Meteors are hard to destroy the earth

Whether an asteroid explodes or falls to the ground depends on the ability of the atmosphere to withstand the compressive pressure. They often take up to 99% of the material before touching the surface of the earth.

The meteorite exploding in the sky of Chelyabinsk, Russia on February 15 has an estimated size from 15m to 17m, speed of 18km / second, with a volume of between 7,000 and 10,000 tons. It exploded at an altitude of about 15-25km, the estimated destructive power amounted to about 500 kiloton of TNT, about 30 times the atomic bomb dropped by Japan in World War II. Such meteorite explosions are rare, because it only happens about once every century. This is the biggest explosion since the 1908 Tunguska explosion in Siberia, Russia. The low-tide monitoring stations calculated the time the meteorite flew into the atmosphere and exploded at 32.5 seconds.

Every day, the earth receives thousands of bombardment pieces of meteorite that range in size from a few atoms to a basketball. Meteors can plunge into the earth's atmosphere with a theoretical minimum speed of about 11 km / sec, but mostly concentrated in about 17 km / sec. Most meteorites rush into the atmosphere, the air layer in front of them will be strongly compressed, creating a shockwave with tremendous compression pressure that heats this gas and the meteorite, while stimulating matter on this meteorite ignites and glows, forming a long trail of light when viewed from the ground that we call a supernova.

Meteorite smoke trail left the central Russian sky on February 15. (Photo: RIA Novosti)

It is also the pressure from the layers of gas that repels, and the pressure imbalance between the anterior part and the back part of the asteroid that causes it to a certain extent, cannot stand but explodes. The deeper you go, the thicker the air density, the greater the pressure on the meteorite, the more it loses its material and the easier it will explode. It is estimated that meteorite takes about 95-99% of the mass. Its head from going into the atmosphere to the ground.

Meteor stars are a common phenomenon but difficult to meet because their passing time is too short, while most of them are covered by bright light when they rush into the earth during the day. Large meteorite explosions occur regularly throughout the history of the earth, but become rare in the few thousand short years of human civilization. Moreover, most of them occur on the ocean or in uninhabited areas. The Tunguska event in 1908 until 1927 was recently surveyed because it was located in a remote area of ​​Siberia.

An asteroid that explodes or falls to the ground depends on its ability to withstand the pressure caused by the atmosphere. In addition to high volume, high velocity, it must also be composed of high density, durable materials. According to the US Space and Aeronautics Agency (NASA), small asteroids or meteorites break down in a majority atmosphere that is not made of iron and nickel that are more durable and can reach the ground. Indeed, from the above observations, we can estimate the density of meteorite falling in Russia on February 15 at about 2700-3900kg / m ³ , that is, the composition is mainly from rock. Moreover, the asteroid's movement angle with the ground is quite oblique, so the distance to the ground is longer and the flight time is longer, increasing the likelihood of it exploding before touching the ground.

The "killer asteroids" , with a diameter of 1 km or more, will reach the ground and are enough to cause a terrible collision with a huge, destructive power such as a catastrophe. completely dinosaurs that once dominated our planet about 65 million years ago.

Some suggested that this meteorite in Russia could not be detected because it flew in the daytime completely inaccurate. Astronomers have telescopes to cover the entire 360 ​​degrees of the sky, day and night, even if they have dedicated telescopes to observe the sun. The reason this meteor is not detected early is because its size is not large (only about 15m), with distance from outside the space, it is difficult for telescopes to observe, confirm and affirmed it was a meteorite that rushed towards the earth. When light burns and explodes, this meteorite is even brighter than the sun.