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Trick or Treat!

Week of November 11, 1998

On the night of the last Halloween (October 31, 1998) I decided to take my 25 centimeter telescope out and set it up in my driveway. Someone on the USENET newsgroup sci.astro.amateur suggested that people with 'scopes take them out that night, so that the neighborhood kids could get a chance to see the Moon and Jupiter when they were out anyway trick-or-treating. Regular readers here know that I am a sucker for a chance to lecture about astronomy, so out came the 'scope.

That night, lots of kids and adults saw those nearby objects through my telescope, many of whom were seeing them for the first time. There were gasps of awe when they saw craters and mountains on the Moon, but the real showstoppers were Jupiter and Saturn. As one neighbor of mine said, ``You read about Saturn having rings all the time, but you don't understand until you see it for yourself!''

IMAGE OF JUPITER The other thing that surprised them was being able to see the moons of Jupiter (as well as the belts of clouds on the ``surface''). I guess that shouldn't surprise me; people that have never looked through a telescope before have no reason to know that you can see the moons. But remember, Galileo discovered the four big moons of Jupiter with what was really a pretty bad 'scope. Still, seeing them with your own eyes for the first time is quite a thrill. Actually, it's kind of funny: I did a quick calculation, and it looks to me like the four big moons of Jupiter are easily bright enough to be seen with the unaided eye. The reason you can't is that Jupiter is so bright it drowns them out; it's like trying to see a firefly resting on a spotlight. Imagine if Jupiter were painted jet black... the four moons would be just visible to the keen observer, and their motion around the invisible planet would be obvious after only a few days.

One of the (many) reasons Galileo was persecuted by the Church in the seventeenth century was because he stated that the Earth was not the center of the solar system. He listed as his reasons the phases of Venus and the fact that the moons of Jupiter orbit Jupiter itself and not the Earth. Imagine how his life-- and all of ours-- would have been different if the moons were easily seen to be circling some other body. Perhaps science would have progressed much faster, and by now we'd be living on those moons. Or perhaps people would have thought the dark planet evil, and it would have held reason and rational beliefs back. There's no way of knowing, but sometimes it's fun to think about how things might have been, had the Universe just been a little different.

©2008 Phil Plait. All Rights Reserved.

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