There is a space ship (accelerating upward). Books say that "gravity" at roof and floor is different.
Disproof ; There are two probes (accelerating upward). Position of the two is apart vertically (distance is the height of the space ship). "Gravity" at the two will be the same.
Many books explain bending of light with an elevator cabin in free fall. Now, two elevator cabins are falling before an observer's eyes. Falling speed of the two is different because starting points of falling is different. Does the observer observe different bending of light (gravity g is the same) ?
P.S. In many books, light ray is coming from the outside of the elevator cabin. In some books, light source is set on the wall of the cabin. In the former, falling of the cabin will have no effect on light ray (imagine a cabin without wall). In the latter (if the emission theory is true), behavior of light ray will be easy to imagine.
For a 10 seconds, an elevator cabin accelerated upward and stopped. Number of waves of light that appears and vanishes during that time will be the same.