Moon

The **Moon** (or Earth's Moon) is Earth's only satelite, and is the fifth largest satellite in the Solar System. Orbiting the Earth at a average distance from Earth is 384,000 kilometers from Earth, The Moon does not rotate around its obliquity, its gravitational influence slightly lengthens Earth's day and is the main driver of Earth's tides. The Moon is classified as a planetary-mass object and a differentiated rocky body, and lacks any significant atmosphere, hydrosphere, or magnetic field. The Moon has a diameter of 3,474 kilometers, which is approximately 1/4 of the Earth. Its surface gravity is about one-sixth of Earth's (0.1654 g).

The Moon drifts away approximately one centimeter from earth each year due to tidal interactions. In addition, six hundred-thousand million years from now, total solar eclipses will no longer be possible. However, before this happens, it also has a effect of annular eclipse (or Ring of Fire) or a partial solar eclipse which could happen.

## Orbit

The Moon orbits the Earth at a barycenter 1,700 kilometers below the Earth's surface every 29.17 days. Being tidally locked to its primary, this makes only one side of the moon visible to Earth. It is believed that the Moon is slowly moving away from Earth, and if the two are not destroyed when the sun reaches the red giant stage, the orbital center of the two objects will be further from the Earth.

The prevailing theory on the Moon's formation was that an object the size of Mars named Theia hit the Earth at an oblique angle, which caused a large amount of rock and dust to spew out. This dust collected into the Moon since it was outside the Roche Limit. The moon used to be way closer, but as the tides grew, it pushed the moon away. Until 1.7 billion years ago, the Moon was 24,000 km away from Earth and was bigger in the sky.

Around 4.5 billion years ago, after the collision of the Moon, the Moon was formed and the Moon was very closer to Earth and was bigger in the sky. At 4.3 billion years ago the South Pole Aitken Basin was formed after a collision of a large asteroid. Afterwards, the Moon suffered heavy bombardment and basins were formed as a result of creation of volcanic seas or lava seas. However due to non-atmospheric existence, the volcanism had gone away. Also, during bombardment times, the intermediate cratering formed in the lunar highlands, creating numerous intermediate craters. After the bombardment times, the ray craters on the Moon had formed until today.

## Moon Phases

There are four principle phases of the Moon. These are the new moon, first quarter, full moon and last quarter.

* New Moon: At new moon the Moon is between the Earth and the Sun, and is invisible as it presents its night side to the observer. This could have a effect on solar eclipse.
* First Quarter: A week after new moon comes first quarter, when the Moon is a quarter of the way around its orbit.
* Full Moon: Full moon occurs at just under 15 days. As at new moon, Earth, Sun and Moon are again aligned, but this time the Moon is opposite the Sun in the sky.
* Last Quarter: After full moon the phases then repeat in reverse, the terminator continuing its passage across the disk, through the gibbous phase to last quarter.

There are four secondary phases of the Moon. These are the waxing crescent, waxing gibbous, waning gibbous and waning crescent.

* Waxing Crescent: After the new moon, the sunlit portion is increasing, but less than half.
* Waxing Gibbous: After the first quarter, the sunlit portion is still increasing, but now it is more than half.
* Waning Gibbous: After the full moon (maximum illumination), the light continually decreases.
* Waning Crescent: Following the third quarter is the waning crescent, which wanes until the light is completely gone — a new moon

## Supermoon

A **supermoon** is a full moon or a new moon that nearly coincides with perigee, the closest that the Moon comes to the Earth in its elliptic orbit, resulting in a slightly larger size of the Moon as viewed from Earth. The real association of the Moon with oceanic tides has led to claims that the supermoon phenomenon may be associated with increased risk of events like flooding, earthquakes and volcanic eruptions.

The opposite phenomenon, an apogee (furthest distance from the Earth) or a full (or new) Moon around apogee, has been called a micromoon.

## Links

1. https://www.timeanddate.com/moon/phases/ - Moon Phases - Lunar Calendar
2. https://nextfullmoon.org/ - Next Full Moon