links for 5 August

The Fermi Paradox is back, via Slashdot. The Fermi paradox, for those of you who don't know, is basically the following question: if there are so many examples of extraterrestrial intelligence, as a lot of people believe, how come none of them have contacted us yet? This ties in to one of my favorite overmathematizations, the Drake equation, which computes the number of extraterrestrial civilizations in our galaxy by multiplying seven factors, most of which we have no good idea of. The result is a number with a ridiculously huge margin of error; depending on who you ask, the number of extraterrestrial civilizations that we might be able to here could be anywhere between zero and a million or so. Good expositions of the Drake equation usually point out that we have no way of predicting, for example, the average lifetime of a civilization. One particularly interesting resolution I've seen of the Fermi paradox is that other civilizations decide that they just don't care about talking to other species and spend all their time looking at the local equivalents of Internet pornography and reality television. I'm not saying I believe this, just that I've heard it. A bit more plausible, I think, is the idea that civilizations evolve so quickly that a civilization that was where we'll be in the year 3000 (if we don't kill ourselves first) wouldn't be interested in talking to us. (If you think 3000 is too soon, substitute some year further in the future.) I think it would be interesting to talk to a civilization that was where we were a thousand years ago, but a lot of people believe that the evolution of civilization is accelerating; Ray Kurzweil is probably the best-known exponent of this idea, called the Singularity. I'm a bit suspicious of it because a lot of the arguments seem to rely on the fact that we remember what happened in the recent past much better than what happened in the distant past.

What autistic girls are made of, by Emily Bazelon in today's New York Times. Disorders on the autistic spectrum are usually thought of has being uniquely the province of boys, but they happen to girls too. There are researchers who think of autism as being an "extreme male brain", and if that's true it kind of makes sense that it would be more common among males than females. Also, apparently it's harder to be an autistic woman than an autistic man because women are expected to understand social networks better than men; I'm kind of curious if this has always been true or if it's a historical accident. Vaguely relatedly, Who's a Nerd, Anyway? by Benjamin Nugent from last Sunday's NYT; people who are considered nerds are "hyperwhite", according to the linguist Mary Bucholtz. (This is "white" in a cultural sense, as in the way white Americans tend to act; I don't think the author intends to say that there's anything genetic about being a nerd.) What I find interesting is that this same tendency towards oversystemization can be called either hyperwhite or hypermale, despite the fact that we usually think of sex and race as being orthogonal to each other. Finally, Mark Liberman comments at Language Log on reactions to Nugent's article, and how in general non-scientific bloggers blogging about science, and non-scientific journalists writing newspaper articles about science, make fools of themselves.

The Probabilistic Method by Noah Snyder at Secret Blogging Seminar. I love when people find out that the probabilistic method exists. For those of you who aren't familiar with it, the probabilistic method is a method used to prove that a collection of objects contains some object with a certain property not by actually finding the thing but by just proving that if you pick an object from the collection, it has probability greater than zero of being the thing you're looking for. It's kind of a mindfuck, because many of its applications are in combinatorics and people expect there to be explicit constructions of things in combinatorics. It's possible to have a group of forty-two people such that there's no five of them who all know each other and no five who don't know each other. But I can't explicitly tell you which people in that group know each other and which don't. (This is an example of a Ramsey number.)