Einstein's theory of special relativity, which includes the postulate that nothing can exceed the speed of light in a vacuum, has been extensively tested and verified through various experiments. While it is impossible to directly measure speeds exceeding the speed of light, scientists have conducted experiments that confirm the predictions of special relativity.
One of the most well-known experiments is the Michelson-Morley experiment, performed in 1887. This experiment aimed to detect the existence of an "ether" medium through which light waves were thought to propagate. The experiment measured the speed of light in different directions, expecting to find variations due to the motion of the Earth through the ether. However, the results showed no significant variation, providing evidence against the existence of the ether and supporting the constancy of the speed of light.
Another experiment that indirectly supports Einstein's theory is the observation of high-energy cosmic rays. Cosmic rays are particles, mostly protons, that travel through space at extremely high velocities. These particles can attain speeds close to the speed of light but do not exceed it. If particles could exceed the speed of light, they would lose energy through a process called Cherenkov radiation. However, the absence of such radiation from cosmic rays indicates that they do not exceed the speed of light.
Additionally, particle accelerators, such as the Large Hadron Collider (LHC), provide experimental evidence for the theory. Accelerators propel particles to speeds close to the speed of light and allow scientists to observe relativistic effects, such as time dilation and length contraction. These observed effects align with the predictions of special relativity.
In summary, while it is not possible to directly test speeds exceeding the speed of light, numerous experiments indirectly support Einstein's theory of special relativity, which includes the postulate that nothing can surpass the speed of light in a vacuum.