already a problem for us in our present state of advancement. There's space debris from the 50s out there. Why isn't that dust?
Just like evolution doesn't happen suddenly, civilizations don't just disappear. And if the universe is so vast and old, we should be seeing civs in transition, like ours.
There's the argument of the dark forest that everyone is in hiding, but accidents happen, right?t Karma. Why don't these UFOs ever make mistakes? Why don't we see the predator civs? Where's all the noise in the universe? Shouldn't there be massive explosions from all the space wars?
I think it's more interesting and a lot creepier that we are alone in the material universe. Of course, this line of thinking leads to God, and that's poison for the "open-minded".
Billions of years for structures of old to break, not just for civilisations to arrive. It's enough time for planetary atmospheres to boil off into space.
> Shouldn't civs advanced enough to build Dyson Spheres
Kessler cascade.
But, once they're actually that big, I think their only possible downfalls are fratricidal conflicts; so my thinking and comments here are mainly regarding pre-Dyson civilisations.
Further aside: on this scale, one thing I want to find out but don't know who to ask, is "how fast do iron and aluminium sublimate in a vacuum at 300 K?"
> They should at least be strong enough to withstand an asteroid hit, and those don't just disintegrate into space dust quickly.
Asteroids come in many sizes, up to "moon"; moons also disintegrate under gravity when they pass the Roche limit, and for other reasons; the rings of Saturn are young on such timescales, 10 million to 100 million years old.
Now I think about it (in favour of your position, but again I'm assuming filters other than fratricide have to happen before Dyson swarms) an expansive civilisation that Dysoned up 10 Mya inside the Milky Way should've turned the galaxy into one of red dwarfs even if the spheres have since disintegrated.
> Space Junk is already a problem for us in our present state of advancement. There's space debris from the 50s out there. Why isn't that dust?
Remember this is in the context of what we can see looking out into the cosmos.
Our space junk is indistinguishable from dust at lunar distance, let alone interstellar.
And 50 years? Every beat of your heart is to your lifetime what 8 Earth years is to the lifetime of Sol.
> civilizations don't just disappear
Yeah they do. Heck, entire species disappear.
> And if the universe is so vast and old, we should be seeing civs in transition, like ours.
Only with sufficiently good telescopes. The actual ones we've got? It's noteworthy when they've got the capacity to resolve stars as more than single pixels.
"he Fermi paradox can be asked in two ways.[note 1] The first is, "Why are no aliens or their artifacts found on Earth, or in the Solar System?". If interstellar travel is possible, even the "slow" kind nearly within the reach of Earth technology, then it would only take from 5 million to 50 million years to colonize the galaxy.[26] This is relatively brief on a geological scale, let alone a cosmological one. Since there are many stars older than the Sun, and since intelligent life might have evolved earlier elsewhere, the question then becomes why the galaxy has not been colonized already. Even if colonization is impractical or undesirable to all alien civilizations, large-scale exploration of the galaxy could be possible by probes. These might leave detectable artifacts in the Solar System, such as old probes or evidence of mining activity, but none of these have been observed.
The second form of the question is "Why are there no signs of intelligence elsewhere in the universe?". This version does not assume interstellar travel, but includes other galaxies as well. For distant galaxies, travel times may well explain the lack of alien visits to Earth, but a sufficiently advanced civilization could potentially be observable over a significant fraction of the size of the observable universe.[27] Even if such civilizations are rare, the scale argument indicates they should exist somewhere at some point during the history of the universe, and since they could be detected from far away over a considerable period of time, many more potential sites for their origin are within range of human observation. It is unknown whether the paradox is stronger for the Milky Way galaxy or for the universe as a whole.[28]"
Seriously though, I wonder what the ramifications to other parts of astrophysics would be if this is true.
I am not a physicist, but my understanding was that multiple different ways of calculating age converge toward the traditional number. For his new estimate seems to be using theories that are still at the fringes of mainstream physics. Based on this, my bet would be on the traditional number.
[1] https://www.youtube.com/watch?v=W4KH1Jw6HBI (Dr. Becky)
One thing about a lot of this from the Big Bang to black holes is that a lot of it makes sense as mathematical concepts but doesn't necessarily translate to something intuitive.
Example: the Big Bang is often described as the Universe starting from a single point. That's an attempt an intuitive explanation but here's another based on the maths. In maths you have the concept of a space that has certain properties. A metric space is a type of space that has, well, a metric. What is a metric? It's a function that defines the distance between two points. So at the start of the Universe, it's more accurate to say the metric between all points was 0. Does that mean it started from a single point? No one really knows. But the metaphor arguably confuses the issue.
One issue is the question of whether or not the Universe is infinite. This is an open question in cosomology. Many suspect it is based on spacetime being incredibly flat based on all our observations. But if you assume the Universe is infinite, how do you reconcile that with the Universe starting from a single point? How does something intuititvely finite become infinite? It sort of breaks down. Simply saying the metric was 0 is less problematic (but also less satisfying, in a way).
There's an awful lot of evidence for the current age estimate. Expanding that by another 13B years should yield a bunch more stellar objects in the expanded age range. There is AFAIK only one such object we've detected, which the article mentions, the so-called Methusalah star [1], which was originally dated at ~16B years [2].
What's more likely: one object is incorrectly dated or the Universe is twice as old as all observations to this point have suggested? I know where my money is.
[1]: https://en.wikipedia.org/wiki/HD_140283
[2]: https://www.space.com/how-can-a-star-be-older-than-the-unive...
To correct this, a new age is calculated which then pushes back that start time.
It seems to me that we have an essential problem here in that whatever metrics we use to calculate the start event time, something will come along which upsets that apple cart.
Mayhaps, we need to look at the various methodologies in use and see what alternatives might be a better fit for the data we collect. It seems to me that these age calculations are based on a number of unverifiable presuppositions.
It might be better to say that we just do not know as we keep getting anomalies that throw whatever estimates we have into doubt, instead of stating with the current confidence that we do.
Just because we do not know now, does not mean that we won't develop the tools at a later date that will clarify the problem. Being honest that we do not know should never be a problem for anyone. It should be an opportunity to rethink the matter and try something else to see if we can solve things another way.
Engineering has to deal with this kind of dilemma and though it may take decades or longer to develop the understanding of why something works or does not work, many times understanding does come even while using the techniques in the mean time.
Aww, the light needs a little nap. No wonder we ( potentially ) got it wrong...!
[EDIT] Wikipedia "Tired Light" article:
> The concept was first proposed in 1929 by Fritz Zwicky, who suggested that if photons lost energy over time through collisions with other particles in a regular way, the more distant objects would appear redder than more nearby ones.
Oh, so, what I might have guessed, "it hits stuff sometimes".
Article goes on to make it seem like there's a lot working against the notion, including that distant images ought to be a lot fuzzier if light's interacting with other stuff along the way.
Wouldn't this being true require upending half of what we know about the nature of photons?
And that I used to visualize the Sun and our solar system doing the multiple corkscrew through space going in from one arm of our spiral galaxy to the next arm of our galaxy.
The current world superpower is barely 300 years. Imagine what could change in a thousand, then a million, then billion…mind-boggling!
Mind-boggled again!
83.13253012048193
According to google the current life expectancy (in 2020) is:
77.28 years
So a touch shy, but almost.
To Scale: TIME: https://www.youtube.com/watch?v=nOVvEbH2GC0
Timelapse of the entire Universe: https://www.youtube.com/watch?v=TBikbn5XJhg
Or to the number of stars in the observable universe - 200 x 10^21. One star / (roughly corresponding) solar system is unimaginably huge and then there's so many of them.
In comparison to some of these other measures, the age on the order of 10s of billion years seems actually surprisingly modest.
We really need to figure out faster than light communication soon, any working theories out there?
The universe is expanding which means we can see more than the age of the universe. The light from far away was carried long as the universe expanded which makes it look like traveled faster than light.
As for shipping the bare minimum, academia has too many smart people competing with each other over too little money. I'd hazard a guess that the "bare minimum" as represented by this paper is considerably higher per dollar than the bar set by someone who uses the word "shipping" to describe publishing.