It's possible, indeed often done in theoretical work, to set the speed of light to one, and express all other speeds as fractions of it. It is, if you will, the natural unit of velocity, and I guess you could think of it as the "base" velocity - but it's not zero in any meaningful sense.

(You could apply some one-to-one transformation to velocity so that lightspeed becomes zero in the derived quantity. But no such that I know of has any physical meaning - it'd just be a mathematical game.)


From another point of view, everything moves at the speed of light. This would be looking at the four-speed, which always has the magnitude of c - it's just that for ordinary objects the overwhelmingly largest components points in the direction of future time rather than in a spatial direction. In this view time dilatation is simply the fact that more of the constant total velocity points spatially so the particle goes slower in time, and photons (and other massless particles) travel in an exclusively spatial direction, so being in a sense timeless.

From this POV the question of the thread title is trivial - the spatial component of your four-velocity can obviously not be greater than your total four-velocity.

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Science is like sex. Sometimes something useful comes out, but that is not the reason we are doing it.
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