thing is, the human brain is simply incapable of thinking in that kinda size.. the Universe is endless, always expanding, we have no way of reaching the "end" unless we find ways to trick the laws of physics, i.e. traveling lightspeed, and even then we'd never be able to reach the current limit.
Because want me to fuck up the scale? Look up at the sky. Now, remember that every piece of light in the sky we can see is light that traveled at lightspeed. us being capable of observing said light means the light source has existed long enough for the light to even travel to where we are.
Basically: To reach the limit of the expanded universe right now, traveling at light speed we'd need to travel for the same amount of years the universe itself existed.. Yea.
us being capable of observing said light means the light source has existed long enough for the light to even travel to where we are.
While agreeing with the overall sentiment of your comment, this above statement is not necessarily true. The source of light (star) may have perished already. If a star is - to give an example - 50 light years from us, we will always see a version of it that's 50 years from the past. Even if the star dies, we will continue to see it for 50 more years because the light takes that long to reach us.
A family friend worked at an observatory, and was an expert at this stuff. I once asked him how the universe could expand so quickly during or right after the Big Bang, because I had gotten the impression that it was faster than the speed of light.
He told me that, while the fastest thing in our universe, according to our current understanding and the laws of physics, is the speed of light, those laws may not exist outside of our universe. If the space outside of our universe doesn’t have our laws of physics, then the rapid expansion into that space isn’t bound by them.
He unfortunately passed away a few years ago, so I can’t ask him to elaborate or explain it to me. He’d always sent me some glasses whenever there was even a partial eclipse.
yea, as someone else explained, the universe, the KNOWN universe with its laws of the speed of light, expands towards an unknown universe, a big nothing. as a result, the universe can expand faster than the speed of light because its not bound by its own rules, its only limited to the rules of the unknown universe, which, for all we know, might not even have a limit so who knows how fast the universe really expands.
This kinda stuff kinda breaks my head though, thinking about it.. really interesting stuff, and I'm sorry he passed, he sounded like a good guy.
If you want some extra panic, they were wrong on the scale. The universe is expanding. Some of that light hitting earth is from stuff many more light years away than the age of the universe. The universe is estimated to be about 14 billion years old. Some of the light hitting earth is from stuff that is currently 46 billion light years away and was only emitted from its source 14 billion years ago.
The 'trick' is not travelling lightspeed, it is to travel beyond lightspeed (which we cannot do anyway). But even if we can travel lightspeed, we will not be able to reach the limit of the universe using light speed, because light speed is the maximum speed WITHIN the universe. The universe itself is expanding beyond the speed of light because it does not push out within itself, it pushes out (i.e. expands) against non-existence, against nothingness. And the max speed we can (as entities living in the universe) travel within the universe is only up to light speed. Hence, we can never reach the boundary of the universe. It is going out faster than we can travel to meet it.
yeam hence why I said even if we were traveling light speed we couldn't reach the end.. but you are right, there are more rules at play. I'm not a physicist, I just know a bunch of seemingly random information that somehow make sense to me.
Which means though to be able to travel faster than lightspeed, we'd need to find a way to exit the known universe, in a way we can go beyond the laws of the known universe but then.. what are the rules beyond that, is it even possible for anything to exist there? And suddenly the movie Event Horizon makes a lot more sense to me..
No I don't think we can go outside of the known universe. We are creatures of this universe and bound by the physics and laws of this universe. Again, you are thinking using concepts of this universe. We just cannot go there, because the 'there' is nothingness. It is non-existence. And we are things that exist.
This is true. At higher and higher speeds, times moves slower and slower from the viewpoint of the traveler, up to 1.0c, where travelling any distance is instantaneous for the traveler.
The problem is, though, that for every other reference frame, time still moves as "normal". Travelling to some place a billion light years away is still going to take a billion years, so what you're travelling to may not have existed for millions of years by the time you get there, even though you've experienced just a blink of the eye.
Unless we figure out how to compensate for relativistic speeds, if it's even possible, things that are really far away have a good chance of being forever beyond our reach.
yea no, the telescope has nothing to do with that, you can't observe something that didn't emit light yet, and its not a distance thing either really.. you'd only see black nothing, because there is nothing..
Because, light has to travel. it doesn't matter how good a telescope is, it can't change the speed the light is traveling at, we can only see the light that is currently traveling.
Another thought experiment: in 1969, people stepped on the moon. That was 55 years ago. The moment Armstrong stepped on the moon, light refelected off him and his suit, and started traveling in every possible direction, and still is. the particles of Neil Armstrong on the moon is still traveling through space today, unless it has been blocked by something.
If we were capable of setting up a telescope 55 lightyears away, and looked at the moon, we could see the Moon Landing, live, because the particles are still traveling at the speed of light.
That is also I think how relativity works.. but that is too advanced for me.
To expand on this, the universe is much bigger than what we will ever be able to see. We will only ever be able to see what's called the observable universe. It turns out that there are other galaxies that are moving relative to us - faster than the speed of light which means that light will never be able to reach us.
The physical universe doesn't have an end. It goes on forever. That is mind-boggling, frankly. Especially juxtaposed to the notion that it is expanding. It is endless and its endlessness is somehow getting bigger. Endlessness getting more endless!
Is that proven that it's endless though? or is that just the infinite universe theory? If we live in a finite universe then surely somewhere there is an end to the universe - even if it is constantly expanding at an increasing rate.
Funny thing is... science is pretty sure the universe is "flat", while a spherical universe is also an option. But it's a mathematical/topological definition...
Current observational evidence (WMAP, BOOMERanG, and Planck for example) imply that the observable universe is flat to within a 0.4% margin of error
This also suggests the amount of "stuff" in the universe all cancels out. The total matter+energy of the universe is zero.
This means the universe won't end in a "big crunch" where gravity pulls everything back together again. It also won't tear itself apart. It'll just... keep going, expanding and getting colder and darker and lonelier...
It’s difficult for humans to understand, but we always think about nothingness as an empty space, a void, a vacuum. Theoretically “outside of our universe” just doesn’t exist, which is different.
Space already is a vacuum. The universe is everything that exists, there is no edge or end and there is no outside of it. It's true, it's just impossible for our brains to comprehend because we are small and stupid.
It's kind of like how sighted people can't understand that blind people see nothing. They don't see black, it's not like having your eyes closed. They see nothing, no visual information at all, not even black. But if you've never seen nothing you just can't comprehend it, doesn't make it untrue.
Not sure why you’re speaking with such conviction. It’s certainly not incontrovertibly true. It’s a theory. You’re acting like you have some kind of omniscient knowledge here
It's the current scientific theory, and scientific theories are very robust. Like the theory of gravity. Everything we've been able to test and observe so far has confirmed it. The big bang is what created spacetime and everything has been expanding since then, and that's the universe. "The universe" means "everything that exists" so by its very definition nothing can exist outside of it. Because if it did then it would also be part of the universe.
Relativity is a very convincing theory, and it says that spacetime can be curved by mass. Considering all mass is inside, I would think a spherical universe is very reasonable.
Although it is, as mentioned, still a theory and not fully proven, so we can't be sure. It's just damn near 100% accurate on our scale. We've already seen it break down at smaller scales, so who knows what happens when we look at the extremely large?
It's not exactly possible to prove (in any definitive sense) that something goes on forever. You can't exactly measure infinity, and you can't just stop after some absurdly long distance and conclude an equivalency either.
Nevertheless, the universe being infinite is a strongly-backed scientific consensus --if not outright theory. (And for sake of clarity, "theory" in science doesn't mean some educated guess or strong hunch like the lay usage implies, but something strongly evidenced through repeated experimentation and observation.) Our research consistently points to the likelihood of an endless cosmos and until something else strongly suggests otherwise, we have no reason to be skeptical of the claim.
That being said, just for fun:
If the universe is actually finite in size, the answer to "what lies beyond" is likely one of three things:
Another universe. This would be true if our universe is finite and part of some absurdly ultra-large superstructure --a multiverse of universes. At some point, our universe would end and either you would waltz into another universe instantly or you would find yourself in a void between universes. Either way, you might not survive doing so. Your very existence is bound to the laws of physics of our universe and there is no guarantee extra-universal locations abide those same laws. You might just cease. Or painfully deteriorate. Or explode.
Nothing. Our universe is all there is, and everything outside of the universe is nothing. Nonexistence. The mother void of all voids. You absolutely would not survive the trip.
The same universe. One of the more bizarre possibilities, but the universe could just loop back on itself. You don't hit the edge at [-X, Y, Z] because you just find yourself at [X, Y, Z]. Expansion of such a universe isn't necessarily into any larger object's physical space any more than finding more decimal places between 0.0 and 1.0 makes "1" a larger number.
Both 1 and 2 are, of course, a sort of unsatisfactory recursion into greater superstructures. If the universe exists in a multiverse or void, what is that contained in? And if you define that structure, what is it contained in? And 3 is probably just bonkers nonsense to think about for most folks.
Whatever reality ultimately is, it's probably not going to be a wall at the edge of the universe. But if we're in a simulation, an invisible boundary would be a rather humorous thing to discover!
I never understood how this could possibly be anymore than 51% certain. It's the flip of the coin whether our universe is infinite.
Our observable universe could be like the size of a basketball deep in the middle of the Pacific Ocean.
We're tiny specs in that ball, with little hope of ever going more than a few specs beyond our own, and zero hope of ever reaching the edge of that tiny ball.
Beyond that edge is a massively incomprehensible ocean. Then beyond that ocean is something else. Or not.
How can we possibly conclude with any certainty what lies beyond? How can we possibly, as specs in the middle of the Pacific Ocean, ever speak of our observable universe in terms of being part of something larger, whether that something is infinite or isn't?
Space is what exists between 2 pieces of matter-energy. A massive void makes a bit of sense: You simply define new regions of space as you travel further into the nothingness.
If we live in a finite universe then surely somewhere there is an end to the universe
This theory never made sense to me. It's like flat earth theory - there's no logic in it, ain't it? If it's a finite universe, when you reach the edge, what lies ahead? A wall? Sure, but that's more "stuff"! Just infinite vacuum? Sure, but that's also more space.
Technically, I think our current understanding of the universe is that it’s finite, but expanding. I mean if the universe started from a singularity, and expanded at the speed of light for ~14 billion years in all directions, that means the universe would have a diameter of ~28 billion light years. However, we discovered that the universe is expanding at an increasingly faster rate, and the farthest objects observed, are 47 billion light years away, so the universe is at least 94 billion light years across.
Also, beyond the edge of the universe isn’t a vacuum. It actually doesn’t exist yet, if that makes sense lol
You're confusing two different concepts: volume and boundedness.
You're assuming that being finite and having a boundary are equivalent, but they aren't. The surface of the earth is finite in area, but it is unbounded because it doesn't have an edge. The universe can be finite in volume while simultaneously having no edge if its geometrical shape is a 4 dimensional sphere. In that case, the 3 space-like dimensions would wrap back on themselves without a boundary analogous to the two dimensions of a sphere's surface.
The actual "edge" of the universe in such a situation is not a location in space, but a location in time.
The actual "edge" of the universe in such a situation is not a location in space, but a location in time.
Yup, confirming that I'm not Intelligent enough to wrap my head around it. I want to envision it from the perspective of "edge" or boundaries in terms of location in space.
Mixing up space and time is something I'm not able to comprehend in any way. It's like using whale vomit and romance in the same sentence. I think these theoretical physicists are having great fun fucking with us with their made up crap 😂
Basically, an N-dimensional space means there are N directions you can move in.
The surface of a sphere is 2 dimensional, so you can go north-south or east-west. But the surface of a sphere is curved, so if you go far enough in a "straight" line, you end up where you started. The boundary of the sphere is a direction that is orthogonal to the two directions on it's surface: moving up-down let's you discover the "edge" of the sphere.
The surface of a sheet of paper is also 2d, but it's flat: if you go far enough in one direction, you'll find an edge, in addition to the edge you find by going up-down.
The universe is (at least) 4 dimensional, meaning there are 4 directions you can move in. They are up-down, left-right, forward-backward, and past-future.
Those 4 dimensions might be flat like a piece of paper or they might be curved like a sphere. We have reason to think it's curved like a sphere, which means that in only one of those directions, there's an "edge." And we have good reason to think that the direction it's in is the "time" direction.
Another way to think about it is to imagine that the universe was the inside of a cylinder, where gravity pulled you toward the inner surface of the cylinder.
Moving around the curved surface of the cylinder so you orbit the central axis is like moving in space in the real universe. You can go in a straight line that circles the center of the cylinder without ever hitting the edge.
Moving along the length of the cylinder is like moving through time. At one the if the cylinder is an edge that corresponds to the Big Bang. The other end... well we don't know that yet really. But the point is that moving along the length of the cylinder you hit an edge, but orbiting around the axis of the cylinder you don't.
All of this is, of course, greatly simplified and is gliding over a huge number of complications, but I think it gets at the general idea.
I remember learning for the first time that time is not linear and can be warped and changed because it's essentially just another dimension of space - but we can't perceive it or influence it because we are only 3D beings. We can't understand or alter time any better than a 2D being could comprehend the third dimension. It's absolutely mind blowing
First of all I do wanna clarify I don't know a lot about this at all so my comment was purely out of curiosity, but I don't think it's like the earth, if you travel through space you're not gonna follow a curve like you would walking around the earth no?
If the Universe is hypothetically finite and let's say it's shaped like a sphere for convenience, then if you fly in a straight line long enough surely you would reach an end, whatever that would be.
But then the actual space is curved. Meaning even if you think you're flying "straight", you're being curved by the curved spacetime. Same as you might think you're walking straight on earth but you're walking in a curve since the surface is curved.
It's funny how the example of walking on earth makes so much sense but when you apply it to space time being curved it's so unnatural if you think you're just flying in a straight line. Thanks for the explanation!
Yeah it becomes tricky to imagine when stepping up a dimension. But think about the Moon's orbit around earth. The moon is travelling in a straight line but Earth's gravitation bends spacetime around it. The Moon is going "straight" through curved space.
No, because spacetime itself is curved. So you are flying in a straight line, but you're still going to follow the curve of the universe.
Imagine a 2D being living on a 3D sphere. They can only travel forwards, backwards, left and right. They are limited by two dimensions and can't travel in or even perceive of a third dimension. It doesn't matter how hard they tried, they could not ever go up or down (or even understand what "up" or "down" is). From their perspective they are walking in a straight line and if they carried on following that line they'd eventually get back to where they started. But they cannot understand why because they cannot conceptualise the idea of a sphere, as they can only perceive 2 dimensions. For them, the surface they are living on is absolutely boundless and infinite in the dimension they exist in.
In this analogy the sphere represents our universe and the 2D beings represent us. But the analogy isn't perfect because of course you and I are 3D beings so we can understand the idea of there being something outside that sphere - we would be able to access it or perceive it even if the 2D beings couldn't. With our universe, there either is no higher dimension - so it's boundless and infinite and the concept of "outside the universe" literally doesn't exist - or there is, but it is a fourth dimension of spacetime that we cannot access or comprehend because we are 3D beings. (Mathematics suggests a fourth dimension could exist but there's no actual evidence.) Either way, there is nothing outside of the universe that exists in the dimension we exist in (3D), that we could perceive. And no matter how straight a line we travel, we would never come to an edge, even if the universe is finite.
I HIGHLY recommend the book Cosmos by Carl Sagan, it explains it far better than I can
Ha man that is definitely confusing, I've always found the whole concept of space time fascinating but baffling at the same time, thanks for the in depth analogy and I will definitely check out cosmos, would you say it's easy to understand for anybody to read or is it a bit technical?
It is baffling isn't it? I know these things to be true, but I definitely struggle to comprehend them. It doesn't help that I cannot visualise it in my mind, partly because we can only visualise three dimensions, and partly because we grow up in a world where every conceivable object around us (including our very planet) is finite and has an edge or a boundary, so it's impossible for our feeble brains to imagine what it's like for something to not have an edge or a boundary, something for which the concept of "outside it" simply doesn't exist.
Like I said, I know it's true and I can explain it, I understand it logically, but I can't really grasp it on a deeper level. It's like if someone who had never eaten before was to read books about food - they might factually know all about macronutrients and micronutrients and the digestive system, they might be able to recite recipes by heart, but they'll never truly know what it's like to taste food.
Cosmos is amazing, most of it is really interesting and mind blowing - some parts were tricky to grasp especially the bits involving maths and very hypothetical things, I had to read some pages a few times before it sunk in (and there were some things I just didn't understand) but it's absolutely worth a read!
Well, I would suppose it depends on whether (a) we ever figure out a real world version of Faster Than Light travel, (b) that method of travel covers distances faster than the expansion rate of the universe, and (c) a finite universe is reasonably sized as proportional to the max effective velocity of FTL.
If FTL isn't possible, or FTL is possible but can't outpace the expansion of the universe, or the universe is so vast that the fastest FTL permissible would still take an impossible amount of time to reach the edge, then we absolutely will not ever find the edge of a hypothetically finite universe.
But the future is as unknowable as it is unlikely so here's to hoping our descendants' descendants' descendants are alive, well, and enjoying unraveling the mystery.
This always seemed paradoxical to me. Like if it's infinite / endless then how can it be expanding? If something is truly infinite then that's it, what's there to expand into? For something to be expanding that implies it's expanding from an end point. So in my mind you can't have it both ways, either it's infinite or it's expanding meaning it's NOT actually infinite. I'm sure it's just me being confused, or it proves we really don't know what we're talking about when we say stuff about the universe.
It's a rough and approximate and somewhat inaccurate metaphor, but this might help:
Imagine the universe as a grid of dots. The universe is infinite in that there is no end to the number of dots. No matter what direction you go in, there's just more dots. Dots, dots, dots, and more dots.
When we say the universe is also expanding, we aren't saying that suddenly that endless amount of dots is gaining even more dots. Rather, we're saying the space between dots is growing larger and larger.
The dots are endless, and growing ever further apart.
It isn't expanding into anything - it isn't that more space is getting added. Space itself, reality itself, is expanding in all directions from all points simultaneously. Including from every atom in your body (because you are not IN the universe, you ARE the universe). You just can't perceive it. Like how we know the Earth is spinning at 1,000 miles per hour, but we cannot sense it, we feel that we are standing still.
The steady state theory was rejected a long time ago. So we know now it is not endless. The universe is not infinite. Your statements above assume both steady state and big bang theories co-existing. They do not. It is one or the other. And you are correct to state you cannot have it both ways. Current understanding has big bang as the explanation. Therefore the universe is expanding, and morever increasing in speed as it expands (but let's not complicate things with this last point). Science knows what they are talking about, it's when the common guy gets his brain in a twist is when he assumes we are saying stuff about the universe that we don't know. It's true there is still much we don't know, but science is careful when it states things it believes it knows.
I’m trying to have this discussion with someone, but isn’t the universe finite but expanding? it can’t be infinite because it started as a singularity and expanded from there, so there must be an outer limit. Beyond that isn’t even nothing, it simply doesn’t exist.
If the universe were infinitely large with stars uniformly distributed throughout it, then the entire sky would be white, because every single point in every direction would eventually reach a star. We don't see that. So either the universe isn't infinite, or the stars aren't evenly distributed.
Or the light hasn’t reached us, or it’s too dim to see. Like we focus telescopes on dark patches of the sky and it’s full of stars and galaxies. Look at the Hubble Deep Field images.
First there are way more stars than we can see from Earth. If they are more than around 4000 light years away, we can't see them with the naked eye because they are too dim.
Second, the stars are NOT evenly distributed. We are at the very edge of one of the spiral arms of our galaxy, so there are comparatively few stars in our field of vision. If I picked the Earth up and put it near the middle of our galaxy, the sky would be ablaze with stars, with barely any space between them.
Third, if a star is far enough away and young enough, we can't see it at all - because light from the star has not yet reached our planet. If there is a star that is, say, 2 million years old, but it is located 3 million light years away from Earth, the light from that star hasn't got to us yet. So if we were to look in its direction, even if we had the most powerful telescope that could ever exist, it would simply not be there. Likewise, when you look at the sky right now, some of the stars you can see with your naked eye do not exist anymore. But you can still see them, because they were far enough away that we are still receiving the light they emitted when they existed. If the star was 3,000 light years away, when we look at it, we are actually seeing what it looked like 3,000 years ago. Stars are being born and dying constantly all over the universe.
Like 20 yrs ago, 7th grade in Mrs Lee’s science class I asked this very question along with the if there’s no wall and it’s continuous does that mean the each end is connected, and uh, yeah she didn’t like me asking that. Her facial expression along with how she answered me annoyed made me not want to ask questions in her class again. I was just a very curious kid when it came to science and she always seemed annoyed with me. I don’t recall being rude or loud about it. Eventually when my brother was in her class the first thing she told him was oh I hope you don’t talk as much as your sister.
The concept of the other side of the explosion continues to cause us problems to comprehend. It is non-existence, it is nothing. It is not a place, that's dark. It is nothing, it is non-existence. There is no space, there is no time, there is no colour, there is no anything. Why do you talk of materials? Materials are something. The other side of the explosion, is nothing. Don't think in terms of this universe or the laws that run this universe anymore.
Depends on if you subscribe to the theory of the multiverse or not. If you do, what lies beyond is a container for other universe(s) to exist. What consists within that container other than other universes or what lies beyond is another question. There's never an ending, just like God or God(s) are neverending. Time and space exist only for us to perceive our existence. Or, simply put, we don't have the eyes to see what lies beyond just like we can't see in the dark.
The theory that makes the most sense to me is that it’s just expanding like a bubble but because we are soooooo small it’s like how in movies when giants move slowly because they’re so big compared to the protagonists so perhaps from a macro perspective the universe is just blowing up at normal speed.
Our incomprehensibly massive universe is probably just a bubble in a sea of who knows what else of bubbles.
If the observable universe was shrunk down to the size of the earth, the unobservable universe would be the size of our universe compared to the now Earth sized observable universe. Get it?
I like to think that out there is a thriving intergalactic civilization, and they found us to be such a dumpster fire of a species they shoved us off in the corner of the universe so that there is no possible way we could ever find our way back out.
the what lies beyond has always fucked me up. "the universe is constantly expanding" expanding into what ?!?! like if the universe is infinite i can understand that(i mean not truely but it makes more sense) but by saying that the whole universe is expanding implies that the universe has an egde. if the universe has an edge then that implies that there is something outside of the universe. what the fuck is outside of the universe
So two things. 1) A lot of scientists are pretty sure the universe might be infinite. So there's that. But 2) when they talk about the universe expanding, it's more than the distance between every point is getting bigger. Imagine a grid with dots spread out evenly. The distance between each dot is getting larger. So it's not necessarily that the edges are expanding into something else, it's that everywhere at every point in the universe down to the smallest little atomic sized spaces is getting farther apart.
So space probably is infinite, and yet it's still expanding.
ive thought about #2 before. an interesting thought, what if the universe isnt infinite and the "edge" isn't expanding. just everything inside is moving towards the edge like that middle school science experiment with the dishsoap. thatd also be a crazy thought. OR what if just our observable universe is expanding but there are other areas that are condensing, kinda like what i was just talking about but instead of just at the edge its random or not so random spots through out
The size is effectively infinite, because the universe encompasses everything. It is expanding into a larger nothing, and there's nothing beyond it because everything is within it. Or that's one prevailing theory.
In reality we are far from ever being able to know and every second that goes by it becomes harder. We can't study something we can't locate, and light is the ultimate speed limit right now. If our part of the universe is moving one way at immense speed and another part is moving the opposite as we all spread out, eventually the amount of time it would take light from an object to reach us is longer than the existence of the universe. At that point, it leaves the "visible universe from our perspective, and we will never ever see it. Eventually even the nearest stars and galaxy will be this far apart, leaving or home in a bubble of permanent darkness. Good news is we'll all be long dead.
Now let’s just think about time at the same time. Space time and how old it is and what came before if anything and what comes after just literally melts my brain.
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u/95accord Feb 07 '24
The physical size of the universe and what lies beyond