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If the universe is infinite in extent does that mean that the big bang was a local event? originally appeared on Quora: the place to gain and share knowledge, empowering people to learn from others and better understand the world.

The Big Bang doesn’t exist and it never existed, nor do cosmologists believe it to have existed. The Big Bang is a point in time defined by a mathematical extrapolation.

An analogy is knowing that the rate of climb for a plane is 700 feet per second. If the plane is at an altitude of 7000 feet. You can extrapolate to a point 10 seconds ago when the plane had an altitude of 0 feet. It doesn’t mean 10 seconds ago that happened. Or at 11 seconds ago the plane was 700 feet below the surface of the Earth. We just just understand that the plane didn’t climb at 700 feet per second for more than 10 seconds.

This is exactly the same as the Big Bang. When physicists or cosmologists or astrophysicists speak about “the Big Bang” they mean “the era of Big Bang cosmology” which is a multi-billion year era where the evolution of the Universe is described by the Friedmann-Robertson-Walker-LeMaitre metric.

The Big Bang being 14 billion years ago tells us that something has to have changed by that point in time.

So there is no “point” where the Big Bang was, it was always an extended volume of space.

So how big was the Universe when it started?

When physicists speak about what came before the era of Big Bang cosmology, it describes it in two phases. The first phase is about explaining the way that the Universe became big, flat and homogeneous enough to support Big Bang cosmology. However, the Universe began, it almost certainly wasn’t nearly homogeneous and flat — that’s just an incredibly unlikely initial condition.

In the early 1980s Guth, Linde, Steinhardt, Albrecht realized that there was a way inside of General Relativity for the Universe to naturally evolve to a state that we observe (nearly homogeneous initial conditions). The amazing thing about this mechanism is that it is almost independent of how the Universe actually started. This mechanism is called inflationary cosmology. I would say that it is confirmed and simply waiting a Nobel prize to be conferred upon it.

Inflation doesn’t address how big the Universe was when it started, it just takes a bumpy Universe and makes it big and smooth. What happened before inflation is known as pre-inflationary cosmology.

Pre-Inflationary Cosmology

What predates inflationary cosmology is very speculative and could explain how big the Universe was when it underwent its era of inflationary cosmology which then led into Big Bang cosmology.

Coleman-Deluccia bubbles is a plausible scenario for what occurred before the inflationary era. Coleman-Deluccia cosmology gives rise to finite size bubbles of new Universes that are infinite in proper-distance (geometry is weird). This is no different than if you remove a point from a sphere, then this finite space can be stretched out to be an infinite plane. Below the North Pole maps out to infinity:

When you have plane, how do you know that it’s not a sphere? In the case of Coleman-Deluccia bubbles, you make little spheres (3-spheres) from the outside, but for people in the bubbles, they’re like infinite planes (3-dimensional planes). So the confusing moral of the story is that the Universe could have started out as a finite sized bubble, but we (as resident inside the bubble) view it as an infinite Universe.

It would be amazing to verify this (or any other) version of pre-inflationary cosmology. Unfortunately, it looks very plausible that inflation will have wiped away all the pre-inflationary information (inflation has a nasty tendency to do that). So we may never know for certain where the Universe came from. And that begs the question where is it going!!

http://www.forbes.com/sites/quora/2017/03/07/the-big-bang-was-not-a-single-point-in-time/#444a1542d9fb

Good to see even Barbie ages

When the world was created, you were also created to beautify it. You have done your work perfectly for all the world is smiling for you today.

Happy women's Day to all the wonderful woman out here.

Hi Sir, I'm not fear about life. In fact, I live mylife to the fullest. :) It's just that I'm afraid to reply back in mingle2 . :)
[/quote Fear of replying back is genuine and you are in denial... if you were in fact living fully not only would you be responding here you would also be elsewhere having a wonderful time not fretting over being afraid of responding lets get real here or as Charlie Brown asserts " There is no problem too big, that I cant run away from?? lol

Nothing really so I won't be disappointed when nothing happens.

hahahahahaha I think it is YOU mister who stops :-)

I suppose.. but that would kinda suck.. wouldn't you think

Yes, things have changed over the years. I've always been the the little quiet person. I've changed over the years. Yes, I'm still introverted but I'll speak for myself now. People around me are starting to respect me more.