The sun is the core of the solar system, about 150 million kilometers away from the earth, it is a massive star. It is with the existence of the sun that the solar system was born, life on earth and human beings were born. Therefore, to some extent, the sun is also the mother of life on earth, and the mother of human beings.
The sun is a big fireball that constantly glows and heats. Only when these light and heat are transferred to the earth, there is a beautiful ecosystem and the birth and evolution of life. So why does the sun glow and heat, and what is its burning pattern? Before humans knew about nuclear fusion, many people thought that the burning of the sun was similar to the chemical burning on the earth.
However, there is no oxygen in the universe, it is a vacuum environment, and chemical fuels cannot keep the sun burning for 5 billion years without extinguishing it. So this answer was denied by scientists. Until Einstein put forward the mass-energy equation, we gradually realized the two application modes of nuclear energy and the more advanced combustion mode of nuclear fusion.
The raw materials required for nuclear fusion are very simple, that is, the ubiquitous hydrogen element in the universe, and the sun is a celestial body formed by the aggregation of hydrogen elements. The super pressure and internal temperature ignited the nuclear fusion at the center, turning the sun into a huge nuclear fusion reactor.
The light and heat that the sun emits all the time is the radiant energy released after the nuclear fusion reaction at the center of the sun’s interior, which is released to the surface. Therefore, as long as the nuclear fusion at the center of the sun continues, the sun can continue to burn, so can the sun continue to burn? the answer is negative.
Any combustion requires raw materials, as does nuclear fusion, although its raw material is hydrogen, and the hydrogen element contained in the sun is also very large. However, the sun is a mass celestial body, and the hydrogen element it contains is also limited. When all these hydrogen elements are consumed, the nuclear fusion at the center will also stop.
Without the transport of nuclear fusion energy at the center, the sun would not go out. So here is a question: How long will it take for humans to know after the sun’s nuclear fusion stops? Is it 8 minutes? Some friends may think that the distance from the earth to the sun is 150 million kilometers, and the speed of photons is 300,000 kilometers per second. According to calculations, it takes 8 minutes for the light of the sun to reach the earth.
Therefore, many friends believe that when the sun’s nuclear fusion stops, the earth will fall into darkness in 8 minutes, and then we will know that the sun has gone out. Is this really true? If you think so, you are quite wrong. The sun’s nuclear fusion and combustion and the transmission of radiant energy are far less simple than we thought.
That’s right, the nuclear fusion at the center of the sun will stop as soon as the hydrogen element is consumed. New photons will no longer be produced at this center, and energy transmission to the surface of the sun will be cut off from then on. But have we thought about the time it takes for the photons from nuclear fusion to reach the surface of the sun? Some people might say that the speed of photons is the speed of light. Isn’t it a momentary thing to reach the surface of the sun?
If you think so simply, you are wrong. The speed of light is indeed 300,000 kilometers per second, while the radius of the sun is 700,000 kilometers. If the light quantum walks in a straight line, it only takes 2 seconds to reach the surface from the center. This is true in theory, but in fact it is not. When the light quanta advances from the inside to the outside, it will collide with countless atoms and electrons inside the sun.
The free path of light quanta in the sun is about 1 cm, and the radius of the sun is 7 billion 200 million centimeters. In this way, light quanta have to turn about 5×10 million bends like a drunkard to reach the surface. Therefore, starting from the central nuclear fusion, the light quanta cannot go straight all the way, but have to go around many bends, and it takes a long time to reach the surface. It takes as little as 5,000 years, and as many as tens of thousands of years.
It takes at least the time that the entire human civilization has now experienced for a photon to reach the surface from the center of the sun. When it comes to the earth from the surface of the sun, there are no particles blocking it. It can reach the surface in a straight line at the speed of light, which only takes 8 minutes.
The complete extinguishment of the sun is difficult to achieve in a short time. The process of “death” of the sun is very complicated and needs to go through several long stages. Based on the mass of the sun, its life span is about 10 billion years. Today’s sun has been burning for 4.57 billion years. After another 5 billion years, the sun’s hydrogen elements will be consumed and hydrogen nuclear fusion will stop.
At this time, the sun began to evolve toward “death”. As the hydrogen is consumed and hydrogen fusion stops, the pressure can no longer constrain the sun’s outer shell. At this time, the inner core shrinks, and the outer shell will continue to expand, and the sun moves towards a red giant star. The transformation becomes bigger and bigger.
A red giant star is an unstable state in which a star has reached its end. Its diameter will continue to grow, swallowing the surrounding orbit. When the sun expands into a red giant, the orbit will extend to the position of the earth, Mercury, Venus, and then the earth will be swallowed. This process will last about 100,000 years. During the expansion of the sun, mass will continue to be lost, the surface temperature will become lower and lower, and it will eventually become a “white dwarf star.”
So does the white dwarf star no longer shine? Of course not. Although the sun has evolved into a white dwarf star after experiencing the red giant stage, it is still glowing and heating, but its brightness and temperature will drop significantly. A white dwarf is actually the core of the sun after collapsing, a very dense celestial body. The white dwarf is not the final outcome. As time goes by, it will evolve towards the final destination, the black dwarf. This is the final outcome of the sun. At that time, the sun is completely extinct.
However, the evolution process from the sun to a black dwarf is too long. At present, scientists have not discovered a black dwarf in the universe. There are two reasons for this. One reason is that the time it takes for a star to evolve into a black dwarf may be longer than the age of the universe. At present, there is no star in the universe to evolve into a black dwarf.
Another reason is that we can’t observe it. We must know that black dwarfs don’t emit any radiation or energy. With the current human observation technology, if there is no energy radiation, the telescope is a blind man and can’t see anything. Therefore, even if there are black dwarfs in the current universe, it is difficult to find with the existing observation technology of mankind, unless we have more powerful observation technology.
It can be seen that the time required for the sun to go out completely is much longer than we thought, at least tens of billions of years or more. Whether mankind can continue to that time is still an unknown. For mankind, even if the nuclear fusion inside the sun stops extinguishing completely, it is difficult for us to truly discover it. Only when the sun begins to expand and transform into a red giant star, We only know that nuclear fusion has ceased inside the sun.
So can human beings wait on the earth until the day when the sun turns into a red giant star? I am afraid it is very difficult. It is necessary to know that before the sun evolves into a red giant, the temperature of the sun’s surface will become higher and higher, and the temperature of the sun will become higher and higher, and the earth will become a fireball. The ambient temperature on the surface is the same as that of Venus. Become a world of purgatory.
If human beings want to survive, they can only leave the earth to live on other planets, such as Mars. And this time may be hundreds of millions of years later, far from waiting for the day when the sun becomes a red giant star. Of course, if human beings were strong enough in science and technology at that time, we still hope to build a closed ecological environment, continue to survive on the earth, and observe the evolution of the sun at close range.