While looking at a large city from a distance, why do the lights seem to twinkle?

Question

And why don't the closer lights twinkle?

Answer 1

Light doesn't necessarily travel in a perfectly straight line through the air. When the air between the light source and yourself contains little air pockets at various different densities, the air pockets act sort of like little lenses, causing the light beams to converge slightly (making the object look a little brighter), or diverge slightly (making the object look a little dimmer).

These tiny "lenses" are changing all the time (because the air density fluctuates), so you'll see the light appear bright in one instant and dim the next--twinkling.

Also, the "lenses" are very localized, so you'll see one point of light appear bright at the same time the point next to it appears dim. That's why you don't see the entire "city" flashing bright & dim all at once.

The reason you notice this effect most for far away lights, is that the light is traveling through more air. That means there is a greater chance that the light will encounter fluctuating air density pockets by the time it reaches your eyes.

You also notice the effect more when the air is warm. Warm air causes turbulence ("stirring up" of the air), which cause the local air density to fluctuate quickly.

Answer 2

It's actually stuff in the air getting in your way. Stuff as in pollutants or just things flying around like dust/dirt. You can't really see the stuff flying around at a distance you can only see it interfere with the lights in the background.

as you get closer the stuff flying around is too small to block the now large lights. so while they continue to pass, less passes in front because the distance between you and the light is smaller...but also the stuff is much smaller when compared to the light because your closer. Kind of the 'squish your head' idea...from far away you can 'squish' someone's head between your fingers but close up your fingers don't spread wide enough.

Answer 3

Same reason the stars light twinkles. Thermal motion in the atmosphere. ~

Answer 4

It's called "terrestrial scintillation". It's caused by the refraction of the light by small-scale fluctuations in local air density related to different temperatures, aided by wind and turbulent mixing.

Answer 5

The light gets distorted because of all of the water vapor between the lights & the observer.

Answer 6

its because of air turbulences in the athmosphere. The more air is between you and the light the more the light is scattered in its path.

Answer 7

I like the other guys answers, but I always thought it was because my sister had just poked me in the eye. You have a sister?