Re: What makes stars/lights twinkle?

Dear Kathy,
    Stars appear to twinkle because their light passes through our moving atmosphere before
it reaches your eye.  Every temperature gradient, every breath of wind, every difference
in barometric pressure cause a slight change in the refractive index of the air in that
area.  And when light passes from an area of one refractive index to another, it is bent
and partially separated into its constituent wavelengths - colors.  Have you 
notice that stars near the horizon twinkle more than stars overhead?  That's because
their light passes through much more of our atmosphere on its way to your eye.
     Enjoy the twinkling and use it to guage how steady the 'seeing' is in your
neighborhood.