Most of us are familiar 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 break this speed limit, there are characteristics of light that do not follow the same rules.
Manipulating them won’t accelerate our ability to travel to the stars, but they could help clear the way for a new class of laser technology.
Physicists in the US have shown that, under certain conditions, waves composed of clusters of photons can travel faster than light.
Researchers have been playing harder and faster with the speed limit of light pulses for a while, accelerating them and even turning them into virtual stands using a variety of materials such as cold atomic gases, refractory crystals and optical fibers. -Stills are slowing down.
But impressively, last year, researchers at Lawrence Livermore National Laboratory in California and the University of Rochester in New York managed to do this inside a hot swarm of charged particles, fine-tuning the speed of light waves within plasma to anywhere from about a tenth of that of light. did. More than 30 percent of normal vacuum speed faster,
It’s more – and less – impressive than it sounds.
To break the hearts of those who hope it will take us back in time for Proxima Centauri and tea, this superluminal journey is well within the laws of physics. Pardon me.
The motion of a photon is locked in place by the weaving of electric and magnetic fields, referred to as electromagnetism. There’s no getting around that, but even pulses of photons within narrow frequencies collide in ways to create regular waves.
The rhythmic rise and fall of entire groups of light waves move through the stuff at a rate described as group velocity, and it is this ‘wave of waves’ that can be tweaked to slow down or accelerate depending on the electromagnetic conditions around it. can be done.
By separating electrons from a stream of hydrogen and helium ions with a laser, the researchers were able to change the group velocity of light pulses sent through them by a second light source, streamlining them by applying braking or adjusting the ratio of the gas. were able to do. Forcing the pulse characteristics to change shape.
The overall effect was due to the refraction from the regions of the plasma and the polarized light from the primary laser used to take them down. Individual light waves still jiggle at their normal speed, even though their collective dance appears to intensify.
In theoretical terms, the experiment helps to overcome the physics of plasmas and puts new constraints on the accuracy of current models.
In practice, this is good news for advanced technologies that are waiting for clues on how to prevent obstacles from turning into reality.
Lasers will be the big winners here, especially the overpowering variety. Old-school lasers rely on solid-state optical materials, which get damaged when the energy is cranked up. Using currents of plasma to amplify or change the light characteristics will get around this issue, but to make the most of it we really need to model their electromagnetic characteristics.
It is no coincidence that Lawrence Livermore National Laboratory is eager to understand the optical nature of plasma, which is home to some of the world’s most influential laser technology.
More powerful lasers are what we need for a whole bunch of applications, from boosting particle accelerators to improving clean fusion technology.
It may not help us move faster in space, but it is the discoveries that will lead us to the kind of future we all dream of.
This research was published in Physical Review Letter,
A version of this article was first published in May 2021.
