[zoke]

I recall reading some years ago that gravitational wave would be used to prove multiverse theory. How would that scale compared to bh-bh or ns-ns mergers?

Also, have read today that this discovery backs inflationary theory, how so?

It seems highly unlikely that they could say a specific bh-bh merger was the cause. It seems implied they are triangulating the source, with two detectors?

[semi-extrinsic]

AFAIK no multiverse theory has yet been put forth that is experimentally testable (even in theory given infinite time, energy etc.) So it's not a proper (falsifiable) scientific theory at present, merely a (in my opinion wild) conjecture.

[mahranch]

> no multiverse theory has yet been put forth that is experimentally testable

Just to be clear here; that's because there is no theory for a multiverse. Not yet, anyways. Nobody has put one forth yet. When you hear "multiverse" come out of physicist's mouth, it's because it's a concept indirectly related to other theories. The current popular theory which involves a multiverse is string theory. When string theorists do the math, there is some evidence that a multiverse is possible.

However, that doesn't mean much. Even if string theory was correct and little strings are really the fundamental component of everything in the universe, the multiverse part of string theory could still be wrong. The theory isn't reliant on it, it just doesn't forbid it.

I also wouldn't say that it's entirely untestable. There are a couple things that could be indicative of a multiverse that some physicists have looked for: http://phys.org/news/2010-12-scientists-evidence-universes.h...

The source isn't the greatest, but it shows that we can look at the CMB for indirect evidence. With higher resolution scanning years in the future, such a theory may be testable. I only mention this because the way your comment reads, it sounds like you're saying a multiverse would be inherently untestable.

[semi-extrinsic]

These are very good points. I do agree that it's possible someone could come up with a testable multiverse-type theory.

[amelius]

How about a theory where spacetime touches upon another spacetime and interacts with it, perhaps through gravity?

Or if spacetime folds back onto itself?

[semi-extrinsic]

You are suggesting possible future events that would provide evidence for a multiverse. That does not make something a falsifiable theory.

Analogy: it could happen that tomorrow Jesus Christ descends from the heavens and brings the day of reckoning. That would prove Christianity to be true, but the fact that this could happen does not make Christianity a falsifiable theory.

A falsifiable theory is a theory that predicts something that we can (in theory) measure today (possibly requiring infinite resources etc).

Your second example (which is not a multiverse theory at all) is actually a good example of a falsifiable theory. People have calculated [1] that if spacetime was folded back onto itself at even just a single point, it would leave a distinct signature in the cosmic microwave background. We do not observe this signature, so we are pretty sure spacetime does not fold back onto itself.

[1] http://arxiv.org/abs/1108.2842

[amelius]

Ok. What if spacetime folds back onto itself over a very long distance? Wouldn't that be (viewed locally, with our limited instruments) as if another version of spacetime touches upon our version of spacetime?

[goldenkey]

Physics will always be based on observations. Consciousness is fundamentally hinged TO observation. I'd argue that the way your brain works is more fundamental to reality than the physics causing a Mhz of conduction throughout your synapses. In summary, all bullshit theories are possible in spirit of deceit. For why should good senses be wasted on a cohesive system when the mind is simply a slave to its own devices?

[ajkjk]

I haven't heard of any credible connection between gravitational waves and multiverse theories.