Watching the Sky Move

This is the first in a series of comments about something I have read recently.

I read an article in the February 2007 Astronomy magazine written by Glenn Chaple called Watching the Sky Move. Glenn writes that he has an unusual interest in watching very slow things enfold such as watching the movement of the minute hand on a clock. Or more pertinent to Astronomy, he spent time trying to actually observe the movements of stars across the sky. He did this on one occasion by sitting very still and watching a bright star, Sirius, move past branches in a tree that were between he and the star. It must have been a very still night as well or the branches would have moved as well causing his attempt to be less interesting.

I found this article interesting for several reasons. Although not recently, I actually have tried to observe the movement of the minute hand on a clock. It is easier with a large clock, by the way. Why? I don’t know – just something I had to do once upon a time long ago. That means not recently – not in the last 25 years. But I did do it and did discover that those minute hands do move while they are being watched.

I have never tried to observe star movement without looking through a telescope. In a telescope, such movement is very apparent because whatever you are looking at does not stay in view very long if you don’t have a motorized telescope to keep things in view.

What causes the apparent movement of the stars? Mostly it is the rotation of the Earth which causes the surface to zoom along at about 1000 miles per hour. Yet star movement is nearly imperceptible.