Clara Moskowitz
SPACE.com
Fri, 07 Dec 2012 09:51 CST


Multiverse_1
© Shutterstock/Victor Habbick
Our universe may be one of many, physicists say. In fact, that's the most likely scenario.
The universe we live in may not be the only one out there. In fact, our universe could be just one of an infinite number of universes making up a "multiverse."

Though the concept may stretch credulity, there's good physics behind it. And there's not just one way to get to a multiverse - numerous physics theories independently point to such a conclusion. In fact, some experts think the existence of hidden universes is more likely than not.

Here are the five most plausible scientific theories suggesting we live in a multiverse:

1. Infinite Universes

Scientists can't be sure what the shape of space-time is, but most likely, it's flat (as opposed to spherical or even donut-shape) and stretches out infinitely. But if space-time goes on forever, then it must start repeating at some point, because there are a finite number of ways particles can be arranged in space and time.

So if you look far enough, you would encounter another version of you - in fact, infinite versions of you. Some of these twins will be doing exactly what you're doing right now, while others will have worn a different sweater this morning, and still others will have made vastly different career and life choices.

Because the observable universe extends only as far as light has had a chance to get in the 13.7 billion years since the Big Bang (that would be 13.7 billion light-years), the space-time beyond that distance can be considered to be its own separate universe. In this way, a multitude of universes exists next to each other in a giant patchwork quilt of universes.

Multiverse_2
© Shutterstock/R.T.Wohlstadter
Space-time may stretch out to infinity. If so, then everything in our universe is bound to repeat at some point, creating a patchwork quilt of infinite universes.
2. Bubble Universes

In addition to the multiple universes created by infinitely extending space-time, other universes could arise from a theory called "eternal inflation." Inflation is the notion that the universe expanded rapidly after the Big Bang, in effect inflating like a balloon. Eternal inflation, first proposed by Tufts University cosmologist Alexander Vilenkin, suggests that some pockets of space stop inflating, while other regions continue to inflate, thus giving rise to many isolated "bubble universes."

Thus, our own universe, where inflation has ended, allowing stars and galaxies to form, is but a small bubble in a vast sea of space, some of which is still inflating, that contains many other bubbles like ours. And in some of these bubble universes, the laws of physics and fundamental constants might be different than in ours, making some universes strange places indeed.

3. Parallel Universes

Another idea that arises from string theory is the notion of "braneworlds" - parallel universes that hover just out of reach of our own, proposed by Princeton University's Paul Steinhardt and Neil Turok of the Perimeter Institute for Theoretical Physics in Ontario, Canada. The idea comes from the possibility of many more dimensions to our world than the three of space and one of time that we know. In addition to our own three-dimensional "brane" of space, other three-dimensional branes may float in a higher-dimensional space.

Columbia University physicist Brian Greene describes the idea as the notion that "our universe is one of potentially numerous 'slabs' floating in a higher-dimensional space, much like a slice of bread within a grander cosmic loaf," in his book The Hidden Reality (Vintage Books, 2011).

A further wrinkle on this theory suggests these brane universes aren't always parallel and out of reach. Sometimes, they might slam into each other, causing repeated Big Bangs that reset the universes over and over again.

Multiverse_3
© Shutterstock/Sandy MacKenzie
Out universe may live on one membrane, or "brane" that is parallel to many others containing their own universes, all floating in a higher-dimensional space.
4. Daughter Universes

The theory of quantum mechanics, which reigns over the tiny world of subatomic particles, suggests another way multiple universes might arise. Quantum mechanics describes the world in terms of probabilities, rather than definite outcomes. And the mathematics of this theory might suggest that all possible outcomes of a situation do occur - in their own separate universes. For example, if you reach a crossroads where you can go right or left, the present universe gives rise to two daughter universes: one in which you go right, and one in which you go left.

"And in each universe, there's a copy of you witnessing one or the other outcome, thinking - incorrectly - that your reality is the only reality," Greene wrote in "The Hidden Reality."

5. Mathematical Universes

Scientists have debated whether mathematics is simply a useful tool for describing the universe, or whether math itself is the fundamental reality, and our observations of the universe are just imperfect perceptions of its true mathematical nature. If the latter is the case, then perhaps the particular mathematical structure that makes up our universe isn't the only option, and in fact all possible mathematical structures exist as their own separate universes.

"A mathematical structure is something that you can describe in a way that's completely independent of human baggage," said Max Tegmark of MIT, who proposed this brain-twistin gidea. "I really believe that there is this universe out there that can exist independently of me that would continue to exist even if there were no humans."

We always tend to think that everything is infinitely in a large distance from the reality that surrounds us, maybe we could talk about different dimensions in which strange and inexplicable energy acting, the equilibrium, in which lies our uni-verse, is an evidence

It would be interesting to give the right value to the level of human science, but I think it would run against the interests of powerful groups that dominate the world ... the same people who create and drive the global economic crisis

I've been explaining multi-verse theories since I first came to Mingle2. It has become much more widely accepted since then.

The article is pretty good except they got the distances wrong on how far light can travel. Those numbers would only apply to a non-expanding universe but in our case we have measured much expansion ... hence greater distances light could travel.

I find all such ideas scientifically underwhelming, but dammit if it don't make for good sci fi.

Certainly nothing reaching the level of scientific theory exist for such.

lol... Here I thought the majority of the society chose not to "believe" in multiverse theories. I would love to read much more on these, I find them fascinating! though I began when I was about 11 to grasp the idea that different dimensions may exist on different planes of existence and through these, travel could be DRASTICALLY reduced. Isn't one of the more widely known the "String theory" whereas an atom holds a string vibrating at a certain frequency which if drastically expanded would be the equivalent of a black hole through which a white hole would correlate to. creating a crease in the space/time continuum?

A good read is Brian Green's "Elegant Universe" which was also made into a documentary movie by PBS that you can rent on DVD.

maybe the dimensions are the gateways to the ends of our universe...

i think they replaced the string theory with the dark matter theory...and possibly dark energy now...

i like Brian green, he explains thing better than most scientists

It could be, I think that the difficulty of the human being is to be able to determine the dimensions of reality as it is perceived, in theory, my mind might contain one or more dimensions

One of the more difficult concepts to grasp is quantum mechanics. The location of an electron around the shell of an atom can only be predicted mathematically because in quantum reality the electron can exist in more than one location at once.

In engineering, reality plays a larger role than theory so the actual location of the electron is assumed to be everywhere at once ... because that is what works. Quantum mechanics works on all matter (apparently) at this level of "smallness" so think about a different way of looking at the universe. If the universe started as a burst of energy that was infinitely small, and then expanded to what it is today, there was a period of time where it existed in the quantum size limits and therefore could have had infinite locations and existences. All may still exist today.

If there are infinite opportunities for big bangs to exist over an infinite amount of time, and each one having an infinite diversity of outcomes. In at least one of them, I get laid tonight!

i was talking to myself in another reality the other day, and i told myself that i did get laid in another dimension... now i wanna move...

In some reality, beer is free!

i heard there is a dimension where weed grows from plants....

I imagine we live in a multiverse and there are an infinite number of universes, simply because I can't imagine the existence of "nothing" which would have to exist if infinite universes did not.

It is like the existence of a zero and a one in computer code. Zero represents nothing. One represents something.

Does nothing exist? It means no thing. A void might exist, which would be like a membrane between universes, but that void would probably be some kind of electromagnetic force.

Perhaps one day we will be more advanced, everything will seem more logical and less "extraordinary", The caveman did not know the gamma rays

even in the other unknow uni-verse happy-hour exist