The speed of light, a limit that cannot be crossed
According to Albert Einstein’s theory of relativity (1879-1955), the speed of light is an impassable limit that cannot be exceeded.
Theoretically, nothing can travel faster than light in a vacuum. Its value has been calculated at exactly 299,792,458 meters per second often rounded to 300,000,000 meters per second, or also 300,000 kilometers per second.
On a human scale, light seems to move instantaneously. However, on the scale of the planets and the universe, light has a finite speed of 300,000 kilometers per second. The best example of this finitude of light comes from the Sun itself: the electromagnetic radiation produced by the Sun and which corresponds to its light takes 8 minutes to reach Earth. If the Sun were to go out, we wouldn’t realize it until 8 minutes later.
It is a constant in physics that influences our knowledge of the Universe. It is valid for all objects that produce light. This means that the speed of light produced by the sun is the same as that emitted by your desk lamp bulb. To talk about the speed of light, we could also talk about the speed of propagation of energy, whatever its form.
No object on Earth or deep in space can move faster than 300,000 kilometers per second. And even to get as close as possible to this speed limit, an object, whatever it is, should receive an infinitely large amount of energy if we refer to general relativity.
(Also read: A new duality highlights flaws in the standard model)
The speed of light exceeded in plasma
If we take into account Einstein’s theory, the speed of light is an impassable limit and a constant. Its speed of propagation is invariable, regardless of its frequency. However, in recent years, researchers have succeeded in accelerating light and slowing it down to immobilization by using materials such as atomic gases, that is to say composed of isolated atoms of the same chemical element. , the temperature of which is very low.
In this new study, American physicists succeeded in accelerating light to make it exceed the fateful limit of 300,000 kilometers per second. In reality, they achieved these results by creating waves of photon waves within a plasma itself. A plasma is like the solid, liquid or gaseous state, a state of matter made up of partially or totally ionized matter. It is therefore a state made up of neutral particles, positive ions and electrons. From an electrical point of view, plasma is neutral.
A photon travels in a vacuum at the normally impassable speed of 300,000 kilometers per second. When it moves within an electric and magnetic field, the speed of the photon is limited. Physicists at the University of Rochester and Lawrence Livermore National Laboratory in California noticed that by creating pulses of photons in narrow frequencies within a plasma heated to very high temperatures, they could create “waves of waves” on which electrons could surf and be accelerated to reach a speed 30% higher than that of light.
(Also read: For the first time, physicists observe vortices of electrons!)
Traveling faster than light: possible or not?
Let’s put things straight: it’s not tomorrow that we will create spaceships using this technology to allow humans to travel faster than light. This will certainly remain in the realm of science fiction for a long time to come.
If that doesn’t make it possible to travel faster than light, this breakthrough in physics could make it possible to develop more powerful lasers than those we use today. Lasers as we know them work thanks to semiconductor materials which have the annoying tendency to deteriorate, the more the energy increases. By using a plasma flow, it would be possible to avoid this problem of deterioration.
These more powerful lasers could enable many advances in areas such as particle acceleration and nuclear fusion technology.
(Also read: This atom laser can generate “eternal” matter waves)
- Goyon, M. R. Edwards, T. Chapman, L. Divol, N. Lemos, G. J. Williams, D. A. Mariscal, D. Turnbull, A. M. Hansen, and P. Michel, “Slow and Fast Light in Plasma Using Optical Wave Mixing”, Physical Review Letters126, 205001, Published 19 May 2021, https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.126.205001