(2-7)  Have a look at the picture, which summarises the situation when the light pulse is initiated and then when it has just hit you.

①  In Nefertiti’s frame of reference, the distance between you and her is y, and the time it took the light pulse to cover it is t.  What, therefore, is the speed at which the light travelled, c ?

②  The distance moved by Nefertiti relative to Cormorant, while the light pulse was in flight, is x. Follow the analysis that you and Pythagoras put together for the sardine experiment, to find r, the distance travelled by the light pulse as Cormorant sees it. Hence derive an expression for the speed of light as Cormorant would measure it.

③  Now Uncle Albert says that these two speeds of light must be the same: c is a constant, irrespective of different frames of reference. So, comparing the expressions you got in ① and ②, what are the only possible ways to reconcile these two apparently contradictory expressions?