Simple orbital mechanics

The Moon is slowly siphoning off the Earth's rotational energy, in a phenomenon called tidal acceleration. This moves the Moon's orbit farther from the Earth. According to Kepler's laws of planetary motion, the Moon must orbit more slowly as it gets farther away. Well, which is it? Is the Moon speeding up, or slowing down? …

How to fix American football overtime

In American football, a neutral position is not really possible. There is no equivalent of a "jump ball" or a "face off". One team, and not the other, must have possession of the ball, giving that team an advantage. This results in the overtime coin flip problem. I'll assume that overtime is "sudden death": The …

The half-life gap

If you sort all the nuclides (isotopes of elements) in order of increasing half life, there are a fairly steady supply of them (on a logarithmic scale) up to a half-life of about 10 million years. There are also about 250 that have a half-life so long that it has never been measured. (And for …