According to foreign media reports, not long ago, at about 8 a.m. local time on April 27, many local people in mississippi, Louisiana and Arkansas in the southern United States heard an unknown loud noise from the sky, and a huge fireball appeared. The fireball swept quickly through the sky and quickly disappeared.
So what is this fireball? Did the spacecraft crash, or was it something else alien?
According to NASA (Nasa), this is not a man-made object, but a fire meteor.
According to nasa scientists' estimates, the meteor that crossed the United States this time has a diameter of about 30 centimeters and a mass of about 40 kilograms. The survey shows that when the meteor was first discovered, it was about 87 kilometers above the ground and reached a speed of 24 kilometers per second when rushing to the ground.
However, it eventually exploded violently and disintegrated over 55 kilometers above the ground. It is estimated that when the meteor exploded, it released about three tons of TNT equivalent energy. At that time, the satellite of the National Oceanic and Atmospheric Administration (NOAA) also observed the flash of the meteor's explosion in space.
In fact, this astronomical phenomenon is very common, and many fire meteor falls occur every year in the world. Just last month, many people in Indiana saw giant fireballs across the sky, accompanied by a loud pop. Mainland China has also had this record, for example, on December 23, 2020, a meteor fell into Yushu in Qinghai.
So what is a fire meteor?
Interplanetary space in the solar system is not empty, there are small bodies such as asteroids and comets, as well as a large amount of cosmic dust and small body debris. The small fragments of the celestial body are meteoroids.
When meteoroids are captured by Earth's gravitational pull and crash into Earth, they can reach speeds of 11 to 72 kilometers per second when crossing the atmosphere. Such a fast speed will cause them to rub violently with the atmosphere, usually in the high air 80 to 120 kilometers above the ground is quickly ablated by the high temperature, showing a trace of light in the night sky, which is the meteor we see at night. If there are more of them at the same time, it is a meteor shower. If the structure of the meteoroid is loose, it will explode in the air due to aerothermal effects and disintegrate, splitting into many fragments.
When meteoroids have a large mass, they intrude into the Earth's atmosphere, and after they are burned out in the high air, they will continue to intrude into the dense lower atmosphere, and then their friction with the air will be more intense, so they will emit a very dazzling light, and sometimes it can be observed by the naked eye during the day. This extremely bright meteor is the fire meteor.
Because the speed of motion is far faster than the speed of sound, fire meteors can also cause sonic booms when they row through the sky. When the fire meteor appears, the roar that people hear originates from this. Supersonic fighters also produce this sound when flying at low and medium altitudes.
Aliens are dangerous
Scientists estimate from observational data that about 200,000 tons of outer space material land on Earth every year, that is, the mass of the Earth increases every year.
However, this increase has little effect on the mass of the Earth, after all, the mass of the Earth is about 6× 10^21 tons. In the course of Earth's 4.5 billion years of life, the cumulative increase in mass is less than one-ten-thousandth of the Earth's mass.
Most of these extraterrestrial materials that land on Earth are relatively small in mass, vaporized at high altitudes, do not fall directly to the ground, and are difficult to attract attention. The mass of the meteors crossed over the United States this time is relatively small and will not cause harm. But if an asteroid or comet crashes into Earth, it's more dangerous.
Here to illustrate, asteroids, comets, meteoroids are all small bodies, but the three are different, meteoroids are usually relatively small in mass, and do not have a fixed orbit like asteroids and comets, while the difference between asteroids and comets is mainly in the difference in composition. As for the meteorite, it is the remains of small unburned objects that land on the ground. Meteorites are mostly made of rock, so meteorites are often called meteorites; if they are iron, they are called meteorites.
Asteroids or comets also produce a huge fireball when they break into the Earth's atmosphere, so they are often called fire meteors when they fall, but their masses are larger than meteoroids, and if they fall to the ground, they may cause harm to people or things on the ground. Even if they explode and disintegrate at high altitudes, the debris will be large and will produce powerful shock waves.
In 2013, an asteroid with a diameter of about 20 meters and a mass of 12,000 tons was crossed over Chelyabinsk in Russia, when the asteroid rushed into the Earth's atmosphere at a speed of 19 kilometers per second and exploded at a high altitude, with an explosion energy of about 400,000 tons of TNT equivalent, injuring about 1,500 people and damaging 7,200 buildings. This is the most severe known explosion of small bodies on Earth since the Tunguska Explosion of 1908.
The 10-kilometer-diameter asteroid that exterminated the dinosaurs 65 million years ago struck a Chixulub crater with a diameter of about 180 kilometers on the Yucatan Peninsula in what is now Central America.
These small objects are not only dangerous, but also numerous. According to statistics, about 27,000 near-Earth asteroids have been discovered. In the asteroid belt between the orbits of Mars and Jupiter, there are also a large number of small objects. However, due to limited technical capabilities, it is currently difficult for humans to respond to and accurately predict such disasters.
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