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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?

#151

Post by zaarn »

rokalakt1337 wrote: post #150
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.

So does this mean speed faster than light is possible?

Two objects can move away from eachother faster than the speed of light as seen by a third observer.

The space between objects can also expand faster than light, the object itself can still not move faster than light. If the space between two objects is expanding faster than light then for all intents and purposes, the other objects no longer exists to another. There is no way to contact or observe that object other than the light that was send your way before space went FTL.

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

#152

Post by wruza »

dragonwriter wrote: post #124
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 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.

But that would be a wrong analogy. Cool thing about a balloon surface is that it expands distances between fixed points on it (ants if you want). But that doesn’t happen exactly the same way to a space inside of a balloon, it just grows at its border without dragging any reference frames.

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

#153

Post by eru »

zaarn wrote: post #151
rokalakt1337 wrote: post #150

Earlier quoted context omitted.

So does this mean speed faster than light is possible?

Two objects can move away from eachother faster than the speed of light as seen by a third observer. The space between objects can also expand faster than light, the object itself can still not move faster than light. If the space between two objects is expanding faster than light then for all intents and purposes, the other objects no longer exists to another. There is no way to contact or observe that object other…

To give another example:

If you have a laser pointer and flick your wrist fast enough, the spot on the ground that your cat chases can move faster than light without violating any laws of physics.

That's perhaps easier to see, if you think of a giant laserpointer aimed at the moon.

Similarly, a shadow on the wall can move faster than the speed of light.

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

#154

Post by pure-awesome »

rokalakt1337 wrote: post #150
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.

So does this mean speed faster than light is possible?

The proper formulation of the light-speed restriction is that no information can travel between two points in space faster than light-speed.

The expansion of space itself doesn't violate that - you couldn't use it to communicate with someone in an FTL way.

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

#155

Post by eru »

spc476 wrote: post #147
pkofod wrote: post #143

Earlier quoted context omitted.

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."

Hmm, but it looks like the universe is flat, doesn't it?

(Or is it flat like a torus, so doesn't need any curvature to go loop on itself?)

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

#156

Post by semi-extrinsic »

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…

Others have mentioned the "expanding ballon" analogy. But personally I find this more intuitive:

Imagine you are baking sweet rolls with raisins in them. When you are proofing your dough, the yeast makes the dough expand in each point, so all the raisins become further apart.

Now imagine starting with an infinite dough. As it is proofing, it will still be infinite, but there will be a measurable increase in the distance between raisins, and the speed of how quickly a specific raisin moves away from another one increases linearly with how far they are apart when you start measuring.

That's all "expansion of space" really is. We can see other stars moving away from our own, and the stars far away are moving away faster than those close to us. And since looking outwards is looking backwards in time, we can only see as far away as corresponds to the first stars that were formed.

And maybe you've heard that we can observe "expansion is slowing down". That is actually the fact that we measure a deviation from linearity in speed vs. distance.

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

#157

Post by Aenyn »

eru wrote: post #153
zaarn wrote: post #151

Earlier quoted context omitted.

Two objects can move away from eachother faster than the speed of light as seen by a third observer. The space between objects can also expand faster than light, the object itself can still not move faster than light. If the space between two objects is expanding faster than light then for all intents and purposes, the other objects no longer exists to another. There is no way to contact or observe that object other…

To give another example: If you have a laser pointer and flick your wrist fast enough, the spot on the ground that your cat chases can move faster than light without violating any laws of physics. That's perhaps easier to see, if you think of a giant laserpointer aimed at the moon. Similarly, a shadow on the wall can move faster than the speed of light.

Wouldn't there be a delay between the time you flicked your wrist and the time the spot actually aligns, due to the limited speed of light?

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

#158

Post by eecc »

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.

Aah of course... somehow we should believe that at some stage something accelerated to an impossible - according to all current observation - speed and then decelerated, somehow dissipating this energy somewhere.

Just to fit a bunch of observations that wouldn't otherwise make sense for the current model.

I remember the story of a chap from Pisa having a hard time trying to budge a bunch of clerics to consider his observations proof that their model was broken. ;)

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

#159

Post by doliveira »

Aenyn wrote: post #157
eru wrote: post #153

Earlier quoted context omitted.

To give another example: If you have a laser pointer and flick your wrist fast enough, the spot on the ground that your cat chases can move faster than light without violating any laws of physics. That's perhaps easier to see, if you think of a giant laserpointer aimed at the moon. Similarly, a shadow on the wall can move faster than the speed of light.

Wouldn't there be a delay between the time you flicked your wrist and the time the spot actually aligns, due to the limited speed of light?

Yeah, and observing this is a good way to see that information isn't actually being transferred faster than light.

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

#160

Post by caspper69 »

eecc wrote: post #158
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.

Aah of course... somehow we should believe that at some stage something accelerated to an impossible - according to all current observation - speed and then decelerated, somehow dissipating this energy somewhere. Just to fit a bunch of observations that wouldn't otherwise make sense for the current model. I remember the story of a chap from Pisa having a hard time trying to budge a bunch of clerics to consider his ob…

No, it is that spacetime itself is expanding. Nothing with mass accelerated to an impossible speed.
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