Question

How do scientists determine motion of objects in the universe??

Answer 1

Usually, Scientists use "Parallax Method" in order to determine the different positions of an object

Hope this helps!

Answer 2

Answer: By Doppler effect

Explanation:

The spectrum of the objects in the universe such as stars and galaxies is taken and studied. The apparent change in the frequency/wavelength of the light suggests the motion of these objects.

If the apparent frequency is greater, the light would be blue -shifted which means it is moving towards Earth and if it is red shifted, it would be moving away from the earth. This is apparent change in observed frequency is known as Doppler's effect which studied to determine the motion of objects in the universe.