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## Main Question or Discussion Point

An observer at the mid point between two frames A and B that are moving toward her, measures each of their speeds to be 0.75c. According to SR, the Lorentz transformation will determine the speed of A and B measured by the other to be less than 1.5c. (in fact less than c)

Being aware of the effects of SR, the observer at the mid point will also be aware that their measurement of the speed of A and B is subject to the Lorentz transformation and therefore is a measure of some speed greater than 0.75c contracted to 0.75c by the Lorentz effect. After accounting for the Lorentz factor that gave their measurement for A and B they find the speed of each is greater than 0.75c.

Since the observer at the mid point is not necessary in the measurements made by A and B, should the observer calculate the speed of A and B as measured by each as a Lorentz transformation of 0.75c, or the greater, untransformed speed?

Why?

Being aware of the effects of SR, the observer at the mid point will also be aware that their measurement of the speed of A and B is subject to the Lorentz transformation and therefore is a measure of some speed greater than 0.75c contracted to 0.75c by the Lorentz effect. After accounting for the Lorentz factor that gave their measurement for A and B they find the speed of each is greater than 0.75c.

Since the observer at the mid point is not necessary in the measurements made by A and B, should the observer calculate the speed of A and B as measured by each as a Lorentz transformation of 0.75c, or the greater, untransformed speed?

Why?

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