Link from yhlee.
Two science questions: If most of the sun's UV comes from sunspots and sunspots have an 11 year cycle with a very low minimum, why doesn't the risk of sunburn vary enough for people to notice it?
When I was googling about the sunspot cycle, I found that it's really a 22 year cycle with the magnetic polarity of the spots alternating from cycle to cycle. How can you tell what polarity a sunspot has? It seems to have been known long enough that it doesn't take especially high tech.
Hypothetical tank bike
Link from sclerotic_rings.
The connection between this and the UV sun is that the bike would also make spiffy jewelry. Even if it doesn't work as a bike, it would also make a superb toy.
And I've gotten around to figuring out how to put images in my posts--satisfying, but a little fiddly. I *think* the proportions for the NASA picture are about right (it isn't square, but if I just copied it without specifying pixels, it got flattened too much) and the bicycle is about as big as it can get without being too pixelly.
The alt="description" thing doesn't work, and I don't see way, but it's easy enough to add non-html captions.