If our planet is rotating and shooting through space, why do we see stars as dots of light instead of blurred lines across the sky?

Question

I’m sitting here trying to sleep and this is keeping me awake.

In: Physics

Answer 1

Because we’re not rotating, or revolving around the sun, all that fast, really. Yes, the Equator is going more than a thousand miles an hour … but it still takes an entire day for the Earth to rotate once. And the stars are far far away. So you don’t have to turn your head very fast at all to keep your eyes fixed on one; the angular velocity has a “per day” as its frequency.

Similarly for “going around the Sun” (takes a year) or “going around Galactic center” (takes 200 million years) – big linear velocities might be involved, but the angular frequencies are pretty small.

Astronauts on the Space Station are going around the Earth about every hour and a half, but even that is just about fast enough to see the Earth move against the stellar background if you pay attention, not enough to blur or streak the stellar dots.

–Dave, turbulence in the atmosphere causes more visual difficulty than the angular motion; it’s why they ‘twinkle’