Relativity and Light
It is not possible for an observer, having mass, to also be a beam of light, or to be 'on' a beam of light.
That conflict results in some confusion in relativity.
Light or electromagnetic radiation has no mass. Light is actually synchronized electric and magnetic fields that always propagate at the same velocity in a vacuum; This constant velocity has been measured and is called c.
Relativity describes changes in the observer's space time when accelerating. The goal was to address what happens when an observer (having mass) accelerates to a velocity near c, assumed to be a limit, or perhaps at or greater than c.
Space time curvature described how the observer's frame of reference, space time, would be affected by gravity when moving near c.
Gravity is a force between masses. As light has no mass so it has nothing to do with gravity.
Unfortunately the relativistic effects on an observer were also assumed to apply to an observer on a beam of light.
That is not possible.
Any conclusions drawn from that invalid context are wrong.
A black hole proposes a point source of gravity could slow down the speed of light so it could not escape; this behavior is called an event horizon. This is wrong.
Gravitational lensing assumes the path of light from a distant observer would be affected by a source of gravity between the object and the observer. That is wrong.
Gravitational lensing was supposedly confirmed many years ago when a star's position was measured precisely near the surface of the sun.
This result was confusing. A strong electric field can affect the path of light's propagation of electric and magnetic fields. The strength of the Sun's electric field is dependent on the mass holding that charge. The strength of the Sun's gravitational field is dependent on the mass of the Sun. The two calculations for the path bending came out the same except the proposed gravity effect was invalid.
Light is not affected by gravity even if relativity implied it is.
Date updated 03/25/2019
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