The mathematics of GPS

The previous post looked into the common definition of Unix time as “the number of seconds since January 1, 1970 GMT” and why it’s not exactly true. It was true for a couple years before we started inserting leap seconds. Strictly speaking, Unix time is the number of non-leap seconds since January 1, 1970. This […] The post What exactly is a...

The time it takes earth to orbit the sun is not a simple multiple of the time it takes earth to rotate on its axis. The ratio isn’t even constant. The time it takes earth to circle the sun wobbles a bit, and the rotation of the earth is slowing down slightly. The ratio is […] The post Unix Time and a Modest Proposal first appeared on John D. Cook.

I looked at Hacker News to see which posts on this site were most popular. I didn’t look at my server logs, but generally the posts that get the most traffic are posts that someone submits to Hacker News. Older posts popular this year Two posts written earlier got a lot of traffic this year, […] The post Most popular posts of 2024 first appeared...

Stirling’s asymptotic series for the gamma function is Now suppose you’d like to find an asymptotic series for the function 1/Γ(z). Since the series for Γ has the form f(z) times an infinite sum, it would make sense to look for a series for 1/Γ of the form 1/f(z) times an infinite sum. The hard […] The post Series for the reciprocal of the gamma...

My nephew recently told me about being on a camping trip and seeing a long line of lights in the sky. The lights turned out to be Starlink satellites. It’s fairly common for people report seeing lines of these satellites. Why would the satellites be in a line? Wouldn’t it be much more efficient to […] The post Starlink configurations first...