What exactly does the sun use for fuel, and why didn't it burn out after 4.6 billion years?

Life on Earth needs energy to survive, and because there are thick layers of rock inside the earth, energy from the center of the earth cannot be transmitted on the surface of the earth. Living things on Earth depend mainly on energy from solar radiation. For example, in a plant food chain, plants fix solar energy through photosynthesis, then conduct it step by step through the food chain to top predators.

It turns out that the sun is a very stable energy source, constantly radiating stable energy, which allows creatures on earth to survive. So the question is, how does the sun maintain stable and continuous energy production?

It is said that 13.8 billion years ago, the universe was born during a big bang. After the Big Bang, tell particleses that protons, neutrons and electrons were gradually formed. 380,000 years after the Big Bang, the atomic structure was formed. Currently, the vast majority of elements in the universe are hydrogen, at 75%. The remaining elements are almost all helium and the proportion of other elements is extremely small, less than 1%.

Even today, the proportion of hydrogen and helium elements still represents 99%. Therefore, almost all stars in the universe are composed of hydrogen and helium. However, stars are actually a little different from other celestial bodies in that they are very massive. For example, the Sun is the only star in the solar system and its mass represents 99.86% of the total mass of the entire solar system.

Because the mass of the sun is enormous, the gravitational pull of the sun will be very strong. The sun's gravity would compress and if there were nono force to counteract it, the sun would be crushed into a point. This is actually not the case, because during the compression process the temperature of the solar core will continue to increase. However, this temperature does not actually reach the temperature of the nuclear fusion reaction. So why can the Sun's core still carry out nuclear fusion reactions?

In the microscopic world, there is a phenomenon called quantum tunneling. This means that reactions that initially require enough energy to carry out will also occur with some probability in the microscopic world, but this probability is very low. Therefore, this reaction did not occur on the earth, but you should know that the mass of the sun is 330,000 times that of the earth, and the number of particles is much greater than that of the earth. Therefore, faced with such an enormous base, this reaction is littlet take place.

However, due to the existence of quantum tunneling, the Sun's nuclear fusion reaction will not proceed as quickly as a hydrogen bomb, and it will not explode a single blow, but will react slowly, slowly. emit energy.

How does the nuclear fusion reaction take place in the heart of the Sun?

Since the temperature of the sun's core can reach 15 million degrees, the electrons in the atoms can obtain enough energy at this time to break free from the chains of the atomic system. nucleus and become free electrons. The matter in the sun The state is in the plasma state.

There are a large number of hydrogen nuclei, helium nuclei, electrons, photons and other particles. When two hydrogen nuclei meet, the atomsThe nuclei are all positively charged. According to the principle of repulsion of similar chargesareas, the hydrogen nuclei must stay away from each other due to electrostatic repulsion. However, under the action of the weak force, there is a certain probability that one of the hydrogen nuclei (protons) will react to generate a neutron, and then the two will combine to form a deuteron. That is to say, there is a proton and a neutron. in the nucleus, it is the first step of the reaction and the most difficult to carry out. The whole reaction is divided into 3 steps and the end result is actually the reaction of 4 hydrogen nuclei (protons) to produce helium-4 nuclei.

During the reaction, there will be a loss of mass before and after the reaction, and this loss of mass will be released as energy. We can calculate the amount of energy using Einstein's mass-energy equation E=mc^2, where c is the speed of light 3*10^8 m/s, E is the energy released and m is the mass lost.

Thanks to the mass-en equationergie, we can know that even if the mass lost is small, multiplying it by the square of the speed of light is still a huge number. Therefore, the sun can produce energy stably. Nuclear fusion can generate external pressure, which can form a dynamic equilibrium with the sun's own gravity. Gravity prevents the nuclear fusion reaction from being particularly violent. In turn, the external pressure generated by nuclear fusion prevents gravity from pressing the sun into one point.

In fact, human use of solar energy is very inefficient. The energy from solar radiation received by the Earth each second is only one 2.2 billionth of the total energy radiated by the sun each second. One ten thousandth of this part of the energy received by the Earth is used by man. In other words, the solar energy used by humans is only one 22 trillionth of the energye total solar radiation.