Albert Einstein suggested that light travels with the same speed of 299,792 kilometers per second in the whole Universe, at this speed a body can orbit Earth eight times per second. Mass and energy were considered as two different entities, but in 1905 Einstein changed the perception by putting forward the Theory of Special Relativity. The equation E=mc2 shows that mass and energy are linked together, a body having no mass can travel with the speed of light, photons do so as they have no mass. Only the powerful particle accelerators like Large Hadron Collider and Tevatron could take the subatomic particles close to light speed. But Physics Nobel prize holder David Gross describes that these particles will never attain cosmic speed limit (299,792 km/s). It would need an infinite amount of energy but that’s not possible. But some physicists think that there exist some entities that can attain speed more than the light but they also follow the cosmic principles as suggested in the special relativity.
The light equivalent to a sonic boom: Objects travelling faster than the speed of sound, establish a sonic boom making a shock wave or sound barrier around it. Similarly objects attaining speed more than light should create a luminal boom. This luminal boom is called as Cherenkov radiation named after a scientist Pavel Alekseyevich Cherenkov. Particles establishing luminal boom create light barriers or shock waves sometime of blue light and can also glow in ultraviolet, but aren’t exceeding the cosmic speed limit.
When the rules don’t apply: Photons are not the only massless entity in the Universe. Empty space has no material substance and hence has no mass. Astrophysicist Michio Kaku said “Since nothing is just empty space or vacuum, it can expand faster than the speed of light since no object is breaking the light barrier. Therefore, empty space can expand faster than light.” Physicists consider this as same with the inflation after Big Bang. Universe doubled in size and its outer edge expanded much faster than the speed of light.
Quantum entanglement makes the cut: Kaku explains if I have two electrons close together, according to quantum theory they can vibrate simultaneously. And take one to hundreds or thousands light years away, they will keep their prompt communication open. The other electron senses this vibration instantly. Einstein might have considered this and rejected the quantum theory. To prove it wrong, Einstein, Boris Podolsky and Nathan Rosen endeavored a thought experiment known as “Spooky action at a distance”.
But now experiments have proved that this “Spooky action at a distance” is actually true and breaks the speed of light.
Dreaming of wormholes: Kaku said “The only feasible way to break the light barriers is through general relativity and warping of space-time”. We call this warping as wormholes, theoretically, these allow something to break the cosmic speed limit by travelling huge distance in a short time.
These wormholes have some exotic matter, holding them open. This exotic matter has been made in laboratories but in a small quantity. In 1988, Kip Thorne proposed a theory of Stable Wormholes to find out the possibility of a wormhole in the presence of that exotic matter (like the one in Interstellar Movie).
Thorne says “After 30 years, the answer is still unknown and we are still away from the final answer.”
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