Is motion constant or discrete?

It is continuous and discrete. The Schrödinger equation describes the continuous evolution of the quantum wave function of massive particles, in the non-relatvisitic limit. However, this is half of quantum mechanics. read more

As “constant” refers to “no change” which is impossible. Different objects can move at different rate under different conditions of forces . Any way some physicist think that motion is discrete in well known smallest steps equal to plank length. read more

Even if the direct effects on particle motion are unmeasurable, defects in the discrete structure could still be observable. Think of space-time like a diamond. Even rare imperfections in atomic lattices spoil a crystal’s ability to transport light in an orderly way, which will ruin a diamond’s clarity. read more

In mathematical physics, equations of motion are equations that describe the behavior of a physical system in terms of its motion as a function of time. More specifically, the equations of motion describe the behaviour of a physical system as a set of mathematical functions in terms of dynamic variables: normally spatial coordinates and time are used, but others are also possible, such as momentum components and time. read more