Such a big asteroid crashed into the earth, and the effect could not be compared with that of nuclear weapons. Because it completely destroys the environmental balance.

The shock wave produced by the violent explosion will sweep the whole earth in a few hours, and all unmasked life within hundreds of kilometers of Fiona Fang will be instantly extinct. If the impact point is in the ocean, waves hundreds of meters high will sweep across the global coast in a few days.

Dust from the Big Bang will stay in the atmosphere for hundreds of years. Let the whole earth fall into cold and darkness. Due to the severe cold and the interruption of photosynthesis, a large number of species began to become extinct. After the dark period passed, a lot of water in the air turned into snow and fell to the ground. The albedo of the earth rises, the temperature drops further, the snowfall increases and the temperature drops continuously, which is also a common phenomenon in the ice age in the history of the earth. This ice age will last for hundreds of thousands to millions of years. At present, most species in the world are extinct because they can't stand the sudden change of climate.

If an asteroid hits the ocean, the environmental balance of the earth will be pushed to the other extreme. After the dark period has passed. Because hundreds of cubic kilometers of seawater are thrown into the upper atmosphere. Water vapor in the upper atmosphere will not drop completely even in the dark period. Water vapor will enhance the greenhouse effect. The temperature on the earth began to rise. When the temperature rises by 5 degrees Celsius. Hydrated hydrocarbons in shallow seas around the world began to decompose, releasing a large number of greenhouse gases, and the temperature further increased. Due to the disappearance of a large number of plants and algae, the regulation of the biosphere on the atmospheric environment has declined, and the temperature may continue to rise above 10 degrees. At that time, it will not be a problem of sea level rise. At this time, most of the algae died and the oxygen content in the air decreased. Environmental deterioration in most parts of the world. A large number of animals and plants became extinct. The high temperature period will also last for millions of years.

This is my answer to another similar topic. It's not plagiarism, is it

However, after careful consideration, I think I can add one point.

About impact energy. The key is speed. Although asteroids hit the earth at different angles, the speed is naturally different. But many friends have overlooked a very important point. That is, asteroids will be accelerated by the gravity of the earth when they approach the earth. So there will never be an asteroid hitting the earth at a very slow speed, and there are almost no retrograde asteroids in the solar system, so there will be no head-on collision. The impact velocity of asteroids is basically spectral.

Generally speaking, the speed at which asteroids hit the earth is about 20~40 kilometers per second.

The power of impact. It is impossible to destroy the earth. Even if the moon falls completely, it will not completely smash the earth. But is it possible to break through the crust? I don't think this possibility can be ruled out. After all, the diameter of 10 km is very considerable compared with the crust with a thickness of several tens of kilometers. If you encounter a weak crust, it is entirely possible to break through. To be clear, this power cannot be compared with nuclear weapons.

The consequences of the impact. The consequences have been mentioned above. According to the theory of "nuclear winter" put forward by geophysicists during the Cold War, it is entirely possible that there will be a super nuclear winter, which will lead to the Ice Age. However, considering the extremely strong influence of the hypothesis in this question, there may be another extreme-extreme high temperature period. This situation has also happened in the history of the earth. The rise of Siberian shield more than 200 million years ago created an extremely high temperature period. But in any case, the extinction of life on earth is inevitable.

About intercepting asteroids mentioned by a friend. Seriously, I'm pessimistic. At present, asteroid interception technology faces at least three major obstacles.

The first is early warning capability. At present, human beings' ability to monitor and warn short-period comets and near-earth asteroids is still relatively strong. The early warning ability of long-period comets and aperiodic comets is almost negligible. For many long-period, aperiodic comets, we often find them in less than half a year, especially Comet Wu Bai, which only takes more than one month from being found to reaching the nearest point of the earth. For comets hundreds or thousands of kilometers in diameter, this warning time is meaningless. And this dilemma is hard to change.

The second point is to change the ability to intercept asteroids. The technical difficulty of intercepting asteroids is inversely proportional to the early warning time. The earlier the warning and the earlier the action, the easier it is to realize the orbit change of small celestial bodies. But in fact, it's hard to do. Let me give you an example to illustrate. If there is an iron asteroid with a diameter of 10 km, then all the nuclear weapons in the world together are definitely not enough to destroy it. We can completely dispel this illusion of "the last line of defense". In fact, among all the schemes, the most realistic and reliable way is to use the spacecraft to carry a nuclear warhead for close-range explosion to achieve the purpose of "pushing away". Another feasible method is "space billiards", which changes the orbit of one asteroid to hit another asteroid. But it's far away. As for the others, they all belong to the category of science fiction.

It is optimistically estimated that in this century (2 1 century), humans may intercept the kilometer-class asteroids. As for those above the kilometer level, let's talk about it in the 22 nd century.

But after all, there is hope and direction to solve the technical problems.

I want to talk about an almost inextricable knot: the weaponization of asteroid orbit transfer technology!

What if someone pushes an asteroid that would not have threatened the earth into a dangerous orbit? This technology is the same as the technology of defending the earth mentioned above, and there is almost no difference in technology.

And the most important thing is: we can predict without any suspense that the asteroid orbital transfer technology will turn 100% into military use, and 99% will be used for war blackmail and even for defending the earth after actual combat, unless the earth faces the asteroid threat prematurely.

You know, the probability of the earth being destroyed by natural disasters may be one in ten thousand, but the probability of the earth being destroyed by war is nine in ten thousand.

How should we face such an extremely difficult choice?