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Author Topic:   Are Multiverses possible?
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 16 of 69 (645399)
12-26-2011 8:23 PM
Reply to: Message 1 by hsweet
12-26-2011 3:45 PM


I'm not really following your reasoning.
Clearly whatever conditions are necessary for one universe to exist were present, since at least one universe does exist. Why are these conditions not sufficient for several universes to exist?
You write:
But to speculate that there are multiverses, we need to establish that there is something from which they can arise — some soil for the plants to grow in.
Well, on the face of it, if there is enough soil for one plant to grow in, there may well be enough soil for more than one plant to grow in --- at the very least this is not a possibility that we could rule out a priori.
Could there have been other points from which other universes arose such as the point from which our universe arose? Behind this question is a hidden implication that is based on our everyday perception of reality. It assumes that there was a time and place from which our universe arose and all other universes could have arisen.
Well, not necessarily. Without committing ourselves to any particular picture of how our universe arose, we may say with certainty that it did so. So why shouldn't whatever-it-was-that-happened have happened more than once?
---
What you need is an argument that makes it absurd for more than one universe to exist, but without making it absurd that at least one universe exists, and I don't think that you're doing a good job here; because so far as I understand your rather nebulous arguments it seems to me that your arguments for suggesting the former (as you wish) also tend to suggest the latter (which you would wish to avoid).

This message is a reply to:
 Message 1 by hsweet, posted 12-26-2011 3:45 PM hsweet has replied

Replies to this message:
 Message 19 by hsweet, posted 12-26-2011 8:49 PM Dr Adequate has replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 17 of 69 (645400)
12-26-2011 8:30 PM
Reply to: Message 14 by hsweet
12-26-2011 6:41 PM


Re: Tegmark
By this logic, if there is a foundation outside of our universe and any other possible universe, it would have to be something other than space, time, matter or energy.
Well, again, this doesn't really do what you want it to do. Let's assume (for the sake of discussion) that your proposition that I've quoted is right. Then from the fact that our universe definitely does exist, we can conclude:
Either our universe has a "foundation" which is "something other than space, time, matter or energy" --- in which case why shouldn't another universe be built on the same "foundation"?
Or our universe has no such "foundation" --- in which case why shouldn't another universe also exist with no "foundation"?
Either way, this stuff about "foundations" doesn't seem to point us towards a reason why there should be just one universe.

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 Message 14 by hsweet, posted 12-26-2011 6:41 PM hsweet has replied

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Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 37 of 69 (645437)
12-26-2011 11:30 PM
Reply to: Message 19 by hsweet
12-26-2011 8:49 PM


Re: multiple big bangs ?
Dr Adaquate, We can not intellectually understand any possible physical reality outside of our universe due to the limitations of our intellects. Human intellect evolved so that we could navigate within the relative universe of space, time, matter and energy so anything else that might possibly exist is beyond our capability.
When we try to think 'outside the universe', we only project what is inside the universe to that 'realm' -- that's all that we can do. My argument is that whatever it is that is non-universe can't be what is within the universe otherwise there would be no distinction between the two.
Well ...
When we talk about "other universes" in the context of the Inflation Hypothesis, we do mean just more spacetime and energy and matter, having a common origin with our own universe.
What makes them "other universes" is causality: the geometry of spacetime is such that what's in the other universes can't affect what's in our universe, and vice versa. It's not that there's (necessarily) an essential qualitative distinction between this universe and the next, just that they're causally isolated from one another.

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 Message 19 by hsweet, posted 12-26-2011 8:49 PM hsweet has replied

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 Message 40 by hsweet, posted 12-26-2011 11:42 PM Dr Adequate has replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 39 of 69 (645439)
12-26-2011 11:41 PM
Reply to: Message 38 by Portillo
12-26-2011 11:34 PM


Yes they are possible. The problem is there isnt a shred of evidence that another universe exists.
There are, in fact, shreds of evidence.
I've referred to the Inflationary Hypothesis. There is some evidence that this is correct. If it is correct, then other universes are a corollary of its correctness.
---
I suppose another piece of evidence, though I'm not sure how much weight we should attach to this, is that it's extremely rare for there to be only one of anything. Can you think of a particular thing which is also the only instance of its type?
For some reason I am more hesitant to reason inductively on the basis of this observation than I usually am, and I don't quite understand the reason for my hesitance --- I just have a vague feeling that it might not be satisfactory.

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Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 41 of 69 (645443)
12-26-2011 11:57 PM
Reply to: Message 40 by hsweet
12-26-2011 11:42 PM


Re: multiple big bangs ?
OK. hypothetical to the hilt, though as with no possible interaction, that leaves us out of the picture.
Well, they needn't remain hypothetical, as I pointed out to Portillo.
If we can establish strong evidence for the mechanism by which our universe began, and if the mechanism for which we have evidence implies the existence of other universes, then we would in fact have evidence for their existence.

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 Message 40 by hsweet, posted 12-26-2011 11:42 PM hsweet has replied

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 Message 42 by hsweet, posted 12-27-2011 12:00 AM Dr Adequate has replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 43 of 69 (645446)
12-27-2011 12:10 AM
Reply to: Message 42 by hsweet
12-27-2011 12:00 AM


Re: multiple big bangs ?
Talk about healthy undertakings! Good Luck.
It's no use wishing me good luck, I'm not a physicist.
Certainly it looks as though some version of the I.H. might well be true. Will we ever know enough to say that it definitely is true? I don't know.
But the mere fact that we can entertain the idea does seem to undermine any attempt on your part to rule out other universes a priori.

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 Message 42 by hsweet, posted 12-27-2011 12:00 AM hsweet has replied

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Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 46 of 69 (645450)
12-27-2011 1:30 AM
Reply to: Message 44 by hsweet
12-27-2011 12:16 AM


Re: multiple big bangs ?
Perhaps far out might be more correct than rule out.
I can attach no meaning to this sentence.
It's when we start hearing other universe descriptions presented as an alternative to the anthropic that we start seeing science getting edgy about religion.
Au contraire. The combination of multiple universes with the weak anthropic principle is one of the zillion instances in which we see religion getting edgy about science.

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 Message 44 by hsweet, posted 12-27-2011 12:16 AM hsweet has replied

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 Message 47 by hsweet, posted 12-27-2011 5:53 AM Dr Adequate has replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


(2)
Message 55 of 69 (645527)
12-27-2011 4:38 PM
Reply to: Message 47 by hsweet
12-27-2011 5:53 AM


Re: multiple big bangs ?
Far out? That's olde hippie talk meaning way beyond the normal scope of things.
Well then, it's not a concept that you can usefully apply, since "the normal scope of things" is something we learn from experience. You can, for example, use your experience of how the world works to see that the following statements graduate from inevitable to normal to "far out":
* I have a head.
* I have a pair of shoes.
* I have a tennis racket.
* I have a tennis court.
* I have an elephant.
* I have a unicorn.
But you have to use your experience, there is nothing a priori about my not having a unicorn. So when it comes to the origin of the universe, you have no basis of experience to say whether it would be more "far out" for there to be one universe, or seventeen, or aleph-zero.

This message is a reply to:
 Message 47 by hsweet, posted 12-27-2011 5:53 AM hsweet has replied

Replies to this message:
 Message 58 by hsweet, posted 12-27-2011 5:24 PM Dr Adequate has replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 60 of 69 (645537)
12-27-2011 5:42 PM
Reply to: Message 58 by hsweet
12-27-2011 5:24 PM


Re: far out
Well, I don't want to get into a deep discussion on the meaning of the term 'far out'. Suffice it to say that discussions on the nature of other universes are in the realm of guesses that have no hope of ever being substantiated.
I wouldn't say that there was "no hope"; and whatever can be said on this subject could also be applied to the remarkable proposition that there is only one universe. How "far out" would that be? At present that too is a wild unsubstantiated guess.

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 Message 58 by hsweet, posted 12-27-2011 5:24 PM hsweet has replied

Replies to this message:
 Message 61 by hsweet, posted 12-27-2011 5:51 PM Dr Adequate has replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 64 of 69 (645549)
12-27-2011 9:24 PM
Reply to: Message 61 by hsweet
12-27-2011 5:51 PM


Re: hope
I would like to have hope too. But I would also want to have a basis for that hope.
Well, as I have pointed out, it is in principle possible for physicists to produce evidence for other universes. So it is simply more accurate to say that there is some hope that one day they will do so than to say that there is "no hope" that they will do so. It may not be a hope in which one can place much reliance, but it's more than nothing.

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 Message 65 by Phat, posted 12-27-2011 10:36 PM Dr Adequate has replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 67 of 69 (645557)
12-27-2011 11:33 PM
Reply to: Message 65 by Phat
12-27-2011 10:36 PM


Re: hope
Its interesting, in the field of psychotherapy, when a patient begins talking about the worlds problems (or the universes) and the Doctor will gently remind them to focus on themselves rather than on some grand picture. Humanity dreams of hope in space, yet we cant even solve our own problems here on this 3rd rock!
Demonstrating the existence of other universes is probably much easier than solving our own human problems, and so it only makes sense that we should try to do that first. Baby steps, Phat, baby steps.
Edited by Dr Adequate, : No reason given.

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