In order to directly demonstrate that in static gravitational field the rate of clocks increases with their distance from the source a simple thought experiment is proposed.
@article{arxiv.hep-ph/0010256,
title = {A thought experiment with clocks in static gravity},
author = {L. B. Okun},
journal= {arXiv preprint arXiv:hep-ph/0010256},
year = {2009}
}