Why is there a normal galaxy sitting at the edge of the Universe?
syfy.com
syfy.com
https://orbitalindex.com/archive/2020-07-08-Issue-72/#more-o...
Earth's atmosphere as a refractive telescope: https://www.scientificamerican.com/article/earth-could-be-a-...
It will take 30 years to get in position but then we can only look at one target? While it sounds very neat, I'd rather fund something we can use more than once, and sooner.
Starship is going to open so many opportunities.
The first fleet helps targeting the second, and all those who come after them.
https://www.youtube.com/watch?v=NQFqDKRAROI (already linked by a sibling comment, but yes, can't recommend this enough!)
Earth is 12700 km in diameter, so such an image would be a bit more than 500px across.
Here is a picture of the Earth that is about 500px in diameter: https://cdn.mos.cms.futurecdn.net/3upZx2gxxLpW7MBbnKYQLH.jpg
As for how to get there, yes, innovative propulsion is required. My idea is that the probe would dive close to Sun and use solar energy (sail? electric propulsion?) to accelerate itself out to hundreds of km/s.
https://voyager.jpl.nasa.gov/mission/status/
Voyager-1 is the fastest at 38,000 mph (61000 km/h) with respect to the Sun, but currently about 90,000 mph (144000 km/h) relative to earth (I guess this fluctuates annually).
Politicians and bureaucrats want immediate results, so a "launch now and see results in 30 years" mission – by which time many of the senior decision-makers will likely be dead – is going to be less attractive than competing missions offering results much sooner.
If you go back through the history of space exploration, it is full of proposals that "by year X we will be doing Y!" which never came to pass, because the money never turned up.
This makes me sad. The entire point of Government is to be an enterprise spanning multiple generations.
Of course, non-democratic systems have their own, equally serious downsides. Consider China: a system which is arguably much better at making long-term investments in public infrastructure than most democratic countries are (witness China's high-speed rail system), but also a system which ruthlessly suppresses dissent and locks up over a million of its citizens in "re-education camps"
In practice, hereditary absolute monarchy suffers from the problem of the dud heir: Marcus Aurelius is remembered as one of the greatest Roman Emperors, his son and successor Commodus is remembered as one of the worst.
Not in a democracy. The point of a government in a democracy is to serve the current will of the people. The government itself might last many generations, but its goals and motivations change with every election cycle.
https://arxiv.org/ftp/arxiv/papers/2002/2002.11871.pdf
for downlink can't they launch a few extra sats that just sit around the Sun and form a big virtual dish (via baseline interferometry or what's that occult DSP magic called these days)?
For comparison Voyager-1 is now at a distance of 40 AU only.
Big layman here. I only skimmed this link but this stood out to me.
If galaxies and stars at the other “end” formed out of matter resulting from the big bang, just as the matter we are made of, how did we get here at the same time that that matter got there?
Is it because speeds faster than light are possible, and around the big bang all matter was spread near instantly at that speed? I don't understand how matter of the same “kind” was spread throughout the universe all at the same time without traveling at speeds greater than the speed of light. Because if we watch the ”opposite” direction from where the big bang occurred we don't really observe matter in a state closer to its original state, or parts of the universe in radically different states - which should result from that matter traveling further than the matter we are made of, as for us to now catchup with light that is “younger” than that towards the core of the universe. Am i missing something?
On the traditional balloon model, the surface of the balloon represents space itself. Those dots on the surface of an expanding balloon are not moving relative to space (the surface of the balloon), and so despite the distance increasing between us, the rate of increase of that distance is not bound by the speed of light, which only limits passage through spacetime.
The wikipedia page on redshift describes well how redshift applies to objects which are in space that is expanding: https://en.wikipedia.org/wiki/Redshift#Expansion_of_space
I have a terrifying theory on this (granted, the Earth will be long gone). What if the universe is not actually expanding in the sense that it is being propelled by an initial explosion, but instead falling towards a much greater mass - the end of time so to speak, where all mass ends. Considering that gravity is a "weak force", the scale of such a mass makes me uncomfortable to think about.
Perhaps what we observe as the fabric of space-time itself "stretching" is actually a similar process to what happens to matter as it enters a black hole?
Carlo Rovelli and others propose that black holes actually only appear as they do to us due to the extreme time dilation, and similar to how a photon's "perspective" is that it's experiencing all of time at once, a black hole's perspective is that it's basically a massive explosion that occurs at essentially the same moment it forms. So under this hypothesis, a black hole never reaches a true singularity, but as close to a singularity as physically possible, and then it almost instantaneously bounces back like a taut rubber band that's stretched back as far as it'll go. From our perspective on the outside, it's an intense explosion occurring in very slow motion, and from the perspective on the inside, it's an intense explosion happening all at once.
Rovelli posits a Planck star, not a singularity, exists past the black hole's event horizon, and the Planck star is the state of maximal compression between the black hole and white hole phases. And somewhat related to this, if I understand the theories correctly, our universe might be a supermassive white hole, and we might hold the perspective of being inside of a super(super)massive black hole that's turned into a white hole and is exploding and jettisoning everything inside of it. Or some stage after that. The ultra-compressed energy before the Big Bang would be an (extremely massive and dense) Planck star.
I have no idea how likely the Planck star theory or white hole universe theory might be, but my blind speculation is that if it's true, maybe dark energy is whatever's fundamentally responsible for gravity/curvature causing our white hole explosion to bend some outer medium - the hypothetical potential medium which our black hole/universe originally formed in - and interact with other extreme contractions and explosions also happening in that medium, in complex and multivariate ways. Maybe a white hole being pushed into or prodded or yanked by many other black holes and white holes from different directions and angles could be perceived from the inside as accelerating expansion of space at certain scales.
Maybe this is happening recursively, even; maybe that outer medium is itself within another even greater medium, which also is within another greater medium, etc. Maybe the nesting depth is small, or near-infinite, or infinite. Or maybe there is no outer medium to our universe, in which case that whole idea's shot.
And I'm not sure if this could be related, but Rovelli suggests the hypothetical Planck star cycle of black hole to white hole applied to primordial black holes that formed in our early universe could explain dark matter, so even without the outer medium idea there could be something here that helps us understand our large-scale observations. Maybe there could be some relation to the "dark fluid" and negative energy idea, too: https://en.m.wikipedia.org/wiki/Dark_fluid
I have absolutely no clue if your or my speculation is reasonable or not (there's currently zero evidence of any sort of outer medium, as far as I know), but the general concept of our universe being the result of a black and/or white hole does definitely seem to interest a lot of physicists.
I’ve been yelling like a crank for a while that a black hole is actually a massive explosion we see in (ultra) slow motion, so it’s really cool to hear I’m not alone, and that other people call it a “planck star”. I haven’t heard anyone connect that to the big bang being a white hole, but it does make a lot of sense, even if we currently have no direct observable evidence or even any theoretical predictions.
Thanks for sharing, now I can follow along the research.
Maybe the downvotes (which seem to no longer outweigh the upvotes?) are because you said "is actually" rather than "might actually be". Humility and uncertainty is crucial in science. Even for a field that's much more testable, and even for a leading scientist in a field, let alone some random speculator on the internet. It's fun to think and talk about these things, but especially as total amateurs, we should never claim anything with even a little bit of confidence.
My own speculative stuff I posted above is probably all dead wrong and hopelessly confused; I'm just throwing it out there as stuff that's popped into my head. And Rovelli may be wrong, too, though he's a highly-respected theoretical physicist and has published several papers about it. And even if the Planck star and black hole/white hole theory is true, it may not necessarily mean it has anything to do with how our universe started; that's just additional unsubstantiated speculation by me and some other people, and not anything Rovelli has claimed, though his theory seems to have increased discussion about that topic.
Here're some resources:
https://phys.org/news/2014-02-astrophysicists-duo-planck-sta...
https://en.wikipedia.org/wiki/Planck_star
https://en.wikipedia.org/wiki/White_hole#Big_Bang/Supermassi...
Kind of like a graph of 1/x, where everything behaves predictably, but there's that one point that doesn't fit?
Rovelli hypothesizes this never actually happens and is not physically possible, and rather, when the most physically extreme possible level of curvature does occur, it "snaps back". If true, this ensures black holes do actually behave predictably, and physics doesn't actually break down; it just gets as extreme as it can possibly get.
So under this hypothesis, x gets really high, but the universe prevents it from ever reaching infinity. This would also potentially resolve some paradoxes related to black holes.
I really appreciate your comments! If you're interested in hypothesizing about physics, I think it would do you a lot of good to learn at least a bit of math to go with it.
Not disagreeing, I just wanted to suggest that the ideas come first, right? The math simply frames the ideas in a way that we can quantify and discuss, while also providing a "line in the sand" that other ideas must be compatibile with in order to be accepted among other the ideas that have already crossed that line. Those are very important things, but I would suggest that they are merely supporting an original idea that does not require math to intuit.
I almost never really think or talk about physics in general. This thread just caught my eye.
https://en.wikipedia.org/wiki/Magnetospheric_eternally_colla...
The situation you described would result in a game of universal pong, in which matter is passed from one side of the universe to the other before reaching a critical point where it bounces back. Obviously I have no means of validating the "Plank star beyond the horizon" theory, but nor can anyone else can prove differently at this point.
We can see the past, but we can’t go there, like an observer inside event horizon looking out, they can see light coming in, but can’t leave.
We can’t see the future, but when we are going there, like an observer falling into the event horizon. They can’t see what’s inside, but they can fall inside.
As we experience time, it’s like we are falling into a black hole made of time.
Space itself is getting larger, everywhere, all at once. The scale factor of the universe is getting larger. New space is constantly being "made". Every second, every kilometer in the universe grows by 2.2×10^-18 centimeters. If no other forces were in play, it'd carry everything along with it and pull everything a bit further apart. However, local forces like gravity and the strong and even the weak nuclear force are more than sufficient to hold everything together despite this, so the expansion cannot be locally observed.
That's a small number, but the universe is very big. The hubble constant is usually represented in km/s/Mpsc (kilometers per second per megaparsec), and in those units it comes out to 68. So, every second, every Megaparsec in the universe grows by 68 kilometers. The more parsecs between us and some distant thing, the more space is growing between us and them every second.
For reference, our nearest galactic neighbor is Andromeda, which is 67 kpc away, so about 100 meters of new space is created between our galaxies every second. That being said, Andromeda is heading towards the Milky Way at 110 km/s, so it easily overcomes this and will crash into us any day now^W^W^Win 4.5 billion years.
> However, local forces like gravity and the strong and even the weak nuclear force are more than sufficient to hold everything together despite this, so the expansion cannot be locally observed.
After some time, the scale factor of the universe grows, so that 1 new meter is 1.05 old meters. But, by hypothesis, as this happens, our meter stick contracts, so that it ends up being just 0.952 new meters (= 1 old meter) long. Why? Did the physical laws governing iron atoms change so that they pack more densely than before?
And if so, why do all particles pack at exactly the same new density? Shouldn't it differ from molecule to molecule?
The dominant factor on this scale is the strong nuclear force, which governs interactions at the scale of quarks - much smaller than molecules.
In the sense that it did not become 0.952 meters long. It didn't "become" anything - it did not change at all. The universe grew around it, or perhaps "underneath" it. More space appeared for it to exist in. It's like putting an iron rod in a 10 meter square house, then moving the walls out another meter.
Edit: let me phrase this another way. Let's imagine that you and I were pulling on the bar at either end. We could pull it forever and ever and it would never come apart (unless it rusted and became brittle or something, but let's imagine it doesn't). That's because we aren't putting in enough force to overcome the forces which are holding it together. Well, the expansion of the universe is putting like 10^-20 times less force into it than our arms would be.
This is a very different idea from "it's the same amount of space, but bigger", which is what I understand by the claim that a scale factor is increasing.
No, there is no scaling of matter or light. It just has a bigger space to play in.
If I understand what you’ve written already, the essence of the answer in terms of mekkkkkk’s question (for reference: “ Sorry for also asking a space 101 question, but since the fabric of space is expanding, does that mean that things are getting bigger as well? Naively, it would seem that way. In your balloon example, the dots would get bigger.”), I think the answer would be:
Anything held together (for example by gravity, or the force that keeps out atoms together) is not growing along with the universe simply because those forces are (for now) stronger than the expansion.
This does produce an interesting side question though: aren’t we (humans) shrinking in relation to the universe? Or, without the click-baity phrasing: isn’t the universe growing without us?
Yep.
(thinking emoji)
(thinking emoji)
(mindblown emoji)
However, that questions a different future I’ve seen in popular science talks: That the future becomes dark because of expansion. That makes less sense to me now, since it would seem that a merged set of galaxies would keep plenty of local stars in the skies. Assuming that stars are born as fast as they die (but I don’t recall seeing an answer to the ratio of star births vs star deaths at a local level).
Also, the age of star formation will eventually end. Stars will stop forming somewhere between 1 trillion and 100 trillion years in the future.
So the I wonder if everything expands along with the universe, does it mean that from outside, things moving at the speed of light in our universe, are potentially moving at speeds greater than the speed of light within our universe? If i was watching from outside, a rectangle moving at the speed of light in our universe, would one of its edges be moving away from me at the speed of light + the speed of expansion? If it makes sense.
I know you want me to cheat and set aside all of these complications and just imagine a rectangle moving at the speed of light, but such an answer would be nonsensical.
But the answer to the more specific question, "does the expansion of space make something move faster than the speed of light?", is "no", but it does cause the distance between objects to increase faster than the speed of light. To an external observer (which is inherently difficult to reason about, for the record), these objects would appear to "move" away from one another faster than lightspeed. However, the very idea of "movement" is rooted in the context of spacetime, and is bounded by the speed of light, so it's a confusing/nonsensical question.
e.g. after 10^18 seconds, would the diameter of a hydrogen atom still be the same? or is it scaled to be huge (relative to now) ?
Maybe this is the ‘wind’ preventing the electron from reaching the nucleus :)
This sounds like a measurable (in principle) pressure. But you say it cannot be locally observed. So how do we actually know it is happening?
I have heard for many, many years that "space itself" is expanding, but never got a sense of what that meant from all the explanations. It's always sounded to me like doubletalk. Probably because I'm dumb.
What I have heard about observations of the expansion of the universe is that objects appear to be moving away, and I've never been able to understand how we know it is not "ordinary" motion.
This just sounds weird, like I thought that Newtonian or Einsteinian physics explained objects with velocities regardless of what those velocities are. I thought there were somehow complete, you know?
I don't really understand any of it, but I read a popular account of relativity by Einstein, and you know, the examples were very 100 years ago, trains, light, geometry and stuff. No magic.
Space literally expanding seems like this star trek thing jumping out of nowhere, and it's confusing to me where it comes from, even though I appreciate that it's orthodoxy nowadays.
Maybe the point is the magic has something to do with general relativity?
For the expansion to have a significant impact on relative distances, the distances involved have to be so extreme that there's no real other interaction between the objects you're measuring from.
That doesn't contradict strict conservation of energy - it just adds another energy source that has to be accounted for when balancing everything.
It might contradict the aphorism "energy is never created or destroyed", but I'm not sure that was ever science.
It's more fun to think about it in terms of thermodynamics. Can that extra energy be used to reverse the second law of thermodynamics? I'm guessing not - it's so diffuse that it's probably impossible to use it to reduce entropy. The math for actually doing those calculations is well beyond what I know, though, so I'll just say that one's no more than a guess.
The usual response of “it only affects space between galaxies not inside galaxies” is deeply unsatisfying, and feels like it must be an oversimplification.
What I think is meant, but I absolutely want someone wiser to confirm or refute, is that the rate of expansion is proportional to distance, and therefore so small inside a single galaxy it can be ignored.
What I don’t know is: can any orbits still be stable in an expanding universe?
(In theory I could simulate the orbits question easily; in practice, last time I tried to do astrophysics maths I made an elementary mistake).
I am not that person. But I feel like this can't work -- if all space is expanding equally, in proportion to its own extent, then we would perceive no expansion at all. If two points start out 1 light year apart, and over time 1 light year expands to be 10% longer than it was before... and also, everything in the universe expands to be 10% larger in all spatial dimensions... then the distance in meters between the two points hasn't changed, because meters grew too.
Really? These structure constants never involve any units of distance? Isn't distance changing at all levels?
If I have a meter stick, and then space expands by 10%, you're saying that my meter stick will end up being 0.91 new-meters long, yes? Wouldn't that require the structure constants to change, to allow for the same molecules to take up less space?
Let’s come at this from the other direction: if everything including the space between atoms and galaxies expands by 10%, how do you tell the difference between an old-meter and new-meter? For this to be observable, something has to still scale by the old-meter, or you wouldn’t be able to observe a difference at all. That something would be the physical constants with units, like the speed of light. This means the electrical force governing the chemical bonds in your meter stick will still try to restore the distance between them to their original old-meter distance, but in new-meter units.
Then if you define the actual meter by the length of your meter stick, or the physical constants, you end up getting the same meter that everything not macro-scale “snaps back” to.
The meter-long stick you put into that space to measure it is still one meter long at some time in the future because the force that pulls the space apart (dark energy) doesn't pull on the matter that makes up the meter stick strong enough to overcome the forces that hold the stick together. But even if it did, the idea of one meter hasn't changed its definition. It's just the tool you used to measure one meter has broken.
It obviously affects all space, inside galaxy or outside of it. Let's just check the rough math, not even bothering about the fact that expansion was not linear. The universe expanded to around 100BLY in about 10BY, i.e. got ten times bigger than its potential light cone. So, for every "initial" 1km, there is additional 9km in 10BY timespan, or 0.0009mm per year, or 0.00003nm per second. The general ratio is around 1e-17 per second per length unit.
Proton size is around 1e-15m, Planck size is around 1e-35m. A thousand Planck units per second is not that much, really. And on sub-milliseconds it just loses its effect completely, due to that Heisenberg guy. (If we take my bullshit math seriously, I mean.)
Of course, if you calculate out far enough time, you would eventually end up with the observable universe getting smaller (because the stretching of spacetime would take away more space than was added by light reaching us from further away), down to our galaxy, and eventually everything getting torn to shreds, even down to protons...
In the "near" term, the effect is so small that we have much more to worry about from the sun expanding in a few billion years than the Big Rip.
Like other gravitational effects, locally, spatial expansion would manifest as a pseudo-force, but be too weak to overcome the nuclear and electromagnetic forces that keep matter bound.
However, Friedmann cosmology is only a large-scale approximation. A more realistic model is swiss-cheese cosmology, which comes with a different metric within the 'holes', and spatial expansion might indeed not act on galactic scales (though I would image it to have an indirect effect as boundary conditions at the edge of the hole have to be matched; I'm no expert on this part of the story, though).
Every second, the tiles on the floor push away from all their neighboring tiles by one tile width and new tiles appear in their place. The tiles are small enough that the dancers are easily able to adjust their step/grip on eachother to simply maintain their dance routine.
However, even tho the dancers can stay together, the couples drift apart at an ever increasing rate. They start 10 tiles apart, after one second the couples will be 20 tiles apart from eachother, 40 tiles apart after 2 seconds, 80 tiles apart after 3 seconds (a new tile is being inserted between each pair of existing tiles). My tiling math is probably slightly off, but I think this illustrates the exponential increase in expansion.
The dancers are quarks, atoms, molecules, planets, galaxies, etc. Their grip on eachother is big enough to overcome the relatively small adjustment in the space that was created between them.
A few questions using this analogy arise.
Do the new tiles actually appear between the dancers, or is it more a case of the force of friction the dancers are applying to the floor prevents those tiles between them from moving apart ?
So when 'new space' is being created, is it created around strongly bound things and the things simply slide around through this new space to maintain their current configuration, or do the 'strong' forces prevent new space being formed around them ?
If the new space is not being created, what happens to the energy that would have gone into the creation of the new space ? Does it simply get applied to the nearest point where it can squeeze in more space ?
If the space is being created and the dancers pull themselves together to overcome it, where does this extra energy come from ?
As for the big rip, I always thought it was the equivalent to the dancers finally getting tired and not being able to hold onto eachother hence giving in to the expansion of space. ie. It happens around the heat death of the universe when everything has dissipated its kinetic energy so much that the energy of the expansion is more than is left in the system to keep things together.
“Due to the expansion increasing as distances increase, the distance between two remote galaxies can increase at more than 3×108 m/s, but this does not imply that the galaxies move faster than the speed of light at their present location (which is forbidden by Lorentz covariance).”
But from outside we can move faster than the speed of light? Sorry having trouble getting my head around this.
I think you're getting tripped up on a variation of this idea, e.g. moving a laser pointer across the moon's surface faster than light. https://www.universetoday.com/109147/how-a-laser-appears-to-...
That's unknown. The observable universe is all we know for sure and there's evidence that there is both something beyond what we can observe, which conforms to what we know as space and matter, and something beyond that (whatever existed around the big bang locality).
By definition, there can't be. Evidence implies something we can observe, which would mean it isn't beyond the observable universe.
Are you saying the observable universe is bounded to our Hubble volume?
Of course, but basic reasoning isn't evidence. Again... "evidence" implies something that can be observed, and something that can be observed, by definition, lies within the observable universe.
>Are you saying the observable universe is bounded to our Hubble volume?
I'm saying the observable universe is bounded to what we can observe, and evidence of something beyond the observable universe is a contradiction in terms.
I don't know how I can possibly make it simpler.
great sci fi plot, the earth is the center of the universe because anything out side of our sphere can’t be observed by our consciousness and ‘collapse’ into existence :)
That's an arbitrary definition. We can't observe our local past events or even non-local events, yet we use them as theories/evidence depending on context (eg Red Shifted galaxies as evidence of expansion). Reasoning about past events would affect other future events is just as much evidence. That's how physics experiments are generally conducted.
but if the usual laws of physics apply to that outside "observer" then it will not be able to observe photons from those objects.
the usual assumption is that space is basically infinite but we can only observe our own "observable universe" sphere of it. every point in space has its own universe basically.
see also cosmic light horizon: https://www.thedallasgeek.com/single-post/2018/06/11/Our-Cos... (the difference between regions we can communicate with and regions from where a photon coming toward us will eventually reach us)
For any still confused, there is also a 'raisin bread' model (which I prefer because it's 3D, unlike the surface of a balloon). The raisins are galaxies, and the bread is the space between them. As it bakes, the raisins get further apart, even though the raisins aren't moving through the dough.
(Although galaxies also have movement through space, this isn't what is causing them to get further apart.)
Raisin bread, oh I love thee even more today.
The balloon is a 2D expansion in 3D space, which is a better analogy for our 3D universe expanding in 4D space. From the viewpoint of a particular dot you see the exact same thing no matter what 2D direction you look. There is no center.
I agree that the balloon is more confusing, but it is more correct in that it doesn't lead to ideas like "the point where the big bang happened".
This is a conflation of two different things. Most of the current evidence points to a universe which, when it began, was already infinite in size, but infinitely dense. In that model, it remains infinite in size, but is also expanding.
The answer to this in the early universe is called inflation, which you can tag onto Alan Guth around 1981 or so. It involves spacetime itself stretching. Originally, everything was nearby and so it was all evened out -- about the same temperature, density, and so on, then it just gets pulled apart and "writ large" in a twinkling.
all we have is the sphere of light that can reach us. That doesn't imply anything about a global universe frame
First of all, the big bang didn't happen somewhere, it happened everywhere. There's no "center" of the universe that everything is moving away from. The universe did not start from a point, it started from a small scale factor and the scale factor rapidly increased.
Assuming the universe is infinite (we're not sure), you could think of it as expontentially more infinities being created all the time. Say you take a 1-dimensional line and put tick marks 1cm apart, to positive and negative infinity. Then you multiply every tick mark position by 2. Two times infinity is still infinity, but the nature of the infinity has changed: it's scaled up by a factor of two. You could then subdivide it again, adding markings in between, 1 cm apart. You can think of these new markings as representing new centimeters which have appeared on your 1D line. This is happening to the universe in three dimensions.
Now, instead of doing this by discrete intervals, just do it constantly, so the scale factor is always expanding. Any two points are always moving apart from each other at the rate of this expansion, let's say 1cm/cm/sec. Now, introduce an attractive force between objects (e.g. gravity) which obeys the inverse square law. If the objects are sufficiently close to one another, they'll move towards each other at a rate faster than 1cm/sec, which would overcome the expansion force and allow them to remain together. In the real universe, the fundamental forces have this effect, and this is why we don't observe everything flying apart on local scales.
Now let's say that the maximum speed limit is 10cm/sec, and light travels at this speed across our 1D line. If we have two objects 2cm apart, then the distance between them will grow by 2cm in one second. In that time, light from each will have travelled the same distance and met one another. Now, they're 4cm apart, and in the next second will travel 4cm apart, twice as fast. Light can still make this journey. At the next tick, they're 8cm apart, and light still makes it. 2/16th of a second later and they'll be 10cm apart and moving away from each other at the speed of light.
At this point, no future emissions will reach them. However, we haven't been emitting discrete light pulses - galaxies continuously emit staggering amounts of light. So, the space between them is full of light which is constantly making the journey towards the other end. If no other factors were at play, they'd still be receiving old light from each other forever. But there are other factors at play: the inverse square law, combined with the increasing redshift, will eventually reduce the light to effectively nothing.
These factors are sufficient to extend the effective observation duration of distant objects well after they've crossed the lightspeed event horizon. To recontextualize this into our real universe, we can look at extremely distant objects like GN-z11, which is 32 billion light years away. If light were to re-tread this distance, it would require twice the current age of the universe to complete the journey. However, this light only took 13.4 billion years to reach us, because it was emitted when the universe was much closer together, and carried towards us on the "flow" of expanding space time, while the object was carried away from us on that same "flow" - faster than the speed of light.
Oh, and it's also worth noting that the rate of expansion wasn't always consistent. Check out this wiki: https://en.wikipedia.org/wiki/Inflation_(cosmology)
But yes, it is accellerating, and if it continues to do so, eventually it will overcome gravity. But like I said, this depends on an incomplete understanding of physics, and the current evidence suggests (inconclusively) that this outcome is unlikely. Check out dark energy if you want to learn more.
https://news.ycombinator.com/item?id=24424912
But I'll give you another analogy anyway. Say you put two rocks into a mass of water in an environment without gravity (e.g. the ISS), then freeze the water, causing it to expand. The expanding ice will cause the rocks to become more distant from each other, but they're not "moving" in local terms - the manifold in which they exist is itself expanding. That said, the frozen water and the rocks both exist in space, and the expanding ice moved the rocks through space. But, in this metaphor, there is no second, external "space" - the water itself represents space.
And so to for our universe. Space itself isn't a part some other, second "space" that it's expanding into (at least not so far as we're aware). The existence of somewhere for space to expand "into" is not necessary for the expansion to take place. Remember, it's the scale factor which is changing, not a discrete object (i.e. the universe) physically expanding.
Physics stack exchange
Its a lot like looking at a number line. That is infinitely long in both directions. And if consider all real numbers, it is infinitely expandable.
(I can't help but wonder what Douglas Adams would make of this sort of thing - or the present time, for that matter.)
https://www.eso.org/public/archives/releases/sciencepapers/e...
I don't like that phrase. It suggests the possibility that this galaxy might not exist, that this could be observational error. I think it does exist. We understand exactly how it exists because we can observe it existing. The more accurate phrasing might be "it's not understood how it could have evolved so quickly".
>the theoretical models are wrong, or at least (and more likely) incomplete.
This could absolutely be observation error. Messups in science happen all the time. You never take a single data point at face value without question, in any field. The spectrum might be polluted by another more distant object, the line matching might have been faked by some other intervening medium, the modelling for the lensing galaxy could be wrong. I agree, it looks good.
But it could totally be a mistake.
Remember not long ago when neutrinos were thought to have been observed moving faster than the speed of light? Cold fusion?
Before people jump on the idea of re-evaluating Einstein's theories, it's always good to get more people looking at the data, independently verifying it, thinking about it. In a few months, it's likely that this blip will disappear like most others.
Are astronomers that confident in their models that the inferred shape of this galaxy is bizarre? I'd love to have that level confidence in software.
>Clearly, the theoretical models are wrong, or at least (and more likely) incomplete. Obviously, there’s more to learn about galaxies that exist at the edge of the observable Universe.
I am reminded of that tale about how "Eureka!" is not exclamation of good science but instead "That's odd.". This article is saying "That's odd." in a way that signals we are on the verge of new scientific discovery.
Well, I mean, if you spend years mathematically validating your programs...
I seem to remember reading that "islands" of spacetime could do that.
So, no it's not moving faster than light. The space between it and everything else is expanding.
https://www.space.com/33306-how-does-the-universe-expand-fas...
https://starchild.gsfc.nasa.gov/docs/StarChild/questions/que....
If so, seems like they should write "13.700 billion" for the first part. I'm a little suspicious of this number as-is.
Looking for a source for those numbers, I found this[0]:
> While previous estimates were 13.7 billion years old, give or take 130,000 years, new predictions hone in with more precision- at around 13.77 billion years, plus or minus 40 million years.
Which is much less precise and feels a lot more believable.
[0] https://www.labroots.com/trending/space/18295/light-bang-rev...
More boringly, measurements of the curvature of the universe mean this is probably not the case.
We cannot prove the absence of light in a place that is already so far away that it's light will never reach us. Do you agree? We can prove what we can observe, and from that proof we can make inferences about what we cannot observe.
The entire premise of dating our universe is based on its observed rate of expansion. This was accomplished by extrapolating data from observable light and tracing it back to the so called Big Bang.
I see a lot of problems with this one dimensional assumption, which to me seem really obvious.
First of all, let's assume that we actually got it right this time and accurately traced light back to the Big Bang - how can anyone be sure that it was the first and only Big Bang?
Pangea, the super continent, for instance - many may think of as a single place and time in history, but in fact it's more likely that many Pangea's have come and gone in various states as the planet roils on. There will likely be another in the far future.
Perhaps the Big Bang was merely a "localized" event and there are Big Bangs occuring in distant places whose light will never reach us. Perhaps we have gone through many Big Bang / Big Crunch cycles. We simply cannot prove it one way or the other, and so to take a strong position on this would be unscientific.
More food for thought - imagine that the universe has already been through a near infinite number of Big Bang / Big Crunch cycles, it begs the question, do we reset the clock every time or do we let it run?
In my opinion, currently accepted theory is akin to believing that the Earth is the center of the universe and the sun revolves around us. We were wrong about that too.
This was always my view of the state of the universe from childhood onward. The Void of space is infinite, and within that Void our universe could be one of an infinite number of other universes that we will never know about because they are so far outside our ability to observe them. Perhaps there is as as much relative distance between universes in the Void as there is between galaxies in our own universe.
This concept is the only way I've ever been able to accept that our own universe has a measurable size.
Was it ever a mainstream view? I thought it was just a conjecture, leading to the 'big crush', and was disproven long ago, way more than 2 decades ago.
> The entire premise of dating our universe is based on its observed rate of expansion
Also there's the cosmic microwave background radiation. We have mapped it, and this has also allowed us to corroborate when the universe has formed, what temperature it had, and when large scale structures appeared.
There's probably other sources that allows us to estimate the age of the universe.
> how can anyone be sure that it was the first and only Big Bang?
We can't. But it is an irrelevant conjecture outside of philosophy, we can't observe anything before the big bang.
> but in fact it's more likely that many Pangea's have come and gone in various states as the planet roils on
Sure, but that's a planet. We can't extrapolate much from that and apply to the universe at large.
> Perhaps the Big Bang was merely a "localized" event and there are Big Bangs occuring in distant places whose light will never reach us
Unobservable, therefore unfalsifiable, therefore unscientific. Philosophy again.
> imagine that the universe has already been through a near infinite number of Big Bang / Big Crunch cycles
Unless the rate of expansion starts to slow down or we have indication that it will ever reverse, there's no big crunch. The rate of expansion is increasing
> currently accepted theory is akin to believing that the Earth is the center of the universe and the sun revolves around us
Not really. You are dismissing generations of people dedicated to the study of these things. We have a pretty good idea of what's going on based on the scientific method, not conjectures from single individuals.
There are things that we don't know yet. On a macroscopic scale, dark matter. Things don't really behave as they should based on observations, so this is why we have dark matter as a hypothesis. There could be another mechanism, research is ongoing. But as far as the macro universe goes, that's the major thing we don't understand yet.
Most discoveries will likely come from a better understanding of the 'building blocks', of which quantum physics is at the forefront.
There's probably much more we don't know yet. But the age of the universe, as we observe it, is not among them.
Unless space wraps around like a globe and we'll all meet at the "south pole" (with the big bang being the "north pole") or something to that effect. Which is itself wild, unfalsifiable conjecture, but there are other ways for a Big Crunch to happen other than the expansion of space slowing down or reversing
I completely agree. Apologies if my comment above rubbed anyone the wrong way. The point you just made was my overall point. Our concept of time is confined to our current existence / cycle - that's what I meant by the sun revolving around the Earth comment, but others were correct when they responded that as a current metric that's not really useful.
Where do our theories come from, if not single individuals?
How would one disprove the ultimate fate of the universe?
What if it is increasing because it is falling towards a great mass on the other side of the universe? That would still count as a big crunch in my opinion.
The term "multiverse" is used to describe the collection of multiple universes.Some have speculated that time has no direction in the multiverse and that time in each universe may be different. If our universe is cyclic, it makes sense to reset the clock because it may have run in a different direction last time or next time.
You then make an analogy about "Pangaea" as if you alone are the brilliant shining light of reason, but if you took just a small amount of time to read even Wikipedia you would find, for example, that several super-continents have formed and broken apart over the history of the Earth. The very first section of the Wikipedia article on Supercontinents lists eleven of them! [https://en.wikipedia.org/wiki/Supercontinent#Supercontinents...]
I for one see a lot of problems with your one dimensional analysis and obvious lack of awareness on these topics. In my opinion, your currently insufficient knowledge is akin to believing that the Earth is flat because you can't personally see curvature on the horizon.
Seriously though, I recommend you take the time to read about 'the entire premise of dating our universe', all the many decades of development, criticisms, refinements and confirmations of the current best theory. You'll find that it's an amazing subject, that all of your concerns have been poured over for the past century in great detail, that many brilliant people have worked out fantastically brilliant methods for figuring this out... and then finally, maybe, you'll be ready to read about the various cyclic cosmological models.
Somebody like Graham Hancock is actually delivering more people to the pipeline of scientific understanding than Richard Dawkins. We don't want to hear it but it's true. Similar things are true of WebMD and doctors, Elon Musk and space research. All the time the domain experts are shooting themselves in the head because the true opposition isn't a cruder wrong idea - it's apathy. Creationists at least give a shit about what version of events took place, the population that doesn't care is much larger. There is no critical mass of creationists that is going to undermine scientific research but the universities being defunded by an apathetic public turning hostile because they believe we're a waste of dollars - that is only a matter of time.
Science and expertise are an ecology - the people on the edge only exist because of a bigger enterprise capable of providing support. So it's not great that the stories the general public and scientists tell themselves are starting to sound like a protagonist antagonist relationship.
That being said however, making certain fields more accessible to the populace often comes with the price of a false sense of understanding. You see this a lot in medicine with WedMD, where heuristics that largely ignore the deeper pathophysiology have empowered some to believe they are more knowledgeable than their doctors.
This must be doubly true for the more abstract forms of physics - where any simplified analogy is going to give rise to false notions via extrapolation. I think there has to be some sort of balance between the two
In Japan there exists an institution called Ningen Dock. Almost nobody in the West has heard of it outside of Randox Research which is astonishing as most Japanese people visit it once a year. I believe this is a psycho-social-medical institution. It purports to be a medical institution but it's something more.
Youtubers describe their experiences of Ningen Dock if you're curious.
It works like this - most people in Japan visit the 'dock' - a metaphor from shipyards. There is a brain dock, a heart dock, a lung dock and so on. Every major hospital has this department where the patient is checked head to foot once a year. Here is the important part. They are given a grade sheet - the sort a schoolteacher awards students. Here you see your kidney was given a B-, a liver a C-. These are hints about your lifestyle choices. Perhaps you should feel bad. In one more year there will exist another Ningen Dock. I believe this institution is responsible for a superior resilience against lifestyle disease that overwhelms healthcare in other developed states. It's preventative healthcare taken seriously instead of mouthing platitudes about lifestyle choices while back in Western reality you're never far from a fatty who knows they're making mistakes. It could be you or me!
Now Sir Gwern and other analytical thinkers of HN will have spotted the problem. False positives leading to needless surgeries. This is how Western doctors are trained to think and they find Ningen Dock incomprehensible. If though we assume Japanese MDs are not idiots and positive externalities exist from the Ningen Dock then it could easily be paying for itself. The hypochondriacs don't menace the healthcare system. Their energy is redirected to superior choices. For everybody the locus goes away from the doctor and analysis and toward being responsible on your health to the best of your ability - guided by timely medical advice. The system also develops a giant database of longitudinal information which can be used to spot health patterns across populations - to enhance targeting of the analytical process. I'm sure there are lots of other tangible advantages I haven't mentioned.
So that is patient empowerment - but the tribalism aspect is important too. The system is saying to the people - we're on your side, we're on the same team, we are in your corner, we are working for you. A lot of people don't feel that way and it needs to be said. Think of the rise of ASMR videos. Hundreds of millions of people watching supposed doctors treating them. There's something there. Just the insistent affirmation would be positive for mental health.
This is a pretty bold statement. You are arguing that psuedoscience is resulting more people being scientific than actual science is?
Such an extraordinary claim needs some significant evidence behind it.
If you have a compelling story you may be motivated to sip on the subject. After a time you probably shrug off the old understanding and get to something more robust and probably more scientific.
I acknowledge some people will head into annoying dead ends - but you have to respond to the question of whether you prefer some people to be wrong and some people get to better places - or if you want most of those people to have checked out altogether. After all it seems to me that longer people ponder on it the more it is they converge on something - often something true or useful. Those are your choices. If you want to call me a liar then I suggest taking this seriously means getting a whole lot better at telling stories that go in the direction you approve of instead of what to the inside looks like doubling down on accuracy but to the outside looks like obfuscation.
Practical test - A lot of scientists are concerned about CO2 emissions and climate change. A lot of the population thinks they're full of shit because of politics. Some people have noticed though - that there doesn't exist a conflict of interests in getting improved technologies that happen to reduce CO2 emissions. Just as many right wingers are going to buy passive houses, closed loop energy, solar panels, Teslas as left wingers. Instead of perusing this thought a lot of people veer off into sermonizing on the topic - but I have to wonder why anybody gives a shit about the means when it seems like pushing on one lever gets instant blowback and pushing on the technology lever wins friends every time. It's almost as if all these groups have ulterior motives different to the public facing ones.
>Just as many right wingers are going to buy passive houses, closed loop energy, solar panels, Teslas as left wingers.
I also don't know that this is actually true. I as only able to find "what do you want to buy" polling for cars, but in a study surveying actual solar usage, it's 34% democrat and 20% republican.
https://www.autoblog.com/2016/10/26/democrats-tesla-republic...
https://grist.org/article/republicans-are-buying-rooftop-sol...
But I think this is also a false premise - that somehow conspiracy theory nuts have the same impact on public perception of science as one of the most public scientific issues with consensus from tens of thousands of scientists including basically 100% of the leading experts in the field. And the fact that there are long term economic advantages for things like solar, etc. that don't take into account at all whether or not you believe in man made climate change.
On the stats - that's a rabbit hole I won't go down today but every time I've seen people talk about alternatives to the system the left and right become like a long married couple ending each other's sentences.
>And the fact that there are long term economic advantages for things like solar, etc. that don't take into account at all whether or not you believe in man made climate change.
Sure.
> But I think this is also a false premise - that somehow conspiracy theory nuts have the same impact on public perception of science as one of the most public scientific issues with consensus from tens of thousands of scientists including basically 100% of the leading experts in the field.
There I think you're making a mistake. Literary people think Proust is awesome. A lot of people have read Dan Brown. Who is having more impact? You're making a face now - I can see through the interneticals.
Age is a relative thing. I say I'm xx years old based on the date of my birth. But I existed as a fetus before then. I existed as an ovum before that. I existed as stardust for billions of years before that. Perhaps I can mull over what it means to exist, and when "me" came to be, but when I have to enter my age while filling out some form I'm not going to write a philosophy essay. For practical purposes I am xx years old, and for practical purposes the universe is 13.7 billion years old.
According to [1], the ratio is about 5.56E-10, so I guess this would contribute about a year to the age of the universe, so.. not that much. I guess I answered my own question.
However, this does pose an interesting question about the age of the universe in extreme gravity wells doesn't it? Or am I misunderstanding something?
[1] https://www.quora.com/How-much-time-on-earth-is-1-hour-in-sp...
or maybe 13 billion years is from the frame of reference of the Cosmic Microwave Background? that would make more sense. I'm going to check again then edit this comment.
(i am not a physicist, not an authoritative source on this)
edit: so it turns out that the age of the universe is given from the frame of reference of the CMB rather than from Earth's frame of reference.:
> Measurements of the cosmic background radiation give the cooling time of the universe since the Big Bang
> Cosmic time, or cosmological time, is the time coordinate commonly used in the Big Bang models of physical cosmology.[1][2][3] Such time coordinate may be defined for a homogeneous, expanding universe so that the universe has the same density everywhere at each moment in time (the fact that this is possible means that the universe is, by definition, homogeneous). The clocks measuring cosmic time should move along the Hubble flow.
To facilitate the restaurant?
https://www.goodreads.com/book/show/13.The_Ultimate_Hitchhik...
(The first book is "Hitchhiker's Guide to the Galaxy," there are 5 books, one of which is titled "The Restaurant at the End of the Universe")
Which, as you will already know but others may not, the brilliant TV series was adapted from (not the books):
(Iconic music: Journey of the Sorcerer by The Eagles.)
I guess the “as seen from our current vantage point” is understood, but to me the needless emphasis of that perspective just muddies things, no?
Anyone of you downvoters care to enlighten me?
Either way it’s a pretty uninteresting difference in tense.
It's not confusing at all. It's because the long-worshipped, conventional big bang theory is wrong. The universe doesn't have a beginning or end. It's eternal. The original sin of that theory is that it's tainted with forced space for a deity belief at the center and always has been. The universe cycles unevenly through phases of motion, it doesn't magically start from nothing and then 'die.' The conventional big bang theory is as bad as any other children's tale going, it's up there with Santa Claus.
We're going to find a lot more supposed abnormalities like this over time. They're not abnormalities, it's the entrenched incorrect theories that are the problem.
The universe (everything that exists) is drastically larger than we already think it is. Humans are arrogant, we didn't realize the extent of the micro world, and the same exact mistake is being made at the macro scale. What they think is a singular ~14-15 billion year old universe, is nothing more than one collection of galaxies, there are many more like it nearby (many as in trillions and trillions). The micro world was far smaller than we imagined; the macro world is far larger than we're imagining. It's the same mental mistake playing out, caused by the same arrogance. What's beyond the 'universe' that we can see so far? More massive collections of galaxies, similar to the one we inhabit that we mistakenly call the universe.
How do you explain the apparent accelerating expansion of the universe, i.e. that the farther away something is, the more redshifted it gets?
How do you explain the cosmic microwave background radiation enveloping us in all directions?
What the universe really is, is a simulation. We are trapped in it.
"Lightspeed limit": this is because the simulation has a finite computing power. You can either move in time normally, or you can move in space. If you go to the max allowed speed, there's no processing left over to simulate time, therefore time stops for that entity. At intermediate speeds, slow down time accordingly.
"Planck length": resolution of the simulation. It's discrete, and you can't go any smaller.
"Heisenberg uncertainty principle": another simulation optimization. Instead of simulating all particles, just use a probabilistic function. You actually don't have to simulate it, just the macroscopic effects, unless there's an observation. In which case you can compute either the position or speed of the particle. See also: atom orbitals
"Superluminal" expansion: it's just so we don't try to get to other galaxies, which are only being simulated in a macro scale. This was left by the developer to turn the 'lightspeed bug' into a feature. Also closes bug UNIVERSE-001 where the background radiation was still visible, but other galaxies visibility was off due to performance concerns. Now they can be enabled.
"Dark matter": other civilization experiments that we don't have permissions to see. Still there and interacting with matter. Bug is still in the backlog.
See, anyone can come up with whacky stuff.
Any habitual stoner could tell you that. Once your blood THC levels are high enough, the secrets of the universe will unfold before you. And it's 100% certain, because I mean, you totally observed it, Man!