How big is the entire universe?

Re:How big is the entire universe? by mootothemax on Wednesday July 25, 2012 @08:41AM (#4290592)

Perhaps the most disturbing of which would be the fact that, by definition, at some distance, there would have to be a duplicate of yourself.

Wouldn't it also mean that there are an infinite number of duplicates out there? Including one typing this very comment, but who typos and leaves the "s" off "duplicates"?

I'm very much not a mathematician nor physicist, can this really be true if the universe is infinite in size? Asking as a layman, at what point when dealing with infinite possibilities and probabilities does something become certain? That's what really terrifies me.

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Re:How big is the entire universe? by nessus42 on Wednesday July 25, 2012 @11:23AM (#4291346)

If the universe is flat, and therefore infinite, yes it means that most probably there are an infinite number of identical duplicates of you. It does not mean, however, that there are any duplicates of you that make a particular typo. I should think that there are an infinite number of such duplicates for any given typo, BUT it may also be the case that such worlds are impossible. E.g., physics is deterministic enough and chaotic enough that there is no slight nudge to the initial conditions of a world that will result in such a minor eventual difference to occur.

I.e., just because there are an infinite number of parallel worlds, doesn't mean that every imaginable thing occurs in them. What occurs in a parallel world, must be possible.

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Re:How big is the entire universe? by mattstreet on Wednesday July 25, 2012 @12:24PM (#4291635)

I think you make a very important point. Even if the universe was infinitely large, there might be a point where past that the conditions can't exist that would allow something like our planet to function. For infinity to grant you duplicates of yourself the possibility must exist within that "zone of infinity". Gravity for example might be stronger or weaker.

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Re:How big is the entire universe? by andyjohnson0 on Wednesday July 25, 2012 @09:13AM (#4290724)

Including one typing this very comment, but who typos and leaves the "s" off "duplicates"

There would be an infinite number of those, too.

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Re:How big is the entire universe? by creamyhorror on Wednesday July 25, 2012 @04:47PM (#4292941)

What if the universe is empty beyond a certain distance from the origin/central point, like a tiny explosion in the middle of an unending emptiness? Then there wouldn't have to be duplicates of you.

(This is about the same thing as the question asked below about whether infinite size implies infinite mass.)

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Re:How big is the entire universe? by nessus42 on Wednesday July 25, 2012 @05:20PM (#4293121)

In a flat universe, the universe starts off infinitely large and infinitely dense at time 0. As the universe expands, it gets less dense. Imagine an infinitely dense rubber sheet that starts to stretch at time 0, and after time 0 it is no longer infinitely dense, and it keeps slowly stretching forever, getting less and less dense over time. That's the universe as it is currently envisioned.

But our "Hubble sphere" is in no way special compared to other Hubble spheres. Our Hubble sphere is the part of the universe surrounding us from which light has arrived. Outside that sphere, nothing has a causal connection to us, since nothing can travel faster than the speed of light.

I.e., it just wouldn't be the case that our Hubble sphere is full of stuff and all the other Hubble spheres are are so different as to be empty.

Unless, of course, everything we know is wrong.

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Re:How big is the entire universe? by goatforce5 on Wednesday July 25, 2012 @12:31PM (#4291683)

"And best of all in possible worlds / nothing is impossible" - The Shamen

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Re:How big is the entire universe? by nessus42 on Wednesday July 25, 2012 @05:22PM (#4293130)

Sure they are. Impossible things are impossible, even in an infinite number of possible worlds!

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