Answer depends on whether you are talking about how the rod looks visually to them (in which case a receding rod appears contracted but an approaching rod appears elongated, see https://en.wikipedia.org/wiki/Terrell_rotation ) or if you are talking about how they assign coordinates to the rod in their own rest frame, using a system of rulers and clocks which are at rest and synchronized relative to themselves (like in the illustration at https://faraday.physics.utoronto.ca/GeneralInterest/Harrison/SpecRel/SpecRel.html#Exploring with synchronization based on the procedure described at https://en.wikipedia.org/wiki/Einstein_synchronisation ), which was what Einstein was concerned with in his original SR paper. In terms of the latter, if they measure the back end and front end of the moving rod simultaneously using their own clocks and rulers, they will always find the distance to be shrunk by the gamma factor regardless of whether it's moving towards or away from them.
On Sat, Sep 7, 2024 at 3:25 AM Alan Grayson <[email protected]> wrote: > For an observer moving toward a rod of some fixed length in a rest frame, > the rod shrinks, but what happens when the observer is moving *away* from > the rod, given that the gamma factor remains unchanged? > > -- > You received this message because you are subscribed to the Google Groups > "Everything List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/everything-list/02981fe3-8c92-41e4-aa3c-98b57be89e54n%40googlegroups.com > <https://groups.google.com/d/msgid/everything-list/02981fe3-8c92-41e4-aa3c-98b57be89e54n%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/CAPCWU3JQifyaz4h%3DJd6iJK8oYaAvMW9GBRCiyRCAHLkTCFoO7A%40mail.gmail.com.
