Around 4.5 billion years ago when the Earth still was cooling down from a Lava glowing soup. It had a close neighbour called Theia.
Theia was close to the size of Mars, unfortunately Earth and Theia orbits around the Sun was crossing.
And one fateful day they met...
The impact was so catastrophic that an enormous amount of debris was kicked into orbit around
the Earth creating rings like a mini Saturn.
These rings then coalesced and cooled to become the Moon.
The Moon is the fifth largest satellite in the Solar System. It's a quarter the diameter of Earth but only 1⁄81 its mass.
If you're measuring the center-to-center distance from the Earth to the Moon, the distance would be about 384,403 kilometers/238,857 miles.
The average distance between Earth and Moon is approximately 30 times Earth's diameter.
If you could fly to the Moon at a constant speed of 1000 kilometers per hour, which is the speed of a fast passenger jet, it would take sixteen days to get there.
The light needs 1.26 seconds to travel this distance.
The Moon is in a tidal lock (or captured rotation)
this occurs when the gravitational gradient makes one side of an astronomical body always face another, an effect known as synchronous rotation.
This is why the same side of the Moon always faces the Earth. A tidally locked body takes just as long to rotate around its own axis as it does to revolve around its partner.
This causes one hemisphere constantly to face the partner body
The Moon is the brightest object in the sky after the Sun, although its surface is actually very dark, with a reflectance similar to that of coal.
When you look up at the Moon you'll see "oceans" marked by dark volcanic maria that fill between the bright ancient crustal highlands and the prominent impact craters.
These dark areas are sometimes called "The Man in the Moon" It's the image of a human face, head or body that certain northern hemisphere traditions perceive in the disc of the full moon.
In the southern hemisphere the disc of the moon is seen as inverted and the Man in the Moon difficult to perceive. Southern hemisphere cultures tend to perceive other images such as the Moon rabbit.
The Moon's current orbital distance, about thirty times the diameter of the Earth, causes it to appear almost the same size in the sky as the Sun,
allowing it to cover the Sun nearly precisely in total solar eclipses.
This matching of apparent visual size is a coincidence.
Earlier in Earth's history, the Moon was closer to Earth,
and would have had an apparent visual size greater than that of the sun.
If the Moon were in a circular orbit close enough to the Earth and in the same orbital plane, there would be total solar eclipses every single month.
However, the Moon's orbit is inclined or tilted at more than 5 degrees to Earth's orbit around the Sun so its shadow at new moon usually misses Earth.
Earth's orbit is called the ecliptic plane as the Moon's orbit must cross this plane in order for an eclipse (both solar as well as lunar) to occur.
In addition, the Moon's actual orbit is elliptical, often taking it far enough away from Earth that its apparent size is not large enough to block the Sun totally.
The orbital planes cross each year at a line of nodes resulting in at least two, and up to five, solar eclipses occurring each year; no more than two of which can be total eclipses.
The tidal force is a differential force. Consider three things being pulled by the moon:
the oceans nearest the moon, the solid earth, and the oceans farthest from the moon.
The moon pulls on the solid earth, but it pulls harder on the near oceans, so they approach the moon more causing a high tide;
and the moon pulls least of all on the far oceans (on the other side of the planet), so they stay behind more, causing another high tide at the same time.
The first human-made object to reach the surface of the Moon was the Soviet Union's Luna 2 mission on 13 September 1959.
The United States's Apollo 11 was the first manned mission to land on the Moon.
A total of twelve men have landed on the Moon.
This was accomplished with two US pilot-astronauts flying a Lunar Module on each of six NASA missions across a 41-month time span starting on 21 July 1969 UTC,
with Neil Armstrong and Buzz Aldrin on Apollo 11, and ending on 14 December 1972 UTC
with Gene Cernan and Jack Schmitt on Apollo 17 (with Cernan being the last to step off the lunar surface).
All Apollo lunar missions had a third crew member who remained on board the Command Module. The last three missions had a rover for increased mobility.
The ongoing Lunar Laser Ranging Experiment measures the distance between the Earth and the Moon using laser ranging. Lasers on Earth are aimed at retroreflectors planted on the Moon during the Apollo program, and the time for the reflected light to return is determined.
India, Japan, Europe (ESA), China, Iran, Russia and some private companies are planning future manned Moon landing missions from 2020-2032.
The Moon affects Earth's rotation so it's being slowed by the friction between the oceans and the ocean floor.
This will continue to happen until Earth's tidal bulges align with an imaginary line running through the center of the Earth/Moon system,
then Earth's rotation will cease slowing down.
This will take a few billion years but when it does happen:
Earth's day will be a month long (960 hours a day).
By then the Moon will be twenty-five percent farther away.
If we were on the Moon looking back at Earth, we would see the same face of Earth,
just as now we see only one face of the Moon.
And if someone were still on Earth: the Moon will have moved far enough away that it appears much smaller.
And there will be no more solar eclipses..
Sources: Wikipedia en.wikipedia.org/wiki/Moon
, Unverse Today www.universetoday.com/19718/fo…
and starryskies starryskies.com/articles/2007/…