with the hyperbola ( X − − 1 / α α ) 2 − − T 2 = 1 / α α 2 . It turns out that at t = ± ± ( x + 2 / α α ) the time becomes singular, to which Fulton & Rohrlich & Witten remark that one has to stay away from this limit, while Kastrup (who is very critical of the acceleration interpretation) remarks that this is one of the strange results of this interpretation.