Happy Vernal Equinox 2016! But What Does That Mean?

Saturday is the vernal equinox! Well, Saturday night is, depending on where on Earth you are. The moment happens at 04:30 UTC on March 20 this year, which is, for example, March 19 at 10:30 p.m. Mountain (U.S.) time, where I live. But what does that mean, exactly? Why, let my friend Joe Hanson explain it to you in an episode of "It's Okay to Be Smart" The equilux point he makes is a good one. It's even worse than he describes; our atmosphere scatters sunlight, spreading it out. That's why we hav...