The rocket, launched in 2015, sent NASA's DSCOVR probe 1.5 million kilometers from Earth, facing the sun. But the rocket did not have enough speed to enter an independent orbit and continue around the sun, and it was supposed to burn up on re-entry according to normal procedures, and did not return to Earth's atmosphere due to loss of control.
But since February 2015, the abandoned Falcon 9 rocket upper stage, which is 14 meters long and weighs nearly 4 tons, has always been in a wide orbit around the Earth. Its precise motion has been difficult to predict because it is affected by both the moon's and the sun's gravity as well as the Earth's. But it is now safe to conclude that it will hit the Moon on March 4 at a speed of 2,600 meters per second and will create a crater about 19 meters in diameter.
So will the satellite fall to Earth? The answer is: yes, it's normal for satellites to fall. Artificial satellites are about 800 kilometers from the ground, where there is still very thin air, so there will be resistance when running, resistance makes the satellite in the orbit slow down, but gravity does not change, so the centrifugal force is not enough to balance the Earth's gravity, artificial satellites will be pulled back to the atmosphere by the Earth. As a result, artificial satellites are equipped with their own thrusters to replenish the lost speed and ensure that the satellites remain smooth. However, all equipment has a useful life, so when satellites reach the end of their useful life, they fall off, and of course, it's up to scientists to decide where to drop them. The famous "Mir" space station in 1986 launched more than ten years to do a lot of work, and finally due to equipment aging, failure, the need for a lot of money to repair, continue to work is not worth it, so scientists bear the pain to let it fall down.
Of course, artificial satellites operating in predetermined space orbit, in the design life is generally not fall down, because the Earth's gravitational force on it and the centrifugal force of the satellite to maintain a state of balance. It appears to be very stable as it spins itself around rapidly during its rapid orbit. Just in case, scientists have also set up an automatic correction system on the satellite, which reacts appropriately when the satellite goes out of its orbit, generating a push to allow it to operate normally. So, generally speaking, a properly functioning satellite will not fall.
The universe is unpredictable, air resistance in near-Earth space, the pressure of solar radiation and the gravitational pull of other planets and other changes in external factors will hinder the normal operation of satellites, but also may result in the normal operation of satellites out of control and fall off the possible. February 9 news, Space Exploration Technologies SpaceX February 3 launched 49 satellite chain, 40 will be due to the impact of geomagnetic storms brought about by the scrap. effects of geomagnetic storms and will be scrapped. These satellites could fall off at any time.
And if they do, will they hurt people? There is no need to worry about this, because the Earth has a thick layer of atmosphere, as for the falling satellites, will be friction with the atmosphere and produce high temperatures, the vast majority of the atmosphere will be burned out (which is the result of the people expected), not burned out to the ground is very small.
And the moon is not the same, due to the lack of atmosphere to protect it from space debris damage, so it has countless natural impact craters above, small diameter of only a few tens of centimeters or even smaller, large diameter of more than 200 kilometers. It is estimated that the total number of craters larger than 1 kilometer in diameter on the lunar surface is more than 33,000, which can be said to be already full of holes. This type of meteorite impact energy are very huge, if the Earth was also hit by such an impact, it will be very large-scale destruction of the Earth's ecological environment, and even cause species extinction.