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Max Tegmark's infinite universes

drkitten said:
That is correct.

And it is precisely because Tegmark claims, in the teeth of the evidence, that in an infinite space, every possibility must be included, that he is wrong.
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Cite?

For a counter, I cite Tegmark:
I certainly wouldn't claim that "something must exist in reality because it is conceivable"; the point of the article is merely that it can exist, and that we shouldn't be so dismissive of big ideas just because they seem weird.
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This thread was the first time I have heard of Tegmark, so I claim no special knowledge. However, this quote (and many others on the same page I linked) seem to contradict your interpretation of Tegmark's speculations.
 
herewith a quote from Max Tegmark's website to inject some context into his "wacky ideas"
"
devildance.gif
Every time I've written ten mainstream papers, I allow myself to indulge in writing one wacky one, like my Scientific American article about parallel universes. If you don't mind really crazy ideas, check out my bananas theory of everything. This includes musings on the dimensionality of space and time and on the universe containing virtually no information. If things anthropic make you foam at the mouth, try this. You might enjoy this trialog if you're interested in the question of life, the universe and everything without the equations. "
 
Apathia listen up!

I had never seen that Monty Python. It's right on. Thanks!

If you're so old and are as offtrack as I, write me. I can use all the kitten nutcases I can find but closed minds with limited background don't fit.
 
roger said:
This thread was the first time I have heard of Tegmark, so I claim no special knowledge. However, this quote (and many others on the same page I linked) seem to contradict your interpretation of Tegmark's speculations.
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You're not reading the context of that particular quote properly.

Tegmark was responding to a perceived similarity between his ToE and the old proofs of the existence of God; basically, the idea that merely defining something was enough to make it come into existence.

Tegmark's point was that his TOE itself was not necessarily true, only plausible. (Actually, I'm not sure he would go as far as "plausible" -- perhaps merely "cannot be ruled out.") But if his theory were true, then it would also be true that all definable objects must exist.

I.e. his theory states that all definable concepts exist, but his theory itself might be wrong.

I'm simply going further and stating that his theory itself is wrong, with overwhelming probability, for the reasons I've outlined earlier.
 
calvert said:
Doesn't this also imply that a billion, or trillion years ago I was sending this same e-mail somewhere?
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Well, certainly not a billion years ago...unless you are a single celled organism from the Precambrian and you owned your own cybercafe.

(I smell sitcom.)
 
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This is Calvert. I think you are serious about this topic. Trouble is, no one yet can explain virtually anything. Must make it hard to try to explain. I like the people who start throwing equations at you. I admit they are at least in some ways "smarter than I". But, when questioned, I have not yet run into ONE who can interpret his math into English. They fold and dissappear. Your math is basic and makes sence. You conclusions, however do not. I am asking Real Questions. Does anyone have Real Answers??
 
Hi. Sitcom sounds good.

You miss the point---or am I taking bait? If time is just as infinite as space-- of course assuming space is infinite in the first place, then in an existence comprising all possible outcomes why can't I have written this trillions of years ago?
 
calvert said:
Hi. Sitcom sounds good.

You miss the point---or am I taking bait? If time is just as infinite as space-- of course assuming space is infinite in the first place, then in an existence comprising all possible outcomes why can't I have written this trillions of years ago?
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Wrong question.

Again.

Yes, it's certainly possible that time and space both repeat in such a way that all events repeat themselves without limit. But it's by no means necessary. There are lots of examples of infinite aperiodic sequences.

So Tegmark's theory that whatever is possible must happen is therefore mathematically invalid. If you want to back off on that slightly and claim that whatever is possible may happen, you're on much sounder ground. But, of course, that statement is a truism -- it's essentially a restatement of the definition of the word "possible."
 
Why Not????

May I have written this same e-mail a trillion years ago????????????:eek:

This thread merged with the thread "Why Not????", started by you with a similar topic.
Posted By: Locknar
 
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There was no 'trillion years ago'? I'm pretty sure there was a 'trillion years ago'. Things may have been very different, though.
 
There is no "a trillion years ago" where science is concerned (post big bang.) Depending on how you view time, there was probably no "a trillion years ago" period.
 
calvert said:
May I have written this same e-mail a trillion years ago????????????:eek:
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You know, there's a perfectly cromulent thread you already started on this topic.

The answer was "no" in that thread.

It's still "no" in this thread. I'm sure it will be "no" in the next thread you start, until you get sanctioned for spamming.
 
drkitten said:
It does not. Just because something is infinite doesn't mean that it contains all possibilities.

As a simple example, the number 0.353535353535.... has an infinite decimal expansion. The irrational number 0.101001000100001000001... has an infinite decimal expansion that does not repeat. This simple example shows that infinities need not repeat themselves.

But notice that the digit 2 doesn't appear in either number. This shows that even an infinite process need not include all possibilities.
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That is a good way of putting it.
 
First off, Tegmark writes a lot of very very solid papers on observational cosmology. That part of his work is certainly not crackpot.

drkitten said:
Not all infinite sequences are ergodic, although I suspect that "almost all" of them are.
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It's difficult or impossible to find real physical systems that are not ergodic. Generally speaking there are a few conservation laws (like energy, momentum, etc.), but because of quantum mechanics anything that doesn't violate those laws happens. The only way it can not happen is if the weight for it is precisely zero, and the only way I know for the weight to be precisely zero is if there's a conservation law forbidding it.

So Tegmark's view that anything that's not inconsistent will happen in an infinite universe isn't coming out of nowhere, it's coming out of a rather solid physical intuition.

drkitten said:
Which means that somewhere there is a universe that consists solely of Royal Daulton figurines except for the exact center, which is a torus four km in circumference and made of caramel nougat.
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Consider the "concordance" model of cosmology (that's the simplest model we know of that explains all the observational data). It's got various properties, but the one that matters most for this discussion is that it underwent inflation in its past, and that it has zero spatial curvature (it's "flat"). The latter implies that the universe is spatially infinite, and probably also temporally infinite towards the future. The former implies that the "initial" conditions for each part of the universe were set by quantum fluctuations that happened during inflation.

Quantum fluctuations are governed by a continuous probability density, the one I referred to above. That density is only zero on states that are forbidden by conservation laws. Combining those together, it's not easy to evade the conclusion that there is somewhere a giant tongue made of caramel nougat with "nya nya drkitten" written on it in squid ink.

So how can we escape that absurd conclusion? One way is to drop the assumption that the universe is flat on large scales. There is of course no observation evidence for that, since we can only see a finite piece of the universe. It's just that it's the simplest assumption that is consistent with data.

Another is a much more fancy idea based on "holography", which basically says that the universe doesn't really have a continuous infinity of states in it, even if it's spatially flat, because long distance gravitational correlations reduce the entropy to a finite value. Or in other words, that giant tongue made of nougat doesn't exist in any normal sense of the word "exist". That idea can be made precise in certain contexts, but not so far in cosmology.

Other than that, I'm not sure how to escape it.
 
Actually, I did write this email a trillion years ago. But that damn dial-up connection at the time was so slow, I just knew it would take forever to post! ;)
 
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