Parallel Universes: Are They More than a Figment of Our Imagination?

[mwight]

[wuliheron]

I don't know who this author is, but she got a few things wrong.

 

First off, one of the attractions of the Many World's theory is that it does not require the participation of the observer. Instead, it relies on what is called "Quantum Decoherence" where environmental noise causes the collapse of the wavefunction.

 

Second, multiverses are not synonymous with parallel universes. This one requires a bit more explanation than the first.

 

Because supposidly nothing can move faster than the speed of light anything which is beyond our "light cone" cannot influence our universe and, thus, for all practical purposes can be considered another universe. The Big Bang theory implies that the universe is expanding and, therefore, the mass in the universe should be getting further and further apart. The recent observations that the big bang has accelerated also support this idea. Nonetheless some recent observations indicate that the mass of the universe may be homogenously distributed no matter how far back in time we observe the universe. Along with the long established observation that spacetime appears flat overall, this implies that there are parts of the universe outside our lightcone and we live in a multiverse where many universes all share the same space-time continuum.

 

Parallel universes, which in themselves can be multiverses as well, do not share our dimensions of spacetime. For example, one possible parallel universe is called Mirror World theory. In this theory if you could shrink down beyond 10^-33m you would find yourself suddenly increasing in size and inhabiting a universe with different laws of physics. In the mirror world what would be gravity in our universe might be size or electric charge and these physical properties would be connected to those in our universe. In this way the action-at-a-distance of the physical forces we observe would have prosaic answers in the mirror world (and vice versa) and if we could only figure out what they are in the mirror world it would all make sense to us.

 

The Many Worlds theory proposes an infinitely growing number of parallel universes (whether or not they are multiverses) and together they describe by a single quantum wavefunction that progresses in a very deterministic fashion. The mathematics of the modern Standard Theory of quantum mechanics are very deterministic, but behave so strangely that no language can really express them clearly. Chinese is perhaps the best language for describing QM, but even it has its limitations as far as I know. Essentially they are described by a deterministic wavefunction rotating in an infinite number of dimensions and whenever you introduce infinities into physical equations you get bizarre results.

 

Third, there is another way that time travel into the past is possible. A physicist in Conneticut is actually attempting to build a time machine as we speak. The idea is that if you could warp spacetime enough you could establish a link to the past, but you could only go back in time as far as to when the machine was first turned on. Avoiding the grandfather paradox would then be a simple of matter of what is called "Temporal Loop" theory. Essentially the theory states that it is impossible to change the past, but you can influence the past. In other words, you could go back in time and save your own life because, obviously, you did so or you would no longer be alive. If it is a fact that you did go back in time and save your life then no matter how hard you might try to avoid doing so it would happen because, again, it already did happen.

 

Recently someone posted a thread here about how astronomers found evidence that the mass in the universe follows a fractal pattern. Such patterns involve significant "clumping" which is a contradiction of other astonomer's observation of the homogenous distribution of matter in our universe. Each new astronomy headline tends to contradict the last and the reason for this seems to be that astronomers have only recently acquired the instruments they need to serious observe the universe as a whole. In addition to their new instruments, they could really use a quantum theory of gravity.

Edited November 14, 2008 by wuliheron

[joeblast]

I don't know who this author is, but she got a few things wrong.

 

First off, one of the attractions of the Many World's theory is that it does not require the participation of the observer. Instead, it relies on what is called "Quantum Decoherence" where environmental noise causes the collapse of the wavefunction.

imho, 'an observer' would logically fall under 'environmental noise' which would fall under 'quantum decoherence' - is there something inconsistent about that?

 

Second, multiverses are not synonymous with parallel universes. This one requires a bit more explanation than the first.

 

Because supposidly nothing can move faster than the speed of light anything which is beyond our "light cone" cannot influence our universe and, thus, is for all practical purposes can be considered another universe. The Big Bang theory implies that the universe is expanding and, therefore, the mass in the universe should be getting further and further apart. The recent observations that the big bang has accelerated also support this idea. Nonetheless some recent observations indicate that the mass of the universe may be homogenously distributed no matter how far back in time we observe the universe. Along with the long established observation that spacetime appears flat overall this implies that there are parts of the universe outside our lightcone and we live in a multiverse where many universes all share the same space-time continuum.

hm...relate to braneworld scenario? i.e. if our familiar 4d brane is floating in higher dimensional space and other 4 branes had the capacity to exist simultaneously within the 'same general volume' as the one we're stuck to? as I understand the string theory part of the idea, we've got open ended strings that are attached to our 4d brane and looped ones like gravity that are not 'attached'...open ended ones being all the stuff we're physically made of and most particles...

 

Recently someone posted a thread here about how astronomers found evidence that the mass in the universe follows a fractal pattern. Such patterns involve significant "clumping" which is a contradiction of other astonomer's observation of the homogenous distribution of matter in our universe. Each new astronomy headline tends to contradict the last and the reason for this seems to be that astronomers have only recently acquired the instruments they need to serious observe the universe as a whole. In addition to their new instruments, they could really use a quantum theory of gravity.

as I understand, its always been from the standpoint of 'homogeneous on large scales', extrapolate to fit

[wuliheron]

imho, 'an observer' would logically fall under 'environmental noise' which would fall under 'quantum decoherence' - is there something inconsistent about that?

 

No, there is nothing inconsistent about that. However the original author spoke of the Copenhagen Interpretation which implies that the wavefunction never collapses unless there is an observer. This view has been loosing popularity as experiments seem to support the idea that the wavefunction collapses almost instantly.

 

hm...relate to braneworld scenario? i.e. if our familiar 4d brane is floating in higher dimensional space and other 4 branes had the capacity to exist simultaneously within the 'same general volume' as the one we're stuck to? as I understand the string theory part of the idea, we've got open ended strings that are attached to our 4d brane and looped ones like gravity that are not 'attached'...open ended ones being all the stuff we're physically made of and most particles...

as I understand, its always been from the standpoint of 'homogeneous on large scales', extrapolate to fit

 

Brane theory is short for Membrane theory. Instead of focusing so much on strings noadays, it focuses on the membranes they create as they move through spacetime. However, you are correct that the Mirror World scenario is a version of String Theory. Unfortunately, recent calculations have indicated that there might be anywhere around 10^10^500 possible solutions (a wild guess really) for String Theory.

 

In addition, String Theory postulates "compactified" dimensions. These are dimensions that are too small for us to see with the human eye and is similar to what Einstein speculated about our temporal dimension. In his view, if we were large enough we would be able to see the past, present, and future simultaneously because the passage of time is an illusion. In other words, we can only see the present because the dimension of time is simply too large for us to grasp, just as an ant cannot grasp the size of the earth. Similarly, the compactified dimensions of String theory would explain the action-at-a-distance we observe as the fundamental forces of gravity, electromagnetism, etc. This is more similar to Fractal Geometry, with its fractional dimensions, and really has little to do with whether the observed mass of the universe is homogenous or not.

 

The one exception no string theory can do without would be the dimension of gravity which would connect our universe with another. However, this is a rather loose use of the term "universe". If it interacts with our universe, then it can properly be referred to as a part of our universe. Hence the use of "Mirror World" rather than parallel or multi universe. This is sometimes referred to as the "background dependent" nature of String theories. Like Relativity, String theories are "metric" (ie- geometric) theories. This has nothing to do with parallel universes which would be at right angles (an infinite or nearly infinite number of right angles) to ours and not interact with our universe.

 

If you are interested, one of the hottest new fields in theoretical physics is known as "Noncommutative Fractal Geometry". At its heart QM is a noncommutative theory, that is, it does not obey the commutative law of algebra that says if A+B=C then B+A must also equal C. It is hoped by many that this approach might reduce the number of possible string theores to a more managable level. Whether the String Theories ever pan out or not, they have helped to bridge the gap between mathematics and physics which had grown substantial over the last century. In my opinion, if progress is to be made reconciling QM and Relativity we will need all the math people can bring to bare on the subject.

Edited November 15, 2008 by wuliheron