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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?

#121

Post by sytelus »

devnulloverflow wrote: post #116
laurencei wrote: post #115

Earlier quoted context omitted.

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?

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…

I'm bit confused. Regardless of expansion, these objects are right now > 13.8B ly away. So the light from them still needs that much time to get here. If light from them has arrived sooner, we would see less redshift and perceive them as a closer. No?

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

#122

Post by edf13 »

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…

The “nothing” is the one thing I find fascinating ~ maybe it’s our human brains that can’t get it but it just doesn’t work for me!

There has to be something doesn’t there?

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

#123

Post by sytelus »

marzell wrote: post #70
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…

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'?

One of the interesting things is that if everyone of us did manage to travel almost at the speed of light then time stops and you can be in universe wherever you want in matter of your seconds. In other words, whole universe just becomes giant wormhole and you teleport from wherever to wherever in matter of seconds at whim. If you reach to the edge of time dimension, the space dimension basically seize the exist.

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

#124

Post by dragonwriter »

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…

The expanding balloon analogy is often used with the wrong audience and badly misleading there: the surface of the balloon is a 2d analogy for the universe and it's expansion, rather than the interior of the balloon being a 3d analogy.

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

#125

Post by paulmooreparks »

lacker wrote: post #99
leggomylibro wrote: post #98

Earlier quoted context omitted.

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.

True, but we can see galaxies that are already over the "light horizon." In other words, we can see light emitted from those galaxies when they were within the light horizon (the point where they were receding from us at less than c), and that light has a causal effect on us. Light emitted from the galaxy now, however, will never reach us because it is already receding from us faster than the speed of light.

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

#126

Post by gpderetta »

leggomylibro wrote: post #101
lacker wrote: post #99

Earlier quoted context omitted.

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.

I guess that makes sense, thanks. I was wondering if it might have been something like the theories of what might happen much later in the universe's life, where things eventually get so far apart while still accelerating that light can't travel between them. But it couldn't be something like that if we can see the other galaxy, right?

At some point in the far distant future the night sky will be black, with everything being beyond our visible edge of the universe.

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

#127

Post by undreren »

sytelus wrote: post #121
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…

I'm bit confused. Regardless of expansion, these objects are right now > 13.8B ly away. So the light from them still needs that much time to get here. If light from them has arrived sooner, we would see less redshift and perceive them as a closer. No?

The light we see is from when the galaxy was closer. As the light left the galaxy and travelled towards us, the universe expanded "between" the photons and the galaxy.

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

#128

Post by undreren »

devnulloverflow wrote: post #116
laurencei wrote: post #115

Earlier quoted context omitted.

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?

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…

The ant and balloon analogy is really good from an intuition stand point. Great explanation! Well done :)

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

#129

Post by misterman0 »

edf13 wrote: post #122
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…

The “nothing” is the one thing I find fascinating ~ maybe it’s our human brains that can’t get it but it just doesn’t work for me! There has to be something doesn’t there?

Don't you find the fact there is something to be equally weird? I mean, first there was nothing and everything was as it should be. Then: something! And time!

This is why I think the notion of free will is wrong. The initial nothingness wasn't nothing. It was mass, but without time. The way the particles were arranged in this nothingness determines a future that has already been carved in mass.

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

#130

Post by vidarh »

edf13 wrote: post #122
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…

The “nothing” is the one thing I find fascinating ~ maybe it’s our human brains that can’t get it but it just doesn’t work for me! There has to be something doesn’t there?

A way of thinking about it is that space isn't "something". Space is just the gaps between "something".

It seems like a lot of people think of the universe as a sort of container/volume that things exist inside, and then what is "outside the box" is a natural question, because there is a boundary to pass.

If you instead think of it as simply a description of the extent of a set of objects, it's easier. Picture a simulated universe with no fixed boundary, just a set of objects with coordinates.

"The universe" is just the set of objects, and it's volume is just the volume encompassing all of those objects at any time. The simulation doesn't contain any "space". Space in the simulation is just an absence of objects, and there's nothing special about "outside" or "inside" in that situation. If the objects move further away, the universe gets bigger. If you "travel" to the edge of the universe, and travel further, the universe gets bigger. If you try to traverse the current "edge of the universe", the edge moves with you.

There are theories where there might be something "outside" our universe in one or more dimensions, but there's no reason why something absolutely needs to have an "outside".

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