We can Measure speed of any object only if observed from a fixed point but Is there anything still in our universe? If not then how are we finding speed of planets solar systems stars and even galaxies?
First of all there is nothing still in our universe. Our planet Earth is moving on its own axis at the speed of 460 meter/second and revolving around the sun at the speed of 30 km/sec. Our solar system is moving at the speed of seventy thousand kms towards the bright star Vega in the constellation of Lyra.
Our solar system is also moving in our galaxy Milky Way towards the galactic center in a spiral form at the speed of 792 km/h.
Our whole galaxy Milky Way is moving at the speed of 2.1 million km/h towards the constellation of Leo and Virgo, towards a thing we don’t really understand yet, called ‘The Great Attractor’.
So how can we measure speed of these celestial bodies? It can be measured by taking the light of the star as center that is so far away that its change in position respective to ours is negligible when observed for short period of time.