Can Cherenkov radiation make particles move faster than the speed of light?

"Light bursts", also known as Cherenkov radiation , are a type of electromagnetic radiation with a predominant short wavelength, manifesting itself primarily as blue light.

Since Einstein's theory of relativity was born, the speed of light has become a very important constant in the physical world, which is c=299792458m/s. In other words, the speed of light is about 300,000 km per second.

Einstein believed that no object in this world, including microscopic and macroscopic objects, can reach the speed of light, let alone exceed the speed of light. Therefore, the speed of light has become an important parameter in many physical formulas and many famous laws have been derived from it, such as the mass-energy equation E=MC^2, in which E represents energy, M represents mass and C represents the speed of light.

In other words, energy and mass can be converted into each other , the mass of an object multiplied by the square of the speed of light is the energy contained in that object.

Einstein believed that no object in this world can reach the speed of light. (Illustration: Zhihu).

Einstein also obtained the mass-increasing effect of speed and the time-dilation effect of speed from the limit of the speed of light , that is, the faster the speed of motion, the more obvious the mass-increasing effect, the faster the speed will make time pass more slowly, when reaching the speed of light, the momentum will become infinite and time will stand still.

This locks the speed of motion of our world and the motion of any object cannot reach the speed of light, let alone exceed the speed of light.

All of this illustrates a problem. In our world, the speed of light is the limit. No motion of an object can exceed it. Otherwise, momentum would be infinite and the universe would collapse; time would stand still, everything would stand still.

This is called the speed of light barrier . However, why do many researchers still believe that the phenomenon of "light explosions" can cause particles to reach speeds faster than normal light?

In our world, no object's movement can exceed the speed of light. (Illustration: Zhihu).

We know that a sonic boom is a shock wave produced when an object moves at a speed exceeding the speed of sound. It is a shock wave front formed by the 'accumulation' of sound waves produced by an ultrasonic object. Accordingly, a light burst is understood as a vibration wave produced when an object moves faster than the speed of light.

But theoretically, the so-called substance that exceeds the speed of light in the medium can only be extremely small particles, for example neutrinos have only extremely small mass, almost no electromagnetic force. In this way, in mediums such as water, ice, glass, etc., its speed can exceed the speed of light.

Because neutrinos are uncharged, they do not interact with matter, so trillions of neutrinos can pass through any object, but they leave almost no trace. But among them, one or two special particles of these neutrinos will collide with the atomic nucleus of the matter, the collision at extremely high speed will break the atomic nucleus and create so-called subatomic "shrapnel" , the collision point at the initial speed will be slightly lower than the speed of light, but over time, the speed of these "shrapnel" can exceed the speed of light, leading to the phenomenon of "light explosion".

Cherenkov radiation is similar to the sonic boom phenomenon caused by supersonic flight. (Illustration: Zhihu)

To capture these neutrinos, scientists built the IceCube Neutrino Observatory in Antarctica. This observatory does not use a large-diameter telescope to observe space like a conventional observatory, but is set up at a depth of 1.6 km in the ice with more than 5,000 sensors to record neutrino rays that occur after they collide with atomic nuclei, thereby determining where these neutrinos come from.

"Light burst", also known as Cherenkov radiation, is a type of electromagnetic radiation with a predominantly short wavelength, manifesting itself primarily as a blue light ray. It was discovered by Vich Cherenkov in 1934, so it is named after him.

Cherenkov radiation is similar to the sonic boom phenomenon caused by supersonic flight , that is, when a charged particle moves at a speed exceeding the speed of light in a medium, it will create a cone-shaped electromagnetic wave in the medium, characterized by a blue light. 

Cherenkov radiation is a type of electromagnetic radiation with a predominant short wavelength. (Illustration: Zhihu).

In fact, not only can the subatomic fragments of neutrino collisions exceed the speed of light in the medium, but many particles can move faster than the speed of light in media such as water and ice, such as the radiation phenomenon of atomic nuclear reactions and acceleration through particle accelerators, particles, cosmic rays, etc.

So we have to strictly define the limit of the speed of light, the constant c=299792458m/s is just the speed of light in vacuum, and the speed of light in vacuum is called the maximum speed.

The so-called superluminal phenomenon of the light burst does not violate Einstein's theory of the speed of light, the speed of light in a vacuum is still the unbreakable speed of motion in the universe.