Our planet would be doomed if it were not for the Moon
What if the moon were at 420 kilometers away from Terra? As it would seem? And what would happen to our planet? It’s a condition almost impossible, because our natural satellite tends to move away and not to approach, but there are those who, on the web, tried to imagine how the Moon would be at the same distance, more or less.
‘To date, the distance between the Earth and its satellite is 384,400 km , a figure that could increase over thousands of years’ , says Luis Barbier, an astrophysicist at the Goddard Space Flight Center of NASA, but only as long as the orbit of the moon will reach an amplitude greater than 50 percent of the current one. ‘Some time ago, we also tried to imagine what would become of us if we lived without the moon, what would be the effects on the tides, and the Earth’s rotation axis. It is coming off an analysis almost catastrophic. But if it happened the other way around? If the Moon approached more than it should? At that distance (more than 400 kilometers) it would arise from the west and set at east’ (which does not happen in real life). The Moon orbits around the Earth counter-clockwise when viewed from the North Pole down to Earth in a synchronous manner and normally much slower. At that distance, however, would greatly increase its speed (one full turn in 90 or 130 minutes). The Moon and the Earth are at the same distance with two opposing forces: gravitational / centripetal (which attracts) and spins (which removes it because of its rotation). The two celestial bodies are stretched along the line that unites them, but if the satellite exceeds the safety distance measured from the center of our planet’s tidal forces increase it so hard to overcome its gravity that keeps it together until it literally goes to pieces. This deadline is called Roche limit, and depends on the radius of the celestial body larger (the Earth) and the ratio between its density and that of the satellite (the Moon).
If the distance diminishes so drastically, the gravitational force would increase dramatically, threatening, sooner or later, to crush us. For sure we would have a shortest month (no more than about 30 days). The tides would suffer significant consequences, and the waters would surely be redistributed, causing tsunamis. We’d have dramatic consequences on land and on the earth’s crust, resulting in earthquakes. Not to mention unthinkable repercussions on the climate and life of humans, animals and plants. As mentioned eventualities to happen, are quite unlikely for several reasons. First of all, the Moon moves away of 3.5 cm per year and then if approached, according to the principle of the line of Roche, our Moon would be destroyed at a distance of 18,261 km. In that case it would create a belt of debris, like that of Saturn, surrounding the Earth.