Does the sun have a life span? How long can life on earth last?

It is only a matter of time before the universe and the products of nature have life. The sun is formed by the fusion of radioactive material-based particles of various planets, and planets are just like the sun. After losing the radioactive source of the surrounding planet, it is cooled and solidified and transformed into liquid crystal, and the liquid crystal loses its high temperature reflection. The space pressure wraps the liquid crystal, and the airflow is encrypted and converted into water vapor, which falls into the body surface and gathers into water. Water enters the high-temperature inner layer along the cracks of its own solid, and the hot and cold collision erupts and the volcano erupts. With the existence of mountains, plains and valleys, after a long time, more water vapor and water flowing from outside air fell into them, resulting in marine rivers, which evolved to adapt to the living conditions and had natural products. Space products, such as stars, planets and satellites, in fact, satellites have not played a role in defending other stars. It should be said that they are declining stars, comets and meteors scattered by comets. This is how the products of the universe spend their lives, and human beings in nature are very clear.

Of course, the sun can't exist forever, but the life of the sun is much longer than that of the earth. The sun collapsed from a nebula of hydrogen and helium. Due to the high temperature and high pressure in its core area, hydrogen nuclei condense into helium nuclei here, and the light and heat we receive on the earth come from this process. The sun has been in such a main sequence stage for most of its life and maintained a relatively stable state. According to the mass estimation of the sun, its life span is as long as 65.438+0 billion years, that is to say, the hydrogen fuel in the core of the sun can be continuously fused for 65.438+0 billion years. At present, the age of the sun is 4.6 billion years, so the life of the sun is just over half.

After more than 5 billion years, hydrogen fuel will be exhausted, helium nuclear fusion will start, and the sun will expand violently into a red giant. At that time, the earth may be directly swallowed up by the expanding sun. Or the sun may expand between Venus and the earth's orbit, causing the earth to be scorched. In a word, life can't survive on that kind of earth.

However, life on earth is likely to last less than that time, and may be extinct before that. This is because as time goes on, more and more helium gathers in the core of the sun, which leads to faster and faster nuclear fusion reaction, so the temperature of the sun will gradually increase. It is estimated that the brightness of the sun will increase by 1.1%every1billion years, which means that in less than 2 billion years, the increasingly hot sun will make the earth's temperature too high, leading to the evaporation of liquid water on the surface and the destruction of life on the earth.

Therefore, in the future, mankind needs to find ways to avoid such an outcome. One way is to reduce the heat radiated to the earth by shading, so as to keep the temperature of the earth normal. Another way is to push the earth away from the sun, which can also make the earth receive less heat. Another way is to leave the earth and find or transform another livable planet.

Youth of the sun: the burning of hydrogen

So what will happen when the sun finally comes to the end of life? To answer this question, we must first understand how Sun Chu shines. Stars are formed in huge nebulae, most of which are composed of hydrogen, helium and a few other elements. Gases have mass, so if you put enough gases together, they will collapse under their own gravity.

This contraction process will generate a lot of heat (called "Kelvin-Helmholtz contraction" in astronomy), which will cause the core gas to heat up until these gases are ionized (that is, the electrons in its nucleus leave the nucleus and become free electrons, which will cause the atoms to be charged). When a critical condition is reached, the nuclear fusion process between hydrogen atoms begins, and hydrogen atoms (each containing one proton) fuse into helium atoms (including two protons and two neutrons).

This process will release a lot of energy in the form of light and heat, which will produce expansion force from the inside out, thus preventing others from further collapse. When these two forces reach equilibrium, a star is born.

There is enough hydrogen fuel in a star to keep it shining for billions of years. But these fuels will run out one day. By that time, almost all the hydrogen fuel in the star has been converted into helium by nuclear fusion. At this time, our sun has been unable to generate enough energy and strong outward pressure to resist the influence of its own gravity, so it will continue to collapse inward under the action of its own gravity.

The aging of the sun: the burning of helium and the destruction of the earth

However, as more and more hydrogen substances fall into the core after nuclear fusion, the helium core in the center of the sun is getting bigger and bigger, and it begins to collapse under its own gravity. This situation will also release energy, of course, not through nuclear fusion, but through simple compression and heat generation. This process produces extra light and heat, which makes the sun particularly bright during this period. But this force also causes the sun to expand, which will turn into a red giant. The light of the red giant shows a red hue, because compared with the current sun, the temperature of the outermost layer of the red giant sun will decrease correspondingly because of its greatly increased volume, so the color will appear redder.

A study in 2008 showed that when the sun enters the red giant stage, its radius will become extremely huge, and the outermost layer will reach almost 65.438+0.7 billion kilometers away, thus engulfing all mercury, Venus and the earth. It takes about 5 million years for the sun to complete the transformation into a red giant, which is almost an instant compared with the life of a star.

In addition, the brightness of the sun increases by about 10% every10 billion years. Therefore, the so-called "livable zone" around the sun will gradually change. The so-called livable zone refers to the area with moderate distance around the star, so its surface temperature is moderate, allowing water to exist on the surface of the planet in liquid form. At present, the livable zone of the solar system is roughly between 0.95~ 1.37 astronomical units (AU) from the sun.

With the increase of solar luminosity, this area will gradually move outward. When the sun finally turned into a red giant, Mars had been classified as a livable zone before that. At the same time, when the earth is too close to the sun, it will gradually dry up under the action of more and more sunlight and heat, the oceans will all evaporate, and the water molecules will be decomposed into oxygen and hydrogen under the action of ultraviolet rays and all of them will escape into space-long before the sun really devours the earth, the earth has become a barren land.

Our destiny

In the process of the gradual disappearance of oxygen and hydrogen on the earth, nitrogen and carbon dioxide in the atmosphere will gradually become the main components of the earth's atmosphere, just like Venus's atmosphere today, although we can't say whether the concentration of carbon dioxide in the earth's atmosphere at that time will be as amazing as Venus's today. The answer to this question will depend in part on how many volcanoes will continue to erupt on the earth at that time and whether the plate movement on the earth will still be active at that time.

We hope that by that time, our descendants will be strong enough and wise enough to emigrate to Mars and even other more distant planets in the solar system before such a fate comes, so as to avoid this catastrophe.

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