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© Copyright 1998 and 2002 Jim Loy
For quite a few years, I had the following theory about why stars twinkle:
As viewed from earth, stars are very tiny objects (they have small angular diameters). So, the light of a star is focused, by the lens of the eye, onto a tiny portion of one of your light receptors (rod and cone cells) in the eye. The air moving in the atmosphere, wind and other air currents, makes the image of a star move around. I don't think that this normally blots out the image of a star. I think that this makes the image of the star occasionally rest between the light receptors of the eye, making the image of the star disappear. I have been looking for mention of this theory in astronomy books. So far, I have been unsuccessful.
My theory has suffered a couple of setbacks. First, when I view a dramatically twinkling star, the twinkling seems to be identical (in synch) in both of my eyes. And when I view a twinkling star out of focus (with the image spread out by the bifocal portion of my glasses), the star still seems to twinkle. Both of these would seem to indicate that the twinkling is caused by actual changes in apparent brightness of the star, in turn caused by the intervening air turbulence.