Hello everyone - newbie here. Am I right to say that stars twinkle because of regions of the atmosphere being at different (and varying) temperatures and pressures etc., giving rise to a variation in refractive index and consequently a shifting image of the observed object? If so, why don't I observe planets to do the same thing? I thought it might be because planets appear much brighter, but then don't some stars shine more brightly than some planets at times? Thanks.