the photon clock or all clocks slow down in motion . c is constant but
the time its passing threw changed so its ass iff c changed but it
dint.
Mass changed ..with the time change .
neutrons have more mass when farther from the earth and less mass when
nerest as time is faster or closer together and less mass near earth
.gravity is a time slope around mass .
light bends passing mass as time is closer together and 10 ticks takes
less space at c.
c is the speed but time is not the same on both sides of the photon so
its path is a curve in the curve of time around mass.
no two points in the universe are at the same time
http://community.webtv.net/GravityPhysics/WhaleSteamEngineA