Not long ago, Vanderbilt University physicists planned to use the world’s largest atom smasher, the Large Hadron Collider, to cause matter to travel backwards in time and things were looking up for time travel. Now, Hong Kong University of Science and Technology physicists say they have proved that nothing can travel faster than the speed of light which pretty much puts an end to the dream of time travel as well as faster-than-light warp drive.
“Einstein claimed that the speed of light was the traffic law of the universe or in simple language, nothing can travel faster than light,” the university said on its website.
The possibility of time travel was raised 10 years ago when scientists discovered superluminal – or faster-than-light – propagation of optical pulses in some specific medium reports HeraldSun.com.au. It was later found to be a visual effect, but researchers thought it might still be possible for a single photon to exceed light speed.
“The study, which showed that single photons also obey the speed limit confirms Einstein’s causality – that is, an effect cannot occur before its cause,” the university said.
The team found that, as the fastest part of a single photon, the precursor wave front always travels at the speed of light in vacuum. The main wave packet of the single photon travels no faster than the speed of light in vacuum in any dispersive medium, and can be delayed up to 500 nanoseconds in a slow light medium. Even in a superluminal medium where the group velocity (of an optical pulse peak) is faster than the speed of light in vacuum, the main part of the single photon has no possibility to travel faster than its precursor.
Warp drive, proposed a faster-than-light propulsion system where a spacecraft so-equipped might have traveled at velocities greater than that of light.
In other words, time travel and warp drive are out but Photon Torpedo’s are still possible.
Flickr photo by vladeb