http://bartleby.net/173/7.html Albert Einstein (1920): "There is hardly a simpler law in physics than that according to which light is propagated in empty space. Every child at school knows, or believes he knows, that this propagation takes place in straight lines with a velocity c = 300,000 km./sec. At all events we know with great exactness that this velocity is the same for all colours, because if this were not the case, the minimum of emission would not be observed simultaneously for different colours during the eclipse of a fixed star by its dark neighbour. By means of similar considerations based on observations of double stars, the Dutch astronomer De Sitter was also able to show that the velocity of propagation of light cannot depend on the velocity of motion of the body emitting the light. The assumption that this velocity of propagation is dependent on the direction "in space" is in itself improbable. In short, let us assume that the simple law of the constancy of the velocity of light c (in vacuum) is justifiably believed by the child at school."
At first some children hesitated but then the evidence presented by de Sitter finally convinced them that Einstein was absolutely right.
Max Tegmark's conviction is based on even more evidence and reductio ad absurdum: The speed of light is independent of the speed of the source - de Sitter hammered it. It is also independent of the speed of the observer - Michelson and Morley hammered it. Finally, if the speed of light were not constant, you'd see things moving backward in time, and you don't see things moving backward in time do you:
http://ocw.mit.edu/courses/physics/8-033-relativity-fall-2006/readings/symmetry.pdf Max Tegmark: "Observed properties of speed of light. Does speed depend on motion of source? No! Does speed depend on motion of observer (frame)? No! Does c depend on source motion? Does speed of a bullet depend on speed of rifle? Does sound speed of a gun shot depend on speed of rifle? Binary stars provide great test. If velocities add, then... You'd see things moving backward in time. Answer: No dependence on source motion observed (and should be dramatic). Does c depend on observer motion (frame)? No 1st order effect had been seen. Michelson-Morley experiment hammered it. But they saw no fringe shift at all! So c appears not to depend on frame."
http://www.youtube.com/watch?v=5PkLLXhONvQ Max Tegmark: "We all believe in relativity, relativity, relativity. Yes we all believe in relativity, relativity, relativity. Everything is relative, even simultaneity, and soon Einstein's become a de facto physics deity. 'cos we all believe in relativity, relativity, relativity. We all believe in relativity, relativity, relativity. Yes we all believe in relativity, relativity, relativity."
http://www.krugozormagazine.com/main/content/9-2009_Enshtein-3.jpg "The Riverside Church in New York, west portal - upper line, second of right. In 1930, during a stay in New York, Albert Einstein and his wife visited the Riverside Church, too. During the detailed guided tour through the church Einstein was also shown the sculptures at the west portal. He was told that only one of the sculptures there represented a living person, and that was he himself. What Einstein is supposed to have thought in that moment when he heard that information and saw himself immortalized in stone? Contemporaries reported that he looked at the sculpture calmly and thoughtfully."