The moon used to be a mars-sized asteroid which incidentally collided with the Earth 4-4.5 billion years ago. Most of the mars-sized asteroid's debris joined the Earth through gravity. The leftover debris was charged into orbit with the Earth in a disk-like formation. Part of the Earth's mantle was also launched into orbit because of the collision. This whole process increased the Earth's mass dramatically. Over a long period of time, the debris that were orbiting the Earth, started to hit each other and clump together. This turned out to be our moon in the end that orbits us nowadays, although practically the same size it used to be much closer to the Earth.

    The moon happens to cause tides in the Earth by gravity, which help us in transportation, energy, and prevent large bodies of water to freeze, like lakes, etc. Although, we would still get tides without the moon, since we still have the Sun, it would not be much. Only 12 hours a day would we get different tides in one place, but since we barely have a delay time for different tides, which is at Quarter Moons every month. Also, the Sun is only 46% effective in creating tides on Earth, compared to the moon. So the moon contributes in creating tides twice as much as the Sun.

    The Moon also helps us obtain light even when we are not facing the Sun （this means nighttime）, by reflecting the light of the Sun back to Earth.

    One important factor about the moon is that it locks our planet into a stable rotation, and position with the sun. Resulting in the equator always facing the Sun to give balance to the temperature on the Earth. Planets that don't have large moons, rotate without stability. Where sometimes, the poles face the Sun and the equators do not. If that happens, the planet spin on the axis, of which the top is at the closest point to the Sun. That point will reach extreme high temperatures, since it constantly faces the Sun, whereas the opposite pole will be extremely cold half of the year. These extremes will exterminate all complex life on the planet. Due to drag between the Sun and the Earth, our moon is moving far from us, although slowly but surely. After we lose our moon, the Earth will not remain its stable position, sooner or later it will tip and all complex life will die. Life would still be possible, when the Earth returns back to it original position, life will start afresh. Although it is noted that since it will not have its stability, the Earth will wobble too, destroying life again and life will start anew every time, in a cycle.

    月球曾是一个体积与火星相当的星体。而在40-45亿年前，它与地球发生了巨大的撞击。其大部分撞击碎片因受引力影响，被地球合并，地球的质量因而大大增加。余下的，则是一个似圆盘状的星体，并围绕地球旋转。此次撞击中，地球部分表层亦被激射出去，在太空中绕地球旋转。这些撞击碎片，经年累月之后，逐渐互相粘合到一起，形成一个星体，而这个星体，就是今天我们所熟知的月球了。而它的体积，在撞击前曾经和地球相差无几。

    月球通过自身的引力，给地球带来潮汐。这使得我们在运输、能源方面大受其益；且湖泊等大型水体也因此不致被冰冻。诚然，没有月亮，地球也会因太阳而有潮汐，但是，要小很多了。一天每12个小时，我们便可在同一个地方看到不同的潮汐。每个月，上弦月或下弦月时，不同的潮汐都会如期而至。此外，太阳在引起潮汐方面，其效率只有月球的46%.换言之，月球贡献的潮汐，有太阳的两倍之多了。

    月球对地球至紧要的，是使地球的自转得以稳定，而对太阳的位置亦保持恒常。因此，赤道总能正对太阳，地球的温度便能达到均衡。一个恒星，如没有体积合适的卫星，那么它的自转会极不稳定。这样的行星，有时会以南或北极面对太阳，而非赤道。试想如果行星以南或北极正对太阳的转轴自转，那么一极会因始终正对太阳而温度极高，而另一极则会在半年中极度寒冷。如此极端的温差，会导致地球上的高级生命难以生存。由于太阳和地球之间有牵引力，月球正离我们不断远去，只是过程十分缓慢。一旦当我们失去月球，地球将难以保持自转轴的稳定，地极迟早会倾向太阳，高级生命将不复存在。当地球恢复的合适位置，生命又将重生。而由于地球的位置不是持久稳定的，生命又会被摧毁。生命的生灭会不断上演