The Illusion in Einstein’s Relativity of Simultaneity According to Albert Einstein’s railroad track thought experiment for the stationary observer standing at midway between two lightning strikes the two flashes occur simultaneously, but for the moving observer do not occur simultaneously. I show that the relativity of simultaneity is based on an illusion due to the moving observer’s inaccurate observation. Kazmer Ujvarosy This pandemic year I had time to organize boxes full with my notes and unpublished papers and came across a paper I wrote in 1979 on the subject of Albert Einstein’s relativity of simultaneity. That year, reading the February 19, 1979 issue of Time magazine, I learned that 1979 marked the centennial of Einstein’s birth on March 14, 1879. The article in Time also made known that Einstein “was a Merlin, conjuring up astonishing new notions of space and time, changing forever man’s perception of his universe—and of himself.” Being intrigued, I decided to make myself more familiar with relativity in order not to fall behind the times. So I started to study several books on the subject. One of these books, entitled Relativity (Crown Publishers, New York, MCMLXI), was written by Albert Einstein himself. Here, attempting to demolish Isaac Newton’s basic assumption that time is absolute, that time is universally the same, Einstein is asking us to imagine a long straight railroad track. Two bolts of lightning strike the track at two points and at the same time. A stationary observer, standing on the embankment at point M, midway between the two points, sees the two flashes at the same instant and thus concludes that they occurred simultaneously. Just as the bolts hit, a second observer on a train passes directly in front of him at high speed. According to Einstein to the second observer the bolts do not seem to strike simultaneously, because he is moving toward one flash and away from the other, therefore the light from one flash will reach him sooner than the light from the other flash. Thus, what the stationary observer sees as simultaneous lightning strikes, the moving observer sees as not simultaneous. Now, the question is: Which of these views is wrong? Neither, according to Einstein. The two bolts strike both simultaneously and at different times. Einstein reasons that measurements of time depend on the choice of the reference frame—in this case, the train or the midpoint along the embankment. We thus arrive at the important result, Einstein wrote: “Events which are simultaneous with reference to the embankment are not simultaneous with respect to the train, and vice versa (relativity of simultaneity).” In spite of Einstein’s reasoning it seems absolutely logical that if there will be a difference between the two observations at all—both taken precisely at point M, midway between the two simultaneous flashes—, it will be due to the slowness of the moving observer’s sensory perception, as compared to his velocity.