This video may say very important principle about Gravity. When atom (absorb?) or radiate photon, electron shell change its form in it's instantaneous time. And generate a Force. We know about light pressure generally. The Sun's light pressure is used by Japanese IKAROS, too. The instantaneous shape is similar to "The Primer Fields". These videos are very important, too.
The speed of light C is constant in vacuum. The C will decrease in midium such as glass or air etc. However, the light out into vacuum again, the speed increase to the C again. It is as if the light ignore the law of conservation of energy. This nature of light may produce the gravitational acceleration. (201306162331)
"We ran more than 250 experiments, improved the facility over 3 years and discussed the validity of the results for 8 months before making this announcement. Now we are confident about the measurement,"