PDA

View Full Version : the multiverse



Gomar
2011-Nov-24, 06:43 PM
After watching that Brian Greene show about the possibility of a multiverse, I am convinced there is one.
Yes, the show was slick, with lots of CGI, etc. Better than the Carl Sagan Cosmos show of 30 years ago for sure.
However, the points were solid, and clearly made.
If there are many galaxies, then why cant there be many universes? Ok, I buy it. Why cant there be many big bangs
going off all across space? Maybe there are millions of BBs right now. That is indeed like saying given infinite time, any
cards dealt to players will eventually repeat.

However, I do not agree that somewhere there is a Hitler who is an astronaut, or a DaVinci who is a serial killer, or a Monroe
who lived to 91, or an Einstein who is a cook, or a Columbus who thinks its silly that the Earth is round.

Cougar
2011-Nov-25, 02:09 AM
After watching that Brian Greene show about the possibility of a multiverse, I am convinced there is one.

I'm far from convinced. Ten or 15 years ago, the mainstream explanation was that space and time began with the big bang. Any talk of 'before' was met with, "There was no before. Time started with the big bang." Since then, the thinking swung around to, "Wait a minute. We don't really know if there was a 'before' or not." And I agree with that. We don't know if time started with the big bang or not. How could we?

Notice Brian Greene said "might" a lot. Well, sure, it might be this, it might be that. It's easy to speculate. But in this case, how in the world do you (or anyone) plan to verify? Oh, I understand that string theory, in its search for a unique solution describing our universe, discovered that the number of possible viable universes was an embarras de choix (http://www.merriam-webster.com/dictionary/embarras%20de%20choix). I think the jump from there to concluding a multiverse is a leap waaaay too far.

KhashayarShatti
2011-Nov-25, 08:10 AM
After watching that Brian Greene show about the possibility of a multiverse, I am convinced there is one.
Yes, the show was slick, with lots of CGI, etc. Better than the Carl Sagan Cosmos show of 30 years ago for sure.
However, the points were solid, and clearly made.
If there are many galaxies, then why cant there be many universes? Ok, I buy it. Why cant there be many big bangs
going off all across space? Maybe there are millions of BBs right now. That is indeed like saying given infinite time, any
cards dealt to players will eventually repeat.

However, I do not agree that somewhere there is a Hitler who is an astronaut, or a DaVinci who is a serial killer, or a Monroe
who lived to 91, or an Einstein who is a cook, or a Columbus who thinks its silly that the Earth is round.

I think to think of multiverse as similar universes may be wrong before thinking of the interconnection between them. May i give an example: There is one hospital but many people around the world get treated there. Also there are universities with common departments but with many different colleges similar to The university of Cambridge. From an engineering point of view there may be "The Control & Management Universe" and "The Archive Universe" and of course "Our Universe" but they may have common DUT(Device Under Test). When we think of the current state of our universe(the present) These universes may be using the same "time" but in a PWM manner. You see if we think of a digital world, which was unkown even to Einstein, we see that thousands of mobile phones use the same communication station......
In general infrastructure of the universes may be different. It seems to me a kind of multidimentional matrix(multiplexed) using the same space but one is currently allowed to use the range of c0. This kind of science in engineering must be highly focused and used in cosmology. The question is "Why are we limited by physics?", and can this limit be changed?
I think this limit and the universe limit is our understanding of how to deal and tackle with it without disturbing multiplexed multiverse.

Cougar
2011-Nov-25, 03:38 PM
It seems to me a kind of multidimentional matrix(multiplexed) using the same space...

Like I said, speculating: easy. Verifying or supporting: hard.

Argos
2011-Nov-25, 03:49 PM
The problem with the multiverse idea [at least the idea of an analogous world] is how come we experience only one of the versions [exactly this one weīre living in], and are not aware of our analogousī experience? Why canīt we toggle between the multiverses?

Cougar
2011-Nov-26, 02:33 PM
Why canīt we toggle between the multiverses?

Well, either our universe is not a video game, or we just haven't found the right button. :whistle:

Solfe
2011-Nov-27, 04:20 PM
Better than the Carl Sagan Cosmos show of 30 years ago for sure.

In some other universe, another version of me just spontaneously burst into flames.

I loved the Brian Greene books and the TV show, but it is not as good as Cosmos.

I took the work to be:
A) An excellent introductory piece on how sciences works, I especially loved the contradictory sound bites from scientists. Talk about a creative way of making a weakness (sound bites) into a benefit. It also highlights how science figures can be in disagreement without actually taking it personally.
B) A cautionary tale on what can be imagined but but not tested.
C) A general overview of how the very large and very small don't fit together with our current framework.
D) Lots of historical references which the reader/watcher can use as starting points to gain further knowledge.

kevin1981
2011-Nov-27, 10:22 PM
After watching that Brian Greene show about the possibility of a multiverse, I am convinced there is one.

Thats fine, but we have no evidence to say there is or there is not. My opinion is, there could be, but we have no evidence to suggest there is,
so it is just fun speculation.

Argos
2011-Nov-28, 02:04 PM
Well, either our universe is not a video game, or we just haven't found the right button. :whistle:

Funny, but maybe itīs just a stupid philosophical nonsense.

pumpkinpie
2011-Nov-28, 09:10 PM
After watching that Brian Greene show about the possibility of a multiverse, I am convinced there is one.
...However, I do not agree that somewhere there is a Hitler who is an astronaut, or a DaVinci who is a serial killer, or a Monroe
who lived to 91, or an Einstein who is a cook, or a Columbus who thinks its silly that the Earth is round.

I didn't watch the show, but I did read some of his most recent book, The Hidden Reality.

Before reading that I wasn't quite convinced of multiverses, and I definitely wasn't convinced that there is another identical or near-identical version of me out there. But the book helped me somewhat understand the logic behind this.


I'm going to try to explain this from memory, as sort of an exercise of whether I understood and can clearly explain what I read.

The first (I believe) "multiverse" addressed in his book is not one(s) that arose from various big bangs, but from the same one we came from. We have an "observable universe" which contains everything we, on Earth, have the capability of observing. This is limited by the age of the Universe-let's use the round number of 14BY. So we cannot see anything that's so far away from us that its radiation has to travel longer than that to reach us. (Due to inflation the true diameter is something in the 90 billion light year range, but to avoid complication I'm going to talk in travel time, not distance.) So you can imagine that we are in the center of a bubble that is 14BY in radius. The farthest we can see is not all the way back to the big bang, but about 300K years after that when the universe became transparent. We observe this as the leftover radiation from the big bang, called the cosmic microwave background. Virtually the same radiation in all directions.

http://img851.imageshack.us/img851/2895/wmap.th.jpg (http://img851.imageshack.us/i/wmap.jpg/)


Then say there is a civilization in a galaxy 7BLY away from us. They have a universe that has the same dimensions as ours, with some features overlapping what we can see but some reaching beyond our cosmic horizon.

http://img804.imageshack.us/img804/4829/wmap2.th.jpg (http://img804.imageshack.us/i/wmap2.jpg/)


Repeat this exercise....

http://img828.imageshack.us/img828/7373/wmap3.th.jpg (http://img828.imageshack.us/i/wmap3.jpg/)

Now here's the "ah-haa" moment for me. There is a set number of atoms in our observable universe. (10^95? That's what number is sticking in my head, but like I said I am doing this all from memory so I could be way off.) They have come together in just the right configuration to make the galaxies, stars, planets, and everything we see including you and me. Each observable universe of the same size has the same number of atoms. They all come together in different unique configurations, right? Well, no. Since the universe is infinite, there is an infinite number of arrangements of atoms, but only a finite number of atoms in each arrangement. Statistically there has to be repetition. Another me out there. Or just slight enough of a difference that the world is almost the same as it is now, but Einstein was a cook.

Now remember....this does not address other big bangs, parallel universes, or anything of the like. Only what arose from "our" big bang.

I'm not a cosmologist (though I did take a grad level course) so I am COMPLETELY open to corrections or questioning of either Greene's explanation or my interpretations of it.

Cougar
2011-Nov-29, 10:46 PM
Since the universe is infinite....

Once you make this assumption, almost anything goes. Of course, the odds are ridiculously tiny, but they have to be nonzero because of that infinite thing, which is still an assumption at this point.

I'm surprised Greene would call what you described above a "multiverse." That's just our same old Universe, but noting that much of our Universe is outside our horizon, and that every galaxy has a different "visible Universe," but it's all encompassed in the same, one Universe.

astromark
2011-Nov-29, 11:20 PM
Conceptual understanding is complicated by held belief structures preconceived.

and I explain it like this... We have good well reasoned argument that there most likely was a 'Big Bang.'

Was it the only one ?. and when you look at just that question you are drawn to 'probably not'.

The argument or suggestion that this Universe 'Might' be just one of many is not unreasonable.

If the circumstance of physics transpired to launch itself on a change of state and the great expansion begins.

Why would it only ever have happened once ?. ( Thats a familiar point.)

So its not just a theory. It becomes a higher probability when all considerations are made.

Cougar
2011-Nov-30, 01:45 PM
We have good well reasoned argument that there most likely was a 'Big Bang.'

Oh, we have much more than that. The reasoning goes along with observations. Several independent ones.


Why would it only ever have happened once ?. ... It becomes a higher probability when all considerations are made.

I don't think so. Problem is, "all considerations" are essentially philosophical at this point. AFAIK, there is not one observed phenomenon that supports the idea that there is more than one universe. In this case, it is difficult to even imagine an observation that would be an indicator that there is more than one universe. Anyone?

Gomar
2011-Nov-30, 05:09 PM
Given the age of the universe as only around 15B years, I sure do not believe that somewhere there is a Hitler
who is a physicist, or an Einstein a fuhrer of Germany, as there isnt enough time. First, a homo sapien species
has to evolve on another planet that looks human, and then all genes have to come together to make a copy of
an Pushkin, or a Jimi Hendrix, or a Mozart, or Marilyn, or Picasso, or anyone whose talents we lost too soon.
However, all those people, because of different nurture/surroundings/culture would've become plumbers, lawyers,
taxi drivers, car salesmen, cooks, Vegas show girls.
However, is it possible that given a multiverse, some universe is 472B years old? or another only 128years old?

pumpkinpie
2011-Nov-30, 06:06 PM
I'm surprised Greene would call what you described above a "multiverse." That's just our same old Universe, but noting that much of our Universe is outside our horizon, and that every galaxy has a different "visible Universe," but it's all encompassed in the same, one Universe.

He might not have. I'd have to go and check the book. But the main point I wanted to address was that there could be an identical copy of me out there, and his description made, for me, the possibility go from zero to slight. :D

Cougar
2011-Nov-30, 08:10 PM
However, is it possible that given a multiverse, some universe is 472B years old? or another only 128years old?

Yes. Vilenkin's "eternal inflation" speculates that our expanding "bubble universe" is a decay product of an all-encompassing background inflation, which is still inflating superluminally. Other bubble universes may also decay, similar to ours, and one may have done so "472" billion years ago, although the very concept of the duration of time becomes problematic when comparing between bubble universes. With continuing inflation going on between all bubble universes, No bubble will EVER expand into another bubble.

A very tough idea to provide any observational support for.

Cougar
2011-Nov-30, 08:17 PM
But the main point I wanted to address was that there could be an identical copy of me out there, and his description made, for me, the possibility go from zero to slight. :D

Vilenkin made a point of this. If there were an infinite number of bubble universes, then not only is there an identical copy of you "out there," but there are an infinite number of identical copies of you.

My feeling is, if your theory contains an infinity, then there's something wrong with your theory.

Daffy
2011-Nov-30, 08:34 PM
My feeling is, if your theory contains an infinity, then there's something wrong with your theory.

May I ask why? Not to be argumentative, but that seems like speculation, right? Which is discouraged here---or is negative speculation encouraged? This is a real question; I am not being intentionally rude or flip. I am really just trying to understand how things work here. You just based an opinion on a "feeling." Is that OK? If so, why?

Shaula
2011-Dec-01, 08:20 AM
My feeling is, if your theory contains an infinity, then there's something wrong with your theory.
Bad news for QED then. Or do you mean an infinity you cannot renormalise out?

Cougar
2011-Dec-01, 01:59 PM
May I ask why? Not to be argumentative, but that seems like speculation, right?

Well, that's why I identified it as my personal feeling, not a truism or a mainstream consensus. The opinion, however, is not purely emotional. In a famous paper, Hawking and Penrose showed that within the structure of general relativity, a singularity will always form once a black hole event horizon forms. In other words, spacetime curvature becomes infinite, density becomes infinite, etc. This signals a problem with the theory. As Harvard GR prof Tony Rothman pointed out:



"We mentioned that the FLRW cosmology begins with a singularity. This is a much more serious breakdown than a flat tire or a cracked engine block. It is, in fact, a physical impossibility -- a region where the laws of physics break down altogether and even spacetime comes to an end."

Cougar
2011-Dec-01, 02:14 PM
Bad news for QED then. Or do you mean an infinity you cannot renormalise out?

Well, yeah. QED was unworkable with the infinities. There was no theory of Quantum ElectroDynamics with the infinities in there. With some clever mathematical trickery, they were removed from the equations. As I understand it, it is not known why this trick works, only that it certainly does. :clap:

Shaula
2011-Dec-01, 03:27 PM
Well, there was a theory of QED - it just had some embarrassing gaps in when you tried to calculate the 'wrong' thing. But I know what you mean.

Cougar
2011-Dec-02, 02:40 AM
Well, there was a theory of QED - it just had some embarrassing gaps in when you tried to calculate the 'wrong' thing. But I know what you mean.

It was a similar problem in the formulation of the electroweak theory (http://en.wikipedia.org/wiki/Electroweak_interaction) (another Nobel). They kept running into infinities... couldn't figure it out... and what they needed to get rid of the infinities was right under their noses for several years. It was the Higgs mechanism. An interesting 2010 book about Peter Higgs and the evolving science of his day (he's 82 now) is titled Massive, the Missing Particle that Sparked the Greatest Hunt in Science, by science writer Ian Sample.

Mike Holland
2011-Dec-06, 07:12 AM
I want to sort out a confusion that I have. We are here talking about multiple universes, maybe an infinite number and maybe not. There is also a theory that at every event which can go one of two ways, the universe splits into two universes, one where the cat lives and one where it dies. Is this a completely separate multple-universe theory?

Regarding one point raised earlier, if there are an infinite number of universes this needn't mean there are an infinite number of me's. I may exist in this one, while there are an infinite number with no Mike Holland in them. An infinite number of universes can still all be unique, just as you can find an infinite number of points on a line without repeating yourself.

Mike

Substantia Innominata
2011-Dec-13, 11:09 PM
I want to sort out a confusion that I have. We are here talking about multiple universes, maybe an infinite number and maybe not. There is also a theory that at every event which can go one of two ways, the universe splits into two universes, one where the cat lives and one where it dies. Is this a completely separate multple-universe theory?

Yes, definitely so. And, this (differentiation) most probably is not the original motivation behind the differing terminology*, but.. the hypothesis you have in mind, of course, first and foremost arises out of an interpretation of quantum physics and, as such, does normally prefer speaking about the (many) "worlds" instead, I think only rarely about "universes" or a "multiverse". ;) The two concepts will have to be differentiated at any rate. You could well have both, for all I know. A multiverse.. and on top of that the case of MWI being true as well. Moreover, it could then still be true in all the universes, or in many of them, or in just a few, or even only in a single one. Since this would obviously depend on whether the quantum mechanics behaved the same "across the board", or not. In other words, whether the laws of nature were bound to operate in exactly the same fashion "only" universally (=everywhere in a universe), or indeed multiversally (everywhere in the multiverse). The latter just implies that such universes exhibiting natural laws in any way different from those that we experience in ours, would be precluded.


*I guess the somewhat trivial reason is that, as an idea, the MWI is also much older than quite about any ever seriously discussed multiverse hypothesis, and back in those (Hugh Everett's) days it just hadn't been particularly fashionable to speak about a "multiverse". Perhaps, the term itself wasn't even coined yet, or by then only allowable in the realms of science fiction, though I'm not sure at all. Others on BAUT can tell you more (and more correct), and this isn't even why I find myself replying. That comes next.


Regarding one point raised earlier, if there are an infinite number of universes this needn't mean there are an infinite number of me's. I may exist in this one, while there are an infinite number with no Mike Holland in them. An infinite number of universes can still all be unique, just as you can find an infinite number of points on a line without repeating yourself.

Thank you!