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johne1618
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Would General Relativity predict that two initially parallel light beams will converge due to their energy curving space-time?
John
John
Dmitry67 said:This is correct, light beams create gravity.
However, when it was discussed here about 1 or 2 y ago, I remember that someone (with much deeper knowledge of GR - I am just a layman) told me that:
2 parallel light beams going in the same direction do not attract (even they attract the surrounding objects)
2 parallel light beams going in opposite directions do attract.
The first fact might be clear if we look at 2 massive objects, separated by some distance, flying in the same direction. In their inertial system they collide, say, in 1s. For an external observer, this process would take longer because of the time dilation. The faster 2 objects are flying the longer it takes. You can think about the case N1 as a limit where v --> c (it takes forever)
P.S.
Interesting problem: what is Jean's mass for the light itself? :)
The concept of parallel light beams converging refers to the phenomenon where two or more parallel light beams come together at a single point, known as the focal point, after passing through a lens or other optical device.
Parallel light beams converge due to the curvature of the lens or the shape of the optical device they pass through. This curvature causes the light rays to bend towards each other, eventually meeting at a single point.
Parallel light beams converging is a fundamental concept in optics and is used in a wide range of applications, such as in telescopes, microscopes, and cameras. It allows for the manipulation and focusing of light, enabling us to see distant objects and magnify small ones.
The convergence of parallel light beams is affected by the curvature and material of the lens or optical device, as well as the wavelength and intensity of the light beams. The distance between the light source and the lens also plays a role in the convergence.
No, parallel light beams cannot converge without a lens or other optical device. The curvature and material of the lens are necessary for the bending and focusing of the light rays. Without a lens, the light beams would continue to travel in a straight line, without converging.