How far is mankind from extinction? How dangerous is the earth?

We often say that the earth is like a huge spaceship, carrying countless lives on it, and of course, we are galloping in the universe ourselves.

But you know what? In the process of the earth's rapid shuttle in the universe, the road is very dangerous. There are many unknown risks threatening the earth all the time, and of course there is life on it.

From about 500 million years ago to today, as far as we know, the earth has experienced at least five mass extinctions, each of which will lead to the destruction of at least 60% of the earth's life.

Some of these extinctions were caused by super volcanic eruptions, some by asteroid impacts, and some by supernova explosions. The most certain one occurred when dinosaurs were extinct by asteroids 65 million years ago.

So what's the next step? Will the sixth mass extinction happen?

At present, it will definitely happen, just a matter of time and way.

Because the universe is really dangerous, I always want to kill people. The extinction of mankind is not unpredictable in science. The following five ways will easily lead to the extinction of life on earth again.

Asteroid impact event

Asteroids in near-earth orbit outside the earth are the biggest threat to earth spacecraft. Most of them originated in the asteroid belt and were ejected into the inner solar system by Jupiter's gravity.

They began to orbit around the sun near the earth's orbit. Their orbital periods are basically the same as those of the Earth, and the orbits of some asteroids will overlap with those of the Earth, increasing their risk of hitting the Earth.

So how big is their threat to the earth?

In our previous understanding, the orbit space of the earth around the sun seems empty, very empty and without danger.

In fact, this is because our perspective is too small. If we stood outside the solar system, you wouldn't think so.

The picture above is a map of known asteroids. If you look at it this way, you will find that there are too many time bombs hidden around the earth. And the earth is not as empty as we think.

The above picture shows more vividly the movement of asteroids around the earth in a 20-year cycle. At present, more than 2,000 of these asteroids will pose a great threat to the earth.

Here is a typical example, and it is also an asteroid that is recently thought to be likely to collide with the earth in 2068: the destroyer.

This asteroid was discovered in 2004. Its orbital period around the sun is 323.6 days, while the orbital period of the earth is 365.3 days. This period is quite close. If their orbital planes are very close, the risk of collision will definitely be high.

From the above picture (red is the star of destruction, blue is the earth), it can be seen that before 2029, its orbit eccentricity is very small, but after it meets the earth in 2029, its orbit will change greatly due to the gravity of the earth;

Scientists have calculated the orbit of this asteroid, and estimated that the probability of it hitting the Earth in 2068 is11.5 million.

However, its longest semi-long axis is only about 450 meters. If it really hits the earth, it will release 50 times as much energy as the Tunguska Big Bang, but such a big asteroid will not destroy life on the earth.

You know, the asteroid that hit the dinosaur was at least 10 km in diameter.

In addition to the destroyer, there are 1950DA asteroids and Benu asteroids near the earth's orbit, all of which are threats to the earth.

So when the earth shuttles through the universe with life, there are many dangers hidden around it. Whether humans will become extinct in the future is anyone's guess, but it is certain that asteroids will hit the earth.

If humans can survive on asteroids, there are other dangers waiting for us in the universe.

Gamma ray burst

In the Milky Way, the frequency of gamma ray bursts is still relatively high, at least once a century, which is a very powerful energy burst. The energy released instantly is equivalent to the energy released by the sun in a lifetime, and the brightness is very high.

There are many reasons for gamma ray bursts, but the only thing we can be sure of is that when two neutron stars merge, they will produce energy jets. If they are aimed at the earth, powerful electromagnetic radiation will instantly destroy the earth's atmosphere and all electrical equipment.

The atmosphere, especially the ozone layer, has been destroyed, and only extinction awaits mankind.

Fortunately, this kind of high-energy event will only pose a threat to the earth within 6000 light years from the earth, and it must also be aimed at the earth.

In this case, the probability is greatly reduced.

Other celestial bodies intruded into the solar system.

The solar system shuttles through the Milky Way, but there are many wandering stars, star fragments, planets and star black holes in the Milky Way. These celestial bodies wander in the Milky Way, and they have no fixed laws of motion.

They will have a certain chance to get close to the solar system and even cross it.

For example, 70,000 years ago, a brown dwarf named Scholz star crossed the Oort cloud in the solar system. It is a failed star, and its mass is not very great. Because it was far away from the celestial bodies in the solar system, it did not cause any harm.

If a star with a large mass or a planet with a small mass passes through the solar system, the orbits of the planets in the solar system will be disturbed by gravity, and even the planets will be expelled from the galaxy.

Although the probability of such an event is as low as one in a billion, if it does happen, the earth will freeze in a short time and human beings will become extinct.

supernova

The above picture shows the famous Crab Nebula, which was produced by the explosion of a death star in A.D. 1054. At that time, humans witnessed the explosion of this star.

Different elements in the figure indicate the existence of hydrogen, oxygen, silicon and other elements. The energy released by supernova explosion is also quite huge. If the earth is within 10 light-years of this supernova, then human beings may become extinct.

This kind of supernova is very rare, and its frequency is estimated to be once every 10 billion years.

If mankind can survive the above disasters, then the final disaster will definitely kill mankind.

sun

The orange, purple and green lines in the above picture represent the brightness, radius and temperature of the sun respectively. It can be seen that from now to the future, its luminosity and radius will continue to increase, and the speed will be faster and faster.

It is estimated that in a short period of 2 billion years, the energy output from the sun will increase to boil the seawater on the earth, and the whole earth will lose control of the greenhouse effect like Venus, and all life will be extinct.

Therefore, human time is actually limited, which is why human beings are now vigorously exploring outer space and considering interstellar immigration, because any measures to protect the earth are only delaying the time for human beings to leave the earth.

We don't want to see that the earth has been destroyed by us to the point where it is uninhabitable before humans leave the earth.

Therefore, we live on the earth all the time in danger. These dangers warn us to protect the earth and prepare to leave it.