Gelial's Blurbs

The Earth does in fact rotate around the Sun and the empirical evidence is: the shift in the stars’ parallax angles.

However, from a fundamental point of view, that is, from the point of view of the fundamental nature of space (as the “stage” where stuff happens), it is actually irrelevant whether it’s the Earth that rotates around the Sun or the other way around.

And the fact that this is irrelevant is far from trivial.

The same is true of a simpler situation. If two objects are moving in straight lines (at constant speeds), it is irrelevant which object is actually moving.

Galileo was the first to write about this relative property of motion (in straight lines at constant speeds), and Newton was the first to put it into a mathematically useful form. However, it was Einstein who deduced the true significance of the fact that motion is relative.

His two theories of relativity are precisely about the implications of the fact that motion in space (and time) is relative.

There are a number of fascinating things that have to do with the fact that motion is relative – things like Noether’s theorem and conservation laws (eg, Why is energy conserved? What does that really mean, anyway?), and why gravity is the key to make accelerated motion also relative. Unfortunately, I don’t have the time nor the inclination to give a lecture here.

Suffice it to say that the fact that motion is fundamentally relative is the cornerstone of much of modern physics.

Copernicus certainly never dreamed that his heliocentric hypothesis would be at the center of something so much bigger and so much more important than just our solar system.