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RECENT POSTS IN THIS TOPIC

Marcel-Marie LeBel: on 11/26/18 at 1:48am UTC, wrote Jonathan, I guess you are the reason why this 2008 ! old blog surfaced up...

Jonathan Dickau: on 11/20/18 at 17:50pm UTC, wrote Sorry again... I should have read more of the linked attachment before...

Jonathan Dickau: on 11/20/18 at 16:07pm UTC, wrote Sorry, Some of these arguments appear vacuous, or depend on hidden...

Moshe: on 4/3/08 at 23:16pm UTC, wrote Thanks Anthony. I see some difference between the two scenarios: the...

Anthony Aguirre: on 4/3/08 at 19:31pm UTC, wrote Moshe, I don't think it's quite as simple as that. To elaborate on what...

Moshe: on 4/1/08 at 0:30am UTC, wrote Seems to me that the confusion here is assuming that two objects that are...

Anthony Aguirre: on 3/31/08 at 16:17pm UTC, wrote In recognition of FQXi of Doomsday week, suppose the world ended tomorrow. ...


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September 27, 2021

CATEGORY: Blog [back]
TOPIC: If the world ended tomorrow, would we notice? [refresh]
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FQXi Administrator Anthony Aguirre wrote on Mar. 31, 2008 @ 16:17 GMT
In recognition of FQXi of Doomsday week, suppose the world ended tomorrow. In particular, suppose that, as discussed in Kate Becker's fun article, we live in a 'false vacuum', that can decay to a lower energy state. The decay would take the form of a bubble of 'true' vacuum that grows at the speed of light, smashing into us with enormous energy without warning, annihilating everything we hold...

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Moshe wrote on Apr. 1, 2008 @ 00:30 GMT
Seems to me that the confusion here is assuming that two objects that are completely identical are necessarily one and the same object. Without this confusion the answer to the question seems straightforward: if the world ended tomorrow, then those of us (say in the multiverse ensemble, just to avoid MWI issues) encountering the bubble will notice, those who don't encounter the bubbles will not notice. Those two "worlds" were identical up to that point, but are no longer so. They were not the same "world" even up to the point when their history was identical, the same way that two identical tennis balls are not a single tennis ball.

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FQXi Administrator Anthony Aguirre wrote on Apr. 3, 2008 @ 19:31 GMT
Moshe,

I don't think it's quite as simple as that. To elaborate on what is troubling, imagine the old thought experiment of the star-trek teleporter that disassembles you, then creates a perfectly identical copy elsewhere. If you would be willing to use one of those, then I submit you should be troubled by the scenario I outlined, as follows. Suppose the teleporter transported you to some immensely faraway place. That should not change your willingness to get in, which is presumably based on the idea that there is a continuity of experience between 'you' and 'your re-creation' far away. But then how is there any difference between this continuity of existence, and the one that would exist across a version of you ended by bubble annihilation, then continued in a different branch of the wavefunction, or continued in a faraway place in the universe?

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Moshe wrote on Apr. 3, 2008 @ 23:16 GMT
Thanks Anthony. I see some difference between the two scenarios: the teleporter presumably is some complicated but perfectly causal process. The relation between the new and old self is perfectly deterministic. The unitary evolution here is what provides the continuity. My perception will probably not be continuous, but that is not very different from sleeping. It is much easier for me to think that two people that happen to be identical up to a point in time (in a specific slicing etc.), but which were never in causal contact, are just two different people, I see no reason to count them as the same.

The MWI version is less straightforward for me, but I suspect it is because I don't really understand it.

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Jonathan J. Dickau wrote on Nov. 20, 2018 @ 16:07 GMT
Sorry,

Some of these arguments appear vacuous, or depend on hidden assumptions I choose not to adopt. Recent papers by Cumrun Vafa and collaborators throw water on many of those arguments and/or the assumptions (look at arXiv:1806.08362 and arXiv:1806.09718 for starters). I will explicate.

First off; I think Paul Steinhardt (one of Vafa's co-authors, whom I met at FFP11) has given compelling reasons (explained in Scientific American articles) why Inflation is suspect, or is questionable as the true early universe cosmology.

Second; it is distinctly evident that the universe is getting run down over time, as evidenced by the 2nd law of Thermodynamics. This leads many to conclude the universe will have a cold dark end. So if the cosmic expansion continues we do not live in a stable vacuum per se.

Third; given Vafa's reasoning and in light of such evidence; it stands to reason that the stable vacua of String Theory lie solely or mainly in the pre-decoupling era of the cosmos, where there a balance of particle annihilation and particle pair creation.

As it turns out; the absence of catastrophic events like those described by Becker is one of the reasons used by Steinhardt to rule out the Inflationary Universe hypothesis. So it seems silly to use an unproven or questionable theory to rule out other theoretical considerations.

All the Best,

Jonathan

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Jonathan J. Dickau replied on Nov. 20, 2018 @ 17:50 GMT
Sorry again...

I should have read more of the linked attachment before writing. I read the blog post and glanced at the other, but I see there is more to the cited stories. It's sort of like judging a paper by its abstract or a book by its cover. I'll recuse myself until I've taken time to digest, next time around.

Best,

JJD

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Marcel-Marie LeBel wrote on Nov. 26, 2018 @ 01:48 GMT
Jonathan,

I guess you are the reason why this 2008 ! old blog surfaced up in the

"New in blog"...

- Still waiting for this year's contest...

All the bests,

Marcel,

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