Why does a tiny asteroid in the universe bring disaster to the earth?

The Tunguska River is located in the northwest of Lake Baikal in Siberia, Russia, and a dazzling blue light cuts through the sky. After several loud noises, the virgin forest within 2 150 square kilometers was razed to the ground and more than 800,000 trees were destroyed. Fortunately, this area is sparsely populated, with only three casualties. This is the famous Tunguska Big Bang. For many people, the cause of the big bang is still a controversial topic.

Lodging trees in Tunguska forest

Over the past 100 years, there have been more than 1000 academic papers related to the Tunguska incident, and the analysis of its reasons is also varied. According to the calculation afterwards, the Tunguska Big Bang was equivalent to 1 30 million tons of TNT explosion equivalent, about 1 000 times that of Hiroshima atomic bomb, and also equivalent to the explosive power of the largest hydrogen bomb made by the United States and the former Soviet Union. You know, no one knows about the nuclear bomb, and Tunguska has not detected nuclear radiation.

nuclear explosion

What caused the Tunguska incident? Investigators first found aborigines and Russian immigrants in nearby villages to understand the situation. By comprehensively analyzing the descriptions of many witnesses, we can roughly draw the following process: 17 At about 7 am, a dazzling light first appeared in the clear sky, which moved in the sky and was almost as bright as the sun. Then there was a sound like an artillery explosion from the east. The shock wave knocked people down and some people were thrown several meters away. The sky seems to be covered with fire, people feel the strong hot air blowing, which is almost unbearable, and clothes seem to be on fire. One after another, huge fireballs in the sky, accompanied by huge explosions, flew to the north. The forest was smashed, the top of the tree was broken, the doors and windows were broken, and some wooden houses were destroyed. There was an explosion in the distance, the whole ground shook violently and the house shook with it.

Asteroids hit the earth.

Through the investigation results of Russian expedition and the reports of Russian media at that time, we can know that this should be a typical meteorite fall. But strangely, no craters, huge meteorites or smaller meteorite fragments were found in the core area of the Tunguska Big Bang. All you can see is a fallen tree, and some trunks are even completely shattered. This is one of the reasons why there are many explanations for the Tunguska Big Bang.

Formation of impact crater

Almost all astronomers have focused their eyes on an asteroid numbered 20 12 DA 14. This asteroid with a size of 20× 40m is passing through the air at an extremely fast speed, which is lower than the orbit of many artificial satellites, so it is enough to attract the attention of western scientists. The Goddard Si Tong Observatory in the United States took a radar image of this asteroid.

On the same day, another asteroid close to the earth was ignored. It broke through the sky from southeast to northwest near Chelyabinsk, Russia and fell to the ground. The diameter of this asteroid is also about 20 meters, and the speed of 18.6 km/s produces a high temperature above 2000℃, which makes this meteorite unable to bear enormous pressure. It began to collapse and disintegrate about 23.3 kilometers from the ground, producing a huge explosion shock wave, destroying the doors and windows of houses along the way, and injuring more than 2,000 people by glass fragments.

Map of falling of Chelyabinsk meteorite

Afterwards, scientists inferred from the collected data that the diameter of Chelyabinsk meteorite was about18m, and the mass before entering the atmosphere was about 1. 1 10,000 tons. Its explosive power is equivalent to the explosive equivalent of a 500,000-ton TNT atomic bomb, making it the most destructive meteorite falling event observed by human beings in recent years.

It is worth noting that after the fall of the Chelyabinsk meteorite, no huge meteorite fragments were found, and no craters were found on the ground. Because the local population is sparse, everything is calm after the doors and windows are repaired. Astronomers and meteorite lovers only found some meteorite fragments the size of fingernails near an ice-breaking hole in Lake CheBalkur.

Chelyabinsk meteorite fragments

The same size is about 20 meters. 50,000 years ago, another meteorite landed in the Arizona desert, causing completely different damage. It has just smashed a big pit on the ground with a diameter of1.18km and a depth of170m. Through computer modeling, scientists concluded that this was a crater caused by an iron meteorite hitting the ground at a speed of 12.8km/s, and the explosion produced100000 tons of TNT equivalent.

The huge crater in Arizona

If the Tunguska Big Bang was also an asteroid that attacked the earth, how big would this asteroid be? Its diameter is also about 20 meters, and various indications show that it is a stone meteorite similar to the Chelyabinsk meteorite.

Why are they all stone meteorites with a diameter of 20 meters? The explosion equivalent of Chelyabinsk meteorite is 500,000 tons of TNT, and the explosion equivalent of Tunguska Big Bang is as high as 6,543,800 tons, but it didn't cause the same crater in Arizona? This problem has puzzled people for many years. The explanation of these problems is that the damage caused by meteorite falling is related to its composition, speed, falling angle and falling position.

First, the composition:

Asteroids in space are usually divided into three categories: iron meteorites, stone meteorites and iron meteorites. Iron meteorites are hard and dense, and are not easy to decompose under the strong friction with the atmosphere, so they generally fall to the ground as a whole, which is very destructive to the surface, so it will cause great craters.

A huge meteorite

Stone meteorites are made up of many small mineral particles gathered in space. When they enter the atmosphere at high speed, strong friction will make them produce high temperature, and meteorites will disintegrate and explode at high temperature and pressure, thus forming shock waves in mid-air. But before the meteorite fragments fell to the ground, many of them had been melted and turned into fine particles that were difficult to find. Therefore, stone meteorites are less likely to cause impact craters on the ground than iron meteorites.

Some people think that comet fragments, not asteroids and meteorites, caused the Tunguska Big Bang, but later field investigation evidence overturned this view. Scientists found a large number of tiny meteorite particles on a large area of fallen tree fragments, which proved that the explosion was caused by an asteroid, but the time was close to the encounter with Comet Cohen.

Second, speed.

The rotation of the earth has an angular velocity, and the revolution of the earth around the sun also has a forward speed. When these two velocities are superimposed, the relative velocity of a point on the surface in space is very different from that of an asteroid. When they collide head-on, asteroids will fall rapidly and their destructive power will increase. When they meet in the same direction, the speed of meteorites entering the atmosphere will be much slower, and the destructive power will naturally decrease.

Shock waves will form in front of the warhead flying at high speed.

Third, the angle of impact

Scientists believe that the reason why the Tunguska meteorite is similar in size to the Chelyabinsk meteorite, but it can produce a huge explosion equivalent is precisely because the falling angle between the Chelyabinsk meteorite and the ground is about 20, while the falling angle of the Tunguska meteorite is much larger, about 30 ~ 40.

In the process of falling at high speed, the air in front of the meteorite will be severely compressed, and a strong explosion shock wave will be generated around it. The destructive force in front of the shock wave is the strongest, and the lateral destructive force in the shock wave will drop rapidly. Therefore, the incident angle of a meteorite determines its destructive power. It is also a stone meteorite with a diameter of 20 meters. The explosion equivalent of Tunguska is more than 20 times that of Chelyabinsk meteorite.

The falling angle between Chelyabinsk meteorite and the ground is about 20.

Fourth, the descending position.

Chelyabinsk is a small town in south-central Russia with a small population. Therefore, although the Chelyabinsk meteorite has an explosion equivalent of 500,000 tons of TNT, it only caused glass breakage and scratches. The Tunguska Big Bang happened deep in the Siberian forest. Although the destructive power is huge, the losses caused are very small.

If the same fall happened in a densely populated urban area, it would be a huge disaster.

Tunguska event is a meteorite falling event caused by an asteroid hitting the earth. The reason why it can cause great damage and can't find traces is the superposition of its composition, falling speed and angle.