10 ms·

Short answer: it's only older than the universe if you ignore the error bars of the estimate.

by novia 7y ago

TallGuyShort 7y ago
And it's only older than the universe if you assume the Big Bang was the beginning of the universe, which there's really no evidence to suggest. Pretty much everything else in the universe all seems to suggest that it all originated from a similar point in time and space and that it rapidly expanded outward. Okay. But what was going on in this particular space back then is completely unknown, so... could there have been some stars forming already from matter that wasn't part of the Big Bang? Why not?
- jerf 7y ago
  Even ignoring complicated questions about gravity and space metrics and their evolution over time, if a big bang occurred in an occupied region of space, we'd see the results of these two things crashing together. We see similar, but much smaller, such things all over the place in space. We do not see any collisions best explained this way.
  - dmix 7y ago
    What would it even look like if it was occupied space? Uneven expansion?
    - jerf 7y ago
      Colliding bits of material produce light. Even colliding hydrogen clouds produce detectable signatures. If, for the sake of argument, two big bangs occurred and we could see where they met, there would be a large visible region in the universe putting out some sort of photons. (Not necessarily visible ones.) More subtle things would be visible too, like, yes, interacting gravity fields, but it wouldn't take such clever analysis; the impact points would literally light up in the sky.
  - TallGuyShort 7y ago
    As I've said in another comment, in most of the time since the Big Bang space was been extremely sparse. If there's 1 example of a star that could maybe be older than the rest of it, what makes you think we'd be seeing collisions more frequently if some stuff existed at the time of the Big Bang. I'm not even suggesting there was a second Big Bang that immediately preceded the one we already talk about. But other than theory, we know nothing about pre-Big Bang conditions, so I don't see how we can reason with confidence about how nothing within the current bubble of the observable universe could possibly have existed outside of that bubble at any point. Maybe with the star's current direction it's consistent with the same Big Bang, but we seem awfully confident about conditions we've never observed.
    - jerf 7y ago
      Because as "extremely sparse" as it may be, colliding gas clouds still light up. To try to express in English what properly ought to be math, space is really, really, really empty... but it isn't really, really, really, really empty. Everywhere there's a bit of at least hydrogen gas, and we'd probably see it if even two of the emptiest regions of space were colliding. I'm presuming this is happening at some non-trivial relative velocity on the grounds that it's hardly a "big bang" if it's actually in the same velocity vector as the location in which it occurs, and doesn't have any new material coming out. You're kind of overextrapolating the "we know nothing about pre-Big Bang conditions" based on the English phrasing of a more mathematical idea. We can eliminate some things, like as we are discussing, the possibility that the Big Bang occurred in an already-existing universe in some way that it could create a visibly older star showing up a mere 100-200 light years from us. I can't eliminate the possibility that there's some "collision" happening out of our past light cone, or that a Big Bang occurred and that taking into account metrics of space this time, that it simply "blew" all the old universe out of our past light cone as our universe inflated. But I can eliminate the idea of some older universe being something we could co-exist in local space with. It would produce visibly obvious results that we do not see, a fairly violent cataclysm that would have results that we could see. As we parse the Cosmic Microwave Background, we're parsing twitches and fluctuations far, far smaller than such an event would have created. This would be writ large on the sky, not something that could sneakily inject a star into our galaxy that we only notice after hundreds of years of astronomical observations. We can't make very many positive assertions about pre-Big-Bang conditions, but we can make a few negative ones like this. I'd also point out it's not an intrinsically crazy idea. Some variants of String Theory hypothesize situations in which it would be possible for a "Big Bang" to occur in an existing universe like ours, due to membrane collisions. It could well have happened elsewhere. It just doesn't seem to have happened in our past lightcone.
- cbzbc 7y ago
  (That) Space was also created by the big bang.
  - TallGuyShort 7y ago
    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.
    - deleted 7y ago
      [deleted]
    - amelius 7y ago
      The universe is expanding. This started at some point, and I suppose the theory says that it started at the point where there was no space.
      - TallGuyShort 7y ago
        Correct me if any of the following is wrong, though: when we say the universe is expanding, we mean that matter is spreading out. The further apart the matter is, the faster it's spreading out. If we back-trace the position of stars, they all coincide at roughly the same point in time and space. This led us to believe that at some point in time all of this matter was together, incredibly dense, and in a very "hot", high-energy state. This led to the prediction that has since been confirmed, that from the furthest reaches of the observable universe, we would see cosmic background radiation. And as time goes, that cosmic background radiation is getting further and further away, so the observable bubble is expanding. Maybe I have some of that wrong, but that's my understanding. None of that means that the fabric of space (as in space-time) is actually expanding. And even if it did, none of that means that nothing could have existed outside of the observable bubble billions of years ago, and could have since been passed by the observable edge and now be inside that observable bubble. Unless maybe the source of the background radiation was still dense / high-energy enough to absolutely obliterate everything in it's path. And maybe it was? But I just don't see how we can reason about what was outside of the observable bubble.
- bardworx 7y ago
  But why would that matter? If, like you said "...all originated from a similar point in time and space and that it rapidly expanded outward", any star forming next to it would be pushed out of the observable edge. Hence, no one would ever know if a star was there in the first place.
  - TallGuyShort 7y ago
    Our universe in it's recent state is incredibly sparse. What would have pushed a star out of the observable edge, exactly?
    - svachalek 7y ago
      The Big Bang was not (or not only) an expansion of matter, it's an expansion of space itself; the known universe is an enormous place that expanded out of a microscopic one. If there was space before the Big Bang, presumably it's been displaced by the sudden appearance of the entire universe as we know it. Not just the things in it but all the empty parts too, especially the empty parts.
- sorenn111 7y ago
  Quark Gluon Plasma (observed at the RHIC), at really early in the universe there was too much temperature and pressure to have stars or even atoms. At least that's my understanding.
  - TallGuyShort 7y ago
    Yes but Quark Gluon Plasma existed immediately following the Big Bang. We arrive at the Big Bang by reverse engineering lots of evidence we see in the universe. What evidence is there that nothing else currently inside the bubble of the observable universe could possibly have been there, very far away from the Big Bang, at the time of the Big Bang? I don't see why I'm being down-voted because as of yet no one has answered that question. I'm not saying the Big Bang didn't happen. I'm saying we have no observations that give us any confidence we'll never encounter something that wasn't part of the Big Bang. This star actually pre-dating the Big Bang is extremely unlikely, I agree. The simpler explanation is the uncertainty in it's age estimation. But equating "the observable universe" with "stuff that originated in the Big Bang" is an assumption we simply don't have much reasoning for, other than we haven't seen much other stuff. But then... we also don't see many stars this old.
    - semi-extrinsic 7y ago
      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".
      - labster 7y ago
        I don’t care where you have your Big Bang, Just as long as there’s no Big Bang, nuclear power, or homeless shelter in my back yard.
      - ergothus 7y ago
        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 make sense if space isn't infinite. (or is it infinite, and just getting "more" infinite, in the way that the space on the number line between 0 and 1 is infinite, but "less" infinite than between 0 and 2?
joe_the_user 7y ago
I thought the answer was more like "all our figures are quite rough currently and a lot of work needs to be done". They mention that the current universe age fits "within the bars", for example but also mention arguments for universe being younger as well, which would again put the measurements at odds. Basically, both of these values involve a string of assumptions and while getting every single one of them to high accuracy is a remarkable achievement, the chance of some glitch in either measurement is significant.

Short answer: it's only older than the universe if you ignore the error bars of the estimate.

by novia 7y ago

Short answer: it's only older than the universe if you ignore the error bars of the estimate.

And it's only older than the universe if you assume the Big Bang was the beginning of the universe, which there's really no evidence to suggest. Pretty much everything else in the universe all seems to suggest that it all originated from a similar point in time and space and that it rapidly expanded outward. Okay. But what was going on in this particular space back then is completely unknown, so... could there have been some stars forming already from matter that wasn't part of the Big Bang? Why not?

jerf 7y ago
Even ignoring complicated questions about gravity and space metrics and their evolution over time, if a big bang occurred in an occupied region of space, we'd see the results of these two things crashing together. We see similar, but much smaller, such things all over the place in space. We do not see any collisions best explained this way.
- dmix 7y ago
  What would it even look like if it was occupied space? Uneven expansion?
  - jerf 7y ago
    Colliding bits of material produce light. Even colliding hydrogen clouds produce detectable signatures. If, for the sake of argument, two big bangs occurred and we could see where they met, there would be a large visible region in the universe putting out some sort of photons. (Not necessarily visible ones.) More subtle things would be visible too, like, yes, interacting gravity fields, but it wouldn't take such clever analysis; the impact points would literally light up in the sky.
- TallGuyShort 7y ago
  As I've said in another comment, in most of the time since the Big Bang space was been extremely sparse. If there's 1 example of a star that could maybe be older than the rest of it, what makes you think we'd be seeing collisions more frequently if some stuff existed at the time of the Big Bang. I'm not even suggesting there was a second Big Bang that immediately preceded the one we already talk about. But other than theory, we know nothing about pre-Big Bang conditions, so I don't see how we can reason with confidence about how nothing within the current bubble of the observable universe could possibly have existed outside of that bubble at any point. Maybe with the star's current direction it's consistent with the same Big Bang, but we seem awfully confident about conditions we've never observed.
  - jerf 7y ago
    Because as "extremely sparse" as it may be, colliding gas clouds still light up. To try to express in English what properly ought to be math, space is really, really, really empty... but it isn't really, really, really, really empty. Everywhere there's a bit of at least hydrogen gas, and we'd probably see it if even two of the emptiest regions of space were colliding. I'm presuming this is happening at some non-trivial relative velocity on the grounds that it's hardly a "big bang" if it's actually in the same velocity vector as the location in which it occurs, and doesn't have any new material coming out. You're kind of overextrapolating the "we know nothing about pre-Big Bang conditions" based on the English phrasing of a more mathematical idea. We can eliminate some things, like as we are discussing, the possibility that the Big Bang occurred in an already-existing universe in some way that it could create a visibly older star showing up a mere 100-200 light years from us. I can't eliminate the possibility that there's some "collision" happening out of our past light cone, or that a Big Bang occurred and that taking into account metrics of space this time, that it simply "blew" all the old universe out of our past light cone as our universe inflated. But I can eliminate the idea of some older universe being something we could co-exist in local space with. It would produce visibly obvious results that we do not see, a fairly violent cataclysm that would have results that we could see. As we parse the Cosmic Microwave Background, we're parsing twitches and fluctuations far, far smaller than such an event would have created. This would be writ large on the sky, not something that could sneakily inject a star into our galaxy that we only notice after hundreds of years of astronomical observations. We can't make very many positive assertions about pre-Big-Bang conditions, but we can make a few negative ones like this. I'd also point out it's not an intrinsically crazy idea. Some variants of String Theory hypothesize situations in which it would be possible for a "Big Bang" to occur in an existing universe like ours, due to membrane collisions. It could well have happened elsewhere. It just doesn't seem to have happened in our past lightcone.
cbzbc 7y ago
(That) Space was also created by the big bang.
- TallGuyShort 7y ago
  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.
  - deleted 7y ago
    [deleted]
  - amelius 7y ago
    The universe is expanding. This started at some point, and I suppose the theory says that it started at the point where there was no space.
    - TallGuyShort 7y ago
      Correct me if any of the following is wrong, though: when we say the universe is expanding, we mean that matter is spreading out. The further apart the matter is, the faster it's spreading out. If we back-trace the position of stars, they all coincide at roughly the same point in time and space. This led us to believe that at some point in time all of this matter was together, incredibly dense, and in a very "hot", high-energy state. This led to the prediction that has since been confirmed, that from the furthest reaches of the observable universe, we would see cosmic background radiation. And as time goes, that cosmic background radiation is getting further and further away, so the observable bubble is expanding. Maybe I have some of that wrong, but that's my understanding. None of that means that the fabric of space (as in space-time) is actually expanding. And even if it did, none of that means that nothing could have existed outside of the observable bubble billions of years ago, and could have since been passed by the observable edge and now be inside that observable bubble. Unless maybe the source of the background radiation was still dense / high-energy enough to absolutely obliterate everything in it's path. And maybe it was? But I just don't see how we can reason about what was outside of the observable bubble.
bardworx 7y ago
But why would that matter? If, like you said "...all originated from a similar point in time and space and that it rapidly expanded outward", any star forming next to it would be pushed out of the observable edge. Hence, no one would ever know if a star was there in the first place.
- TallGuyShort 7y ago
  Our universe in it's recent state is incredibly sparse. What would have pushed a star out of the observable edge, exactly?
  - svachalek 7y ago
    The Big Bang was not (or not only) an expansion of matter, it's an expansion of space itself; the known universe is an enormous place that expanded out of a microscopic one. If there was space before the Big Bang, presumably it's been displaced by the sudden appearance of the entire universe as we know it. Not just the things in it but all the empty parts too, especially the empty parts.
sorenn111 7y ago
Quark Gluon Plasma (observed at the RHIC), at really early in the universe there was too much temperature and pressure to have stars or even atoms. At least that's my understanding.
- TallGuyShort 7y ago
  Yes but Quark Gluon Plasma existed immediately following the Big Bang. We arrive at the Big Bang by reverse engineering lots of evidence we see in the universe. What evidence is there that nothing else currently inside the bubble of the observable universe could possibly have been there, very far away from the Big Bang, at the time of the Big Bang? I don't see why I'm being down-voted because as of yet no one has answered that question. I'm not saying the Big Bang didn't happen. I'm saying we have no observations that give us any confidence we'll never encounter something that wasn't part of the Big Bang. This star actually pre-dating the Big Bang is extremely unlikely, I agree. The simpler explanation is the uncertainty in it's age estimation. But equating "the observable universe" with "stuff that originated in the Big Bang" is an assumption we simply don't have much reasoning for, other than we haven't seen much other stuff. But then... we also don't see many stars this old.
  - semi-extrinsic 7y ago
    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".
    - labster 7y ago
      I don’t care where you have your Big Bang, Just as long as there’s no Big Bang, nuclear power, or homeless shelter in my back yard.
    - ergothus 7y ago
      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 make sense if space isn't infinite. (or is it infinite, and just getting "more" infinite, in the way that the space on the number line between 0 and 1 is infinite, but "less" infinite than between 0 and 2?

joe_the_user 7y ago

I thought the answer was more like "all our figures are quite rough currently and a lot of work needs to be done". They mention that the current universe age fits "within the bars", for example but also mention arguments for universe being younger as well, which would again put the measurements at odds. Basically, both of these values involve a string of assumptions and while getting every single one of them to high accuracy is a remarkable achievement, the chance of some glitch in either measurement is significant.