Sunday, September 17, 2006

Anticrepuscular Rays

APOD: 2006 September 17 - Anticrepuscular Rays Over Florida

NASA's "Astronomy Picture of the Day", APOD, is my first stop on the Internet every day. Every selection is worthy. Accompanying explanations are always interesting, thought provoking and linked to other interesting stuff.

For example, the explanation for today's picture of anticrepuscular rays states that the rays appear to converge due to the straight lines of light being projected onto the spherical sky forming great circles.

Hmmm... Something twists my rusty spatial visualization gears. I can't help but think that, while true enough that a plane projected through a spherical shell forms a circle, it's not great circles that we're seeing.

If the earth were flat (and it is pretty flat from our human perspective) we'd see the same thing. The rays would converge just like railroad tracks running off to the horizon.

I'm splitting hairs again, and I could be wrong, but hey, it beat the hell out of moving on to see how many people were killed in Iraq overnight or what religionist pissed off how many others of his ilk, how we've got to get involved in Darfur or what a war with Iran would look like.

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