The Earth and the Moon may share an orbit, however, the moon’s orbit is slowly degrading around the Earth, what does that mean for human beings, as the Moon slowly approaches the amount of activity we see in our oceans will increase as the gravity of the moon comes closer.
While the moon will likely skip our atmosphere, at its rotational speed around the Earth, it won’t really truly collide, it will merely fall into the earth as it gets closer, eventually acting as a satellite in our orbit and dropping right into the surface.
Yes, the debris from the Moon will likely fall back on Earth but in about 7 billion years.
According to the giant impact hypothesis, the Moon was created from matter ejected by a collision between the young Earth and a planetoid body (protoplanet) the size of Mars named Theia. This impact would have occurred 100 million years after the birth of the Solar System, or 4.468 billion years ago. The Moon was formed by accretion of part of this cloud of debris, in a very short time, of the order of a century.
Since the formation of the Moon, the tidal forces transfer part of the angular momentum of the Earth gradually to the orbital moment of the Earth-Moon couple. The Moon is currently moving away from Earth by approximately 38 mm per year while an Earth day is lengthening by approximately 23 µs per year.
Current calculations suggest that in about 50 billion years, the Moon will stop moving away from Earth. At this point, the Moon will take approximately 47 days to circle the Earth and the Earth and the Moon will be locked to each other.
These calculations do not take into account the evolution of the Sun during this period. In a billion years, the increase in solar radiation will have evaporated the oceans of the Earth and will have eliminated most of the tidal forces.
In about 5 billion years, the Sun will have fused all of the hydrogen from its core into helium and will begin its evolution from the main sequence of the Hertzsprung-Russell diagram to enter the red giant phase.
The brightness of the Sun will increase to 2,730 times the current solar brightness in 7.6 billion years. It will lose about 33% of its total mass, which will cause the orbits of the planets in the Solar System to expand. The orbital distance from Earth will increase by more than 150% of its current value.
The Sun will swallow Mercury and Venus before reaching a maximum radius of 1.2 astronomical units and continue to burn until the core reaches a limit temperature of 100 million Kelvin. Then it will start to collapse on itself. The outer layers will be ejected creating a planetary nebula.
The friction of the Earth with the chromosphere of the Sun will reduce the Earth’s orbit. These effects will offset those related to the loss of mass from the Sun and the Earth will probably be engulfed by the Sun.
The ablation and vaporization caused by the fall of the Earth on a declining trajectory towards the Sun will remove the crust and the earth’s mantle, before finally destroying it after 200 years at most. The last trace of the Earth will be a very slight increase (0.01%) in solar metallicity.
But before this happens, most of the Earth’s atmosphere will have been lost to space and its surface will consist of an ocean of lava with floating continents made of metals and metal oxides as well as icebergs of refractory materials, with a surface temperature reaching more than 2,130 ° C.
Friction with the solar atmosphere will reduce the Moon’s orbit around the Earth. When the Moon approaches a distance of18,470 km to Earth, it will cross the Roche boundary and begin to dislocate into a ring system. This ring system will then start to fall apart and the debris will fall back to Earth.
Consequently, if the Earth is not engulfed by the Sun it will remain without Moon in orbit around what will remain of the Sun, a white dwarf of a size equivalent to the Earth, very dense and very hot. The Sun will then take 100 billion years to fade out.
