Physicists Broke The Speed of Light With Pulses Inside Hot Plasma


 Most of us grow up well known with the prevailing law that limits how quickly information can travel through empty space: the speed of light, which tops out at 300,000 kilometers (186,000 miles) per second. 

While photons themselves are unlikely to ever break this speed limit, there are characteristics of light which don't play by the same rules. 

Manipulating them won't hasten our ability to travel to the stars, but they could help us direct the way to a whole new class of laser technology. 

Physicists in the US have shown that, under certain conditions, waves formed up by groups of photons can move faster than light. 

Researchers have been interpreting hard and fast with the speed limit of light pulses for a while, speeding them up and even slowing them to a virtual stand-still using several materials like cold atomic gases, refractive crystals, and optical fibers. 

But impressively, previous year, researchers from Lawrence Livermore National Laboratory in California and the University of Rochester in New York directed it inside hot swarms of charged particles, altering the speed of light waves within plasma to anywhere from around one-tenth of light's normal vacuum speed to more than 30 percent faster. 

A photon's speed is locked in place by the entwine of electrical and magnetic fields referred to as electromagnetism. There's no getting around that, but pulses of photons within narrow frequencies also jostle in ways that forms regular waves. 

The rhythmical rise and fall of whole groups of light waves moves through stuff at a rate described as group velocity, and it's this 'wave of waves' that can be twisted to slow down or speed up, depending on the electromagnetic conditions of its surrounds. 

By stripping electrons away from a stream of hydrogen and helium ions with a laser, the researchers were able to change the group velocity of light pulses send through them by a second light source, putting the brakes on or streamlining them by altering the gas's ratio and forcing the pulse's features to change shape. 

Lasers would be the great winners here, especially the insanely powerful variety. Old-school lasers rely upon solid-state optical materials, which tend to get damaged as the energy cranks up. Using streams of plasma to increase or change light characteristics would get around this problem, but to make the most of it we really need to model their electromagnetic characteristics. 

Ever more well-built lasers are just what we need for a whole bunch of applications, from ramping up particle accelerators to improving clean fusion technology. 

It might not help us move through space any faster, but it's these very discoveries that will make hasten us towards the kind of future we all dreaming of.


This research was originally published in Physical Review Letters. 

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