Have Cosmologists Lost Their Brains?

There’s a peculiar long article in the New York Times science section today by Dennis Overbye, entitled Big Brain Theory: Have Cosmologists Lost Theirs? It’s about the debate raging among a small number of cosmologists about “Boltzmann Brains”, and the article does a pretty good job of explaining what the debate is about.

This seems to be a debate that is mostly taken seriously by people who live near the coast in California, with the article quoting Susskind and Linde (Palo Alto), Lisa Dyson and Raphael Bousso (Berkeley), Hartle and Srednicki (Santa Barbara), Albrecht and Sorbo (Davis), and Sean Carroll (Pasadena). One of the few from further inland who is quoted is Don Page (Edmonton), described as a “prominent voice in the Boltzmann debate” who argues with Hartle over the issue of whether to count humans differently than insects since we have consciousness. Page’s recent arguments that God may like having lots of universes around are not quoted. On the other hand , Andrei Linde has a lot to say about what all this has to do with reincarnation, with the article ending with this quote from him:

“If you are reincarnated, why do you care about where you are reincarnated?” he asked. “It sounds crazy because here we are touching issues we are not supposed to be touching in ordinary science. Can we be reincarnated?”

“People are not prepared for this discussion,” Dr. Linde said.

Overbye does note that:

If you are inclined to skepticism this debate might seem like further evidence that cosmologists, who gave us dark matter, dark energy and speak with apparent aplomb about gazillions of parallel universes, have finally lost their minds.

and, while he doesn’t quote any such skeptics, I suspect the title of the piece and the way he quotes some of the sillier things respectable cosmologists are saying indicates some sympathy for skepticism about this.

If you do take all this seriously, you might want to discuss it over at Cosmic Variance where Sean has a posting on the topic. In the NYT piece he is quoted as saying:

When you break an egg and scramble it you are doing cosmology

to which his ex-colleague Jeff Harvey from Chicago responds in the comment section:

When I break an egg and scramble it I’m making breakfast. I guess that is the difference between cosmologists and particle physicists.

Update: The New York Times is listing this article as the most popular article on their site (in terms of how many people are e-mailing it to others).

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24 Responses to Have Cosmologists Lost Their Brains?

  1. Joe says:

    I was reading this this morning at the doctor’s waiting room, and I could not helping thinking that these people must have got their probability calculations way off.

    The chance for amino acids to randomly line up to become a functional protein is incredibly small — for a chain of 27000 amino acids that’s 20^-27000. There are not enough multiverses around even for a single molecular of such protein to emerge randomly. The chance for the human genome to auto-assemble is 4^-3000,000,000. This is presuming the required small organic molecules are in abundant supply. Then these randomly formed gaint molecules must fold properly and appear in huge concentrations and close approximity to each other and assemble into the correct cellular struture. The chance for that would be 100^(-10^24) or smaller! And even then you got only a dead, decaying brain.

    The only way for sentient brains to arise is through exponential Darwinian amplification, an process far more powerful than cosmic inflation and bubble universe regeneration – Darwinian amplification simply acts faster and over-powers all of these puny cosmic processes. A suitable universe that supports Darwinian processes is the most likely one to be observed by concious minds.

  2. David Nataf says:


    What is exponential darwinian amplification?
    It sounds like some new age notion.

    And while there are certainly enough multiverses around (if they exist they’re infinite) to have 10^-10^30000 events occur every so often, I personally prefer the hypothesis that these calculations are wrong because they are missing physics/chemistry we have not yet observed or taken into account.

  3. Peter Woit says:

    If you think it’s worth your time to discuss this kind of calculation, please do it over at Cosmic Variance. I don’t want to spend my time trying to figure out how to moderate a discussion that seems to me completely absurd.

  4. KesheR says:

    I don’t believe in this, but it’s funny and tricky, like every paradox, right or not.

    For you Spanish talkers around the world, I have translated the wiki from English:


  5. Kea says:

    I don’t know whether to laugh or cry. Absurdity may be inevitable when physics reaches such a state, but to this level? Thanks, Bee, for the picture of Darth Vader. Cute touch.

  6. Xerxes says:

    I suspect the title of the piece … indicates some sympathy for skepticism

    Don’t forget that journalists do not choose the headlines for their stories. That job is done by copy editors (because it’s mainly dictated by the constraints of page layout and column width), and the journalists often are unhappy with the results.

  7. Bee says:

    Hi Kea,

    Glad you like it, I couldn’t resist. A paper titled ‘Return of the Boltzmann Brains’ seemed to beg for it. I just noticed though that I lost a bet I had running with a friend, the paper didn’t get published (within 12 months). And while I am at it, neither did this paper get published nor that. Maybe he just doesn’t bother? Best,


  8. rrtucci says:

    And then Physicists wonder why their funding is being cut.

    It’s sad that these bozos are well funded whereas people trying to do real physics (e.g., quantum computing) go hungry.

  9. Arun says:

    I would expect that the “overall density” (whatever that means) of Boltzmann brains would be the same as in our observable volume of universe.

  10. I think that there is a real physics puzzle here despite all the silly rhetoric and anthropic absurdity. The problem is that we don’t have any good way to explain the initial low entropy of the Universe. We can take it as given boundary condition, but it does assort somewhat poorly with other notions cosmologists hold dear. I think Sean Carroll is reasonably clear on this.

  11. Eric H says:

    There seems to be a misconception that intelligent people must be nerdy in the most extreme sense. It seems to be an archetype that the public buys into ever since they saw their first Jerry Lewis movie when he was still with Dean Martin. So the more over the top and delusional the idea the more the average joe in the NSF and the hiring committees at universities say to themselves “I don’t get this. He must be onto something”. Of course it helps if the person with the idea has complete overwhelming confidence in the non-ridiculousness of the idea.

  12. chris says:


    the entropy of the universe is quite easily understandable with the help of classical rg arguments, see e.g. http://arxiv.org/abs/0706.0174v2
    only die-hard string believers seem to have problems explaining it.

  13. alex says:

    Lubos has a sane, reasonable and I think correct article on why these sorts of calculations are wrong.


  14. oohay says:

    Actually LM’s article is completely insane even by his standards. In particular, Sean C goes to great lengths to make it clear that neither he nor anyone else believes in the existence of B Brains, but of course LM thinks that all of the cited authorities do believe this. In fact his whole style of reasoning is very typical of people suffering from paranoia. For example, he thinks that it is wrong to ask why the initial entropy of the world should have been low, since asking such a question means that you are conspiring to subvert the second law of thermodynamics.

    Anyway his post serves a useful unifying role: we are told that Sean Carroll’s errors are essentially the same as those of people who believe in global warming. Ergo, if you think that LM is full of it on climate issues, you can safely deduce that his views on the foundations of thermodynamics are absolute crackpot material. Which indeed is how people in the field regard them.

  15. Bee says:

    Eric: So the more over the top and delusional the idea the more the average joe in the NSF and the hiring committees at universities say to themselves “I don’t get this. He must be onto something”. Of course it helps if the person with the idea has complete overwhelming confidence in the non-ridiculousness of the idea.

    I have no idea why you think this is the case, but this impression is definitely completely off. Funding and hiring is in my impression still based on very conservative evaluation of a person’s research program. If hiring committees would set up their shortlist based on the criteria ‘I don’t get this.’, I’d throw a couple of my unpublished more wacky drafts on the arxiv and stop worrying about getting tenure. Without meaning to insult anybody, I think one can afford working on such stuff if one has reached a certain level of seniority and doesn’t have to bother any longer what people think of it. (That is to say, I will leave the wacky stuff in the drawer until I’m 60.) Sean has to make quite some effort to clarify what the actual physics is behind that more bizarre discussion. Media attention might become a factor of increasing importance for funding and hiring – that could indeed be, and it is a development I dislike very much. Best,


  16. Eric H says:

    I agree with your last sentence about media attention and consider it an echo chamber between that and funding and hiring decisions by administrators. Ultimately, I was having fun with them because they deserve it for being spineless and sucking the air out of the room for other scientists more deserving. I agree with an earlier comment about using thermodynamics and conservation of information as the final arbiter to decide if something is wrong. Until the people in control of these decisions start doing that they deserve any derision they get. (“Funny” is always better than “rude” in targeting one’s derision, and generally more effective.)

  17. Chris,

    I checked out the paper you mentioned. If I’m not mistaken, the authors assumed that the universe started in a pure state with entropy zero. That should simplify the task of getting an initial low entropy Universe.

  18. Gazouille says:

    Peter & guys,

    I’m not on topic but.. well

    Today, somehow by clicking on links this site I ended up here
    Where did I click was my question :).

    Pathetic page, but still I listened to that Susskind’s interview.

    He’s pretty clear on that the only thing wrong with string theory and the landscape is Peter Woit and Lee Smolin. We’re saved, phew.

  19. Manuel Pace says:

    “What is consciousness but the animal feeling of being alive.”
    Charles Saunders Peirce.

  20. Pingback: Not Even Wrong » Blog Archive » Science, and a Bit of Religion

  21. John Gribbin says:

    All the people who say that the numbers involved are so extreme that they can be ignored are way off beam. If the multiverse is infinite, anything can happen an infinite number of times, provided it has non-zero probability. No matter how large a number is, it is literally infinitesimal compared with infinity.

  22. jpd says:

    Not quite, there are many types of infinities.
    if there are possibilities corresponding to the Real numbers,
    and if there are successes corresponding to the Natural numbers:
    both are infinite but the probability of success is still zero.

  23. Pingback: Not Even Wrong » Blog Archive » Krauss on Boltzmann Brains

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