Why Stuff Is Hard, at the Everything Seminar. I asked this in physics class in high school and never got a satisfactory answer. I suspect I'm not alone here. I was told it was some sort of electromagnetic repulsion between the outermost electrons, but apparently the Pauli exclusion principle is really doing most of the heavy lifting.
Mark Chu-Carroll at Good Math, Bad Math comments on the way math is taught at certain religious schools. If you don't want to bother reading the post, check out the course descriptions at one such school. They all start out "Students will examine the nature of God as they progress in their understanding of mathematics". The descriptions of the non-mathematics courses begin similarly. Today I was reading parts of Laplace's A Philosophical Essay on Probabilities (available in Hawking's anthology God Created the Integers: The Mathematical Breakthroughs That Changed History); among other things, Laplace mocks the idea of Pascal's wager. I couldn't help but thinking of what Laplace is said to have said to Napoleon when asked why he didn't mention God in his work on celestial mechanics: "I had no need of that hypothesis."
Compound interest isn't intuitive, from Adventures of BruteForce; if you invest a little money now that's like investing a lot of money later. People just aren't set up to understand exponential growth, which isn't surprising; unrestrained exponential growth isn't common in the situations for which we evolved. A population can't keep doubling every ten years without pretty quickly running out of space; a sum of money can. There's a persistent rumor that Ashkenazi Jews are actually better equipped for understanding this particular sort of abstraction than other classes of people, because of certain unique historical circumstances -- for quite some time they lived among Christians, who were forbidden to lend money for religious reasons, but these same Christians wanted to borrow money, and therefore turned to the Jews, who were not subject to those same religious laws. The Jews who were better at understanding this fact ended up with more money themselves, their kids didn't starve, and supposedly this explains why about a quarter of Nobel laureates are Jewish. I can't find exact numbers overall. One thing I can find is in this Wikipedia article which says that "Of American Nobel Prize winners, 37% have been Jewish Americans (19 times the percentage of Jews in the population) [...]" But I'm not sure who they count as "American". (Wikipedia used to have a list of Jewish Nobel laureates, but it's been deleted.)
It would be interesting if this were true, because it seems to imply that evolution can work ono the scale of a few hundred years. As humanity heads more and more towards working with its brains instead of its hands, will we get smarter? (On the other hand, at least at the present time in the United States, intelligence and number of children seem to be inversely correlated; it seems difficult for Darwinian evolution to work in a population when almost everyone survives long enough to have children.)