Originally Posted By: Bill
Originally Posted By: Bill 6
The stronger the object's gravitational field the greater that variation and on that basis - as a star collapses the rate of departure of a beam of light traveling away from that (fixed location) source gradually reduces to zero in some cases.

Well, that is obviously wrong.


Imagine that you are looking at a light source located in your reference frame and some distance away from you. The source emits beams of light in opposite directions which, in a certain period of time as determined by your clock, travel identical distances away from that source:-

<----------•---------->

The source now starts accelerating across your line of vision and again emits beams of light in opposite directions which, in a certain period of time as determined by your clock, travel different distances away from their source:-

<---------------•----->

From your point of view, as a distant observer, the beams are moving at different speeds relative to you due to the fact that their source is accelerating.

The light source is now (hypothetically) located at a fixed distance from a black hole. On the basis of the principle of equivalence the respective beams will similarly travel at different speeds away from their source:-

• <---------------•----->

From your (distant observer) point of view the beam that is traveling radially toward the centre of gravity is moving faster away from its source (and relatively to you) than the beam that is headed in the opposite direction (you cannot, of course, actually see those beams).

"Light travels faster...toward the centre of gravity than away from it." (Nigel Calder, 'Einsteins Universe')

Originally Posted By: Bill
The speed of light, measured in any reference frame, is always the same.

In the above detailed event relative to a black hole... the speed of light is only determined to be constant by a local observer whose rules and clocks are physically affected by the gravitational field.

The speed of the respective beams of light is not the same as far as the distant observer is concerned.