What is motion

[studiot]

Our universe contains some (unknown) very large number of particles.

It is also our tenet that our laws of physics should be such as to also apply to a universe with a different number of particles.

That is they should be invariant to the number of particles.

 

So what is motion (ie what are the observables and what do they mean) for a universe containing a single particle?

[Ophiolite]

Is there any field present?

[studiot]

No fields, potential wells or other restrictions are defined other than what the particle 'creates' by virtue of its own existence in an otherwise empty unbounded universe.

[swansont]

Motion is defined with respect to something else. A single particle is at rest with respect to itself, and if that's the only reference you have, then it's at rest. But it's not a realistic scenario.

[md65536]

So what is motion (ie what are the observables and what do they mean) for a universe containing a single particle?

 

Probably the same as in our universe. There is no absolute motion; so with nothing to move relative to there would be no relative motion either.

 

If it's a point particle perhaps you could consider the universe a singularity, with all measures of distance contracted to zero, so all motion occurs across 0 distance.