Slashdot Mirror
A Skeptical Look At The Multiverse
sjanich writes "The NY Times has a short, interesting article on multiverse theory. The author, Paul Davies, writes: 'This idea of multiple universes, or multiple realities, has been around in philosophical circles for centuries. The scientific justification for it, however, is new.' It is quite an interesting read. The author is a Physicist and pretty good science writer." Davies is not kind to the multiverse theory.
http://www.hedweb.com/everett/everett.htm
Taking the multiverse theory at face value, therefore, means accepting that virtual worlds are more numerous than "real" ones. There is no reason to expect our world -- the one in which you are reading this right now -- to be real as opposed to a simulation.
I mean, what's the problem with this? Until we find evidence to the contrary, it remains a distinct possibility. And it borders on the realm of so-what. Is the knowledge that you're actually a participant in a very large simulation going to change how you live your life?
I mean, are you annoyed that when you fall, you accelerate at exactly 9.8 m/s^2 (in a vacuum) towards the center of the earth, without fail? Those unimaginative programmers...
THIS THING CAN TURN ON A DIME, MACROSSZERO STYLE ALSO FUCK BETA, ~NYORON
Davies refers to, but never explicitly states one particular point: Most of the multiverse theories are inherently untestable, because we're completely isolated from the other universes. These are theories that don't predict or even suggest anything. How meaningless can you get?
This is a good general point. Solipsism is uninteresting. Subjectivism & deconstructivism are often taken to similar absurd extremes by stupid people, including respected critics.
He makes the analogy between theology & these scientific non-explanations. Religion is personally very meaningful, but metaphysics isn't science. Consequently a classic metaphysical question, "How many angels can dance on the head of a pin?" is the canonical meaningless question.
The word that springs to mind is sophomoric. It reminds me of High School, when one friend asked another "What if you're really insane & just dreaming all of this?" The answer was of course, "So what? You've gotta pretty much live your life the same way anyway."
Assembly is the reverse of disassembly.
Why is nature so ingeniously, one might even say suspiciously, friendly to life?
Well, this is one to ponder, granted that you consider life to be basically an earthbound form or entity. It always amuses me that there is talk about whether this place or that could support life. Just because we, as earthbound beings, rely on certain conditions to live, who is to say that other lifeforms would live in something that we'd consider completely destructive to our own very nature. How do we know that there aren't life forms out there that don't depend on breathing molten gold in the same way we need to breathe oxygen? Or to take it even farther, who says they need to breath at all?
But to come back on topic, I think that the multiverse theory is a very interesting one. I think it's possible. Why? Because it's interesting that way. =0)
*slight crashing sound*
Everywhere he says life could not exist in any other universal properties and constants should be modified to state "life as we know it."
quote:
Life would probably be impossible with more (or less) than three dimensions to work with, so our seeing three is then no surprise. Similar arguments apply to other supposedly fixed properties of the cosmos, such as the strengths of the fundamental forces or the masses of the various subatomic particles.
Why exactly is life impossible with more than 3 dimensions? He subscribes to the fundenmental flaw that all science fiction writers subscribe to: all alien life forms breath, walk on legs, and "see" through eyes. Sure, it's hard to change a human actor on a movie screen by too much, but the world of books and pages ought to be able to create something better.
I also agree with the other post that says, paraphrased, if we live in a giant simulation, does that make existance different? If you can't get out of, or control the simulation, what difference does it make? I, for one, am not worried about hyperintelligence alien giants looking at me showered naked, and the like.
Along those same lines, if we can eventually create computer simulations with sentiant beings, why can we not create a universe with different parameters and force life to exist within it?
Lastly, if we can't get out of this universe into another one, what difference does it make? And if we somehow break the barrier and jump universes, the link between them makes them one universe with localized properties doesn't it?
-Ryan
AUWYHSTOT (Acronyms are Useless When You Have to Spell Them Out Too)
It is worthwhile to point out that cosmological
diversity is only one kind of "multiverse" theory.
In it, all of the various universes are embedded
in a larger space. Such theories are not therefore
unscientific, in the sense of being intrinsically
unfalsifiable, or unverifiable: Because the various
universes have topological relation to one another,
there is a continuum of existence connecting them,
and they may interact in yet unforseen ways. Our
current inability to design experiments to detect
such interactions is merely an artifact of
ignorance.
But there are many other forms of ontological
multiplicity which do not involve topological
continuum. The outstanding example is the
Everett interpretation of quantum mechanics.
In that theory, rather than the actual state of
affairs in the universe being the sole real
instantiation of the phi wavefunction, created
by the act of observation (as in the classical
Copenhagen interpretation of Bohr et al), the
quantum wave function is considered to be a
representation of the distribution of an infinite
multiplicity of alternatives, all equally "real".
I find the Everett interpretation to be much
preferrable, on several grounds, not the least
of which is that it is consistent with the
mathematical concept of probability distribution
in a way which the Copenhagen interpretation is
not, but others disdain
it because it implies the real existence of
entities which are not, so they say, in principle,
detectable. Again, this complaint fails because
it is an argument from ignorance: The current
inability, at a given level of human understanding
and technology, to design a verifying or falsifying
experiment, does not relate to the truth or falsity
of the hypothesis. Cophenhagenists are quite
comfortable supposing that unseen cats are undead,
and any truth not currently known is not yet true.
I think this is a much larger leap of faith than
is needed to create a working understanding.
-I like my women like I like my tea: green-
Science: A Skeptical Look At The Universe
The NY Times has a short, interesting article on universe theory. The author, Paul Davies, writes: 'This idea of single universe, or single reality, has been around in philosophical circles for centuries. The scientific justification for it, however, is new.' It is quite an interesting read. The author is Physicist and pretty good science writer." Davies is not kind to the universe theory.
The existence of intelligent life does require the universe to be large and complex. The multiverse interpretation demonstrates a related point: the probability of intelligent life arising in this universe might be low, or even very low. You don't need the multiverse interpretation to work this out, but it does make it a lot clearer. The ET searchers often express the assumption that our existence shows that intelligent life is likely to have a probability greater than one (because here we are). The fallacy that the size/complexity of the universe (which came first) caused intelligent life (which came later) is an easy mistake. You really need the multiverse interpretation to see that it is a selection effect fallacy. Note that the multiverse interpretation doesn't have to be "true" to fill this role, just one consistent way of looking at the issue.
This isn't a case of anthropomorphism or earth-centrism or anything like that. It's an outcome of basic physics (it does take into account that physics may be different in other universes, though).
To take a simple example at the grossest level: imagine a universe in which symmetry broke in such a way that instead of three macroscopic spatial dimensions resulting, there were only two. A two-dimensional universe would be incapable of hosting structures of very significant complexity such as multicellular lifeforms. There would be strict limitations on size becaues a 2-D lifeform cannot possess any kind of internal transport system for alimentation or circulation - it would simply fall apart (try drawing one and see how internal channels effectively divide the creature into pieces).
Four dimensional universes (and higher order dimensional spaces) also have topological problems which would make life difficult though you'll have to look those up for yourself.
Even in three dimensional universes, very slight modifications to the relative strength of the four fundamental post-symmetry-breaking forces would make the universe appear very different.
There will be universes composed entirely of radiation - but radiation does not interact well enough to form structures spontaneously.
There will be universes where stars shine but never explode, thus elements heavier than helium are never released from their cores - and you can't get interesting chemical reactions from just hydrogen and helium.
There will be many dark universes where star-sized agglomerations of matter simply do not ignite at all, thus energy cannot be concentrated sufficiently enough in any one place to fuel a biosphere.
Even if you had hot stars and an interesting array of elements it may still be devoid of life if there was no possible *simple* (and thus common) combination of those elements available to provide a molecule like water - slightly more than weakly polar, which remains liquid at a range of useful temperatures (warm enough to enable chemical reaction at a significant rate, cool enough to allow stable reaction products).
It's all very well to postulate "energy beings" or Horta-style silicon-based lifeforms but basic physics just doesn't make these very likely. There are strong practical reasons why all life on Earth is based on water and carbon compounds. There may be other constellations of physical laws which could generate a universe complex enough to support life, but there are far, far more that couldn't, no matter how good your imagination is.
The May issue of Scientific American contains a much more in-depth article on parallel universes, which has enough points in common that it might have inspired the op-ed piece.
Teaser for the article is here. To get the whole thing, you either have to have a subscription or wait until next month.
The gist of it is as follows:
In principle, these other "universes" can interact with our own, but in practice they're far enough away that it doesn't matter. Physical laws are likely similar.
Re. an infinite universe, the article states that a finite universe would leave artifacts in the cosmic microwave background that weren't seen.
These parallel universes are utterly unreachable, as the space between them a) exists in a different coordinate system that puts it in our past from our point of view, and b) is expanding exponentially quickly, dragging other universes away from ours at mind-boggling speed.
As far as I understand it, interaction between these universes wouldn't be possible without violating some of the ground rules involved (the history tree could be thought of as a state transition diagram for all possible states of a closed system; if it's closed, it can't interact with anything else).
If you call this a "real" universe, then Everquest and the reality hosting the United Federation of Planets are also real universes. It depends on your point of view (and what you mean by "real" in this context).
The existance of "universes" of the first type is certain if the universe is infinite, from information theory arguments. The infinite or non-infinite nature of the universe is something that can be empirically tested (though the final test - waiting for every part of it to come within our observation horizon - is impractical).
The existance of the second type of universe hinges on the nature of the scalar fields proposed in the various inflationary models. In principle, this is testable, either by recreating the energies required or by observing distant parts of the universe that are undergoing inflation.
The existance of the third type of universe is not testable, due to the requirement for closed systems. So it's pretty much a moot point.
The existance of the fourth type of universe is a metaphysical question, whose answer depends on what you mean by "exist".
The full article has a lot of additional discussion, and pretty pictures. By all means pick up a copy, if the topic interests you.
> > Why is nature so ingeniously, one might even say suspiciously, friendly to life?
> Well, this is one to ponder, granted that you consider life to be basically an earthbound form or entity. It always amuses me that there is talk about whether this place or that could support life. Just because we, as earthbound beings, rely on certain conditions to live, who is to say that other lifeforms would live in something that we'd consider completely destructive to our own very nature. How do we know that there aren't life forms out there that don't depend on breathing molten gold in the same way we need to breathe oxygen? Or to take it even farther, who says they need to breath at all?
Also, when people start arguing that the universe is uniquely suited for life it is useful to ask them what percentage of the universe is actually hospitable to life AWKI.
A thin crust at the surface of a few planets, out of the entire volume of the universe? It looks to me like the universe was "designed" for something else altogether, and life found a few rare, small cracks to hide in. As well to say that the lobby of a fine hotel was designed to harbor dust particles.
Sheesh, evil *and* a jerk. -- Jade
Paul Davies is a religious person. And so when there are two competing theories, one of which includes his ideals of religion, and one which does not, he will choose the first if there is no other evidence given. The reason that the multiverse theory is postulated is to give a kind of evolutionary account of the cosmology of the universe. Who knows if there are other universes, or if they are anything like our own? We certainly will never know.
But Davies' favored alternative is a much less viable option. To explain away the existence of our world with something that's even more complicated, such as God, is no explanation at all. Explanations reduce complex things to simple things. And if God can create something as complex as the universe, he must clearly have at least that much complexity within Himself.
We've seen this conflict before. Look at these well designed humans! How could they have possibly arrived upon this Earth? Surely only a being as complex as God could have accomplished such a wonderful feat! This was the great argument of the last two centuries, and the consensus is that evolution and natural selection form a much better explanation than divine creation.
And I guess not much has changed since then. Look at this well designed universe! If things were only slightly different, no life could have been formed at all. Surely there is a divine influence at work! But whenever you drop something like God into your explanation, you've only made your job harder. Now instead of explaining life or the universe, you have to explain the existence of this vastly powerful and mysterious creature that made it all take place.
The other possibilities, though possessing many flaws, are much more plausible. It's much more plausible to think that many universes were created, and that only those suitable for life actually developed life, than it is to think that there is only one universe, whose existence can only be explained though divine creation.
I understand it lets you get away with not having to treat the observer of the quantum event as seperate and somehow special.
This seems less arbitrary to me... Copenhagen's interpretation makes a big assumption about the role of the observer.
THIS THING CAN TURN ON A DIME, MACROSSZERO STYLE ALSO FUCK BETA, ~NYORON
and one I had not heard before.
I think the real point is, not that he finds the idea of us living in a "simulation" abhorrent or impossible, but that any theory from which such a conclusion logically follows is something that cannot be considered scientific - such a theory is exactly equivalent to a religious doctrine in which unexplained events are attributed to the supernatural (unexplained "miraculous" events in our universe could be just defects in the simulation, or even deliberate effects caused by the simulators, after all).
And that sort of thing just flies in the face of centuries of doctrine and methodology in science, about what science really is.
I think it's an interesting argument; I find myself somewhat inclined to agree - depending on the type of multiverse we're talking about, anyway.
Energy: time to change the picture.
This should not be in the "Science" heading it's just creationist political opinion.
It's the opinion of a well-known scientist, who isn't particularly kind to the Creationist argument either (he calls it unsatisfying and unscientific in the article, if you would notice).
Man do you know anything about this guy? Check out his home page: http://aca.mq.edu.au/pdavies.html. He is a professor of Natural Philosophy. You don't seem to be familiar with this term, however it's the simply the old name for what we now call Science. It does not in any way make him a "philosophy professor". This guy has done much work (and written books about) cosmology, gravitation, and quantum field theory. He's published 25 books and over 150 papers to places like Nature and The Journal of Physics. Pretty hard core. Don't be so quick to dismiss someone because you don't understand their title.
Also, as a previous post pointed out, he hinted at a basic problem with multiverse theories: many are unfalsifiable. Unfalsifiable theorys cannot be tested, and are thus scientific. So yes, maybe some fantastic equations someone gets imply there may be other universes out there, however if they are completely separate from ours, then we cannot test whether or not they exist. It's like asking if God exists or not, no experiment can disprove his existence (or indeed prove it), and thus it's not science!
This article was his scientific opinions of a theory which deals with cosmology, which is one of his primary areas of study. Maybe you don't agree with what he has to say, but it is clear cosmology is something he knows at least a little about!
Mathematicians say that some infinite sets can contain more members than other infinites sets, eg the set of real numbers is more highly populated than the set of natural numbers (effectively integers). This holds wherever one infinite set can be mapped onto a subset of another infinite set. Also in that particular case the set of real numbers that can't be mapped is larger than the set that can. So it's meaningful to postulate, on statistical grounds, that the number of sterile potential universes is larger than the number of fecund potential universes.
Imagine that your car begins making a strange knocking sound when you brake. You take your car into the autoshop to find out what's causing the problem. Without even looking under the hood, the mechanic explains that the reason your car is making the sound is because there are infinitely many universes with different versions of you and your car, and you just happen to live in the universe where the car began making a knocking sound. Odds are, you'd look for another mechanic. The multiverse theory essentially uses the same logic to explain (or explain away) features of the universe such as the gravitation or planck constant. As such, its basically a huge non-explanation. Regardless of Davies particular bias, his main point is that the theory is practically devoid of explanation and is about as meaningful as saying "God did it". When Davies invokes the term "falsifiable", he isn't claiming that there couldn't be evidence to support it, but rather there could never be a way to disprove the theory. The lack of criteria for falsifying multiverse theories is problematic because there could be other, more fruitful theories that explain the same observations as a particular version such as Brane Theory. Returning the above example with the mechanice, compare the two rivals theories for the noise: a) infintely many universes with different parameters for the car's noise level when brakes are applied. b) the brake-pads are worn out. A is just as valid a theory as B; the difference is, you can disprove B, and apply B to tell you something about the car (it needs new brake pads). Which theory do you think is better? For a final bit of flame; yeah, maybe people dislike multiverse theories because they mean are universe isn't "special"...but my feeling is that multiverse theories have such appeal is because they're a neat sci-fi prop, not because they have any real value.