Physicists Calculate Number of Parallel Universes
October 16, 2009 by Lisa Zyga
The strongest limit on the number of possible universes is the human ability to distinguish between different universes. Credit: Linde and Vanchurin.
(PhysOrg.com) -- Over the past few decades, the idea that our universe could be one of many alternate universes within a giant multiverse has grown from a sci-fi fantasy into a legitimate theoretical possibility. Several theories of physics and astronomy have hypothesized the existence of a multiverse made of many parallel universes. One obvious question that arises, then, is exactly how many of these parallel universes might there be.
In a new study, Stanford physicists Andrei Linde and Vitaly Vanchurin have calculated the number of all possible universes, coming up with an answer of 10^10^16. If that number sounds large, the scientists explain that it would have been even more humongous, except that we observers are limited in our ability to distinguish more universes; otherwise, there could be as many as 10^10^10^7 universes.
To work these numbers out, Linde and Vanchurin looked back to the time shortly after the Big Bang, which they view as a quantum process that generated lots of quantum fluctuations. Then during the period of inflation, the universe grew rapidly and these quantum fluctuations were "frozen" into classical perturbations in distinct regions. Today, each of these regions could be a different universe, having its own distinct laws of low energy physics.
By analyzing the mechanism (called "slow roll inflation") that initially generated the quantum fluctuations, the scientists could estimate the number of resulting universes at 10^10^10^7 (a number which is dependent on the model they used). However, this number is limited by other factors, specifically by the limits of the human brain. Since the total amount of information that one individual can absorb in a lifetime is about 10^16 bits, which is equivalent to 10^10^16 configurations, this means that a human brain couldn't distinguish more than 10^10^16 universes.
Requiring that the human brain must be able to count the number of parallel universes may seem inappropriate, if not arrogant, but Linde and Vanchurin explain that dealing with the quantum world is different than our everyday lives in which quantum effects can be safely ignored. A crucial part of their calculation here is an investigation of quantum effects on supergalactic scales. In this kind of scenario, the state of the multiverse and observations made by an observer are correlated (similar to the Schrodinger cat experiment, where the outcome can be determined only after it is registered by a classical observer).
"When we analyze the probability of the existence of a universe of a given type, we should be talking about a consistent pair: the universe and an observer who makes the rest of the universe 'alive' and the wave function of the rest of the universe time-dependent," the scientists write.
As the scientists explain, the calculation of the number of universes is an important step toward an even larger goal: to find the probability of living in a universe with a particular set of properties. What are the chances that we live in a world in which the laws of physics are these laws that we currently observe? Answering this question requires finding probabilities that depend on knowing about other universes, among many other challenges.
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More information: How Many Universes are in the Multiverse? arXiv:0910.1589v1
via: Technology Review
© 2009 PhysOrg.com
Feb 19, 2007 |
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hm, maybe I've forgotten what my 8th grade science class taught me. I always thought a scientific theory needed some evidence to support it. Am I missing something?
The researchers obviously didn't take that class.
Also, if one single brain can absorb 10^16 bits of information (also, where did this come from, we're a bit short still on neuroscience, that's a pretty bold claim on uncertain ground), that doesn't necessarily also mean that all the brains would be storing the same 10^16 bits of information or the same paralel universes. Technically speaking two brains, or observers, could observe 2x10^16 bits, right? So the total number of universes, would also depend on the number of observers, perhaps not on a one-to-one basis, but still.
More so, it all seems like this calculation, more belonging to sci-fi than real science, ignores the possibility of other life-forms and thus assumes we are the only observers. What if we is not the largest of brains eh?
Can a monkey tell universes apart?
All in all a lot of hoo-ha.
That's just media. Writing the headline is 90% of the work. Content doesn't really matter afterwards, as long as you got the sucker's attention.
Multipull universes, Blackholes, dark matter, dark energie, Big Bang..... they are writing a new bible!
Knowing enough math to stifle any arguments, tends to make one arrogant and a sloppy thinker. And to top it all, these guys think that their brain size determines the number of universes.
You know, just because someone is affiliated with Stanford doesn't give the right to have just any crap be quoted on serious science forums.
"if one single brain can absorb 10^16 bits of information (also, where did this come from, we're a bit short still on neuroscience, that's a pretty bold claim on uncertain ground),"
Well, the average number of synapses in the human brain is about 10^14. if we give the connection weights of each synapse just 2 bits then we have 10^16 bits.... this would be an upper limit on the correlations a human mind can have with the universe it inhabits. I would suspect that the real number of bits that we use in forming our perception of reality is far lower than this limit. Neural systems are very inefficient at storing information.
Wayne S
In certain moment the structure of complexity of human brain is created and the surrounding pile of less random states would correspond the Universe, directly observable by this brain. For example, if average human brain contains 10^26 atoms, then the observable Universe would contain 10^(26*26) atoms, or somewhat similar number. It would mean, connected effort of more brains would allow us to see our Universe larger.
This could be meaningful interpretation of the above article.
"Technically speaking two brains, or observers, could observe 2x10^16 bits, right? So the total number of universes, would also depend on the number of observers, perhaps not on a one-to-one basis, but still."
I think the point here is that for any singular consciousness that is "measuring" or perceiving the universe, all things other than the "mind" are just more uncertain quantum measurements. The argument in the article about limiting the size of the set that "looks" like our universe is not limited by some dynamics of the universe or physics, but our ability to "look" and know the difference. this is very much like how mathematicians talk about proofs that can be stated in a million symbols or less. Certainly there are mathematical truths with proofs so long that they can not even fit in a human brain. Likewise there are aspects about potential universes in the multiverse that take more bits to characterize than we as humans are able to hold
Wayne S
A legitimate theoretical possibility is not equivalent to a scientific theory. "Legitimate" is not a scientific term.
The statement "there are atoms inside the observable universe" is falsifiable.
The statement "there are atoms inside the human brain" is falsifiable.
The statement "there are universes inside a multiverse" is non-falsifiable.
Bear in mind that it does say "theoretical possibility", not "scientific fact". All that means is that, theoretically speaking, the concept of multiple universes is not inconsistent with what we do know about physics.
As to frajo's comment, and many others on this thread, I would respectfully point out that the claim "it is possible that our universe is one of many" is distinct from the claim "our universe is one of many". This result, then, can be stated as "IF our universe is one of many, THEN there are at most this many other universes." Furthermore, I agree that it seems strange to use the human brain as the model of an observer--but quantum physics itself reserves a special place for the observer. I think it's valid.
can someone explain the difference between the two theories?
So what if we don't know exactly what it is? We do know some things about it - certain properties that must be there. We deduce the existence of dark matter from the fact that the mass of the visible universe is insufficient to cause the effects we see. We can therefore deduce, for instance, the amount of dark matter necessary - it's the amount needed to cause what we do see.
Mathematicians do this all the time. If you know some properties of something, you can deduce others, without having to actually have that "something" in your hand. Is it justified to deny to physicist a method perfectly accepted for mathematicians?
http://www.theoni...tributes
In the Copenhagen model that is true. In the Wheeler model it is not true. Which is why I prefer the Wheeler model to the Copenhagen model.
What makes an atom in my eye more important than the atoms in the box that Schrodinger's cat is in?
Arrogance perhaps?
Mystic thinking maybe?
Sure isn't based on evidence.
Ethelred
yield an infinate number. Sober thought and a hangover will reduce it to less than one per observer!
we should be careful with words when speaking of scientific ideas. "Hypothesis" and "Theory" have very different meanings. A hypothesis is an educated guess and a theory needs some evidence (not proof, which would then make it a "scientific fact") to back it up. I suggest that the term "hypothetical possibility" is more accurate, and that if the hypothesis is not really testable, then is more a exercise in philosophy.
there are infinite ideas that are not inconsistent with known facts, but that does not make them scientifically viable.
What are they really seeking? Fortune and glory?
Or the "Stupidest Theory of the Year" award?
For two observers, this number should then double, and that would then be only the number of conceivable universes, not the TOTAL number.
One would think that the total number would be infinite.
That last comment is an extraordinary leap. Give me a scientific theory for which there is MORE evidence than just that it is consistent with known facts. Go on, give it a shot. Newtonian physics was supported only by known facts, not by any sort of a priori reasoning. At any rate, given that the assumption of multiple universes does not (yet) lead to a contradiction, it makes sense to attempt to deduce the consequences of them. If we don't examine the consequences, we may miss a falsifiable proposition that derives directly from the assumption that there are indeed multiple universes. It's worth it.
Evolutionary theory
Gravitational theory
Electro-magnetic theory
Quantum theory
shall I go on?
The existence of bigfoot is not inconsistent with known facts (though it does challenge our some of our understandings of population dynamics), yet we reject it because there is no evidence to support it.
BTW, Newtonian physics is not a theory, it is a set of laws that governs the field of classical mechanics. It is testable and provable.
Look for Paul J. Steinhardt and Neil Turok. Their Ekpyrotic Universe and Cyclic Universe theories don't need a counter-intuitive concept like the beginning of time. Nor do they need multiple universes. Might hold some appeal for you.
This most interesting argument exemplifies a neo-scholastic method. With all due respect for the greatest thinkers of their time (who doesn't know William of Ockham) we don't want to study again how many angels can dance on the tip of a needle - even if such studies don't lead to contradictions.
The absence of contradiction alone doesn't turn a set of non-falsifiable statements into a potential source of scientific knowledge.
!!! Newtonian physics is not only unprovable, it is demonstrably false. Quantum physics and general relativity blow it right out of the water. Furthermore, I respectfully refer you to David Hume. Even when Newtonian physics was considered absolute truth, the only justification for believing in it was that, so far, it had always appeared to work.
Also, I think it's less about different universes, there should not be bubbles from one universe to the other, with impassable membranes, I regard it more like a continuum between each one, where the laws of another universe start to interfere before becoming dominant.
There are limits to being human, we have to evolve to understand this better, and develop new senses and augment the few ones we have!
The amount of information a human could process in a lifetime limits the number of universes a human could distinguish between, it does not alter the number of universes. A device with more lifetime computational power would be able to distinguish between more of the universes (so what a human would have thought were two identical universes, this device could distinguish as having different properties). I believe the point of the observation is that theories that predict more than the stated number possible combinations of constants are even in principle indistinguishable by unaided humans.
And I thought these fluctuations are how the galaxies and all the matter in OUR universe started. Isn't the author assuming that the BIG BANG was the start of all the multiverses? Possibly the 'BIGGEST BANG'?
Is that correct?
Humans are not able to imagine the difference between aleph-null and beth-one. But the human mind nevertheless can handle those numbers.
So, based on that alone, why are we limited to what only a single individual has the potential to observe... and, while we're at it, why limit the possibility to only human observation? We don't know that much about the human brain, much less the brains of other species.
Theory doesn't mean much until it can be tested, and we're still a long way away from being able to test the theory of observable parallel universes.
on this planet, especially if you studied each one. So nobody could investigate all these universes. This is just sensationalism designed to get research money. We should try to understand the Universe we live in. Occam`s razor says a theory should be kept simple if it is to be useful. So let`s cancel
(10**16)**16 - 1 Universes as not necessary!
I do agree we can deduce many things without taking direct observations. Saying that the earth a the earth has a nickel and iron core is a lot different than saying that because our equations don't work there is a bunch of unmeasureable matter out there. It just happens to be very popular in cosmology to believe in the standard model. when we get some real evidence then that will be confirmed or more likely we will create a new popular model for the universe