## Tag Archives: Mathematics

### Planetary orbital foci

Planetary orbits are not perfectly circular; in fact, they are ellipses. An ellipse is a mathematical shape approximately equivalent to what is typically called an oval. An ellipse, though, meets some very specific criteria. One is that, unlike a circle, it has two foci instead of a single center. Where a circle is defined as [...]

### Choosing random keys

Say you had code that generated random keys. These random keys were 6 letters long, all caps, with no duplicates. Here’s a few, as an example: NTCYAR DHIEWM INBVTX IOELUC RKNBJX GKRANB DRYVQU YIFKTS VAUPSG ALWPOS CERSUY WAHJVM MTXJSZ RNLFXZ VFIEXT VEOKIH What are the chances that the key that you generate will be in [...]

### Idea: OEIS blog

Someone should make a blog based on the Online Encyclopedia of Integer Sequences. Each week (or twice a week, or daily, or something), there’d be a post which would discuss a single sequence. It’d give some glance at the theory and some history behind the concepts, be they Turing machines, prime numbers, set theory, or [...]

### The Feynman point

Famed Physicist Richard Feynman once joked that he wanted to memorize π up to the 762nd digit. Why? Because that’s where pareidolia kicks in, and the digits appear to briefly coalesce into rationality: 3.1415926535 8979323846 â€¦ [727 digits] â€¦ 9605187072 1134999999 â€¦ He would end a hypothetical recitation at that point, the implication being that [...]

### Melting down pennies

Not many people know that there is very little copper in modern pennies. In 1982, they were changed from 95% copper to simply copper-plated zinc. If you cut open a penny made after that date, you’d see the grey-colored metal on the inside. In fact, in 1981, pennies of both recipes were made, and collectors [...]