October 16, 2016 at 04:24AM

Today I Learned: 1) Linked traits were well known to breeders and horticulturalists by Darwin's time (and probably long before then), though there was no explanation until geneticists realized how genetic linkage works. Relatedly, when Darwin wrote "On the Origin of Species...", it was widely believed that domestic animals tended to gain floppy ears from disuse, since they did not need to raise them in alarm as frequently as their wild cousins. (In fact, droopy ears seems to be linked with other traits of youth, which tend to be selected for through domestication.) 2) The Feynman Sprinkler is an interesting physics puzzle. Imagine a standard garden sprinkler. It spits out water, and the resulting momentum transfer causes the sprinkler head to spin. Now imagine you reverse the flow of the pump providing water, so it sucks in rather than spitting out. Put it in a tank of water. What happens to the reverse-sprinkler? The result is... confusing, at least to me. Think about it for a few minutes, then check out the Wiki page on "Feynamn Sprinkler" and see if you can make sense of it. 3) ...how to use CSS classes! Somehow I keep re-learning this over and over again, but I always have to re-learn it anew whenever I take on a new HTML project.