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.

Mostly because space and time are most likely a result of the Big Bang. For all we can tell, "the beginning" was an infinitely dense singularity of space time - there is no "very far from the Big Bang", because, there's no space.

Yes, you can somewhat debate that - we're not entirely clear what happened in the first 10^-33 seconds - but we don't know anything about that.

So you might as well say "what evidence is there that the universe wasn't the spawn of two extremely short-lived green bunnies", and the answer is "none", too.

THat's one theory. Another is Eternal Inflation.

I thought that theory had issues with quantum gravity?

But either way, inflation would happen in that 10^-33 span I mentioned above. We simply don't know.

And even if we assume it holds, inflation is an extremely rapid expansion of space-time, so the idea that there were things "very far from each other" still does not really hold.

And IIRC, Penrose and Hawkings disproved the idea that inflationary models can avoid an initial singularity[1]. I'd be somewhat surprised to see them disproven.

[1] https://en.wikipedia.org/wiki/Penrose%E2%80%93Hawking_singul...

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 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?

> ...but the idea that space is expanding implies an outer "edge"

No, it doesn't.

For example: consider an infinite number of marbles in an infinitely long line, all of them are touching each other.

Now, get an infinite number of helpers stationed along the infinitely long line, and have them all move the marbles in front of them to the right and stagger them out in the process, so that there's now an inch between each marble.

You now have an infinite number of marbles an infinitely long line, but it's a longer line than it started out, because there's now an inch between all the marbles.

You will need infinite amount of energy to insert spaces between these marbles. Can you point us to source of this energy?

The theory of the Big Bang (or at least the variants with an infinite universe) includes infinite energy as part of the initial singularity.

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.

Which leads to the follow up question: if you travel far enough in one direction do you end up where you started? (well, no, not if space expands faster than c).

If it wasn't for the expansion, and if the universe had positive curvature, then yes.

As it stands, there's not only the expansion, but the universe also seems to be flat -- meaning it's spatially infinite, not just borderless. That observation is also compatible with a very, very small curvature, but in that case the size would still be so large that it wouldn't be practically possible to circumnavigate even if it wasn't expanding.

> * ...but the idea that space is expanding implies an outer "edge"

Space expension just means that the metric used to measure distance increases with time. It doesn't imply a border.

Consider the function equivalent to the Euclidian distance on a line : d(x1,x2) = sqrt((x2-x1)^2)

Now, you can consider the function : d2(x1,x2,y) = y * d(x1,x2)

If you view x1 and x2 as positions on one axis and y as a position on the other one, you can think of d2 as the distance between x1 and x2 expanding as you go higher in the plane.

Space expansion works in the same way but y is actually time.

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.

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.

[0,1] is not less infinite than [0,2]. Also the less does not need quotes, there is an ordering of infinities.

Edit: typo

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.

You are probably being downvoted because the big bang, our ability to estimate the age of the universe, etc is believed to be a fact by many including astronomers and astrophysicists. And yet there are so many unanswered questions that it is reasonable to question those things. In this case, it calls into question our age estimation for both planets and the universe.

That's great, but The Big Bang is more or less chasing a status as the canonical answer to an intensely desirable question.

It wants to be the answer, yet the facts don't really align with the premise of the question. We just shoe horn a litter of observations into some post-hoc rationale for how the universe "began" and then we retcon anything that doesn't make sense, when we think more deeply about it.

It's fine to have cosmic background radiation, and elemental distributions and ratios, and sure that all kind of lines up, pointing to some large, highly influential event in the past.

But just because we can chart certain facts doesn't mean the story stops where our charts end.

I'll concede that something really important happened 13-ish billion years ago, and that it represents a significant temporal horizon, beyond which we cannot draw conclusions, yet because we cannot see beyond the peaks of some mountain range does not mean the edge of the world resides on the other side.

All the mental backflips required to rationalize The Big Bang, and then from the other side of your mouth, murmur that it actually wasn't a "bang" but instead an "expansion" really just result in a colossal defrocking of the theory.

  Hey look guys, here comes
  emperor Big Bang in his
  super comfy new clothes!

Sorry, but if it's not actually a bang, don't call it a bang.

And if it seems that we don't really know what was going on, as we try to recreate a march back inward to the hypothetical origin singularity, and every time we try to walk events backward, they stop making sense, we just need to say we don't really know.

The Big Bang is a smelly theory, and it smells wrong. There's a lot of evidence of a really powerful event some 13 billion years ago, and it may have been transformative, but there's no basis to the claim that it was truly event zero.

Just as possible is that we're the fallout of some localized very large bang, that cleared out a radius of space time that is more distant than we can observe. This idea is not interchangeable with the big bang origin story of the universe. It's not an Occam's razor victory in favor of the big bang.

If we are stuck within a spatial temporal crater as the result of a non-unique very large bang, it would mean that we can look differently at how we model the bang, and come up with saner conclusions than "oh, it just popped into existence, and then went kablooey, and that's okay because the very idea of time is bound to that ever even happening at all."

Like, sorry, that hand wavey whitewash doesn't adequately paper over the possibility of retconning some nonsense into the narrative, because it would be a threat to academic authority to say "we don't know" regarding the nature of a hypothetical origin singularity.

I get that there's no evidence beyond the reaches of our deepest observations, but it's lazy to put forward that because we can't grasp at evidence beyond certain terrestrial limits, then we get to say that we know conclusively that the observable limits are known to be the actual limits and thus the assured origin of all space time.

What we should say is that there is a depth beyond which we cannot summon further evidence, and while there seems to be some tumultuous event back there, we don't know what happens prior to that or where that limit comes from.

Because we really don't know.

So your chief complaint is that people call it a bang instead of an expansion? Obviously from my comments you'll see I agree we're a little over-confident in all the specifics, but the question isn't "was it event 0", which I don't think anyone has really claimed, but could events, specifically this star, that occurred outside of the horizon of that expansion now have moved into our visible universe.

If that's not what you're saying I really cannot see what point you're making.