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Efficient-Finding-34 t1_j1gk236 wrote

Reply to comment by AnnonBayBridge in Did you know it will still take 46 billion years to cross the universe at the speed of light? 65 mph = 4.8 * 10^17 years! by NotAndroid545

Yes, the universe is expanding faster than the speed of light. This means that there are parts of the universe which we will never see.

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TLRsBurnerAccount t1_j1gnrmz wrote

It'll be impossible to see, but I really wonder what the expanding edge of the universe actually looks like

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duckiegooseman t1_j1goass wrote

Looks exactly like what you see from earth because it doesn't have an expanding edge, but rather the space between "things" just get bigger, so to an observer sufficiently far away, earth is on the edge of their observable universe

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Artikay t1_j1gszt9 wrote

So if you place Earth in the center of our observable universe, and call it Planet A, then you take two planets on the far opposite ends and call them B and C. Does that mean to Planet A, B and C can be seen, but to planets B and C only Planet A can be seen?

Basically B and C have more than one observable universe between them? It would take exponentially longer for light to reach between stars because there is more space to expand between them?

If there is so much space between ends of the universe could two points be so far apart that light could never get from one end to the other?

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Wind_14 t1_j1gu400 wrote

the last one is the consequences of observable universe though. Yeah there's a point where light simply can't reach the other side, because the expansion is faster than the speed of light, thus limiting the size of the observable universe (of course, this is assuming our prediction/projection is really true which is the farther an object is from the center the faster the expansion rate is between them and center).

And you don't have to assume that earth is the center of our observable universe, since it is (or rather the center of your observable universe is you).

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duckiegooseman t1_j1hf4ic wrote

Yes to the last question. Actually since the universe is accelerating faster than light, every second more and more "things" get so far away they are "lost" to us permanently because light from them can never reach us anymore. At some point far far into the future, our cosmic horizon would be complete emptiness in every direction, and our galaxy would be the only thing that even exists to us anymore.

But to B and C, they don't exist for each other. Information from B can never reach C and vice versa.

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TLRsBurnerAccount t1_j1gp27x wrote

I guess what I mean more I wonder what it's like being beyond the edge of the universe and essentially being crested by the edge

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420binchicken t1_j1gpqoh wrote

AFAIK that’s not really how it works. For them, they are the centre point at which the universe is expanding from. It’s all relative to your own frame of reference. No solar system is more on the ‘edge’ of the universe than any other.

Please someone correct me if that’s wrong. Space is big and weird.

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inventionnerd t1_j1gs85e wrote

This is true if we're going off the belief the universe is infinite. Then yes, everyone can only see in a 46b radius and are therefore at the "center" of their universe.

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sbrt t1_j1gtcr9 wrote

It was explained to me that it is the 3d equivalent of a 2d creature living on a globe that is expanding. I can imagine that but I have no idea if it is accurate.

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ZincMan t1_j1i1jce wrote

Can we judge our location in relation to the “true” center of the universe ? I mean I assume if the Big Bang was centralized, there must be a “core” to that expansion where everything is expanding radially outward…. But now that I think about it, it still might appear as though everything in relation to you is leaving your observable edge of the universe at equal speed regardless.

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inventionnerd t1_j1i2ctp wrote

It wasnt centralized though. Basically the current theory is the universe is/was always infinite and is just a bigger infinite now. The mass might have been far denser and closer together before the space expansion, but it wasnt in like a 1 mm radius sphere or something. It was always in an infinitely sized space.

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gtga1976 t1_j1i4b96 wrote

That's space itself though yes? I assume the mass within space shows differential in red shift relative to earth based on some other central point? Or are you saying everything is travelling away from earth at the same speed?

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inventionnerd t1_j1i8w3u wrote

Not quite sure what you're saying, but no, everything isn't traveling from Earth at the same speed. But I'm saying wherever you are in space, you'd see the same frequency if you look far enough as you see on Earth? So, our observable universe is about 46b lightyears in radius. To us, we're at the center right? We see a redshift of x when looking straight "up" to the very edge of our universe. If we can teleport to this this spot instantly and look around us, we'd still see a universe of about 46b lightyears in radius (just would be mostly different things as you could see from Earth. If you then looked straight "up" from this spot, you'd still see the same redshift of x as you saw when you looked at your current spot from Earth. So, how could you ever tell what the central point is if everywhere you go, you'd have the same size observable universe and same shifts?

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The_Most_Superb t1_j1gu3pk wrote

There is only existence and non existence. Beyond the universe is nothing. Unfathomable nothingness.

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Caveman108 t1_j1gwkoj wrote

Except we don’t know that. If you could travel multiple times the speed of light, ideally many multiples, you could reach the edge of the observable universe. There you very well might just find more universe. We don’t know there’s an “edge.” Just an edge of what we can see.

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museabear t1_j1gpsvz wrote

And what’s on the other side.

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Smartguyonline t1_j1h3xg2 wrote

There is no “other side” of the universe or “before” the Big Bang. Those concepts don’t make any sense.

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DWright_5 t1_j1guykl wrote

Why isn’t the speed of light the speed limit?

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woodlark14 t1_j1hfcgi wrote

The speed of light is how fast an object can move through space, but the universe isn't expanding by motion, it's expanding by changing the size of space. To us an analogy, consider a balloon with objects on its surface. The speed of light is how fast objects can travel across the surface of the balloon, but if the balloon is inflated then the distance between two objects can change faster than that speed.

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ZincMan t1_j1i27ci wrote

I understand what you’re saying but I don’t get how the expansion speed and “travel” speed would have different hypothetical limits. If things are expanding, I’m assuming it’s “relative speed” but it is indeed traveling faster than the speed of light relative to something … or rather why does traveling through space have a speed limit at all?

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woodlark14 t1_j1i3ljj wrote

From the perspective of relativity, everything is always moving at a constant speed through space-time from every perspective. The faster something is moving through space, the slower it is moving through time and vice versa. Light speed is achieved when an object has no mass, resulting in it travelling entirely through space and experiencing no time passing. There's a whole bunch of effects that result from this like length contraction and time dilation.

Space expansion is very different, It has nothing to do with the object you are observing, it is instead a property of the space between you and the object. In a sense neither object has relative motion, instead the ruler you are using to measure the distance between the two is changing it's length.

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ZincMan t1_j1i6t4n wrote

Fucking hell. I don’t even understand your first sentence. However what your 2nd paragraph is saying I think I get. Does expansion not count as moving through space ? I understand expansion speed is relative to the observer, but surely the fastest things could expand away from each other has to be twice the speed of light right ? Like if two objects are “expanding” away from each other at the speed of light in opposite directions… their relative speed to each other would seem as though they are traveling twice the speed of light right ? (Assuming you could observe) I guess my questions is can expansion travel faster than this ? Faster than two objects speeding away from each other at light speed ? I don’t get the difference between travel vs expansion. Is expansion actually Stretching reality itself?

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woodlark14 t1_j1iczf1 wrote

Apologies, relativity is quite hard to explain especially without diagrams. The answer to your other questions is that it is reality that is stretching, the distance between two galaxies becomes larger rather than one of the two galaxies moving into a new space. So it's not limited by the speed of light.

As for your questions about the fastest two things can move away from each other, that's actually a more complicated question than you realise. The issue here is that the maximum speed anything can be observed to be moving at is the speed of light. If you took two objects moving away from you at 0.75c (0.75 times the speed of light) then from the perspective of one of those objects the other wouldn't be moving at 1.5c. Instead it would be moving at 0.96c, and you would notice that clocks on the objects no longer match yours.

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JasonMontell2501 t1_j1gxmnj wrote

It actually is the speed limit for everything except the universe itself

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