Gloomy Wetland

Daily fish fact #497

Tripod fish!

Their name comes from their tendency to rest completely still on their elongated fins, giving them the appearance of a tripod! When they’re still, their fins appear stiff, but interestingly, when the fish are actually swimming they seem flexible; this had lead to some theories that the fish may pump their fins full of fluids to make them stiff but they’re otherwise quite bendy.

St. John, US Virgin Islands

Galileo Galilei, February 15, 1564 / 2019

(image: Galileo Galilei, Sidereus nuncius, facsimile of the 1610 edition)

smell of summer rain

We have three colored segment in this animation. Surprisingly the length of the longest one is always the sum of the length of the two smaller ones.

This is actually a very special case of Ptolemy’s theorem. The theorem gives a connection between the sides and the diagonals of a cyclic quadrilateral. In this case the length of the dashed lines is equal so the theorem can be simplified to the statement above. 

Appleseed (2004)