Shulou(Shulou.com)11/24 Report--

This article comes from the official account of Wechat: SF Chinese (ID:kexuejiaodian), author: SF

A new physics paper points out that in the early universe, gravity could produce light. This opens up a new way for the study of astrophysics and cosmology.

(by Chen Qiang / tr. by Robert Taylor)

A group of physicists said in a recently published paper that gravity can produce light. Wait a minute, according to Einstein's general theory of relativity, gravity is the embodiment of the bending of space-time. Light is a kind of electromagnetic wave, which can also be seen as made up of massless photons. So how can curved space-time produce photons from open space? For this to happen, we need another form of gravity-gravitational waves.

Ripples from time and space when a stone is thrown into a pond, ripples occur on the surface of the pond, spreading outward from where the stone enters the water. When a mass object moves in acceleration, it will also produce ripples in space-time and propagate outward from the position of the object, which is called gravitational wave.

The gravitational waves produced by most objects are very weak, and only those severe astronomical events, such as the merging of black holes and supernova explosions, can produce gravitational waves that are strong enough to be observed. Gravitational waves were first directly detected by the Laser Interferometry gravitational Wave Observatory (LIGO) in September 2015, although gravitational waves cause spatio-temporal changes of no more than 1/1000 of the diameter of a nucleus when they reach Earth.

Physicists say that for gravity to produce light, you need the strongest gravitational waves that can be produced in the universe. This gravitational wave is generated by the inflation of the early universe.

The universe is expanding rapidly. We know that our universe originated from a big bang. About 13.8 billion years ago, the universe expanded from a state of extremely high temperature and density, and dispersed the first batch of matter throughout space. As time went on, the universe became colder and thinner, and matter and energy began to gather to form celestial bodies such as stars and galaxies.

The current cosmological theory also holds that the universe experienced a process of rapid expansion in a very short time shortly after the Big Bang. This process is called "inflation". After the inflation is over, the universe will continue to expand, but at a much slower rate.

High-energy gravitational waves excite the electromagnetic field and then produce light theory studies show that the universe will produce many strong gravitational waves which can interfere with each other after the process of inflation.

Some gravitational waves can superimpose each other until their amplitudes become very large. Some of these gravitational waves may have formed the so-called standing wave pattern, in which the waves freeze in place. The place where the gravitational waves are frozen is where the gravitational energy is extremely high.

In these areas where gravity is strong, physicists have found that the energy of gravity is strong enough to excite any electromagnetic field it may come into contact with, prompting the electromagnetic field to produce light only from the energy of gravity.

The intensity of gravitational waves needed to excite electromagnetic fields to produce light is many times higher than the intensity of gravitational waves that we can detect today. Unless we somehow usher in the second Big Bang, the light produced by gravity may be a thing of the past forever.

In spite of this, the study will have a great impact. Some of the radiation produced by the early universe may have come from light produced by gravity, which may explain why there are small but regular fluctuations in the observed cosmic microwave background radiation. These lights will continue to affect the formation and evolution of matter in the universe, so we need to consider the effects of these lights in future cosmological studies.

In addition, the theory of electromagnetism also tells us that photons are the medium that transmits electromagnetic forces. In the theory of quantum gravity, the medium that transmits gravity is a massless elementary particle called the graviton. This study shows that gravitons can be converted into photons and reveals a novel and subtle relationship between gravity and electromagnetic forces. This may provide a new clue for us to find an "ultimate theory" that can simultaneously describe the four basic interaction forces in the universe (strong nuclear force, weak nuclear force, electromagnetic force and gravity).

References:

Https://arxiv.org/abs/2205.08767

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