Gravity is the curvature of spacetime. So, how curved is the spacetime we are in right now? Let’s start by looking at the effect of curvature in a very simple situation. Two meridians on a sphere, like the red and blue ones in the diagram, will come together and move apart as you follow them along their length. If their separation at the equator is s(0), after a distance d it will be: s(d) ≈ s(0) cos(d/R) where R is the radius of the sphere. The separation will repeat with a period of P = 2πR, so we can say that the radius of curvature of the space these geodesics are in is: R = P / (2π)

I found this story equal parts interesting, silly, and downright creepy: scientists are trying to reconstruct Leonardo Da Vinci’s DNA, with a mixture of swabbing his artworks, tomb-raiding his ancestors, and tracking down living relatives. There’s a fair bit of weird celebrity-fetishism and gene-fetishism. Leonardo did many wonderful things, but all this effort to try to get as much of his genetic sequence as possible seems ... disproportionate. The most interesting thing I learned from the article was that he *might* have had atypically fine time resolution in his visual perception. But even there, surely we can discover much more about that whole subject by studying a large number of living people, rather than obsessing over one person’s genome. https://www.science.org/content/article/have-scientists-found-leonardo-da-vinci-s-dna