Hawking's Multiverse Detector.

[Dinner]

https://www.google.com/amp/s/www.telegraph.co.uk/science/2018/03/18/stephen-hawking-leaves-behind-breathtaking-final-multiverse/amp/

Can one of our astronomers or physicists give us a brief run down on this? Apparently Stephen Hawk's submitted a final paper for publication just weeks before his death and this paper was a big one because he finally thought up a way to test his old multiverse theory (where our universe is just one of an infinite number of universes all of whivh were spawned by the same big bang). I am curious exactly what this test is, how it works, and what it is looking for.

[Buster Crabbe's Uncle]

Hmm. I don't recall seeing Lori anywhere for several days now...

[BeBMan]

Is a multiverse having many universes or is "universe" an outdated concept followed by "multiverse"???

Wondering what the next big thing is then....Maybe a "meta-multiverse" consisting of various multiverses?

[Jon Miller]

There are many different definitions of the multi-universe. Most I think contain no scientific content, some being purely interpretations and others being fundamentally unmeasurable. It isn't clear that Hawkings idea would lead to a multi-universe although he favored that idea as an alternative to a deistic universe.

Oerdin's link was terrible which is why I didn't comment before.

JM
(Some reading

http://backreaction.blogspot.com/2018/03/the-multiworse-is-coming.html

https://www.math.columbia.edu/~woit/wordpress/?p=6551

http://www.wall.org/~aron/blog/wp-content/uploads/2016/09/fine2.pdf

)

[Lorizael]

Not arguing against JM, and he definitely knows way more about this stuff than I do, but two of his links are to people who are kind of famously anti-multiverse (but very smart and credible).

[Dinner]

JM, it was saying Hawking's final paper suggested a way to FINALLY measure and test for other universes. Is that true or tabloid journalism?

[Lorizael]

My understanding based on skimming the paper (very limited, because most of the math is beyond me) is that Hawking and Hertog have made some different assumptions about how eternal inflation would proceed than are usually made. Eternal inflation could imply that quantum fluctuations keep birthing new universes. Traditionally, inflation models don't tell us anything about what those universes might be like. Hawking and Hertog's model, however, lets them assign probabilities to different kinds of universes (based on overall geometry, for example). Some weirder universes (hyperbolic geometry!) come out with a low probability, which means cosmologists can focus on the less weird ones the model suggests. If they know what global properties to look for, theorists can maybe make specific predictions about what effect those universes would have on the CMB, which we could then potentially measure.

There are a whole lot of ifs there, and the paper in no way specifies what to look for in the CMB.

[Lorizael]

But as far as what Hossenfelder might say to that:

When it comes to the landscape at least the problem of finding a probability distribution is known (called “the measure problem”), but it’s still unsolvable because we never observe laws of nature other than our own. “Solving” the problem comes down to guessing a probability distribution and then drowning your guess in lots of math.

...

Conjecturing a multiverse of any type (string landscape or eternal inflation or what have you) is useless. It doesn’t explain anything and you can’t calculate anything with it. But once you add a probability distribution on that multiverse, you can make calculations. Those calculations are math you can publish. And those publications you can later refer to in proposals read by people who can’t decipher the math. Mission accomplished.

[Lorizael]

Hm, I'm thinking I misinterpreted a mention of the CMB in the paper. Scratch the part about other universes impinging on the CMB. Looks like the main thrust is more along the lines of... because their inflation model gives low probabilities to weirder geometries, you don't need to invoke anything super weird or anthropic to explain why we have the universe we have.

See here:

https://twitter.com/AstroKatie/status/975894036161662977

[Dinner]

Ok, so still not testable.

[ZEE]

I believe the gods (including YHWH) are actually members of level 5 Civilizations on the Kardashev Scale that exist in other Universes.

[Broken_Erika]

When we find a way to visit parallel universes, we should call the effect a "Hawking Hole"

[Lorizael]

And here's the Backreaction reaction:

http://backreaction.blogspot.com/201...ry-is-not.html

So as far as how this can get twisted into saying we can detect the multiverse, here's what she says the paper says. If inflation happened, then gravitational waves from that event will lead to the light from the CMB showing B-mode polarization. (This is old news, because we had a false positive on that a few years back that turned out to be the goddamn galaxy getting in the way like it always does.) But anyway... if we do eventually detect that polarization in the CMB, it is strong evidence that inflation happened. And if you agree with Hawking and Hertog's model of inflation, then a particular multiverse (where our universe is likely) is implied.

Hossenfelder, for her part, says that makes as much sense as claiming that "if I find a coin on the street then Bill Gates must have walked by. And a swarm of invisible angels floated past him playing harp and singing 'Ode To Joy.'"

[BeBMan]

When we find a way to visit parallel universes, we should call the effect a "Hawking Hole"

The HawkingHole is our gate to the HawkingVerse

[Buster Crabbe's Uncle]

When we find a way to visit parallel universes, we should call the effect a "Hawking Hole"

I get the reference. Good one.






P.S. We really should, not joking.