Monday, January 5, 2015

Happy Perihelion Day!

Happy Perihelion! Yesterday at 0636 UTC (1:36 am ET) the Earth was as close to the Sun as it will be in 2015. This is called perihelion. The distance change is small (about 1.67% closer at perihelion and 1.67% further away at aphelion in June), but we see the Sun as a little brighter today.

Our orbit around the Sun is almost a circle right now. That means our seasons are caused by tilt of our rotation axis. But there have been times in the past when our orbit was more of an oval. It's fun to think about what that would do to our seasons and climate. The Lensman books by E. E. Doc Smith included a nemesis with a home planet that had an extremely elliptical orbit and the bizarre evolutionary adaptations that led to.