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How did Einstein’s elevator thought experiment predict that gravity bends light?

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gravitational lens — gravity A galactic cluster, about five billion light-years away, produces a tremendous gravitational field that “bends” light around it. This lens produces multiple copies of a blue galaxy about twice as distant. Four images are visible in a circle surrounding the lens; a fifth is visible near the center of the picture, which was taken by the Hubble Space Telescope.

Albert Einstein’s elevator thought experiment predicted that gravity bends light by utilizing his principle of equivalence, which states that it is impossible to distinguish between the effects of gravity and those of acceleration within a local system.12

To visualize this, imagine an elevator with a hole in two opposite walls. When the elevator is at rest, a beam of light entering one hole travels in a straight line and exits the other. However, if the elevator accelerates upward, the exit hole moves while the light is in transit, causing the light to strike the wall lower than the exit hole. To an observer inside, the light appears to follow a curved, parabolic path.12

Because the principle of equivalence dictates that physical effects in an accelerated system must also occur in a gravitational field, Einstein concluded that gravity must similarly bend light. This insight suggested that gravity is not merely a force but a geometric phenomenon, implying that the path of light is curved by the presence of massive bodies.13