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View Full Version : If the Universe is a 3-sphere how big would it be?



WaxRubiks
2014-Jul-21, 09:54 PM
If space is too flat to measure the curve, how big would that make a 3-sphere Universe?

What would be the implications for its age?

WayneFrancis
2014-Jul-22, 01:54 AM
I've heard different values. Afew years ago it was about 250x. I've heard recently 1000x and I've seen explanations of the very early universe that it is like on the order of 1023. Alex Filippenko compare the entire universe to the visible universe may be like the all the galaxies in the visible universe to our galaxy. So is it 250x? 1000x, 200,000,000,000x? or 300,000,000,000,000,000,000,000x? Depends on your supporting data.

As for the "age" nothing really that I know. The universe could be 250x the size of the observable universe or 3x1023 the size of the observable universe or it could even be infinite in size. The time since our big bang remains the same. IE if the universe is 3x1023 larger then the observable universe it isn't like all that had to contract down to the size of what we think our observable universe was 13.8 billion years ago.

John Mendenhall
2014-Jul-22, 02:37 AM
For those of us who remember Ed Sullivan, that means if you look at the sky there will be a really big shew tonight.

Cougar
2014-Jul-22, 12:17 PM
The time since our big bang remains the same.

I agree. The estimated size of the entire Universe, of which the visible part is but a speck, implies little to nothing about the age. We have six or seven totally independent ways to estimate the age of the Universe, and they all converge right around 14 billion years. An excellent book: How Old is the Universe [2011] -- David A. Weintraub.


...if the universe is 3x1023 larger then the observable universe it isn't like all that had to contract down to the size of what we think our observable universe was 13.8 billion years ago.

Almost all of that size relative to the visible Universe occurred during the instant of inflation. I'm going to go out on a limb here and say there is no process that is the reverse of inflation (within the same time duration).