New info on the universe/multiverse - Tegmark

[shunyadragon]

New information raises many questions concerning prior assumptions on models of our universe and the multiverse.

Source: http://www.timeslive.co.za/thetimes/2014/04/25/bye-bye-to-the-universe-hello-to-the-multiverse

Leading physicists such as Tegmark, Brian Greene, of Columbia University, and Astronomer Royal Lord Rees are fully signed-up multiversers.

Some evidence for the multiverse comes from observation.

Since the Big Bang 13.8billion years ago, there has been plenty of time for space to look very different in various directions - huge clusters of galaxies in one direction, vast voids in another - but it does not.

The best explanation is that the early universe underwent a period of unimaginably fast expansion, called inflation.

If there was a period of rapid expansion - a faster-than-light stretching of the fabric of space-time - in the first quadrillionths of a second after the Big Bang, regions of space now tens of billions of light years apart could then have been connected.

Last month a team of scientists announced that their telescope at the South Pole, Bicep 2, had probably discovered gravitational waves - a discovery that would not only back up our models of the Big Bang but provide strong evidence for inflation and the reality of the multiverse.

Recent discoveries such as this suggest that space might have inflated to an infinite extent after the Big Bang. Physicists believe that the inflationary process was capable of creating matter as well as space, in similarly infinite quantities.

In which case, go far enough and you will see an exact "repeat" of the stars and galaxies we see around us, including another planet Earth and another you - and worlds where Elvis lives, where Hitler won World War 2, and where strange creatures like unicorns graze.

"To get rid of that conclusion," Tegmark says, "either inflation is wrong . or space is in fact not infinitely stretchy."

Tegmark's universe of gyrating numbers, of equations coming to life, is one of bizarre possibilities and incomprehensible scale. But his most shocking argument is about the role of humans.

Said Tegmark: "All those galaxies only became beautiful 400 years ago when someone saw them for the first time. If we humans wipe ourselves out, then the entire universe becomes a huge waste of space."

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[shunyadragon]

An important point here is the problem of clinging to the conclusions of one model or another concerning the nature, origins and fate of our universe, and; 'What is the nature of the Multiverse that surrounds our universe?' Our knowledge of Physics and Cosmology is evolving, and expect change and surprises concerning how future models reflect as our knowledge increases.

[Teallaura]

Question: I've always seen the multiverse used to explain quantum - so the contention is that it occurs at the macro as well? I know sci fi portrays it that way.

[shunyadragon]

Question: I've always seen the multiverse used to explain quantum - so the contention is that it occurs at the macro as well? I know sci fi portrays it that way.

Actually the Quantum Mechanics is used to develop models of the Multiverse at the micro and macro level.

[TheLurch]

Question: I've always seen the multiverse used to explain quantum - so the contention is that it occurs at the macro as well? I know sci fi portrays it that way.

Confusingly, there are two different multiverses. One is in the many-worlds interpretation of quantum mechanics. In this view, instead of a particle acting like a probability function, it deterministically takes each of its possible paths, but does so in different universes. So, over time, this builds into a multiverse of all possible outcomes of quantum activities. It's more philosophy than science, and mostly just a way to try to rescue some determinism.

The other multiverse is what's being referenced here: a necessary outcome of inflation. Basically, inflation happens too fast for all of space-time to stop inflating - as a result, there are always corners of the Universe left inflating, even as ours slowed down. Eventually, somewhere outside our Universe, another patch of space-time will slow down and form its own universe. But again, inflation will be happening so fast that there still other areas that keep inflating. As a result, this goes on indefinitely, with new universes being spun off at a regular clip.

The people who actually understand the physics tell me that this form of multiverse is a necessary outcome of inflation. And, since the evidence for inflation keeps piling up, it's looking more and more like we're just one universe of many.

[Paprika]

Confusingly, there are two different multiverses. One is in the many-worlds interpretation of quantum mechanics. In this view, instead of a particle acting like a probability function, it deterministically takes each of its possible paths, but does so in different universes. So, over time, this builds into a multiverse of all possible outcomes of quantum activities. It's more philosophy than science, and mostly just a way to try to rescue some determinism.

The other multiverse is what's being referenced here: a necessary outcome of inflation. Basically, inflation happens too fast for all of space-time to stop inflating - as a result, there are always corners of the Universe left inflating, even as ours slowed down. Eventually, somewhere outside our Universe, another patch of space-time will slow down and form its own universe. But again, inflation will be happening so fast that there still other areas that keep inflating. As a result, this goes on indefinitely, with new universes being spun off at a regular clip.

The people who actually understand the physics tell me that this form of multiverse is a necessary outcome of inflation. And, since the evidence for inflation keeps piling up, it's looking more and more like we're just one universe of many.

Aren't there at least three types of multiverse? a) the many-worlds multiverse, b) one caused by great inflation since the Big Bang, producing regions of different universes within the same space-time fabric c) the one that our universe is part of but the other universes are not contained within the same space-time evolved from our Big Bang?

As I understand it, c) used to be the traditional understanding and b) is a newer, different idea.

[shunyadragon]

Aren't there at least three types of multiverse? a) the many-worlds multiverse, b) one caused by great inflation since the Big Bang, producing regions of different universes within the same space-time fabric c) the one that our universe is part of but the other universes are not contained within the same space-time evolved from our Big Bang?

As I understand it, c) used to be the traditional understanding and b) is a newer, different idea.

There are likely more, and will be more . . .

Actually models that consider our universe as coming out of the expansion in the multiverse do not consider it necessarily an expanding multiverse, and the different universes would not likely be within the same space time fabric. It is more likely that each universe has its own space time fabric beginning with a singularity.

[Paprika]

Actually models that consider our universe as coming out of the expansion in the multiverse do not consider it necessarily an expanding multiverse, and the different universes would not likely be within the same space time fabric. It is more likely that each universe has its own space time fabric beginning with a singularity.

Precisely, they're two different conceptions of "multiverse".

[Teallaura]

Thanks, everyone!

[JimL]

There are likely more, and will be more . . .

Actually models that consider our universe as coming out of the expansion in the multiverse do not consider it necessarily an expanding multiverse, and the different universes would not likely be within the same space time fabric. It is more likely that each universe has its own space time fabric beginning with a singularity.

I find that difficult to believe shunya. If the pocket universes are not all within the same spacetime fabric as the Greater Cosmos then wouldn't that mean the the greater Cosmos itself is not infinite?

[JimL]

Confusingly, there are two different multiverses. One is in the many-worlds interpretation of quantum mechanics. In this view, instead of a particle acting like a probability function, it deterministically takes each of its possible paths, but does so in different universes. So, over time, this builds into a multiverse of all possible outcomes of quantum activities. It's more philosophy than science, and mostly just a way to try to rescue some determinism.

Actually multi-verse or many worlds theory is science as interpreted by the shcrodinger equation. Of course there other interpretations of the schroedinger equation, the main one of which is the copenhagen interpretation which assumes wave funtion collapse, which assumes that all the probabilities reduce to just one upon observation. The majority of physicists, I think with good reason, have abandoned that idea, ie that we create the future by observing it. Neither of the two interpretations are non deterministic though, as there is nothing free willed about observation. What you observe you are determined to observe whether it is through wave function collapse a la the copenhagen interpretation or through the determined evolution of the schroedinger equation in the many worlds interpretation. Thats why the Copenhagen interpretation doesn't really make sense unless we are to believe that the moon only exists because and if we look at it.

[Duragizer]

So, when is somebody going to invent interuniversal travel, anyway? I'm dying to visit some of the universes where my favourite TV shows/movie series never turned to crap.

[Teallaura]

[JimL]

So, when is somebody going to invent interuniversal travel, anyway? I'm dying to visit some of the universes where my favourite TV shows/movie series never turned to crap.

If the many worlds interpretation is true, then you may be there watching your favorite movies in those other universes right now.

[shunyadragon]

Actually multi-verse or many worlds theory is science as interpreted by the shcrodinger equation. Of course there other interpretations of the schroedinger equation, the main one of which is the copenhagen interpretation which assumes wave funtion collapse, which assumes that all the probabilities reduce to just one upon observation. The majority of physicists, I think with good reason, have abandoned that idea, ie that we create the future by observing it. Neither of the two interpretations are non deterministic though, as there is nothing free willed about observation. What you observe you are determined to observe whether it is through wave function collapse a la the copenhagen interpretation or through the determined evolution of the schroedinger equation in the many worlds interpretation. Thats why the Copenhagen interpretation doesn't really make sense unless we are to believe that the moon only exists because and if we look at it.

I agree that the Copenhagen interpretation does not make sense. Various versions of the schroedinger equation are applied and useful in different models of the multiverse including both time dependent and time independent variations. The problems of the observer perspective within a time-space universe is not one where things exist dependent on the existence of the observer.

One of the points of this thread is that many assume the models can conclusively answer certain questions such as; Our universe will ultimately experience a cold death, because the expansion of our universe is accelerating at an increasing rate. At present this is a maybe yes, maybe no.