Multiverse/Infinity Questions

TooMuch2Read · Sun May 22, 2011 10:36 pm

Hi there,

This isn't really my first post; I've forgotten my password after months of neglecting Book Talk, and now I'm kicking myself for having missed out on so many good books. I used to go by 40Helens or something like that.

I'm currently reading The Hidden Reality by Brian Greene, and I'm not able to follow his reasoning in a couple of places.

In explaining why there could be a multiverse with infinite copies of Earth, us etc., he writes:

"in any given patch (of an infinite cosmos), the particles of matter can only be arranged in a finite number of different configurations...this means that conditions in the infinity of far-flung patches--in regions of space like the one we inhabit, but distributed though a limitless cosmos--necessarily repeat."

My two questions are:

1) Can a real entity like the cosoms be infinite? Isn't infinity a concept or idea rather a true enumeration of a system?

2) Why would matter necessarily arrange itself in every possible combination? Couldn't there be limited ways in which it self-arranged?

Thanks for any help. My brain is starting to implode.

Helen

JulianTheApostate · Wed May 25, 2011 2:19 am

Theoretical physics is based on some very abstract mathematical ideas. The concept of infinity is much simpler than many of the other mathematical formulations you need to grasp to understand advanced physics.

To understand the Greene quote, consider the following statement. In any group of 400 people, at least two people will share the same birthday. Similarly, if you accept Greene's hypothesis that there are an infinite number of patches within the cosmos, but a finite number of possible configurations of matter, many configurations will appear an infinite number of times.

tat tvam asi · Wed May 25, 2011 8:51 am

I've wondered the same. But it makes sense when you really consider it. The other question here, in contrast, is how could the cosmos not reach out infinitely?

If it sections itself off into a sphere or some limited shape, then what lies beyond that shape? Is that finite shape contained within yet a larger area of existence? If not, then is it surrounded by nothing at all? If we say nothing at all, then does this void nothing extend out infinitely beyond the finite shape of the cosmos or is the void also finite. If so, then what lies beyond the finite cosmos and the finite void surrounding the cosmos? We're back to square one again in terms of the necessity of an infinite expanse out there, and perhaps even inwardly too. What if there is no such thing as any real void at all and the cosmos simply extends out with no fixed border of any type, just a continuous space with matter spread about forever and ever?

Who knows? But that's what science is for - to try and find out...

...and it's conceivable to gather empirical data that could potentially prove such a thing.

Interbane · Wed May 25, 2011 9:48 am


	Quote: 1) Can a real entity like the cosoms be infinite? Isn't infinity a concept or idea rather a true enumeration of a system?

At some point, the concept has to tie into reality. If the universe isn't infinite, what is it? If there is nothingness beyond the nether, it is necessarily infinite nothingness. This is the appropriate place for the concept, though there are hypotheses with finite systems.


	Quote: 2) Why would matter necessarily arrange itself in every possible combination? Couldn't there be limited ways in which it self-arranged?

It is a necessity if there are infinite "templates" for matter to form. There's nothing stopping there from being an Earth with everything identical except that my nose has a freckle on the left. All history and the entire future of that replica Earth are identical. If the structure of matter puts parameters on what can form, then you're right. It wouldn't be infinite, but so close that there wouldn't be much difference.

johnson1010 · Wed May 25, 2011 3:24 pm

The real issue to boggle the mind here is infinity.

If infinity is actually real, then not only is there, somewhere, a world exactly like ours with another johnson1010 composing this exact post on an exact replica of this thread, there is also a solar system completely packed with duplicate earths exactly like ours where every johnson1010 is typing this post to every booktalk on all those earths.

The craziness of this concept makes me doubt infinity, but that may just be an emotional response. If infinity is a reality, then the above must be true. That is one hell of an "if" though.

tat tvam asi · Thu May 26, 2011 11:59 am

...infinite debate between biblical literalists and others...

TooMuch2Read · Thu May 26, 2011 11:07 pm

Thank you for all the responses.


	JulianTheApostate wrote: ... if you accept Greene's hypothesis that there are an infinite number of patches within the cosmos...

This is the crux of the problem for me. I don't accept the premise, because I don't understand where the matter in the patches comes from.

If it came out of the big bang, there should only be so much of it to go around. Wouldn't we run out of matter, before we ran out of ways to arrange it?

And since the space between galaxies is expanding, won't those patches become increasingly empty?

Tat tivam asi, Yes, an infinite void sounds more acceptable intuitively. Thanks for the clip. I'd seen a shorter version of that one with the beginning cut off, so it was interesting to hear the whole thing.

Interbane wrote:


	Quote: 1) It is a necessity if there are infinite "templates" for matter to form.

Ahh...so this infinite cosmos would include other, presumably endless big bang events? I guess this clears up where the matter would come from.


	johnson1010 wrote: The craziness of this concept makes me doubt infinity, but that may just be an emotional response.

Yes, I'm definitely beset by that emotional response myself.

Helen

tat tvam asi · Fri May 27, 2011 9:30 am

With the discussion of white and black holes in the video clip posted previously, the idea is certainly one where space is itself an infinite expanse, continunous and full of matter throughout. And what we call the BB would then simply be matter from elsewhere going through a black hole in that realm and then emerging through a white hole. And of course since that time some of the matter here in this universe has likewise gone down into black holes and possibly come out of white holes elsewhere making for more even more BB's causing more universes into existence. That is an interesting take on it for sure. Something easily visualized without the complex math.

When approaching the matter in our universe we then need to shift gears and think of it as merely passing through from realm to another realm to another realm. What caught my attention is the part about the LISA satellite taking gravitational readings and having the potential ability to detect the gravitational forces of a parallel universe. And perhaps even a snap shot of sorts of the BB event. At least then, if this data were collected, we could settle several questions.

TooMuch2Read · Mon May 30, 2011 12:44 am

It seemed he was trying to lay out different possibilities in different chapters--saving the one he favored most for later. In the one that had me puzzled near the beginning he presented a flat infinite space with, as I learned in a later chapter, matter coming into existence via potential quantum fluctuations at every point in space. Models with other dimensions were presented later.

Helen

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