Cosmic inflation: 'Spectacular' discovery hailed

[Skashion]

Conceptually my head doesn't get it. I was always terrible at geometry.

 

[Damocles]

At the scales which we can measure, we would see any curvature of spacetime that would indicate any overall "curved shape". Just like if you go really high in the air you can measure the curvature of the Earth and make assumptions from this.

When we measured it, it came out as flat. This means either that the Universe is Torus shaped, essentially it's too big for us to measure curvature no different from you being unable to measure the Earth's curvature from the ground and it looks flat. Or the Universe truly is flat.

Flat is simpler than a bunch of qualifiers.

For the topology of the Universe to fit into other well supported ideas we have, if it is flat then it must be infinite in size. Our observable Universe and Big Bang were just a very tiny expansion within the infinite overall.

This as you might have read is a logical house of cards.

Observable Universe is flat.
Therefore Universe is flat.
Therefore Universe is infinite.

It is an assumption built upon an assumption and the evidence isn't exactly overwhelming, it's just a consequence of how we presume things scientifically.

 

[Damocles]

[youtube]http://www.youtube.com/watch?v=ZlfIVEy_YOA[/youtube]

The father of inflation theory receiving the news for the first time. 5 sigma +/- 0.2 confidence is a nice way of saying "we're dead certain this is right". Love the reactions.

 

[Skashion]

The curvature part I understood already, although still a brilliant explanation. Damocles in very best form. What I don't understand is the assumption that the universe has to be a self-contained sphere to have an end/edge and volume. It seems to me that we're applying 3D human-relatable geometry to spacetime. Hasn't the world of quantum physics taught us the danger of this in attempting to apply macro-level understanding approximations to the micro scale and we don't know enough to be doing that? Or are there very good reasons for making this assumption?

 

[Damocles]

The curvature part I understood already, although still a brilliant explanation. Damocles in very best form. What I don't understand is the assumption that the universe has to be a self-contained sphere to have an end/edge and volume. It seems to me that we're applying 3D human-relatable geometry to spacetime. Hasn't the world of quantum physics taught us the danger of this in attempting to apply macro-level understanding approximations to the micro scale and we don't know enough to be doing that? Or are there very good reasons for making this assumption?

There's no reason and subsequently few assumptions stating that the Universe HAS to be unbounded, it's just a consequence of other ideas. The Torus shape is bounded for those that think that infinity is not a physical phenomena whereas the the flat unbounded Universe is for those who feel that an unbounded Universe is possible and the lack of infinity in human experience is due to our relatively small size compared to the entire Universe and our Earth biased comprehension rather than some inbuilt limit.

When I talk about a "flat" Universe, I mean flat infinitely. Not so much a sphere but infinite planes across our three spatial dimensions. We only have three to measure but it would theoretically be the same across all spatial dimensions so "sphere" isn't really descriptive. You have to remember thought that this is our scientific bias that is thinking this.

We presume that the Universe is the same in all directions as presuming otherwise added unnecessary complications.
We know our observable Universe is flat and expanding.
So due to this we presume that the rest of the Universe is flat and expanding.
This would suggest a flat and infinite Universe. In this sense, infinite means without an edge or boundary.

So there are reasons for this assumption but I think everybody would agree that they are bad ones coming out of convenience rather than evidence.

Something that I believe to be a very good question is that if we had a Big Bang in our observable Universe then did parts of the unobservable Universe have their own Big Bangs or is the Universe smaller than presumed? As the Big Bang is thought to have created spacetime what does this mean for the non-observable Universe in terms of how time is experienced? Due to the way that spacetime has expanded we will almost certainly never find this out as we couldn't travel far enough. However, as the Universe is infinite it would imply infinite mass which is a whole other problem.

Another recent paper I read on this subject in the wake of the new ideas on inflation talks about how the observable Universe/the Big Bang singularity is the "white hole" that we've been looking for (as a black hole would insinuate a white hole due to the ideas we have on entropy and energy).

Again, we've just put a few more balls in the air for physicists to integrate into their models and see how they hold up.

 

[Skashion]

The curvature part I understood already, although still a brilliant explanation. Damocles in very best form. What I don't understand is the assumption that the universe has to be a self-contained sphere to have an end/edge and volume. It seems to me that we're applying 3D human-relatable geometry to spacetime. Hasn't the world of quantum physics taught us the danger of this in attempting to apply macro-level understanding approximations to the micro scale and we don't know enough to be doing that? Or are there very good reasons for making this assumption?

There's no reason and subsequently few assumptions stating that the Universe HAS to be unbounded, it's just a consequence of other ideas. The Torus shape is bounded for those that think that infinity is not a physical phenomena whereas the the flat unbounded Universe is for those who feel that an unbounded Universe is possible and the lack of infinity in human experience is due to our relatively small size compared to the entire Universe and our Earth biased comprehension rather than some inbuilt limit.

When I talk about a "flat" Universe, I mean flat infinitely. Not so much a sphere but infinite planes across our three spatial dimensions. We only have three to measure but it would theoretically be the same across all spatial dimensions so "sphere" isn't really descriptive. You have to remember thought that this is our scientific bias that is thinking this.

We presume that the Universe is the same in all directions as presuming otherwise added unnecessary complications.
We know our observable Universe is flat and expanding.
So due to this we presume that the rest of the Universe is flat and expanding.
This would suggest a flat and infinite Universe. In this sense, infinite means without an edge or boundary.

So there are reasons for this assumption but I think everybody would agree that they are bad ones coming out of convenience rather than evidence.

Something that I believe to be a very good question is that if we had a Big Bang in our observable Universe then did parts of the unobservable Universe have their own Big Bangs or is the Universe smaller than presumed? As the Big Bang is thought to have created spacetime what does this mean for the non-observable Universe in terms of how time is experienced? Due to the way that spacetime has expanded we will almost certainly never find this out as we couldn't travel far enough. However, as the Universe is infinite it would imply infinite mass which is a whole other problem.

Another recent paper I read on this subject in the wake of the new ideas on inflation talks about how the observable Universe/the Big Bang singularity is the "white hole" that we've been looking for (as a black hole would insinuate a white hole due to the ideas we have on entropy and energy).

Again, we've just put a few more balls in the air for physicists to integrate into their models and see how they hold up.

Very interesting. Thank you greatly for your input on this topic. Some of your explanations are utterly fantastic.

Don't we know that the Big Bang already has an effect outside the observable universe i.e. matter created in it has moved outside in those areas moving away from us faster than the speed of light?

Interesting about white holes but I don't understand how you can apply laws of thermodynamics 'before' or to the Big Bang when they didn't exist. Again it seems like one of these human-appealing ideas and then physics sticks two fingers up at us and tells us the universe doesn't work how we'd like it to, it works how it does. As to white holes now in the era of thermodynamics though, why not?

 

[allan harper]

[youtube]http://www.youtube.com/watch?v=ZlfIVEy_YOA[/youtube]

The father of inflation theory receiving the news for the first time. 5 sigma +/- 0.2 confidence is a nice way of saying "we're dead certain this is right". Love the reactions.

Nobel prize winner, lump on it.

 

[Damocles]

The matter outside the observable Universe wouldn't be able to be theorised as it is outside our observable Universe so we couldn't detect it. Our definition of observable Universe grows larger as technology increase but it is presumed that some of the matter created in our observable Universe has moved outside just as a consequence of the expansion of space and general acceleration of matter.

Regarding white holes and thermodynamics, you have to remember that Dark Energy is just a placeholder term for a vast majority of energy that we have calculated to exist but we haven't worked out what it is yet. By that I mean nobody even has a reasonable theory. Complete unknown. A "white hole" spewing energy/matter would account for some of this though it isn't something that is expected to pop up any time soon, it just wouldn't be a massive surprise if it did. Our observable Universe being a white hole itself is a consideration though not a major one at this point.

I do believe that escaping our human need for "common sense" is one of the biggest challenges in understanding physics and effects many mathematicians. With that said, there's enough backlash against this for the hard maths to come through.

One of the things that this discovery does is put another dent in certain SuperSymmetry ideas simply because their hard maths doesn't support reality, which after their failure to predict reactions in the LHC means that you won't see too many documentaries in the future mentioning it with any form of enthusiasm as they once did.

I think the balance works itself out between those wanting the Universe to conform to our ideas and those who want the maths to. The various ideas of 4-13 spatial dimensions is one such example that we can't know through common sense.

 

[west didsblue]

I thought both the observable and unobservable universe both originated from the big bang. My understanding is that the rapid expansion of space after the big bang was much greater than the speed of light (as proven by the fact that the diameter of the observable universe is around 93 billion light years whilst the universe is only 13 billion years old) so it is theoretically impossible for light from the vast majority of the total universe to ever reach earth because of the rate of expansion of it.

 

[BlueHammer85]

Makes me feel so thick reading this thread.

Damocles, how would you explain today's discovery to a 10 year old ?