We measure space objects speed in relation to earth. But since earth is also moving through space, how do we know the true speed of objects without a universal “non moving” point?

Question

The speed of an object is measure relative to the observer. But since all objects are moving in relation to all objects, how can we know the true speeds of things? Wouldnt two observers on different planets measuring an object in space come up with different answers?

In: Physics

Answer 1

All speeds are relative.

On a universal scale, scientists will try to measure the speed of things in relation to the center of the known universe, and use that as a hypothetical non moving point.

But I’m most practices, that isn’t really necessary or useful, what is more useful is having a speed relative to soemthing more useful, like say relative to earth, our home.

Or relative to the sun, which is effectively the center of our solar system.

Or relative to the center of the Milky Way galaxy, or one galaxy relative to another galaxy. That stuff is typically more helpful/applicable