In the book General Physics by L.D.Landau, he mentioned the following in the first and second paragraph
The fundamental concept of mechanics is that of motion of a body with respect to other bodies. In the absence of such other bodies it is clearly impossible to speak of motion, which is always relative. Absolute motion of a body irrespective of other bodies has no meaning.
The relativity of motion arises from the relativity of the concept of space itself. We cannot speak of position in absolute space independently of bodies therein, but only of position relative to certain bodies.
I am not very sure what he means by "We cannot speak of position in absolute space independently of bodies therein, but only of position relative to certain bodies."
My current understanding is that, for an absolute space without respect to any body, we can take any value as the position of a point as we did not specify the origin. Only by referring to some bodies, we can then get a position for the point.
However, I am not very sure about my understanding and I do not know if it is correct. (I feel there is some logical gap there... Why can't we just take any random point in the absolute space as origin? Is it because there is no difference between any two points in the absolute space if we do not consider some objects?...)
These are my thoughts and I am a bit confused... So, how should we interpret this sentence? What is the meaning of relativity of space here?