Dr Photon wrote:
Since Einstein died in 1955, and the Shapiro delay was only predicted
in 1964, then he couldn't have been referring to that.

Sure he could -- Einstein was extremely well-versed in the basis of GR,
and he most definitely knew that the speed of light can vary when
measured over non-local paths. Shapiro's contribution was to realize
that this esoteric aspect of GR could actually be measured, and he went
on to measure it.


Tom Roberts