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A comment on Do we really travel through time with the speed of light?. Parent comment

Re:Do we really travel through time with the speed of light? by cygx on Monday August 31, 2020 @07:25AM (#24330298)
Does that vector also have fixed magnitude?

It's magnitude is called 'mass' (or 'rest mass'/'invariant mass' if you want to differentiate it from the concept of 'relativistic mass', which probably should be retired).

This means we have

    four-momentum = mass * four-velocity
whereas

    three-momentum = gamma * mass * three-velocity
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Re:Do we really travel through time with the speed of light? by alexpetralia on Saturday September 05, 2020 @10:41AM (#24383875)
Not sure if you will find this comment, but I'd be very curious to hear what the magnitudes of "four-force" and "four-potential" are as well!

My layman's research suggest these are, respectively, "electric charge" and "current"?

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Re:Do we really travel through time with the speed of light? by cygx on Monday September 07, 2020 @06:38AM (#24398397)
That doesn't sound right to me. Note that four-force is a generic concept not limited to electromagnetism. Current is the source term of Maxwell's equations, which connect it to the potential via the d'Alembert operator.
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