Multiple Universes

[Chalnoth]

And there's the misunderstanding. It isn't reasonable to assume that every universe would have developed similarly to our own. The multiverse allows for every physically possible value of every physical variable to be a reality for the initial conditions of a subset of universes. For instance, there doesn't seem to be any physical reason why some variables aren't different: for example, the mass of the proton, or the ratio of proton/electron masses, could be different... they just aren't. Charges, spins, masses, half lives, gravitational constant, ratios of this and that... there are lots of variables that could have been different for this universe, but weren't. Some would make heavy elements unstable (difficult for life there). Some would make galaxies difficult to form, or make nuclear fusion impossible, or... etc. Of all the ways our universe could have been, it appears to be incredibly fine tuned for life. The multiverse allows for all the other ways to be realities, and thus the vast majority would be so completely foriegn to us that it is difficult to imagine how life could exist (not that it is impossible, but statistically it seems unlikely).

I don't believe this is true at all. It seems very obvious that the various quantum numbers of these different objects are the way they are for a very specific physical reason. While it is very true that physicists do not today have a good explanation for why these values are what they are, it just seems perfectly obvious that they are the way they are for very specific reasons.

As a quick example, there are a number of particles that do not have well-defined masses. These particles also are very unstable (Due to the dEdt uncertainty). But there are other particles that have very well-defined masses. These are well-defined for a reason. It seems obvious that because, say, protons have the exact same properties here on Earth as they have on, say, Jupiter, that they would have the exact same properties in any universe. And since essentially any elementary particle can be created out of empty space (if there is enough energy in this space), it seems obvious that there is nothing about the particles in our universe that separate them from particles in another universe.

I mean, it's kind of a neat idea that physical laws could act differently in different universes, but I really don't think it holds any water.

Only a small fraction would even contain the familiar planets and galaxies. And, perhaps all of those do contain life. But, how many would contain intelligent life? How many would contain humans? How many would contain humans on this planet? How many would contain us? You see, each time you move to a lower subset, and get closer and closer to our universe, you move to a smaller fraction of the whole. That's the funny thing about infinity (or in this case, perhaps just astronomical): you can have a subset that is both vast and vanishing at the same time; counterparts of us might be unimaginable in number, and still exist in but an insignificant fraction of universes. The same with intelligent life, or life at all.

And now here you're considering variables which are absolutely impossible to evaluate currently, since we do not have a remotely significant sample size to base any assumptions off of.

That said, life, in general, is appearing more and more to be plentiful. Water is a very common substance in many places in our solar system, and thus is probably common elsewhere (an experiment to detect liquid water in distant stars was recently conceived...I'd be interested to know the outcome one a large number of stars are examined). And of the two planets that we know to hold liquid water, we have found life on both of them (Indirectly on Mars...and only microbial life). The third body that apparently has liquid water we haven't gotten the chance to examine yet.

From this, I think that it's reasonable to assume that life in general is very plentiful. But how plentiful is intelligent life? We have no way to know currently. A sample size of one is absolutely insufficient.

I guess that's what I was really wondering about. I wasn't sure if there was any way in computational theory to ascribe a required amount of work to any given calculation. I suppose it takes a certain number of steps, or would require a certain number of memory elements. Perhaps if you use the lowest possible quanta of energy for memory or single process, then you could establish a lower limit on what is physically allowed for a certain calculation to take place. Interesting at least. I suppose that even if such limits could be placed, the differences in required energy would be beneath our ability to measure. Maybe not though - stranger things have happened.

I suppose that might be true. You might be able to assign a relationship between the error of a calculation and the energy required to do said calculation. If there is a good function to describe this, then a simple minimizing of this energy function would result in the minimum amount of energy required to do some computation. This should be easy to do with, say, memory storage, but may not be so easy to calculate for more complex processes.

[SparrowHawk]

Well, let me just say a few words about the first part of your message. Usually when discussing multi-universe theories, the first topic that comes up is how they would differ from the one which we all experience. The standard model, which for now is our best estimation about how to describe our universe, requires 19 free parameters. In other words, there are 19 numbers that we have to go out to the real world and measure -- then plug those into the formulas to get the right answers out of the theory. What the original author ( who is ? ) was tring to say was that as things stand now, physicists have no reason to believe that any of these 19 numbers couldn't be different. Now, maybe they cant be, but if that is the case, we don't yet understand why they can't. However, one can still ask, how many parameters are there, if any ? Is there only one way to make a universe ? 1 parameter, 2, 3 ? We just don't know yet. Multiverse theorys just speculate that however many paramters there are, a universe exists that has each of those parameters realized (ie all permutations).

The last part of your post has a very intresting answer. It stems from quantum information theory, and is not quite what you might expect. In fact, in order to do any calculation, it is theoretically possible to complete it without ANY energy consumption! This remains true as long as you don't ERASE ANY information. It is the erasure of information that causes loss of energy (to heat, etc). (Obviously Im talking about the machine that does the computation...not the setup of the task). It turns out that the minimum amount of energy you need to spend to erase a single bit of information is W = kT ln 2. (Landauer Principle).

For anyone intresting in Quantum Computing, there are an excellent set of notes by John Preskill for his course at Caltech (the first chapter is probably a good read for any enthusiast, but the rest really requires a strong math / physics background )


See
http://www.theory.caltech.edu/people/preskill/ph229/

[Chalnoth]

Kind of OT, but man, I went to look at the lecture notes, and, well, I really need to fix my Mozilla installation in Redhat 7.3. Anyway, I decided to go into Windows to see if I could view the files more easily, and lo and behold, they're ps files (for some reason, I was thinking they were pdf's...) that I can only read easily in Linux. Bleh...

Anyway, really intriguing stuff, I'll definitely have to look into it further.

[Kruno]

Since we are having a physics discussion, I would like to ask if anyone knows the value of a:
Chronon?
Hodon?
I know they are the smallest units of time and space (respectively) but is there any numerical constant for them?

[SparrowHawk]

To view .ps in windows grap

ftp://mirror.cs.wisc.edu/pub/mirrors/ghost/AFPL/gs800/gs800w32.exe

ftp://mirror.cs.wisc.edu/pub/mirrors/ghost/ghostgum/gsv43w32.exe

[Kruno]

IMO a multiverse is just another easy way out.
It seems to be able to explain so much with little reason. (IMO anyway)

IE:
I go back in time, I would end up in another universe which is identical (in parallel with the universe I come from) but the universe accomodates time travel.
Henceforth any changes I make will be disregarded in my universe along with disregarding any paradoxes as no paradox will be ever made with time travel.

There you go, I cracked the time travel mystery with very little reason and no proof.

[Chalnoth]

Originally posted by SparrowHawk
To view .ps in windows grap

ftp://mirror.cs.wisc.edu/pub/mirrors/ghost/AFPL/gs800/gs800w32.exe

ftp://mirror.cs.wisc.edu/pub/mirrors/ghost/ghostgum/gsv43w32.exe

Eh, it's okay. I'm back in Linux now. All I had to do was install the ghostview rpm's from the Redhat CD's (for some reason the source tarballs that I downloaded off the web didn't work). I can view the files just fine now.

[-=DVS=-]

ALL this to much for me to comprehend :p but i do like SCi - Fy :angel:

[SurfMonkey]

Does anybody remember an experiment where single photons were fired through a mask and the number that returned were measured? I seem to remember some vague problem with the number that returned being less than that fired and it seemed to suggest that photons could be slipping out of this universe.

As for actually recognising a different universe that may be a problem for the human subjective experience to comprehend, maybe they are all around us like ghosts of universes and we can't actually attune ourselves to them.

In the same way that biologists can't actually agree what finite rules actually constitute life and so how would we recognise life unless it like the kind our own subjective experience has geared us for.

[Mod]

I made some research, so I found this:

Oficially, you just have dxdp>=h/(2*pi) , because p and x are quantum operators that have this relation: XP-PX=ih/(2*pi) . dEdt comes from first order perturbation theory. The instability comes from other factors, much complicated ( that I don't care to understad).

Maybe you could have a theory that had variable parameter that were set in the big bang of each universe. So, only universes with certain parameters could develop thinking beings, something people call anthropic principle.

[sytaylor]

Originally posted by Mod

Maybe you could have a theory that had variable parameter that were set in the big bang of each universe. So, only universes with certain parameters could develop thinking beings, something people call anthropic principle.

If you are considering mutiple universes then yeah theres no reason why that couldn't happen that i can see, but as mentioned earlier would these be separate or would they exist on a similar/same continu-um(sp?) tis intruiging stuff

[Bigus Dickus]

Originally posted by Chalnoth
I don't believe this is true at all. It seems very obvious that the various quantum numbers of these different objects are the way they are for a very specific physical reason. While it is very true that physicists do not today have a good explanation for why these values are what they are, it just seems perfectly obvious that they are the way they are for very specific reasons.Well, a lot of things that seem to be obvious to you are not obvious to the best minds on the planet. Nearly all physicists agree that there don't seem to be any specific physical reasons why the quantum parameters have the values they do. If it is so obvious, I'm sure they would love to have it explained to them.

It seems obvious that because, say, protons have the exact same properties here on Earth as they have on, say, Jupiter, that they would have the exact same properties in any universe.Wow, what a leap you have made there. You're comparing properties at two locations from one universe which were in causal contact in the initial formation of this universe, and extrapolating that to draw conclusions about other causally isolated universes. That conclusion is anything but obvious. In fact, there is no gauarantee that, because of inflation, distant parts of our own universe do not contain physical parameters different from what we observe locally.

And since essentially any elementary particle can be created out of empty space (if there is enough energy in this space), it seems obvious that there is nothing about the particles in our universe that separate them from particles in another universe.More stuff that seem obvious to you alone. Assume for a moment that one of the current 10 or 11 dimensional hetorotic string or membrane theories is an accurate representation of reality. Particles can be created from space if the space (vibrating string or membrane) has the right energy, tension, vibration, length, etc. There is no reason to assume that in other universes the fundamental lengths of these constructs could not be different, or perhaps the lowest vibrational period is different. Or, for that matter, there could be 8 or 38 dimensions instead of 10 or 11. There could be 4 macroscopic spatial dimensions instead of 3, etc.

I mean, it's kind of a neat idea that physical laws could act differently in different universes, but I really don't think it holds any water.You're entitled to your opinion, but in this case it flies against the view of most scientists. They think it holds water, and so do I.

And now here you're considering variables which are absolutely impossible to evaluate currently, since we do not have a remotely significant sample size to base any assumptions off of.Which is irrelevant to my argument anyway. I agree - life is probably more plentiful than we had once thought. However, while we can't give numerical values to the fractions representing how likely "humans" are, or how likely "we" are, we can nevertheless recognize that the fraction is probably very small. Sometimes just knowing "small" or "large" is enough, and that was the point I was making there.

A sample size of one is absolutely insufficient.Some things can be discovered through logic alone, without the need for physical evidence. For example, were life to evolve again on this planet, how likely do you think it would be that humans would evolve? Not humanlike, but humans. How likely do you think it would be that us humans (meaning, the exact same people that are here now) would evolve again? How likely do you think it would be that you would evolve again? Hell, rewind time just one century and let chance once again interact with people's decisions and events on a day to day basis, and ask yourself how likely you think it is that you would be born again? Even the unique combination of genes from your parents that makes you who you are is a statistically unlikely event, even supposing that your parents still met, were married, and decided to have children. Now rewind the clock four and a half billion years, and ask the same question. Do you see what I'm getting at? Given a trillion Earths under the same conditions as ours, even if we found intelligent life on all of them, how many would you expect to find humans inhabiting, let alone find a Chalnoth to talk to?

So it's irrelevant that our sample size is only one. We can probe the problem with thought alone. It seems obvious that the percentage of "Earths" containing counterparts to ourselves would be vanishingly small, regardless of the sample size.

[Bigus Dickus]

Originally posted by K.I.L.E.R
Since we are having a physics discussion, I would like to ask if anyone knows the value of a:
Chronon?
Hodon?
I know they are the smallest units of time and space (respectively) but is there any numerical constant for them?

I believe the smallest physically meaningful units of space and time are the planck distance and the planck time, which are 1.6 x 10E-35 meters and 10E-43 seconds, respectively. If they have been labeled the Hodon and Chronon, that's something I wasn't aware of.

[Chalnoth]

Originally posted by Bigus Dickus
Well, a lot of things that seem to be obvious to you are not obvious to the best minds on the planet. Nearly all physicists agree that there don't seem to be any specific physical reasons why the quantum parameters have the values they do. If it is so obvious, I'm sure they would love to have it explained to them.

Well, I think it's more because they're more of what I'm slowly becoming: very cautious to jump to conclusions. It also is sometimes very useful to attempt to see what would happen if you could make odd leaps in logic, and see what happens when you do.

Wow, what a leap you have made there. You're comparing properties at two locations from one universe which were in causal contact in the initial formation of this universe, and extrapolating that to draw conclusions about other causally isolated universes. That conclusion is anything but obvious. In fact, there is no gauarantee that, because of inflation, distant parts of our own universe do not contain physical parameters different from what we observe locally.

While it is in that sense, the connection I was attempting to draw is that you can pull particles out of essentially nothing just by managing to get enough energy in that location. Current elementary particle theories also seem to indicate that we have found all the elementary particles that there are to find. It just seems like a bit of a jump to believe that these elementary particles could be different in a different universe. And as for the string theories, those are just theories. They are being continually rewritten and revised. I do have to wonder if they'll ever find a correct answer. Anyway, as far as all of this is concerned, I do have quite a bit more schooling to do. We'll see what I think then...

Which is irrelevant to my argument anyway. I agree - life is probably more plentiful than we had once thought. However, while we can't give numerical values to the fractions representing how likely "humans" are, or how likely "we" are, we can nevertheless recognize that the fraction is probably very small. Sometimes just knowing "small" or "large" is enough, and that was the point I was making there.

No, I don't think that's enough. First of all, we have such a huge universe with such a vast number of stars. Even if the actual probability for humans existing in any one planet similar to Earth where life exists and the planet has no catastrophic collisions for long enough seems small, if there are many such planets, it could very well turn out that the probability of "humans" existing somewhere is very close to 1. But, it's probably very unlikely for another intelligent life form to actually take on a form similar to our own. At least, for the ones we may be likely to ever come into contact with. I don't really see why the relevance of "us" existing on this planet is relevant to anything.

Back to the original idea, the main question that this raises is that if you can keep entropy constant/increasing across the multiverse, you would need to be interacting with universes that are sufficiently separated from your own in the causal chain of events. Yes, if it is indeed possible to select among any of the possible universes equally, then there's no problem contacting one in which there is not your "double" pushing right back. But, if the other universes are easier to contact dependent upon causal distance, then it will be harder to do so.

[Bigus Dickus]

Originally posted by Chalnoth
I don't really see why the relevance of "us" existing on this planet is relevant to anything.It's relevant because of my previous statement that the percentage of universes in which there are "counterparts" to ourselves (i.e., a closely related universe in which there are only small and mostly insignificant differences between it and our own) would be vanishingly small, and you seemed to disagree. Perhaps I misunderstood you. Even if you were to grant that every universe had the same physical constants, all contained life, all contained an Earth, and all contained the human species, you would still find that only a vanishingly small fraction of them would contain actual counterparts of ourselves. The vast majority would contain other people.

Back to the original idea, the main question that this raises is that if you can keep entropy constant/increasing across the multiverse, you would need to be interacting with universes that are sufficiently separated from your own in the causal chain of events. Yes, if it is indeed possible to select among any of the possible universes equally, then there's no problem contacting one in which there is not your "double" pushing right back. But, if the other universes are easier to contact dependent upon causal distance, then it will be harder to do so. I can't think of any good reasons at the moment why a further quantum separation would make establishing contact easier. In fact, I would tend to think just the opposite. All serious theories of time travel, for instance, require that travel is limited to the time span during which the time machine has existed. Similarly, contact between alternate universes may be limited to those close enough to our own to contain counterparts of ourselves who have created an identical machine to ours... perhaps that is the only artificial way to establish contact. Lots of speculation there.

You are right in one sense though... if that is the case, then those counterparts in another universe won't be too happy with us increasing the entropy in their universe for our own gains. :) Maybe that's what you were saying? That it would simply be less of a "hassle" if we established contact with a universe in which there weren't people around to try and muck up our plans?


And, to get things really going in a bizarre direction, I'll let you in what my current thinking is related to this subject; there is no time, or flow of time, and these other quantum-alternative universes are not just a result of different quantum "choices," but different time slices as well. Reality is nothing but a collection of static universes, with an infinite or near infinite subset representing each static "moment," separated in time by the planck time. We remember events in the past simply because there is only one "past" universe that is closely related on the quantum scale but a vast multitude of "future" universes, due to the many possible outcomes of any single given scenario. Conciousness is the result of a very specific ordered relationship among a subset of like universes. The "big bang" created all possible universes and time slices simultaneously (which counterintuitevely has no real meaning, since simultaneous indicates something time dependent, which doesn't exist). Everything that will happen or has happened or can happen is happening, somewhere in the static multiverse.

OK, so I don't really believe that, but it is an interesting idea that explains much of the mysteries of time.

[Kruno]

OT (since I can't get in contact any other way)

Bigus Dickus: You didn't get my PM?
Well I am stealing your sig, k? :)

[Bigus Dickus]

Originally posted by K.I.L.E.R
OT (since I can't get in contact any other way)

Bigus Dickus: You didn't get my PM?
Well I am stealing your sig, k? :)

Sorry, I don't check my PM that often. I'm used to getting either a pop-up, email notification, or having it displayed in the header somewhere that I have a new PM. I'll look in my user control panel and see if I have that option disabled by accident.

But of course go ahead and use the sig... spread the love!

[Kruno]

Hehehe, thanks. :)

[DaveW]

Originally posted by Chalnoth
I don't believe this is true at all. It seems very obvious that the various quantum numbers of these different objects are the way they are for a very specific physical reason. While it is very true that physicists do not today have a good explanation for why these values are what they are, it just seems perfectly obvious that they are the way they are for very specific reasons.


What specific reasons are these? you weren't clear what this special reason was in your entire post. Anyway, of all the possible universes only a small number of them are stable, only a small number of them could form stars, galaxies, intelligent life. To us, the configuration of our universe has a special significance because we happen to live in it. Its like the person who is holding the winning lottery ticket some how believing that the numbers on his ticket were in some way special, but to everyone else who didn't have a winning ticket, it was just a lucky result of chance.


As a quick example, there are a number of particles that do not have well-defined masses. These particles also are very unstable (Due to the dEdt uncertainty). But there are other particles that have very well-defined masses. These are well-defined for a reason. It seems obvious that because, say, protons have the exact same properties here on Earth as they have on, say, Jupiter, that they would have the exact same properties in any universe. And since essentially any elementary particle can be created out of empty space (if there is enough energy in this space), it seems obvious that there is nothing about the particles in our universe that separate them from particles in another universe.


We haven't studied particles from other universes, so why assume they are the same just because they are the same within our universe. Thats like assuming everyone in the world wears kilts and molests sheep, because you live in scotland and everyone around you does the same. ;-)


I mean, it's kind of a neat idea that physical laws could act differently in different universes, but I really don't think it holds any water.

And now here you're considering variables which are absolutely impossible to evaluate currently, since we do not have a remotely significant sample size to base any assumptions off of.


Yet you make the assumption that every universe is the same. What data samples from other universes is that assumption based off?

All we know is that the multi-universe theory fits well with other theories and fills some holes.


That said, life, in general, is appearing more and more to be plentiful. Water is a very common substance in many places in our solar system, and thus is probably common elsewhere (an experiment to detect liquid water in distant stars was recently conceived...I'd be interested to know the outcome one a large number of stars are examined). And of the two planets that we know to hold liquid water, we have found life on both of them (Indirectly on Mars...and only microbial life). The third body that apparently has liquid water we haven't gotten the chance to examine yet.

From this, I think that it's reasonable to assume that life in general is very plentiful. But how plentiful is intelligent life? We have no way to know currently. A sample size of one is absolutely insufficient.


The existance of current or past life on mars hasn't been conclusively proven. But I agree that it is very possible for it to exist outside our own planet.



SurfMonkey:

Does anybody remember an experiment where single photons were fired through a mask and the number that returned were measured? I seem to remember some vague problem with the number that returned being less than that fired and it seemed to suggest that photons could be slipping out of this universe.


I remember the experiment with photons, masks and interference patterns. If there is one slot in the mask and you fire photons through it, you get a certain pattern (a line). If you fire photons through a mask with two slots in it, you get not two, but three lines, because the photons travel like a wave and interfere with each other. What is interesting about the experiment is that even if you fire just one photon though a mask with two slots in it, it will land according to the three line interference pattern. Hugh Everett argued that the single photon was being interfered with by photons from parallel universes which went through the other slot.

[The Baron]

Chal--this is the entire reason why every physicist wants to know what happened in that first 10^-43 second after the Big Bang. What happened then determined the laws of physics in this universe... but who's to say that it can't be different.

[Bigus Dickus]

Originally posted by DaveW
Hugh Everett argued that the single photon was being interfered with by photons from parallel universes which went through the other slot. And I agree with Everett on philosophical grounds. If it smells like a photon, and acts like a photon, then I call it a photon. Not some pseudo-ghost photon that both exists and doesn't exist, in some phantom never never land that collapses when you think about looking at it, but a real photon in a real universe.

Much less philosophical baggage to carry around. And, as said previously, since it neatly handles time travel paradoxes, the anthropic principle, and the nature of time itself, it seems like a good package overall.

[Chalnoth]

Originally posted by Bigus Dickus
You are right in one sense though... if that is the case, then those counterparts in another universe won't be too happy with us increasing the entropy in their universe for our own gains. :) Maybe that's what you were saying? That it would simply be less of a "hassle" if we established contact with a universe in which there weren't people around to try and muck up our plans?

Well, it's not so much about them not being "happy" about it, but that if we do it to a nearby universe, they'd be doing the same to us, essentially neutralizing the result.

Still, there is a huge problem here. Essentially every "multi-universe" theory (or string theory...) is based far enough outside experiment that there, currently, is no reason to believe one way or another that any of the conclusions of the theory are true or not. Personally I have big problems with theory attempting to get ahead of experiment, and I feel that one situation where experiments need to be done is with respect to Bell's theorem. That is, experiments based on Bell's theorem basically produce instant transmission of data, but relativity states that instantaneity is different dependent upon your reference frame, so how is this possible? I feel that experiments must be done examining this instantaneity in different reference frames, though this is far from trivial to accomplish.

[Chalnoth]

Originally posted by Bigus Dickus
Much less philosophical baggage to carry around. And, as said previously, since it neatly handles time travel paradoxes, the anthropic principle, and the nature of time itself, it seems like a good package overall.

Except time travel may well be fundamentally impossible. In fact, very simple logic dictates that it is. That is, why wouldn't there be tourists from the future here now if time travel were possible? Time travel is a really neat idea, but I have a hard time believing we wouldn't have, at some time or another, managed to find somebody from another time.

[Bigus Dickus]

Originally posted by Chalnoth
That is, experiments based on Bell's theorem basically produce instant transmission of data...Really? I must have missed the headlines on that one. You've piqued my curiosity... now I have to go do some reading. Damn you! :)

[Bigus Dickus]

Originally posted by Chalnoth

Except time travel may well be fundamentally impossible.Indeed, it may well be.

In fact, very simple logic dictates that it is. That is, why wouldn't there be tourists from the future here now if time travel were possible?Originally posted by Bigus Dickus

All serious theories of time travel, for instance, require that travel is limited to the time span during which the time machine has existed.

;)