Cure for boredom
This week I have been doing astro with my HL class and today we covered binaries. When I first heard that something like 2 out of 3 stars are binaries I was surprised but thinking about it it's not so surprising. If the stars that were so close together weren't orbiting each other then their gravitational attraction would cause them to collide. To illustrate the point I thought I'd make a binary in interactive physics and was so pleased with the result that i thought I'd blog about it. Anyway when I got home I found out that I did exactly the same thing last year and have blogged about it already. A student asked me this afternoon how I can keep teaching the same stuff every year without getting bored. Well if you can't remember what you do from one year to the next then you never get bored.
Last time I blogged this I didn't know how to make these annoying little gif animation so here's one now. I think it shows nicely the reason why the two dips in the light curve of two equally sized stars aren't the same width. Viewed from the left it takes longer for the blue to cross the red than the red to cross the blue.