Scientists have long been speculated that light has momentum, which is a combination of quality and speed measurements. But photons or particles of light are said to be of no mass, and how their momentum exerts a force on the matter is still largely an unsolved mystery. A new technology can finally solve this 150-year-old problem, using acoustic sensors to “listen” to the elastic waves of laser pulses passing through the mirror.
The German astronomer Johannes Kepler suggested in 1619 that the pressure from the sun’s rays may be the reason for pointing away the position of the comet’s tail from the sun. More than 200 years later, James Clerk Maxwell predicted that the radiation pressure is the result of the momentum of the light electromagnetic field. But since then, scientists have been trying to explain how this happens.
Kenneth Chau, a professor of engineering at the University of British Columbia in Okanagan, said: “So far, we have not yet determined how this momentum can be turned into power or exercise. Because the momentum of light carrying is very small. We don’t have enough sensitive equipment to solve this problem.”
To clarify the truth, researchers in Slovenia and Brazil have devised a new device that can be used to measure weak interactions between photons. The team built a mirror with sonic sensors and heat shields to reduce interference and background noise. They then fire laser pulses on the mirror surface and use sound sensors to detect the elastic waves they produce as they move.
The experimental results show that this elastic wave effect is very similar to observing the ripple phenomenon in the pond. Kenneth said: “We can’t directly measure the amount of light, so our method is to ‘listen’ through the mirror’s elastic wave to detect its effect on the mirror.” Kenneth said, we can track the characteristics of these elastic waves, and it is traced back to the momentum present in the light pulse itself, which opens a door to the final definition and the amount of light momentum present inside the modeled material.
Can light be used to drive a starship? Scientists have been working hard to develop new spacecraft that use the power of light to reduce the time it takes to travel to distant planets.
For example, in 2016, a research team at the University of California, Santa Barbara elaborated on the spaceship program through the “Deep-In”. The program uses so-called photon propulsion technology, a technology that uses lasers to generate light to drive spacecraft.
All spacecraft are propelled by igniting fuel and propelling spacecraft in the opposite direction to achieve space travel. Traditionally, this propellant is a fuel that must be carried on a spacecraft to make the ship heavier and slower. Photon propulsion uses a set of lasers, which means that no fuel is required on the spacecraft. This allows it to accelerate flight for longer periods of time and achieve higher speeds.
Experts say the technology is fully scalable, enabling manned flights on small and large spacecraft. This discovery may ultimately be an important step towards understanding the momentum of light. At the same time, understanding radiation pressure can have many applications. Kenneth said: “Imagine a spaceship driven by a solar sail to achieve space travel on a distant planet. Perhaps an optical tweezer can be designed on the earth to assemble a micromachine. How to effectively use the momentum is very important, it will help Let us achieve more efficient space travel.