A four-dimensional form of this quantity is defined as the zero-th basis vector of an MCRF.
A four-dimensional form of this quantity is defined as the zero-th basis vector of an MCRF. A simpler form of a composition law for this quantity results when setting this quantity equal to the hyperbolic tangent of a namesake parameter, due to the angle addition formula for the hyperbolic tangent. A form of this quantity is the reciprocal of the slope of a world line. A non-intuitive result for this quantity is that it must be added using Einstein's law of addition. Newton's laws are all Galilean invariant, meaning that they are the same when a constant factor of this quantity is applied. It appears divided by the square of the speed of light in the Lorentz factor. Because the proper time along a null line is zero, the four-dimensional form of this quantity cannot be used to define a photon's four- momentum. For 10 points, identify this quantity whose time derivative is acceleration.
A four-dimensional form of this quantity is defined as the zero-th basis vector of an MCRF.
relative velocity [or v]