text: why don't planets twinkle? the usual reason given to why stars twinkle is the random refractions in the earth's atmosphere. well then, why don't planets twinkle? stars and planets do twinkle as their light travels thru the shimmering layers of our lovely planet's atmosphere... but, because the planets are discs and not small points of light - but bigger diameter shining discs ... most of the time planets do not seem to twinkle - but if you look at, for instance, saturn thru a telescope on a night of very unstable upper atmospheric "bad seeing". its useless and like trying to see saturn from underwater with your eyes open. astronomers rate the amount of twinkle in sky objects ( stars and planets ) by a seeing scale.  0-1 is great 5-6 is horrible dancing lights... the olde stargeezer