Andromeda immigrant strain

In 5 billion years, the sun will become a red giant. What will happen to the earth? How does human civilization continue?

I don't think humans will survive that time. If they do, human civilization will be able to leave the solar system and even the Milky Way.

Doomsday sun

Will the sun destroy the world in 5 billion years? That's right, that is to say, the sun ended its life cycle as the main sequence star (the stage when the star shines stably), expanded outward and entered the stage of red giant. In the red giant stage, the surface of the sun is likely to extend to the orbit of Venus, and the solar atmosphere is likely to drown the orbit of the earth. If it was still in its current orbit, it might slow down in the sun's atmosphere and eventually fall into the sun.

The end of life on earth

But in fact, humans on earth can't wait for that time at all, because before that time, the environment of the earth has evolved to be uninhabitable.

We know that due to gravity, the sun's super mass (330,000 times the mass of the earth), in the main sequence star stage, the sun burns hydrogen near the core through nuclear fusion, so that hydrogen condenses into helium, thus gaining energy to generate thermal expansion to resist the gravitational collapse of the core. But as it burns, there will be more and more helium near the sun's core. Because the helium density of four nuclei (two protons and two neutrons) is greater than that of hydrogen, the core density increases, which leads to the increase of core gravity, that is to say, it takes more energy to resist gravitational collapse near the core!

Therefore, with the burning of the sun and the increase of the core density, the burning of the sun is more and more fierce, which directly leads to the increase of the total radiation intensity generated by the sun. According to scientists' calculations, the brightness of the sun increased by about 30% in the main sequence star stage of 4.6 billion years, which means that the sun in ancient times and even in the dinosaur era was not as bright as it is now.

As time goes on, the brightness of the sun will increase, which means that the solar radiation will increase. In this way, the earth will receive more and more solar radiation, and with the increase of solar radiation, the temperature of the earth will also rise. According to theoretical calculation, the surface temperature of the earth will reach the boiling point of seawater in about 65.438+0.5 billion years, which obviously makes it difficult for life on earth to survive at this time. At this time, the end of life on earth is coming.

Of course, this theoretical calculation takes into account climate and other factors, such as the greenhouse effect, and is not simply based on the increase of luminosity. So, maybe by that time, the earth can still maintain a temperature at which life can continue, but there will be another disaster waiting for the earth.

The end of the galaxy has begun.

According to scientists' calculations, Andromeda galaxy is approaching the earth at high speed. On the scale of the universe, in fact, it can be said that the Milky Way is running towards the Andromeda galaxy, but we earthlings have a protagonist aura, and naturally think that fairies are coming for us (_). The first collision between the two galaxies occurred about 3.8 billion years later. At that time, the edges of the two galaxies will collide, and a large number of new stars will be produced in the gas clouds in the collision area, and a large number of edge stars will be thrown out of the galaxies and become lonely wandering stars. But at that time, the earth was not in the collision zone and escaped the first wave of collision.

But as the saying goes? Can't hide from the first day, but can't hide from the fifteenth? Due to the great gravity between the two galaxies, the two galaxies will eventually merge into an elliptical galaxy. In the process of merger, the movement of stars in galaxies is very chaotic. Although there is basically no star collision, chaotic star movements will lead to various gravitational disturbances, and a large number of celestial bodies outside the solar system (such as Oort clouds and Kuiper Belt objects) will break into the solar system. A large number of comets and meteorites will inevitably collide, and the disaster of dinosaur extinction will repeat itself again and again. At that time, if

When the sea dried up, all the fish that could not leave the sea died.

Finally, the red giant stage of the sun opens and the brightness of the sun increases by about 2000 times. The earth will become a purgatory for mankind, and no life can survive. At that time, only the civilization of interstellar travel could continue. According to the current development of human science and technology, we have reason to believe that the earth civilization at that time was free to shuttle through the galaxy. There is a story about extinction in "Three-body": When the sea dries up, all the fish left in the sea die, and only those fish that can survive from the sea survive.

After 5 billion years, all civilizations that cannot achieve interstellar navigation will face death, and civilizations that can survive without the earth and the sun will continue to exist. We don't know how advanced human civilization will be then. All we know is that by that time, they will no longer be on the earth.

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