It doesn’t say that energy is invariant, but I agree my wording is a bit sloppy. I meant to say the invariant associated with energy/momentum 4-vector or something like that.

]]>No. In natural units, velocities are fractions of the speed of light and are dimensionless. The Lorentz factor thus includes terms in 1-v^2 in natural units, which become 1-(v/c)^2 in standard systems.

]]>Let v be a certain constant mathematical number between 0 and 1. Now if you say “the velocity is v” when you’re using natural units, wouldn’t that become “the velocity is vc” in unnatural units? The important difference is that in that case, expressions like exp(v) when in natural units will become exp(vc) in unnatural units and thus have a dimensioned exponent and be invalid, i.e. natural units would in that case also have units but just use them implicitly. Please correct me where I am wrong.

]]>There’s no “trickery”.

]]>Thank you 🙂

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