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San Francisco, 12:51 AM
Wed Nov 11
27 posts in the last 24 hours
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07/31/09
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Although having a smooth surface is important, it's not the reason for the slow spin. Spinning produces a parabolic surface, which is essential for the functioning of the telescope. The telescope wouldn't work if its mirror was flat.
A parabolic reflecting surface has the property that any ray arriving at it parallel to the surface's axis will be reflected towards the surface's focal point, which is located on the axis some distance above the surface. It's at that focal point that the telescope's receiver is located. Since all sources of interest are astronomically far away, all their rays arrive parallel to the telescope's axis, when you point the telescope to the source.
The same principle applies to satellite dishes, by the way.
Anyway, the spin makes the molten glass have a parabolic shape, which hardens as the glass cools down. The mirror is then polished and coated with a reflective material.
Next time you're drinking something off a glass, stir the contents and notice how the edges of the liquid rise while the center moves down. That's your parabolic surface right there, though highly distorted by your finger or whatever you use to stir the liquid you're drinking.
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It happens to me everyday.
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Now, here's the mind-bender. According to Mach's principle if - instead of spinning the coffee in your glass - you and the rest of the universe were to spin together around the coffee, the coffee would still present a parabolic surface to you.
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From what I learned about Palomar, it was a pain in the ass to move a 200 inch diameter lens from NY to CA.
02/12/09
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02/12/09
You mean Moff is like Hastur?
Let's try it out...
Moff! Moff! Mof...auggGHHHHHHHH!!!!!!!H!H!
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02/12/09
*looks in mirror* *puts on Burger King crown*
Yay! I'm the Yellow King!