Comments on: Ep. 79: How Big is the Universe?

By: JerryinWales

JerryinWales — Sun, 23 Aug 2009 20:16:51 +0000

Glad you've raised this (comment 23, from Ronald). Inflation worries me, too.

So inflation in our local bit of the universe ceased at a certain point, why should it have stopped everywhere? Suppose it continued at the "edge" of the universe, and has been inflating ever since at the same rate. That would give quite a large universe – probably what Mr Guth has in mind. Still not infinite though.

By: Ronald

Ronald — Fri, 03 Jul 2009 12:30:09 +0000

With regard to the size of the total universe, it could be even much (MUCH) larger: according to the theory of cosmic inflation, and in particular its founder Alan Guth, the total universe could be at least 10^24 (1 with 24 zeros) times as large as the observable universe.

By: Adrian Morgan

Adrian Morgan — Fri, 19 Dec 2008 07:37:11 +0000

I'm lost on how to reconcile the Big Bang with the possibility that the universe is infinite in extent with no wrap around. If the universe began in a singularity, it's as plain as can be that you can't get to infinity from there. Is the answer that, in this model, ANY GIVEN FINITE REGION of the universe was a singularity at the Big Bang, yet the universe as whole was infinite all along? I have problems with that; multiplying infinity by its reciprocal doesn't give me an answer that I can understand.

Another point: at one point you say that you don't like the wrapped-around cube shape among others, because they're too complicated, but then immediately afterwards you suggest solving that problem by looking for even more complicated shapes as alternatives. This seems rather like looking for an ocean on the grounds that a puddle is too big…

By: frank

frank — Tue, 17 Jun 2008 02:52:30 +0000

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i love you frank xx

have my babies
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By: rajendra kumar

rajendra kumar — Wed, 11 Jun 2008 07:43:56 +0000

If just at the time of the big bang, the universe was a finite singularity,no matter how small, the universe has to be finite no matter how much it inflated or expanded. Of course, there could be more universes outside this one.
However, if the universe was an infinite singularity at the time of the big bang, it had to be a zero or nothing since you can't go lower than that and infinity postulates going as far back as you can. Zero is actually finite and measurable in the sense of being understandable(just as we can understand vacuum or the absence of life). However, zero can not expand by itself without the application of an external force. If the external force was finite(you don't really need infinite force to create the universe), then once again the universe has to be finite.
Therefore, big bang postulates a finite universe. It makes sense too for if birth of the universe was on a finite date, 13 billion years ago or so, it is likely that its size is finite too.
The real problem lies outside this universe. Of course, different universes could have been created by similar big bangs. But the first cause still needs to be explained. And if you say that there is nothing outside the universe, you need to explain nothingness and the place where it exists.