Impossible Measurement?
Discovery: How to measure the one-way speed of light
Most physicists remain unaware of the fundamental distinction between measuring the speed of light in one direction, and measuring the average round-trip speed of light.
Physicists who did distinguish between one-way and round-trip measurements include: Henri Poincaré, Albert Einstein, Edwin Taylor, and John Wheeler.
Round-trip speeds of light rays have been measured experimentally many times, with slightly varying results. But the one-way speed of any light ray has never been measured experimentally. It’s because of a procedural circularity.
For this reason, in special relativity Einstein posited the constancy of the one-way speed of light as a fundamental assumption, “a postulate,” — not an experimental finding.
Nevertheless, I formulated a way to synchronize clocks such that pairs of clocks will be deemed as synchronized both in Einstein’s relativity and in Newton’s mechanics. Since both theories agree on the setup, it becomes possible to use two pairs of such clocks to measure the one-way speed of light. It would constitute a test of Einstein’s postulate of the constancy of the speed of light.
“Seemingly Impossible Measurements”
Kinematics: The Lost Origins of Einstein’s Relativity (Baltimore: Johns Hopkins University Press, 2009), 368-375.
“Understanding Simultaneity”
Master's Thesis, New York University, 1995.
“A Myth about the Speed of Light”
in Science Secrets: The Truth about Darwin’s Finches, Einstein’s Wife, and Other Myths (Pittsburgh: University of Pittsburgh Press, 2011), 172-192.
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BIO
Alberto Martinez is originally from San Juan, Puerto Rico. As a professor at UT Austin, he investigates the history of science, especially Einstein and relativity theory, history of math, historical myths, and Giordano Bruno and Galileo. He is a Fellow of the American Physical Society.
He also researches myths in political news media, The Eyes of Texas, and episodes in the history of money and corruption.
Now, he's finishing writing a novel about Albert Einstein.