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Are there other universes?
February 12, 2002 10:02 AM   Subscribe

Are there other universes? It's mind-boggling to imagine how this might be so, but some scientists think it's possible. But if there's no way to detect something, does it really exist?
posted by Prawn (60 comments total)

 
the question is, are there any universes?
posted by jellybuzz at 10:09 AM on February 12, 2002


If you ask that question, you deny your own Buddha-nature.
posted by gazingus at 10:22 AM on February 12, 2002


"There's a reason some theorists want other universes to exist: They believe it's the only way to explain why our own universe, whose physical laws are just right to allow life, happens to exist. According to the so-called anthropic principle, there are perhaps an infinite number of universes, each with its own set of physical laws. And one of them happens to be ours. That's much easier to believe, say the anthropic advocates, than a single universe"fine-tuned" for our existence.

But there's a problem. If these other universes exist, there's no way for us to detect them."

posted by gd779 at 10:22 AM on February 12, 2002


Well, aside from the "If Helen Keller fell down in a forest, would she make a sound?" aspect of the question (blame Michael O'Donohugh for the quote) this idea always makes me wonder about the nature of the our universe and where exactly (if that term has any meaning for this discussion) these other universes could exist. Is our universe an infinite but bounded bubble, surrounded by other infinite but bounded bubble universes in the unbounded infinitude of creation? Do universes coexist in the same spacetime but 'tuned' to different physical 'frequencies' or something? Do their different physical rules developed from different initial sets of conditions create simultaneous, overlapping existing universes that are inherently undetectable because of their differing natures? Am I handsomer or smarter or richer in some of these other universes? Questions, questions, questions...
posted by umberto at 10:24 AM on February 12, 2002


I read this last week. I think it is a great theory, & provides a better explanation (if the math holds up).
posted by thekorruptor at 10:28 AM on February 12, 2002


"The mountain does not stir, yet it soars through the universe."

isn't many worlds one of the three roads to quantum gravity, like with the anthropic principle and stuff?
posted by kliuless at 10:38 AM on February 12, 2002


Other universes can exist. Their existence is not necessary.

Many worlds is is simply an "interpretation" with no real predictive power.

Other universes can exist alongside us. Quantum computing can be thought of as a way of "borrowing" computing resources from these neighboring universes.

This is all metaphysical. These universes are like invisible friends or the purple dragon who always disappears when you turn your head.
posted by vacapinta at 10:47 AM on February 12, 2002


But if there's no way to detect something, does it really exist?

If you kill a mime, does anyone care?
posted by adampsyche at 11:11 AM on February 12, 2002


Am I really here reading this thread? By so choosing to read this thread I must therefore exist in this universe, but could another me exist elsewhere, beyond detection, and read this thread or choose not to? Same goes for particles in physics. A good read is Search for Schrodingers Cat.
posted by brent at 11:12 AM on February 12, 2002


(For the record, any percentage of infinity is infinity.)

If an infinite number of universes exist, a certain portion of those universes would have developed the technology to travel between universes. A certain portion of those universes (also infinite) would have travelled to our universe. Hence, with an infinite number of universes visiting our universe, our universe would be filled to capacity with extra-universal inhabitants. And it's not, is it?

I mean, come on. Didn't you see that Star Trek: The Next Generation episode!?
posted by Danelope at 12:02 PM on February 12, 2002


How do you know our universe isn't filled with extra-universal inhabitants? Maybe our universe is so boring nobody wants to visit.
posted by UnReality at 12:23 PM on February 12, 2002


Danelope: That isn't true if it is impossible to travel through universes. In an infinite number of universes, everything that is possible would occur. It doesn't mean that everything is possible.
posted by Doug at 12:34 PM on February 12, 2002


danelope: Your argument is not silly but it does not include any time-dependent component i.e. an infinite amount of is also needed for an infinite amount of things to occur.

cf. Olbers paradox
posted by vacapinta at 12:54 PM on February 12, 2002


If there are an infinite number of universes, and anything is possible, then an infinite number of universes contain beings that have developed and used the capability to destroy every universe in existence...

Um... QED.
posted by whatnotever at 1:02 PM on February 12, 2002


That isn't true if it is impossible to travel through universes. In an infinite number of universes, everything that is possible would occur. It doesn't mean that everything is possible.

Not to put too fine a point on it (and not to come across like an axe-grinding idealogue, which I try not to be), but that leaves us with two possibilities. Possibility One is that the universe has been "finely-tuned" for our existence; critics reject that theory because it is allegedly unfalsifiable. (In the recent Intelligent Design thread, I was told that anything that cannot presently be falsified is not a proper topic for scientific inquiry.) Proceeding on that assumption, I examine Possibility Two.

Possibliity Two is that there are an infinite number of universes. By definition, we'll never be able to perceive these universes. Obviously, then, Possibility Two is equally unfalsifiable. This leaves us in a bind. Since neither possibility is "scientific", in the sense that neither is testable, we must presumably reject both possibilities. Since the physical laws of our universe are exceedingly improbable, and since we know from mathematics that events of very small probabilities do not occur absent design or regularity (for a definition of regularity, think of loaded dice) , we must therefore conclude that the physical laws of our universe do not really exist after all.

Or, alternatively, we must reject a narrow definition of science and consider the probabilities of each possibility.

(Obviously, my reasoning is absurd by design. But the point remains that, for any given event of small probability, there are precisely three possible explanations: chance, regularity, or design. Design has been rejected as unfalsifiable. Regularity has not been suggested, and anyway it would tend to suggest the existence of a God, which brings us back to the same alleged problem of unfalsifiability. To successfully explain our universe using chance, you are forced to posit a virtually infinite number of "tries" at getting workable laws of physics -- ie, you have to posit an infinite number of universes. Since anything we can perceive must be part of our universe, we will never be able to perceive other universes and we must reject that theory as unfalsifiable. Clearly, then, if you believe -- as I do -- that science has something useful to tell us about this problem, you have to reject a strict definition of science and let scientific inquiry proceed into the realm of determining probabilities, even if those probabilities aren't precisely falsifiable at the moment.)
posted by gd779 at 1:10 PM on February 12, 2002


Listen. This is all very simple. There are two universes. This one has Krispy Kremes. The other one doesn't.

I'm staying in this one.
posted by Kafkaesque at 1:13 PM on February 12, 2002


whatnotever: one of your axioms, "anything is possible" is not proven, nor is it necessarily true even if we assume that there are an infinite number of universes. (I'm just saying it again, Doug)

Anyway, generating ideas about other universes is a legitimate study in cosmology. It is quite interesting to explore what would happen if we assume that in another universe say...there isn't time.

I think that Danelope's argument is better made within our universe:
1. Assume that time travel is possible(on our planet)
2. Assume that we discover how to travel through time
= There are people traveling to our time now.

or

1. Our universe is infinite.
2. Travel to other galaxies is possible.
3. There is sentient life on other planets
= Aliens are invading us now!!!
posted by goneill at 1:15 PM on February 12, 2002


AHHHHH. I just took a test on this in philosophy about an hour ago. All this appears to be is the Cosmological argument as explained by Derek Parfit (I'm sure there are other philosophers who dealt this this, but its who we studied in class). For a deeper reading of this whole multi-universise deal, read Parfit's "The Puzzle of Reality: Why Does the Universe Exist?", which explains many exciting things from other views that are just like the Maximal (anthropic principle in the link) view and why the All-World hypothosis is the next to least-puzzling explanation of how many universes there are (least puzzling is there are no universes (null theory), but that isn't true unless you subscribe to the neo-matrix view or something).
Also, gd779, there are people out there who believe that our world is "finely-tuned" to our existance. Sinse we are obviously here and alive, how is this world not finely tuned to our existance?
posted by jmd82 at 1:18 PM on February 12, 2002


If there are an infinite number of universes, and anything is possible,

Ah, but why would you think that anything is possible?
posted by straight at 1:18 PM on February 12, 2002


Lets get away from all of this infinite business, because we do infact have limitations such as time.

Of course, as University of Arizona astronomer Chris Impey points out, there are parts of our own cosmos that we can't observe, because light from those extremely distant realms hasn't had time to reach us.

Given the idea that there are possibly stars beyond our observable universe, yet we cannot see them since their light has not had time to reach us means that the extistence of our universe is limited. While acknowledging this, if there are other universes they would not be much older than our own universe since we cannot yet observe them.

Although even if there were other universes, it is possible that they have already whithered and decayed out of existence. Although if they had existed beyond the beginning of our universe, why wouldn't we be able to see it? If it the universe was old enough, we should be able to see it, right?

And not everything is possible. For instance, it is impossible to make a round square.

And if our world is not fine tuned to our extistence would that mean that our extistence is fine tuned to the world? In which case, why doesn't life fine tune itself to all of the other planets in our universe?
posted by crog at 1:27 PM on February 12, 2002


Since the physical laws of our universe are exceedingly improbable

Has that really been demonstrated? How could we possibly know the probability of the existing laws of physics? Are you assuming that every conceivable set of physical laws is equally probable?

Possibility One is that the universe has been "finely-tuned" for our existence

Isn't it far more likely that we are finely tuned to fit the universe's existence? That is to say, we are as we are because the universe is as it is.
posted by straight at 1:29 PM on February 12, 2002


possibly stars beyond our observable universe, yet we cannot see them since their light has not had time to reach us means that the extistence of our universe is limited. While acknowledging this, if there are other universes they would not be much older than our own universe since we cannot yet observe them.

I pitched this book yesterday, but i'm going to again: it's called lonely hearts of the cosmos, and it's by dennis overbye.
Anyway - radio astronomers detect signals at different frequencies, to try to determine where matter is coming from. Radio astronomers can 'hear' the farthest reaches of the universe, because sound travels slower than light, the sound from the big bang is not out of our reach yet. That doesn't make a lot of sense, upon reading it, but it was detailed better in this book.

Anyway - I think that the existence of our universe isn't really in dispute currently, but I do believe that the existence of non-us life in our universe is.

When we think of other universes, we are allowed to let our imaginations run wild. Time and space could not exist. A universe could have completely different physics, ie. gravity does not exist. Other galaxies have our physics laws, but do not have our sun, carbonic life forms.
posted by goneill at 1:44 PM on February 12, 2002


Isn't it far more likely that we are finely tuned to fit the universe's existence? That is to say, we are as we are because the universe is as it is.

You misunderstand the point. (Though, in retrospect, the word "our" was probably misleading.) The problem lies in the very ordered nature of the physical laws themselves.

Here's an example: recent supernova evidence has shown that the universe probably possesses a cosmological constant - a universal "repelling" force that accelerates the stretching of space as objects become further apart from each other. In order for the universe to contain stars and planets, this constant must be fine tuned to a level of a part in 10^120. Such an extreme level of precision is almost incomprehensible. The idea of such a thing ocurring in a single universe by chance alone is completely illogical, and, in fact, requires blind faith. That's why scientists like Steven Hawkings have been forced into this metaphysical "multiverse" proposal -- they know that it is necessary to sustain the chance argument, just as very old universe is necessary to sustain an argument for natural selection.

Here is what a recent article from Science says about this hypothetical "multiverse" spinning off an "infinity" of other universes:

Uncomfortable with the idea that physical parameters like lambda are simply lucky accidents, some cosmologists, including Hawking, have suggested that there have been an infinity of big bangs going off in a larger "multiverse," each with different values for these parameters. Only those values that are compatible with life could be observed by beings such as ourselves. (Glanz, J. 1999. AMERICAN PHYSICAL SOCIETY MEETING: Hawking Blesses the Accelerating Universe. Science 284: 34-35.)

What scientific evidence exists to support the multiverse model? None! Not only is there no evidence, the physics of our own universe requires that we will never be able to obtain evidence about any other universe (even if it does exist). Therefore this belief is, and always will be, based solely upon blind faith. A hypothetical, untestable, complicated model of a super universe is the only logical alternative to a belief in design.

You can claim that both the multiverse and design are proper inquiries for science, or you can claim that neither is, but you cannot claim the label of science for only one.

I should credit God and Science for most of this argument.
posted by gd779 at 1:50 PM on February 12, 2002


One of my new favorite modern myths/urban legends is the story of the Ong's Hat cult, a group of interdimensional travels who discovered the ability to visit these many worlds sometime in the 80s in New Jersey.
posted by euphorb at 1:55 PM on February 12, 2002


Since the physical laws of our universe are exceedingly improbable, and since we know from mathematics that events of very small probabilities do not occur absent design or regularity (for a definition of regularity, think of loaded dice) , we must therefore conclude that the physical laws of our universe do not really exist after all.

Shuffle a deck of cards and deal them out one by one face up. Calculate the odds of that particular series coming up. It's aproximately 7.1e+74 to 1. Do you conclude that the cards didn't come out the way they did?
posted by signal at 2:05 PM on February 12, 2002


The idea of the universal constant has been around for a long time. Great cosmologists (I am thinking of Sandage in particular) have spent their entire lives searching for it. The cosmological constant is the rate at which the universe is expanding, if it is below a certain number then the universe will begin to contract into itself (due to gravity) if it is above that number then it will extand exponentially forever. If it is that number then we will have a closed universe, but a universe that will not close onto itself.

Much of the work that is done in imagining the properties of other universes is interesting to read about, and is readily accessible to lay people (like myself!).
posted by goneill at 2:06 PM on February 12, 2002


the physics of our own universe requires that we will never be able to obtain evidence about any other universe (even if it does exist).

This is wrong. Where are you getting this misinformation from?
posted by vacapinta at 2:07 PM on February 12, 2002


How can we obtain information about other universes other than through speculation?
posted by goneill at 2:13 PM on February 12, 2002


How can we obtain information about other universes other than through speculation?

Through a process called science.

gd779 made the statement "the physics of our own universe requires ...". My training in physics has not revealed to me any such strong requirement.

Today, we have no information about other universes but it is not inconceivable that their effects can be seen and accounted for in any number of ways as "leaking" into our universe.

Hawking himself showed that the so-called impenetrable boundary at the event horizon of a black hole was actually quite permeable.

In any case, I'm bowing out of this discussion. I apologize but I dont want to instigate a creationist debate here. I'm not in the mood.
posted by vacapinta at 2:24 PM on February 12, 2002


This is wrong. Where are you getting this misinformation from?

Why do you say it's wrong? I got it both from the linked article and from God and Science. Read my first post in this thread; it's a quote from the article. Here's another, clarifying quote from the article:

But if these other universes do exist, are we really destined never to detect them? Some theorists have speculated that gravitational energy from other universes might leak into ours, and that someday we might figure out how to detect it. But even the most open-minded cosmologists say that's a long shot at best.

vacapinta: I just previewed and saw your last post, and it's pissed me off. I'm trying my hardest to just improve, through argumentation, my understanding of this issue, and you have to go and take this high-and-mighty, I-don't-need-to-talk-with-the-ignorant attitude. In my opinion, that's contrary to the tolerance and free flow of ideas that MeFi is supposed to encourage.

Signal: Shuffle a deck of cards and deal them out one by one face up. Calculate the odds of that particular series coming up. It's aproximately 7.1e+74 to 1. Do you conclude that the cards didn't come out the way they did?

Ah, now we're getting into the good stuff. Your question is intuitive, I admit, but ultimately fruitless.

Let's try another hypothetical: let's say you shuffle another deck of cards, and deal them out out one by one face up. Only this time, the cards are in perfect sequential order. The probability of this occuring is also 7.1e+74 to 1; precisely the same probability as any other given order of the cards. Yet, if you were to see someone deal the cards as I described, you'd accuse them of cheating. Why? Despite the random nature of both deals, we regard the deals in different ways... again, why? Because one is orderly while the other is appearantly patternless.

The problem is vastly exacerbated when considering the laws of physics, because the probabilities are far smaller.

So, yes, events of small probability ocurr around us every day. But this doesn't get us anywhere, because precisely because events of small probabilities happen every day. The universe only came into existence once. The question is, given only one try, how likely is it that we would get an ordered universe?

So, to return to the beginning, what seperates my deck of cards from yours? On this point, I recommend a book called The Design Inference by William Dembski. According to Dembski, the answer lies in the combination of very small probabilities and specificity. When an event is both unlikely and specific, chance and regularlity can be eliminated and design can be inferred. (People use this logic every day, but Dembski gives you the math).
posted by gd779 at 2:34 PM on February 12, 2002


Ugh. I just glanced in curiousity at the reviews of The Design Inference on Amazon. You're going to have to ignore some of the more ideological "reviewers", including those appearantly on the creationist side of the fence; if they'd actually read the book, they'd know that it doesn't really deal with the issue of evolution at all (There are about 3 pages devoted to that topic, and none of them attempt to argue the merits of any particular position). Dembski's work (his graduate thesis, actually) is an attempt at formalizing our intuitions about design and chance, nothing more.
posted by gd779 at 2:53 PM on February 12, 2002


Did the universe only come into existence once? If you take Many Worlds to be far more literal than you probably should, then every possible outcome of the big bang should have occurred.

We don't know how many possible universes allow for matter to form, for planets and stars to form, or how many do not. We don't know what if any process determines the nature of the laws of those universes. To use your card analogy, gd779, we don't know how many cards there are in the deck or how many times they get shuffled. If they are both infinite or both singular our existence is guaranteed, but why assume out existence was guaranteed?
posted by Nothing at 3:02 PM on February 12, 2002


Despite the random nature of both deals, we regard the deals in different ways... again, why? Because one is orderly while the other is appearantly patternless.

But in actuality, they are both equally as ordered. It's our brain that makes order from the result of the draw.

It seems to me, gd779, that your argument requires that the universe has existed only once, and is the only universe in existance. These assertations may be false. I agree with you that at this point, there is no evidence for multiple dimensions. I don't agree that multiple dimensions are as likely as this universe being designed.

Perhaps this is faulty logic, but we have evidence that a universe can exist. It seems like a logical step to say that perhaps other universes can exist. On the other hand, there is no evidence whatsoever of a being able to manipulate the universe on such a grand scale. Again, I may be wrong, but wouldn't such a being have to operate outside of the universe? Where is the evidence that this can occur?

You make some interesting points. Certainly made me think of the issue differently. I wouldn't say with any degree of certainty that there are multiple universes, or that the universe was designed by some higher form of life. I'll grant that both are possible. But one seems more likely to me.
posted by Doug at 3:07 PM on February 12, 2002


In order for the universe to contain stars and planets, this constant must be fine tuned to a level of a part in 10^120. Such an extreme level of precision is almost incomprehensible. The idea of such a thing ocurring in a single universe by chance alone is completely illogical, and, in fact, requires blind faith.

But to say that this state of affairs is "unlikely" assumes you have some idea of its likelihood in relation to other possibilitites.

To use the card example, you can only state that the odds of 7.1e+74 to 1 because you assume that all possible orderings of cards are equally likely.

For all we know, there are one or more underlying reasons that make our sort of universe much more likely to exist than any other sort of universe. What you call extremely unlikely might seem necessary or inevitable, if we knew more about the universe.
posted by straight at 3:19 PM on February 12, 2002


Quite a few people in this thread don't seem to understand the anthropic principle. To again go back to the deck-of-cards metaphor:

If you shuffle a deck of cards and lay them out one by one, and they comes out in order, you'd be inclined to suspect that there was something very fishy going on, and rightly so. The difference between the deck of cards and the fundimental laws of the universe is that if the laws of the universe were different, you wouldn't BE THERE TO OBSERVE THEM.

For another anology, imagine you are in a large public bathroom with a tiled floor. You pick a random tile to look at and see if it has any interesting propertys that seperate it from the rest. And indeed it does. You're looking at it! Of all the tiles in the room, you're only looking at this one tile! And it's the tile you picked to look at, completely at random! How amazing!
posted by Flimsy_Parkins at 3:37 PM on February 12, 2002


flimsy

that was my original point with the card analogy: probabilities are only relevant before the fact. The probability of anything which already happended is exactly 1.
posted by signal at 3:44 PM on February 12, 2002


What you call extremely unlikely might seem necessary or inevitable, if we knew more about the universe.

That's another really intuitive argument, but it also doesn't get us anywhere. The cosmological constant was only an example, after all; look at the big picture. I say, "this particular law is needed to sustain the planets, and it's unlikely". You say, "it looks unlikely, but their might be other laws that demand that the first law be as it is". But the real question is, how likely is it that those second laws would exist and produce so precise a result? The real question is, how likely is it that all those laws would fit together at all? Absent natural selection and genetic drift, animals can't adapt to their environment; but the laws of physics don't change, so they can't adapt to anything. Absent the multiverse, it's a one-shot proposition. That makes chance unlikely, and it seems to me that you must resort either to the multiverse or to a sense of design.

As Arno Penzias, winner of the 1978 Nobel prize in physics, has said "Astronomy leads us to a unique event, a universe which was created out of nothing, one with the very delicate balance needed to provide exactly the conditions required to permit life, and one which has an underlying (one might say 'supernatural') plan."

Doug:

You...certainly made me think of the issue differently... I'll grant that both are possible. But one seems more likely to me.

I'm trying to provoke discussion, not proselytize. So that's high praise to me. Thanks!

The difference between the deck of cards and the fundimental laws of the universe is that if the laws of the universe were different, you wouldn't BE THERE TO OBSERVE THEM.

Right. So the question is, given what we know about physics, how likely is it that a single instance of the big bang would result in some combination of natural laws capable of sustaining order. In other words, how objectively likely is it that we'd get laws of physics allowing us to be here to observe the laws of physics?

One of us clearly doesn't understand the point here. Maybe it's me, I honestly don't know. But I don't see what your comment proves, beyond the fact that, since we are here, we shouldn't worry ourselves about how likely it is we'd get here through naturalistic mechanisms alone.
posted by gd779 at 3:48 PM on February 12, 2002


Dictionary.com defines universe as

1. All matter and energy, including the earth, the galaxies, and the contents of intergalactic space, regarded as a whole.

and

2. The sphere or realm in which something exists or takes place.

Even the prefix Uni (unus) means "one".

So by definition alone isn't it impossible for two Universes to exist? If another entity similar to the entity that we consider to be "our universe" existed somewhere, then wouldn't we have to rename our "universe" to something else? Since a Universe would be one all-encompassing entity and therefore contain both our "universe" and the other "universe"?

I think what I'm trying to imply is that maybe the existance of another Universe means that we've been using the word Universe incorrectly from day one. But I'm not sure. I know nothing of astronomy.
posted by tomorama at 4:02 PM on February 12, 2002


gd:

how likely is it that a single instance of the big bang would result in some combination of natural laws capable of sustaining order.

this assumes that a) the laws of physics were somehow "set" by the BB b) they could have been different. both points are highly disputable. did the laws of geometry also get set? how about logic? why would physics be more elastic?
posted by signal at 4:15 PM on February 12, 2002


It seems kind of like you are all saying the same thing, or variations of the same thing.
1. The universe was created by the big bang ->We evolved as we are to fit in it.

2. There are many universes and big bangs and different schroedinger's values of the big bang, and we live in this one that supports life.

I think that the problem with 1 is that it is unlikely that 'life' could exist in a universe, what with all of the possible types of universes out there (look at the cosmological constant, if it were only slightly different there would be no galaxies!!!)
The problem with 2 is that, hey, there might not be any other universes, which is what we are discussing now anyway...
posted by goneill at 4:16 PM on February 12, 2002


The big bang was caused by a singularity, which can be thought of as a point with infinite mass and no area. There are no laws of physics or geometry, or logic in a singularity. This is also what a black hole is. So, signal, if things went slightly differently then the universe could and/or would be different.

And tomaroma, Our universe is 'everything' to us, in that we can never not be in our universe, but there could be another 'everything' that we are not privy to.
posted by goneill at 4:19 PM on February 12, 2002


I would argue that if the definition of the word "universe" is causing problems, the definition should be changed. "Atom" originally meant "indivisible unit of matter".

this assumes that a) the laws of physics were somehow "set" by the [big bang] b) they could have been different. both points are highly disputable. did the laws of geometry also get set? how about logic? why would physics be more elastic?

Because unlike geometry/logic, you can concieve of and run simulations in which the laws of physics are different. Physics is based on logic and math, and unlike them it's laws cannot be derived through pondering alone. They must be observed.
posted by Flimsy_Parkins at 4:52 PM on February 12, 2002


You guys think too much.

The universe is BIG, but it may not be infinite. It's just so big we have not yet seen the end of it.

For a comparison that is easier for our minds to grok, our planet Earth is so big that California cannot be seen from New York if you're standing in San Diego, but that's because the planet is curved, and we can't see beyond the horizon. If you could get in the space shuttle and go out into space, you CAN see California and New York at the same time, but you can't see China simultaneously, again because the planet is spherical.

The universe may or may not be spherical. We don't know what shape the universe is. We assume it is infinite because we can't see where the universe ends, but that's as silly as assuming New York isn't there because you can't see it from San Diego. Just a few centuries ago, civilized mankind in the eastern hemisphere assumed there was no western hemisphere because they assumed the world was flat. We now know that was a silly assumption, but we are now making a similar silly assumption about the universe being infinite.

The diameter of our planet, the distance between the Earth and the Sun, and even the distance it takes light to go from point A to point B in one year, all these would comparably be a fraction of a millimeter in comparison to the universe itself. We know this from observation. The universe is SO BIG we can't see where it ends. However, it may not be infinite.
posted by ZachsMind at 5:11 PM on February 12, 2002


I won't speak for the others, but I personally have never said the universe was infinite. For it to be infinite, it seems that it would have to have been expanding for an infinitely long time (or worse, at an infinite rate) since the big bang.

It makes sense to me that the multiverse would be infinite though, and even contain infinite universes.
posted by Flimsy_Parkins at 5:28 PM on February 12, 2002


"But if there's no way to detect something, does it really exist?"

If something does exist that we cannot detect, then do we really exist? Because from that thing's perspective we are undetectable, and by the quoted postulate above, therefore we might not exist.
posted by kfury at 6:36 PM on February 12, 2002


I'm not up on this stuff, but has the big bang since been proved to be any more than a theory? I never really put much weight in it. It's being thrown around here and in that article like it's fact; is that the accepted explanation?

I can't see how the big bang could be a plausible explanation for the universe... that one minute there was nothing and then there was something. Even if there was energy that flexed and created the universe, or whatever the description in the article was, energy is something.

But I really don't want to get heavily into how the universe began because then I would be inclined to bring God into it, and I can see where that discussion might take a turn to.
posted by tomorama at 7:13 PM on February 12, 2002


signal writes: that was my original point with the card analogy: probabilities are only relevant before the fact. The probability of anything which already happended is exactly 1.

i was just thinking it might affect the conditional probability. but like i guess only if existence isn't observed with certainty, if i got my statistics right :)

i was also just wondering if extra dimensions count as different universes or whatever. or like the multiverse or something. cuz i read in the economist about this guy trying to measure the eleventh dimension!
posted by kliuless at 7:26 PM on February 12, 2002


the universe is in the shape of a man....I promise.
posted by Espoo2 at 7:28 PM on February 12, 2002


I'm sticking with pantheistic multiperson solipsism, thank you very much.
posted by mr_crash_davis at 8:02 PM on February 12, 2002


Extra dimentions do not count as different universes, the universe is the shape of a hollow fourth dimentional sphere, and the big bang is generally accepted but does not account, or presume to account, for why anything exists. It's just what happened right AFTER the universe came into existence.
posted by Flimsy_Parkins at 9:00 PM on February 12, 2002


You mean there's other universities?
posted by swift at 10:11 PM on February 12, 2002


gd779: In order to estimate the probability of a particular constant having the value it has, one has to have some idea of how these values are "generated" (for lack of a better term). It could conceivably be the case that the fundamental constants are solutions of particular fundamental (unknown) equations and lie within a very narrow range of mathematically acceptable values. It might turn out to be the case that these values are unique and only this particular set of fundamental constants is self consistent. We don't know. And since we don't know we cannot evaluate the probability of these constants turning out to have their measured values.

Note as well that the parallel universes described in the article are not necessarily mutually isolated. One's existence might have a measurable impact on another. Also they are not infinite in number necessarily. Quite the opposite.

Finally this multiverse theory is conceptually distinct from Everett's and Deutsch's parallel universe interpretation of quantum mechanics, of which a description can be found here. Which raises the intriguing possibility of the existence of two different sets of parallel universes!
posted by talos at 3:51 AM on February 13, 2002


talos: yeah i read that in the economist, too!
To add to the confusion, there is yet another branch of multiverse theory, although this requires only two universes. On the other hand, if it is true, many of the ideas that have been rehearsed in this survey are false: for this theory plans to dispose of inflation.

Ekpyrosis is an idea that is only a few months old, and is evolving fast. It was dreamed up by Paul Steinhardt, at Princeton, and Neil Turok, of Cambridge. It is a version of M-theory in which two branes (in effect, two parallel universes) collide every so often. Such collisions, according to the calculations done by Dr Steinhardt and Dr Turok, would produce almost the same results as inflation. Originally, the theory described only one collision, but now the two researchers have extended it. They believe the two branes clash regularly (say once every few trillion years). Each time this happens, a new wave of creation is started.

Like all the best cosmic creation-myths, this one seems testable. Once again, MAP may provide the answer. Inflation would have produced gravitational waves. These should have imprinted the cosmic microwave background with a recognisable pattern in addition to the one created by the frozen quantum fluctuations. Ekpyrosis would have no such consequence. Absence of evidence is not, of course, evidence of absence, but if the predicted pattern is missing, then inflation, which currently lives by the cosmic microwave background, may end up dying by it.
btw, here's that other article with the guy trying to measure the 11th dimension. has to do with "M-theory" :)
posted by kliuless at 6:50 AM on February 13, 2002


tomaroma - i think that the big bang is the currently accepted model on which scientists run tests, and study the universe. it's kind of like the evolutionary theory of cosmology. sure, it is just a theory, but if it were debunked, it would be a MAJOR deal to astronomy.
posted by goneill at 7:00 AM on February 13, 2002


Fascinating, so it's three sets of parallel universes counting ekpyrosis... Where does it end...?
The 11th (or Nth) dimension doesn't have anything to do with other universes since it's about the 11th dimension of our universe they're talking about. (BTW: The economist link you posted doesn't work...)
goneill: I wouldn't put anything in cosmology on the same level of confirmability as evolution. Regardless I think this page provides a great guide to Cosmology...
posted by talos at 7:45 AM on February 13, 2002


pet-peeve: when cheesy sci-fi shows or books talk about people from another dimension. jeez.
posted by signal at 10:12 AM on February 13, 2002



Lisa: Well, where's my Dad?
Frink: Well, it should be obvious to even the most dim-witted individual who holds an advanced degree in hyperbolic topology, n'gee, that Homer Simpson has stumbled into...[the lights go off] the third dimension.
Lisa: [turning the lights back on] Sorry.
Frink: [drawing on a blackboard] Here is an ordinary square --
Wiggum: Whoa, whoa -- slow down, egghead!
Frink: -- but suppose we exte-end the square beyond the two dimensions of our universe (along the hypothetical Z axis, there).
Everyone: [gasps]
Frink: This forms a three-dimensional object known as a "cube", or a "Frinkahedron" in honor of its discoverer, n'hey, n'hey.
Homer: [disembodied] Help me! Are you helping me, or are you going on and on?
Frink: Oh, right. And, of course, within, we find the doomed individual.
Wiggum: Enough of your borax, poindexter! We need action --[fires his gun six times through the wall] Take that, you lousy dimension! [the bullets fly toward Homer, but spiral around the widening hole and get sucked into it]
Homer: Oh, there's so much I don't know about astrophysics. I wish I'd read that book by that wheelchair guy.

posted by signal at 10:18 AM on February 13, 2002


(talos: links seem to be working now, i think the monkeys that type us into existence were messing around :) what's cool is they changed the sidebar links so they point to some outside material! to wit, "a philosophical debate on the multiverse between Sir Martin Rees and Hugh Mellor."
posted by kliuless at 11:08 AM on February 13, 2002


It could conceivably be the case that the fundamental constants are solutions of particular fundamental (unknown) equations and lie within a very narrow range of mathematically acceptable values. It might turn out to be the case that these values are unique and only this particular set of fundamental constants is self consistent.

I get what you're saying, but here's my question: is there any evidence to indicate that this is the case? It might be the case that the universe could not have turned out any other way, but also it might be the case that the universe was created whole just 10 minutes ago. We have no reason to believe that either hypothetical is plausible, do we? Assuming that our universe did not need to turn out the way that it did, we can compare each of the parameters of our universe (various numerical values necessary to sustain any kind of conceivable order) and calculate those probabilities.

Or am I missing something?
posted by gd779 at 1:38 PM on February 13, 2002


gd779: It might be the case that the universe was created 10 minutes ago as it is, but (aside for philosophical problems) if that is the case we're destined to never know this. So this is a different matter.
Whether or not the universe could or could not turn out another way is a different issue. It concerns our knowledge of the universe and of the underlying physical entities that determine its evolution. Until we have a better understanding of this we cannot venture to assign probabilities for its occurance. We do not know what sets of parameters are consistent with the existence of the universe. It might be that the fundamental constants are interdependent in some (as yet unknown) way or that the slightest difference in their values make expansion impossible. Furthermore we cannot even be absolutely certain that our constants are truly constant, it could be the case that the value of, say, the gravitational constant had a different value during the initial moments of the big bang. So this is a question concerning the state of our knowledge and it is not unreasonable to expect that sometime in the future we will be better able to evaluate this problem more concretely.
We have a similar situation with the emergence of life. We really do not know wheather, given the right conditions, life is bound to arise spontaneously, or wheather it's a one in a billion occurance. That is due to our relative ignorance of the physical processes of self organization. So the number of planets that can support life in our galaxy might be 1 or 1 billion. We cannot even assign probabilities.

BTW the link kliuless posted above, has a really interesting discussion on this topic.
posted by talos at 3:17 AM on February 14, 2002


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