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How Can a Star Be Older Than the Universe?

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Re: How Can a Star Be Older Than the Universe?

#91

Post by mannykannot »

swebs wrote: post #87
mannykannot wrote: post #54

Earlier quoted context omitted.

Perhaps a big bang that's 'just' an explosion in spacetime, rather than of spacetime, would not work with known physics because that concentration of that much matter would be a black hole? Until now, I never thought to ask anyone.

It wouldn't work out because it wouldn't match what our telescopes are observing. This image has a good example of what's happening https://upload.wikimedia.org/wikipedia/commons/c/c7/Space_Ex... You can see that from any given point: 1. Every other point is moving away from you 2. Points further away are moving away at a faster rate This could only work out if space were expanding. If it were an explosion instead, e…

That actually demonstrates the opposite: despite the fact that the images themselves show the expansion of a grid in a two-dimensional space, each of the dots appears, from its perspective, to be at the center of the expansion, unless you either specify an absolute frame of reference, or (which amounts to the same thing) can identify the edge of the expanding region.

Furthermore, our telescopes have only observed from the vicinity of the sun - we have not actually seen what the universe looks like from another star. Of course, we can figure out what it would look like, but if that is your argument, then it is circular.

Re: How Can a Star Be Older Than the Universe?

#93

Post by Filligree »

namirez wrote: post #71
marzell wrote: post #70

Earlier quoted context omitted.

Seriously... what's the difference between 'universe expansion' and 'travel'? A particle can't travel faster than c but it can effectively if the universe expands in addition to its travel speed? Are there any established sci-fi concepts that replace the concepts of wormholes with 'universe compression'?

Yes, it's called Alcubierre Drive, where spacetime is compressed in front and expanded behind a ship to drive it through the spacetime like a gravitational wave. https://en.wikipedia.org/wiki/Alcubierre_drive

Or the Krasnikov tube, where time is tilted such that travel through it (in one direction) takes you back in time (from a stationary perspective).

That's very similar to a wormhole, but without the topological flaw.

Re: How Can a Star Be Older Than the Universe?

#94

Post by Filligree »

tux1968 wrote: post #82
semiotagonal wrote: post #77

Earlier quoted context omitted.

Is it possible that the universe stays the same size and everything within it shrinks?

Don't think there is a way to tell the difference without stepping outside the universe to look back on the system relative to another frame. But AFAIU, there is no edge to the universe with an unknown something beyond the barrier. Space is not an expanding balloon inside a bigger balloon. Ie, there is no space beyond space. Not that i'm truly able to wrap my head around it, but at the moment of the big bang, time an…

> But AFAIU, there is no edge to the universe with an unknown something beyond the barrier. Space is not an expanding balloon inside a bigger balloon. Ie, there is no space beyond space.

Eternal inflation, if correct, states that there is indeed something which our universe is expanding into. (But even if that's the case, that still has nothing to do with the expansion we've been talking about.)

Re: How Can a Star Be Older Than the Universe?

#95

Post by tidenly »

ergothus wrote: post #58
semi-extrinsic wrote: post #49

Earlier quoted context omitted.

All the evidence suggests that Big Bang did not happen at one identifiable point. Instead it happened everywhere simultaneously. So there is no place in our universe "very far away from the Big Bang".

Not the above poster, but I want to understand. I have half-understood thoughts that conflict with each other. Any help showing where I misunderstand is appreciated, but this is probably a failure of my brain to be able to cope. * All space was contained in the big bang, so "everywhere simultaneously" makes sense from that perspective. * ...but the idea that space is expanding implies an outer "edge" (, which doesn't…

A less brain melting way to imagine the "expansion without edge" thing is the classic balloon system. Imagine your entire universe exists across the plain of a semi-deflated balloon and then someone slowly begins to blow it up. The "space" in your 2D world is expanding, but there are no edges.

Re: How Can a Star Be Older Than the Universe?

#96

Post by Filligree »

graedus wrote: post #60
ergothus wrote: post #58

Earlier quoted context omitted.

Not the above poster, but I want to understand. I have half-understood thoughts that conflict with each other. Any help showing where I misunderstand is appreciated, but this is probably a failure of my brain to be able to cope. * All space was contained in the big bang, so "everywhere simultaneously" makes sense from that perspective. * ...but the idea that space is expanding implies an outer "edge" (, which doesn't…

Layman here. To your second bullet, yes, the universe can be infinite but also be expanding. A rough analogy I've heard is that there are infinite points on the surface of a balloon, but if you blow it up more, the distance between any two given points will be greater than it was, so it has expanded. I don't think we know if the universe is infinitely large or not though.

We don't know, but the universe appears to be perfectly flat, which would indicate it's infinite.

That could also just be due to inflation, mind.

Re: How Can a Star Be Older Than the Universe?

#97

Post by Filligree »

inetknght wrote: post #19
yongjik wrote: post #14

Earlier quoted context omitted.

I don't think there's such a concept as "higher-gravity region" in modern physics, unless you're thinking about "in the vicinity of a giant star, black hole, or something equally massive." However, if most of the known universe is sitting next to a gigantic mega-blackhole (or enough of them to cover the whole sky), then surely we would have noticed by now...

> I don't think there's such a concept as "higher-gravity region" in modern physics, unless you're thinking about "in the vicinity of a giant star, black hole, or something equally massive." I think at the beginning of the universe, there might be a lot of regional discrepancies. They might even just be "temporary" regional discrepancies from gravitational waves due to the inherent nature of the universe growing and…

The cosmic microwave background tells us there were practically no discrepancies at all, actually. Not too surprising, since at the densities back then even a small local fluctuation would easily have become a black hole.

The very early universe wasn't perfectly uniform, but it was really, really close.

Re: How Can a Star Be Older Than the Universe?

#98

Post by leggomylibro »

ajay-d wrote: post #59

GN-z11 is a galaxy that's 32 billion light years away. Here's the note from wikipedia: At first glance, the distance of 32 billion light-years (9.8 billion parsecs) might seem impossibly far away in a Universe that is only 13.8 billion (short scale) years old, where a light-year is the distance light travels in a year, and where nothing can travel faster than the speed of light. However, because of the expansion of t…

So, is it possible for an event in the Milky Way to ever affect GN-z11 (or vice-versa)? Or are the galaxies permanently 'read-only' to each other?

Re: How Can a Star Be Older Than the Universe?

#99

Post by lacker »

leggomylibro wrote: post #98
ajay-d wrote: post #59

GN-z11 is a galaxy that's 32 billion light years away. Here's the note from wikipedia: At first glance, the distance of 32 billion light-years (9.8 billion parsecs) might seem impossibly far away in a Universe that is only 13.8 billion (short scale) years old, where a light-year is the distance light travels in a year, and where nothing can travel faster than the speed of light. However, because of the expansion of t…

So, is it possible for an event in the Milky Way to ever affect GN-z11 (or vice-versa)? Or are the galaxies permanently 'read-only' to each other?

There is no such thing as “read-only” in physics. If we can observe the other galaxy, that means it is affecting the particles in this galaxy. Even if it’s just a single molecule in a telescope responding to a photon that hit it from the other universe.

Re: How Can a Star Be Older Than the Universe?

#100

Post by wlesieutre »

Filligree wrote: post #94
tux1968 wrote: post #82

Earlier quoted context omitted.

Don't think there is a way to tell the difference without stepping outside the universe to look back on the system relative to another frame. But AFAIU, there is no edge to the universe with an unknown something beyond the barrier. Space is not an expanding balloon inside a bigger balloon. Ie, there is no space beyond space. Not that i'm truly able to wrap my head around it, but at the moment of the big bang, time an…

> But AFAIU, there is no edge to the universe with an unknown something beyond the barrier. Space is not an expanding balloon inside a bigger balloon. Ie, there is no space beyond space. Eternal inflation, if correct, states that there is indeed something which our universe is expanding into. (But even if that's the case, that still has nothing to do with the expansion we've been talking about.)

> Eternal inflation, if correct, states that there is indeed something which our universe is expanding into.

I don't think that's right. The fact that space gets bigger doesn't mean that space is inside something, it just means space gets bigger.

Disclaimer: not an astrophysicist

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