The cosmic microwave background. Scoured for gravitational waves and signs of collisions with other universes. NASA / WMAP Science Team/wikimediaPosted on 09/30/2015 9:03:31 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.
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.
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.
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 an 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
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 depend 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.
Eugene Lim, Lecturer in theoretical particle physics & cosmology, King's College London
This article was originally published by The Conversation. Read the original article and read other articles from their cosmology series here.
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I don't like government grants coming from taxpayers paying for it.
It is as maddening as having someone get taxpayer support for global warming research.
And it is exactly as unprovable, speculative, and useless.
The_Reader_David: "...an intellectual exercise in trying to avoid the logical consequence of Big-Bang cosmology, that the first cause can’t be physical...It is popular not because it is scientifically compelling, but because it provides committed atheistic naturalists with a way of avoiding the simpler explanation for the Big-Bang."
webstersII: "Yep. The supposedly objective scientists are not at all objective when it comes to those implications. This is similar to one of the reasons Darwin’s writings became popular. The most exciting thing about the Theory of Evolution to many 19th century scientists was how it laid the foundation for atheism based on science.
Insightful and incisive comments all. They suggest to me that you might enjoy, if you're not already aware of it, a group and website that is Christian/Old Earth Creationist/scientific headed by astronomer/apologist Dr. Hugh Ross: Reasons to Believe, at Reasons.org. On point, another astronomer on-staff has a booklet, Who's Afraid of the Multiverse?, and the website's search engine brings up numerous related articles.
Sad, 40+ posts and no sign of Sheldon.
Very Sad.
Can Trump be president in the other universe?
Uhura had Abs before anyone knew the term. And my mother wondered why I was “inside” the TV.
Yes but in that Universe he has hair like Allen West
So you have all these multiverses canceled each other out by its non existences states..its a balance equation that equals zero...
The one unbalance state universe exist because it has the extra variable of time
You're mixing up "state" with "universe." Its like saying if universes come in all different colors, what color exists with no universe? Well no color, right? Because it's the universe that expresses the color.
color -> state
So now we’ll finally get the answerhow the Berenstein Bears became the Barenstain Bears?
Thanks Thud.
So if I understand the multiuniverse concept correctly each parallel universe is partially identical to some degree ...because all possibilities exist ...and each parallel universe is the unique total differences in individual quantum states possible ..then I would you must include non existence as a possibility..
the cat is both alive and dead at the same time..that two states of existence for the cat at the same time... but if that's a possibility then you have to include a third possible that the cat doesn't even exist in the box ...that the cat never existed at all... if you can be both ..states..you can also have neither state
Thank you for that website reference.
I can’t wait to spend some time exploring that, as it represents a pillar of my faith, that science gives us the ability to more clearly see God’s wonders.
You’re very welcome. I know Hugh and Ken personally and couldn’t be prouder of the great work they and the others have done and are doing on the Lord’s behalf. It’s my bedtime, but perhaps soon I’ll fill you in on some background. Meanwhile, prepare to be blessed there.
Walter was much better than Walternate, but Fauxlivia was hot.
Me too! Olivia and Walter.
Daniel chapter five, among many passages, shows there is in fact a realm no further away than the length of a man’s arm, yet totally undetected ... yet someone in that realm can reach over into our realm.
Abso-freekin-lutely!!!
We Probably Haven’t Found Evidence For The Multiverse
Jennifer Ouellette 7 November 2015 11:00 AM
http://www.gizmodo.com.au/2015/11/we-probably-havent-found-evidence-for-the-multiverse/
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