Sunday, 4 December 2016
Belt of Venus and backscattering
Now I know what to look for, I see the Belt of Venus all the time. Here it is this morning. It's the pink glow above the horizon. I was looking north. The darker line below is the shadow of the Earth. The Sun has not yet risen and we are technically still in shadow. It is light because the Sun is lighting the atmosphere above our heads. This morning it occurred to me that when I show red sky at the lab, it is as a result of scattering. The shorter wavelengths are scattered out of the way so the blues and greens are knocked out of line and only the red longer wavelengths get through. But this is a transmission phenomenon. In the picture, the red light has gone past us. So how can I see it? Turns out that it is called BACKSCATTERING. https://en.wikipedia.org/wiki/Backscatter It seems to be a type of reflection, but one that doesn't reflect all rays in the same direction as a mirror would.