We can see the city lights from our front door.

They twinkle.

The video doesn’t really capture very well what the eye sees. I think the twinkling is more pronounced on cold, clear nights. That’s when there is a lot of variation in the air temperature, which can cause twinkling at the air moves around. Windy nights might be good as well, but we haven’t had a windy night without rain and fog, so the lights haven’t been visible then.

I have read that stars twinkle but that planets do not, unless they are visible near the horizon. The reason is that stars are point-sources, while planets are not. The light from a star appears to twinkle because of atmospheric refraction of the light. The refraction would be constant and the light would be steady if the air were still, but the atmosphere is constantly in motion, so the light from the stars has to travel through a medium whose density constantly varies along its path. Planets are actually discs. You can see that with a telescope, but even without a telescope the width tends to suppress the effect of refraction.

This site explains the twinkling by saying that a star’s light follows a zig-zag path, but that’s not exactly accurate. If you stand next to someone and look up at the night sky, you can both see the same star, but the light that falls on your eyes follows a slightly different path from the light that falls on your friend’s eyes. When the light going to your eyes is refracted away from its path, you end up not seeing that light. However, light that was following a different path is refracted into your eyes, so it looks like it comes from a slightly different location. That makes the star seem to move very slightly in the sky, which we see as twinkling.

When I look out at the city lights, the smaller lights twinkle while the bigger, brighter lights don’t. In this case, the small lights are like stars, and the bigger lights are like planets. None of them are point sources, so you might think they wouldn’t twinkle, but their light is passing through the densest and (often) most turbulent part of the atmosphere, which is enough to make them twinkle.