I have heard of two physical phenomena: 1. A photon travelling from one location to another, goes the path that takes the shortest time. (More correctly, the quickest paths has the highest probability amplitude) 2. Time is slowed down in a gravitational field. Is this how gravitational lensing works?: A photon in a distant galaxy chose to travel to earth. Another galaxy with a large gravitational field is in the way. To avoid being slowed down, the photon avoids that galaxy. Instead it goes around it. From earth, it looks like the otherwise straight photon path have been bent by the middle galaxy. Is this how gravity works on all kinds of matter?