Counter-Intuitive Science

That deleterious alleles that fix in a population take exactly as long to fix as beneficial alleles do.

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Now that I didn't know. Can I see the math/reasoning?

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You can see the math in this paper: Maruyama T and Kimura M (1974), "A note on the speed of gene frequency changes in reverse directions in a finite population." Evolution 28: 161—163 (although a special case had been worked out earlier). The basic intuition (to the extent that there is one) is that the only way a deleterious allele is going to fix is if it experiences a number of substantial "lucky" upward fluctuations; if that's going to happen, it's probably going to happen quickly, since otherwise selection will drive it to or near extinction. Of course, the probability that the deleterious allele will fix is much lower than for the beneficial allele, but the time to fixation conditional on fixation turns out to be the same, for a given selection coefficient.

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Once I was walking towards a set of sliding doors. I noticed them open and close for a group of people walking ahead of me, but when I came to them they wouldn't open. Judging that the sensors weren't sensitive enough to detect my modest weight, I decided to leap vertically in the air in the hope that when I came down the extra force of my impact would open the doors. It did not, and couldn't have done.

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Why not?

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Even though you didn't realize it, you were already dead, and ghosts have no weight?

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But if the force with which I came down was sufficient to open the door, then so would be the equal force with which I went up, and the door would (as in fact it did) open when I left the ground, not when I struck it.

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Equal impulse, not equal force (or at least there's no reason to expect the forces to be equal).

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This all goes to show, I think, that the simplest aspects of physics can elude the intuition of the cleverest people.

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Uh huh.