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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?

#141

Post by ggggtez »

techas wrote: post #139
devnulloverflow wrote: post #116

Earlier quoted context omitted.

Your intuition that there is an limited observable distance because is correct. But because of the expansion, that limit is bigger than "speed_of_light * age of universe" . I don't know enough General Relativity to give a solid explanation. But here is a rough over-simplification: Imagine you've spent the last 5 seconds blowing up a balloon, but there is an ant walking on that balloon, starting from a marked spot. In…

If space works as a balloon then the growth happens in all the volume of the universe (not just on the “boundary”). Is that how it works? Doesn’t that imply that we are getting “bigger”?

No. Just because space is expanding doesn't change the electromagnetic forces holding you together.

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

#142

Post by ivoras »

techas wrote: post #139
devnulloverflow wrote: post #116

Earlier quoted context omitted.

Your intuition that there is an limited observable distance because is correct. But because of the expansion, that limit is bigger than "speed_of_light * age of universe" . I don't know enough General Relativity to give a solid explanation. But here is a rough over-simplification: Imagine you've spent the last 5 seconds blowing up a balloon, but there is an ant walking on that balloon, starting from a marked spot. In…

If space works as a balloon then the growth happens in all the volume of the universe (not just on the “boundary”). Is that how it works? Doesn’t that imply that we are getting “bigger”?

(I am not a physicist) As far as I understand the current theory (i.e. our best guess), the 4 fundamental forces are somehow countering the expansion so that, even as everything in the universe expands, including e.g. every single atom, the forces are even stronger and are pulling stuff together.

I think this just opens more questions than it resolves, and would really like to hear a better explanation.

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

#143

Post by pkofod »

kijin wrote: post #118
calvertdw wrote: post #112

Earlier quoted context omitted.

As observed, it's only 13.8, though, right?

No, it's observed as 93 billion light years. That's why we call it the "observable" universe. There is no meaningful spatial boundary at a point that is currently at a distance of 13.8 billion light years from us. We can detect (severely red-shifted) photons from beyond that point perfectly fine! The actual boundary is 46.5 billion light years away in both directions, hence the "observable" diameter of 93 billion. Bu…

I feel so stupid when talking and hearing about physics... but we are not in any meaningful way "at the center" of the universe are we? Or is every point in some sense at the center (a point of reference thing)? I'm asking because why would it be 46.5 "each way"?

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

#144

Post by ivoras »

ggggtez wrote: post #141
techas wrote: post #139

Earlier quoted context omitted.

If space works as a balloon then the growth happens in all the volume of the universe (not just on the “boundary”). Is that how it works? Doesn’t that imply that we are getting “bigger”?

No. Just because space is expanding doesn't change the electromagnetic forces holding you together.

But just thinking of the electromagnetic forces in terms of what is required from them to keep matter together in the context of that same matter effectively expanding faster than the speed of light is... at best weird.

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

#145

Post by mytailorisrich »

TallGuyShort wrote: post #22
cbzbc wrote: post #18

Earlier quoted context omitted.

(That) Space was also created by the big bang.

What's the evidence of that? I'm not arguing, but between cosmic background radiation, doppler shift of stars and the relationship between speed / distance, all the evidence of the big bang I've heard doesn't suggest anything about space itself.

The concept of the "big bang" is not an 'explosion' in pre-existing space, but really is space itself expanding.

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

#146

Post by Filligree »

wlesieutre wrote: post #100
Filligree wrote: post #94

Earlier quoted context omitted.

> 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

Space does get bigger, but that's separate. What eternal inflation is claiming is that some fourteen billion years ago there was a false vacuum collapse, and we're living inside the bubble that resulted, but said bubble is itself still expanding.

It won't ever get anywhere, since space outside the bubble is inflating much, much faster than inside. It means there's a border to our universe, which is expending at lightspeed, but it's far outside the Hubble horizon and thus entirely unreachable.

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

#147

Post by spc476 »

pkofod wrote: post #143
kijin wrote: post #118

Earlier quoted context omitted.

No, it's observed as 93 billion light years. That's why we call it the "observable" universe. There is no meaningful spatial boundary at a point that is currently at a distance of 13.8 billion light years from us. We can detect (severely red-shifted) photons from beyond that point perfectly fine! The actual boundary is 46.5 billion light years away in both directions, hence the "observable" diameter of 93 billion. Bu…

I feel so stupid when talking and hearing about physics... but we are not in any meaningful way "at the center" of the universe are we? Or is every point in some sense at the center (a point of reference thing)? I'm asking because why would it be 46.5 "each way"?

Imagine we exist in a 2D universe, but one that happens to be the surface of a sphere. Any point you pick on that surface is "at the center of the universe."

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

#148

Post by Filligree »

ivoras wrote: post #144
ggggtez wrote: post #141

Earlier quoted context omitted.

No. Just because space is expanding doesn't change the electromagnetic forces holding you together.

But just thinking of the electromagnetic forces in terms of what is required from them to keep matter together in the context of that same matter effectively expanding faster than the speed of light is... at best weird.

The speed of expansion depends on the size of the object. Human-scale things aren't expanding at the speed of light; you need to get to larger-than-galaxy-cluster scales for that to happen.

(In fact space inside galaxies isn't expanding at all, only space between galaxies. But I digress.)

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

#149

Post by [deleted] »

laurencei wrote: post #115
namirez wrote: post #65

Earlier quoted context omitted.

Also, despite the age of the universe (13.8B years), the diameter of the observable universe is 93 billion light years. That's because the universe expanded (and probably still is expanding) faster than light.

Can you ELI5 - how can we observe something 93 billion light years away, if the light has only been traveling for 13.8B years? Shouldnt the "observable" distance be the the age of the universe?

[deleted]

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

#150

Post by rokalakt1337 »

namirez wrote: post #65
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…

Also, despite the age of the universe (13.8B years), the diameter of the observable universe is 93 billion light years. That's because the universe expanded (and probably still is expanding) faster than light.

So does this mean speed faster than light is possible?
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