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The theory of parallel universes is not just maths – it is science that can be tested
The Conversation ^ | 09/02/2015

Posted on 09/11/2015 11:12:05 AM PDT by SeekAndFind

The existence of parallel universes may seem like something cooked up by science fiction writers, with little relevance to modern theoretical physics. But the idea that we live in a “multiverse” made up of an infinite number of parallel universes has long been considered a scientific possibility – although it is still a matter of vigorous debate among physicists. The race is now on to find a way to test the theory, including searching the sky for signs of collisions with other universes.

It is important to keep in mind that the multiverse view is not actually a theory, it is rather a consequence of our current understanding of theoretical physics. This distinction is crucial. We have not waved our hands and said: “Let there be a multiverse”. Instead the idea that the universe is perhaps one of infinitely many is derived from current theories like quantum mechanics and string theory.

The many-worlds interpretation

You may have heard the thought experiment of Schrödinger’s cat, a spooky animal who lives in a closed box. The act of opening the box allows us to follow one of the possible future histories of our cat, including one in which it is both dead and alive. The reason this seems so impossible is simply because our human intuition is not familiar with it.

But it is entirely possible according to the strange rules of quantum mechanics. The reason that this can happen is that the space of possibilities in quantum mechanics is huge. Mathematically, a quantum mechanical state is a sum (or superposition) of all possible states. In the case of the Schrödinger’s cat, the cat is the superposition of “dead” and “alive” states.

But how do we interpret this to make any practical sense at all? One popular way is to think of all these possibilities as book-keeping devices so that the only “objectively true” cat state is the one we observe. However, one can just as well choose to accept that all these possibilities are true, and that they exist in different universes of a multiverse.

Miaaaaultiverse Robert Couse-Baker/Flickr, CC BY-SA

The string landscape

String theory is one of our most, if not the most promising avenue to be able to unify quantum mechanics and gravity. This is notoriously hard because gravitational force is so difficult to describe on small scales like those of atoms and subatomic particles – which is the science of quantum mechanics. But string theory, which states that all fundamental particles are made up of one-dimensional strings, can describe all known forces of nature at once: gravity, electromagnetism and the nuclear forces.

However, for string theory to work mathematically, it requires at least ten physical dimensions. Since we can only observe four dimensions: height, width, depth (all spatial) and time (temporal), the extra dimensions of string theory must therefore be hidden somehow if it is to be correct. To be able to use the theory to explain the physical phenomena we see, these extra dimensions have to be “compactified” by being curled up in such a way that they are too small to be seen. Perhaps for each point in our large four dimensions, there exists six extra indistinguishable directions?

A problem, or some would say, a feature, of string theory is that there are many ways of doing this compactification –10500 possibilities is one number usually touted about. Each of these compactifications will result in a universe with different physical laws – such as different masses of electrons and different constants of gravity. However there are also vigorous objections to the methodology of compactification, so the issue is not quite settled.

But given this, the obvious question is: which of these landscape of possibilities do we live in? String theory itself does not provide a mechanism to predict that, which makes it useless as we can’t test it. But fortunately, an idea from our study of early universe cosmology has turned this bug into a feature.

The early universe

During the very early universe, just after the Big Bang, the universe underwent a period of accelerated expansion called inflation. Inflation was invoked originally to explain why the current observational universe is almost uniform in temperature. However, the theory also predicted a spectrum of temperature fluctuations around this equilibrium which was later confirmed by several spacecraft such as Cosmic Background Explorer, Wilkinson Microwave Anisotropy Probe and the PLANCK spacecraft.

While the exact details of the theory are still being hotly debated, inflation is widely accepted by physicists. However, a consequence of this theory is that there must be other parts of the universe that are still accelerating. However, due to the quantum fluctuations of space-time, some parts of the universe never actually reach the end state of inflation. This means that the universe is, at least according to our current understanding, eternally inflating. Some parts can therefore end up becoming other universes, which could become other universes etc. This mechanism generates a infinite number of universes.

By combining this scenario with string theory, there is a possibility that each of these universes possesses a different compactification of the extra dimensions and hence has different physical laws.

The cosmic microwave background. Scoured for gravitational waves and signs of collisions with other universes. NASA / WMAP Science Team/wikimedia

Testing the theory

The universes predicted by string theory and inflation live in the same physical space (unlike the many universes of quantum mechanics which live in a mathematical space), they can overlap or collide. Indeed, they inevitably must collide, leaving possible signatures in the cosmic sky which we can try to search for.

The exact details of the signatures depends intimately on the models – ranging from cold or hot spots in the cosmic microwave background to anomalous voids in the distribution of galaxies. Nevertheless, since collisions with other universes must occur in a particular direction, a general expectation is that any signatures will break the uniformity of our observable universe.

These signatures are actively being pursued by scientists. Some are looking for it directly through imprints in the cosmic microwave background, the afterglow of the Big Bang. However, no such signatures are yet to be seen. Others are looking for indirect support such as gravitational waves, which are ripples in space-time as massive objects pass through. Such waves could directly prove the existence of inflation, which ultimately strengthens the support for the multiverse theory.

Whether we will ever be able to prove their existence is hard to predict. But given the massive implications of such a finding it should definitely be worth the search.



TOPICS: Astronomy; History; Science
KEYWORDS: multiverse; paralleluniverse; stringtheory; theory
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To: SeekAndFind

I’m more of a parallel dimensions person. Likely Heaven is 2 ft away from where I’m sitting right now. Just have not crossed over yet. Well hopefully that’s the dimension I’m headed for. LOL!


21 posted on 09/11/2015 11:44:54 AM PDT by Georgia Girl 2 (The only purpose of a pistol is to fight your way back to the rifle you never should have dropped)
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To: SeekAndFind
Worst possible parallel universe in Star Trek?

https://www.youtube.com/watch?v=Q-D-CowBL-s

22 posted on 09/11/2015 11:46:07 AM PDT by CedarDave (Hillary for incarceration not inauguration)
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To: SeekAndFind

If true, how would you ever know you are in a parallel universe since it would look the same as the universe you traveled from. Or would there be 2 of you there?


23 posted on 09/11/2015 11:47:07 AM PDT by Robert DeLong (u)
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To: SeekAndFind
The important question is...if the cat's dead, will it bounce?
I may need to call my broker.

24 posted on 09/11/2015 11:47:30 AM PDT by Bratch
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To: SeekAndFind

Ace Rimmer can straighten all this out


25 posted on 09/11/2015 11:47:51 AM PDT by camle (keep an open mind and someone will fill it full of something for you)
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To: SeekAndFind

I could easily explain it, but you'd never understand.

26 posted on 09/11/2015 11:48:27 AM PDT by JPG (What's the difference between the Rats and the GOPe? Nothing.)
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To: Georgia Girl 2

Well the alternative isn’t so bad and even closer!

https://www.youtube.com/watch?v=1NKWop13q7I


27 posted on 09/11/2015 11:49:11 AM PDT by Norm Lenhart ("The road is long...and I must poop." - Volarian Lionheart/Hero of the people)
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To: camle

Isn’t “Ace Rimmer” trying to make excuses for Planned Parenthood funding right now?


28 posted on 09/11/2015 11:50:31 AM PDT by Norm Lenhart ("The road is long...and I must poop." - Volarian Lionheart/Hero of the people)
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To: JPG

Hipster spock ;)


29 posted on 09/11/2015 11:50:58 AM PDT by Norm Lenhart ("The road is long...and I must poop." - Volarian Lionheart/Hero of the people)
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To: SeekAndFind; All

I suggest reading books by Brian Greene or Leonard Susskind.

They MIGHT make it make more sense.

We may never know if it is real, but the theory is sound.


30 posted on 09/11/2015 11:51:35 AM PDT by Conan the Librarian (The Best in Life is to crush my enemies, see them driven before me, and the Dewey Decimal System)
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To: SeekAndFind

"Fascinating!"


31 posted on 09/11/2015 11:52:15 AM PDT by Bratch
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To: SeekAndFind

This article is complete and total nonsense. Multiverses do not exist; there are not 10 dimensions of reality as necessitated by “silly”-string theory.

Dr. Randall Mills, of BlackLight Power, has proven beyond a shadow of a doubt that, according to his Grand Unified Theory of Classical Physics, the world operates according to classical laws at both the macro and atomic scales.

The paradigm-shifting technologies that Dr. Mills first predicted, then later developed, based on his theory - recognizing atoms as real, tangible particles only (not probability waves) - have been validated, including a novel source of energy that will forever change the world as we know it.


32 posted on 09/11/2015 11:55:01 AM PDT by TheTopRead
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To: SeekAndFind
Having no knowledge of physics, I can't understand quantum mechanics or string theory, much less "multi-universes". However, I always come back to WHAT caused the "singularity" to come into existence which preceded the Big Bang?

Personally, I believe this is all an enormous experiment by someone[s] or something we will never comprehend. We still don't even know for certain what gravity is. Also, as physicists progress in their calculations on white boards, they often prove earlier theories wrong. It happened to Einstein, it's happened to Hawkings, and others.

The important question is why are humans the only true sentient beings on this rock and we've found NO indication others exist out there? Yes, I know they could have existed and now extinct before we had the tech to pick up their radio or other communications, or they haven't reached the ability for such comms. Yeah, there could be other dimensions that we don't yet know how to communicate with. I focus on the "singularity".

33 posted on 09/11/2015 11:55:29 AM PDT by A Navy Vet (An Oath is Forever)
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To: SeekAndFind

His real Kenyan birth certificate may exist in an alternate universe...


34 posted on 09/11/2015 11:56:12 AM PDT by faithhopecharity (up)
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To: SeekAndFind
BTW, the multi-universe concept plays heavily into the storyline of this season's The Flash on the CW network.



35 posted on 09/11/2015 11:58:17 AM PDT by Bratch
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To: SeekAndFind

As a good rule of thumb, if something is a major factor in the universe, you are far less likely to discover it looking for tiny influences than those that are blindingly obvious.

Things so common, ordinary and obvious that they are ignored and thought to belong to the ordinary instead of the special.

In this case, instead of looking for subtle overlaps between universes, they should consider if major elements of “our” universe have their organization based in another universe.

As an analogy, imagine if only the living parts of our bodies were parts of this universe, and the dead parts, like bones, hair and nails, belonged to another universe overlapping with ours. This concept shows how very ordinary such an overlap might be.


36 posted on 09/11/2015 11:58:47 AM PDT by yefragetuwrabrumuy ("Don't compare me to the almighty, compare me to the alternative." -Obama, 09-24-11)
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To: SeekAndFind

We can go some where there is no Obama or Clinton, where Vince Foster is still alive, where rap music does not exist, where McDonald’s serves steak, where I’m a multi-billionaire?


37 posted on 09/11/2015 12:00:52 PM PDT by Raycpa
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To: Georgia Girl 2
I have always felt this passage from Judges suggests the existence of a parallel universe. :

Judges 13:19 So Manoah took the young goat with the grain offering, and offered it upon the rock to the Lord. And He did a wondrous thing while Manoah and his wife looked on— 20 it happened as the flame went up toward heaven from the altar—the Angel of the Lord ascended in the flame of the altar! When Manoah and his wife saw this, they fell on their faces to the ground. 21 When the Angel of the Lord appeared no more to Manoah and his wife, then Manoah knew that He was the Angel of the Lord.

38 posted on 09/11/2015 12:02:37 PM PDT by sportutegrl
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To: SeekAndFind; Salamander; All

Thanks To Salamander For The Graphic
Click The Pic

39 posted on 09/11/2015 12:04:43 PM PDT by Fiddlstix (Warning! This Is A Subliminal Tagline! Read it at your own risk!(Presented by TagLines R US))
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To: Georgia Girl 2
I’m more of a parallel dimensions person. Likely Heaven is 2 ft away from where I’m sitting right now. Just have not crossed over yet. Well hopefully that’s the dimension I’m headed for. LOL!

A few years ago, I watched a documentary with a bunch of string theorists who were talking about an infinite number of alternative universes. I couldn't help but think that were I suggest to them that I believed in a literal heaven and hell, they would have told me I was nuts.

40 posted on 09/11/2015 12:09:53 PM PDT by CommerceComet (Ignore the GOP-e. Cruz to victory in 2016.)
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