Friday thirteen come on Friday this month
Somewhere or other I recently mentioned having heard that, because the Gregorian calendar cycle of 400 years is a multiple of 7 days, the 13th of the month is not evenly distributed and falls more often on Friday than on any other day of the week; but I had not done the math myself and did not have the numbers. Now I’ve done it but can’t remember where to post the followup!
Average illumination near the Moon’s south pole, showing which crater floors never (or almost never) see sunlight. Unfortunately the text doesn’t quantify what the whitest pixel means, i.e., how much time the most-illuminated point spends in shadow.
Wobbling time exposure of Regulus and Mars, showing ‘twinkle’ in a novel way.
Roderick Long: Corporations versus the Market; or, Whip Conflation Now. Read it.
My newest incoming link is from Wendy Krieger, whose site you should definitely see if you’re interested in polytopes, duodecimalism or the letter Þ.
This image, which I made a few years ago, is based on a tiling of the hyperbolic plane with triangles whose angles are π/2, π/3, π/7. Other than the 7, which can be changed to any higher integer, I couldn’t vary these numbers without ruining the effect. Recently I thought of a simpler, and thus more general, way to generate the ribbons.
another thought that I’m never likely to have occasion to apply
If one has the luxury of designing a calendar from scratch, it might be good to put leap day at aphelion, where its angular value is least.
