Sun, I am disappoint.
Last Sunday, I suggested that we all take a moment and think about the sun, it’s scale and how it effects (and affects) us. This week, I’ve been thinking about the lack of sun I’ve seen lately. This is New England, which is cloudy often, wet constantly, and must have the least predictable weather in the country. Still, I love it here and when the sun does shine, I think we cantankerous Northeasterners appreciate it a little more. Even if we’re busy pounding down a 32oz iced coffee in January while bitching about Deval Patrick’s office curtains.
All of our thoughts tend to surround the sun’s visible light and heat. We don’t tend to think about the 20 trillion neutrinos that pass through us every second or the far fewer, but more concerning, muons that can wreak havoc with our bodies. We’ve been hearing about neutrinos in the past week, but in a different context.
Another funny thing we don’t see, which makes a big difference, is the amount of UV light that lights up the sky. The sky looks blue, but that’s just the way our eyes are tuned. We see blue better than violet, but to a hawk, which can see into the UV spectrum it would be something else: a violet sky. Of course the hawk is more interested in the small mammals whose urine would appear to glow brightly in these wavelengths.
At shorter wavelengths, UV stars to get both very useful and dangerous. We all know how much fun it is to get a sun burn and the dangers of skin cancer, though I’ve seen statistics that 90%+ of these are non-melanoma and most are not very dangerous (do your homework on personal safety and don’t take my word or the 11 o’clock news’, ask your doctor and get scientifically verified facts), but this is an astronomy blog and I’m not going to get too into this.
The thing UV does FOR us though, which is very important, is it’s our body’s tool for manufacturing vitamin D, which is not an optional nutrient. Vitamin D deficiency can lead to a LOT of problems, and it doesn’t take much sun to get what you need, especially if you have light skin. 20 minutes in bright Boston sun can produce as much vitamin D as 200 glasses of milk. Again, I’m not here to give you medical advice, do what is right for you, just learn what you can and avoid hype.
On the other end of our narrow visible spectrum is infra red. Frederick William Herschel, the guy who also discovered Uranus (go ahead and laugh, there’s no un-funny way to write that), had the good idea in 1781 to put thermometers in each color of the rainbow of light that was refracted by a prism, but also one more, just outside of the red end where nothing seemed to be. His intuition payed off and it became clear that heat was just light outside of the visible spectrum on the red side. The value of this IR light should be pretty obvious. When you use IR night-vision, that’s closer to the visible end of things and colors change dramatically, your black shirt might look white. Go a little further and with the right equipment, you can “see” heat as if it were any other kind of light, but with false colors making it look really trippy.
If there’s a running theme with sun posts, it’s that there’s always WAY more happening than meets the eye (get it?) and when it comes to some of these invisible happenings we literally can’t live without them. Our biology, physiology, psychology and genealogy (as in, ALL the way back) are tied intimately to both the things we see the sun doing and those we don’t. So, the sun does a bit more than just keep us warm and give us enough light to allow for our beloved Ultimate Frisbee championships.