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The Fine Print: The following comments are owned by whoever posted them. We are not responsible for them in any way.
byAnonymous Coward writes:
If light has sufficient mass that its path can be bent by gravitational bodies then it must accelerate as it approaches those bodies and decelerate as it recedes. Ergo, the speed of light cannot be constant.
byMightyMartian ( 840721 ) writes:
This demonstrates a fundamental misunderstanding of what light and gravity. Photons in a vacuum follow the curvature of space, that curvature being gravity. Mass bends space, the more extreme the mass, the greater the curvature, which photons follow. But the photons themselves have no mass.
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byTomahawk ( 1343 ) writes:
Moreover, with space itself being curved, the photons aren't accelerating, they are following a straight path. There's no "slingshot" here, just a straight line (that curves as space curves -- think a line of longitude that is a straight line that curves around the surface of the earth).
The curving lengthens the line, though, delaying the photon from reaching us. The photos travel at c. If there are 2 or 3 visible paths between us and the source, we can use differences in timing of observing some event on the 3 paths to calculate their different lengths, and thus the extent of the space curvature, and thus the amount of mass present.
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byAnonymous Coward writes:
"So how exactly did we prove photons as massless"
Because if they had mass, they would not be able to travel at the speed of light (which is determined by the permittivity and permeability of free space, not by measuring the time of flight of photons).
byqeveren ( 318805 ) writes:
It can never be absolutely proven that the photon has zero rest mass, but physicists can by experiment place constraints on its mass. IIRC it must be less than 10^-17 eV. None of the follow-on consequences of a massive photon have ever been observed.
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byMightyMartian ( 840721 ) writes:
There's this guy who came up with E=MC^2. The photon's energy can be converted to massless particles under certain conditions, such as the production of electron-positron pairs.
byHiThere ( 15173 ) writes:
You're stating accepted theory as if it were fact. This is a category confusion. It will USUALLY give the correct answers, but this is a test of whether it's correct in (certain) unusual conditions.
byWaffleMonster ( 969671 ) writes:
This demonstrates a fundamental misunderstanding of what light and gravity. Photons in a vacuum follow the curvature of space, that curvature being gravity. Mass bends space, the more extreme the mass, the greater the curvature, which photons follow. But the photons themselves have no mass.
Energy bends space. Parallel laser beams emitted from opposing directions have a (absurdly small) gravitational attraction.
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