# Should uniform motion be distinguished from rest?

Aristotle distinguishes motion and rest. For him rest is simply the potential of motion but not motion itself.

So a seed before it blooms into becoming and being is at rest; a football before being kicked is at rest.

Classically, after Galileo, we distinguish rest from motion only as a special point on a continuum; and that which is contingent (by reference to a frame); in a strong sense it is not distinguished at all.

Hence we can say, all things are in motion and there is no rest anywhere (as rest is a special motion).

But equally; and perhaps more perceptively - or perhaps not; and with one eye on Parmenides; we can say all things in themselves are at rest in themselves; and only their relations with others are in motion.

After all - shouldn't rest be considered as more fundamental than motion; being something always prior?

The rest frame of relativity is at rest by definition. More concretely the COBE experiment shows the earth's velocity relative to the visible universe as a whole taken as a rest frame beyond which no other larger frame is known.

I think you can make arguments both ways. Really what you are doing is defining two terms "rest" and "motion." You can define them any way you please, so long as they do not confuse.

The Chinese, in particular, have a strong tendency in their philosophy to talk about relative motion, exactly as you suggest. Their philosophies appear to my Western eyes to be more about harmonies than the concrete "positions" Western thought tends to love.

There is also some prior art down this debate in terms of coordinate systems. Netwonian physics works only in so called "inertial" frames. For example, we love to use a coordinate system called ECI (Earth Centered Inertial) to do satellite motion simulations. Because the earth's CG remains at a fixed point, and it is an inertial frame, the physics is actually really simple to calculate using that frame.

However, the Earth is spinning. For many ground based situations, ECI isn't quite desirable because a point that we would call "fixed on the earth" is hurtling through space at quite a rapid pace in ECI terms (because that spot on the Earth is having to rotate around the Earth's CG). For such ground based simulations, we turn to relative motion and use ECEF (Earth Centered; Earth Fixed), which measures everything in terms of relative motions with respect to the ground. This lets us do lots of physics very easily (such as throwing a ball in a game of catch).

However, there's a quirk. The Earth's frame of motion is a rotating one. There are funny non-Newtonian effects that show up when you try to apply Newtonian physics in a rotating (non-inertial) frame. These are things like the Coriolis Effect which can be frustratingly confusing when one begins doing fast movements. The path satellites take look absolutely wonky when viewed in ECEF, due to these effects.

What I take away from theses two physics based situations is that there are situations where exploring relative motion and relative rest are very meaningful. However, there are situations where those terms do not capture reality in a way which is easy to discuss or manipulate, so in those situations such definitions for "motion" and "rest" could lead to very unusual discussions.