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(New Scientist)   String theory may limit threat from Boltzmann brains - conscious entities that randomly pop into existence in outer space   (newscientist.com) divider line 10
    More: Hero, string theory, Boltzmann, Boltzmann brain, speed limits, History of the Universe, modeling, mathematical analysis, entities  
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4357 clicks; posted to Geek » on 22 May 2013 at 4:44 PM (1 year ago)   |  Favorite    |   share:  Share on Twitter share via Email Share on Facebook   more»



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2013-05-22 06:34:56 PM
4 votes:

Abner Doon: This article doesn't appear to make any sense at all.


That's partly because the theory itself doesn't make any sense. It's based on a horrible misunderstanding of very basic probability theory. The most remarkable thing is how widespread the fallacy is among otherwise-intelligent people.

The argument goes like this:

1) There are two possibilities: the universe is real, as we observe it; or I am a Boltzmann brain, observing (i.e.dreaming) an imaginary universe.

2) If Boltzmann brains actually exist, they and their imaginary universes must eventually hugely outnumber real universes

3) Therefore, if someone observes a universe and if observers are distributed randomly across people and Boltzmann brains, it's overwhelmingly likely that any randomly selected observer is really a Boltzmann brain,

4) In general, I should prefer the explanation that does not require my observations to be special, therefore I am (probably) a Boltzmann brain, because most observers are.

Now, you may think that reasoning is so absurd that I just made it up/cribbed it from Douglas Adams to make the advocates of Boltzmann brains look silly. But I didn't. That really is the argument.

There are so many things wrong with this reasoning that it's hard to know where to start, but what it basically boils down to is this: It makes no sense to argue for probabilities when you have a sample size of one. The logic in step 4 -- sometimes called the Copernican principle -- works pretty well for astronomers a lot of the time; but not always. For example:

-- There are lots of solar systems, until proven otherwise we should assume ours is pretty typical (probably true, although binary systems with planets are looking to be more common than once thought)

-- There are lots of stars, we should assume ours is average (true, at least for the class of stars ours belongs to)

-- There are lots of galaxies, ours should be average in size, shape, and position relative to other galaxies (largely true)

BUT you can't reason like that about the whole universe, not even if you pretend that infinitely many other universes might possibly exist, because by definition you only get the one universe. And, like my son in kindergarten, "you get what you get and you don't get upset". Maybe the universe is "unlikely" in some abstract space of possible universes, but if so, that's just what it is.

If you spin a roulette wheel once and it comes up with zero, you don't conclude that the wheel is rigged; you conclude that it's impossible to draw conclusions from one spin of the wheel.
2013-05-22 05:01:34 PM
3 votes:
Makes me wonder if the Futerama space brains were inspired by this, given the nerd level of their writing staff....
2013-05-22 03:44:32 PM
3 votes:
The big brain am winning! I am the greetest! Mwa-ha-ha-ha! I must now leave Earth for no raisin!
2013-05-22 05:57:57 PM
2 votes:

nmemkha: String Theory: The first religion spawned by science.


Absolutely not true. Animism, magic, alchemy, and standard religion are all based at a fundamental level on attempts to explain repeated observations.
2013-05-22 05:29:10 PM
2 votes:
Mentor of Arisia would like a word with you, to discuss his Visualization of the Cosmic All.
2013-05-22 03:43:51 PM
2 votes:
www.startrek.com

Amused and not a little bit concerned.
2013-05-22 08:07:17 PM
1 votes:

Iluvbeer: This is the sh*t these otherwise incredibly smart people are spending their time on?  Space brains and infinity?  How about focus on this: My frozen enchiladas say to microwave them "8-9 minutes", but after I microwave them for five, the edges as burned.  What cooking time is correct?


Ask a lowly engineer. Scientists are concerned with more important matters, like space brains.
2013-05-22 07:28:47 PM
1 votes:
This is the sh*t these otherwise incredibly smart people are spending their time on?  Space brains and infinity?  How about focus on this: My frozen enchiladas say to microwave them "8-9 minutes", but after I microwave them for five, the edges as burned.  What cooking time is correct?
2013-05-22 07:03:57 PM
1 votes:

theorellior: Mad_Radhu: But wouldn't the expansion of the universe and growing entropy eventually limit the formation of these entities and their lifespan? Yes, maybe quantum mechanics somehow makes it possible for a fully formed mind to pop out of the quantum foam, but one it appears it will probably "die" because of a lack of energy to process.

The lower the level of available energy, the slower the thinking process. Because absolute zero is never reached, the brains will simply think more and more slowly, until the twilight of the Universe is encompassed by a single thought never quite being finished.


"Now where did....I put.... my.....gla...ss...e........."
2013-05-22 06:31:59 PM
1 votes:

Mad_Radhu: But wouldn't the expansion of the universe and growing entropy eventually limit the formation of these entities and their lifespan? Yes, maybe quantum mechanics somehow makes it possible for a fully formed mind to pop out of the quantum foam, but one it appears it will probably "die" because of a lack of energy to process.


The lower the level of available energy, the slower the thinking process. Because absolute zero is never reached, the brains will simply think more and more slowly, until the twilight of the Universe is encompassed by a single thought never quite being finished.
 
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