Why does the Earth have a Moon and how does it affect our planet?

Illustration, Photo: Shutterstock

The moon, Earth’s natural satellite, has surrounded our planet for billions of years, and before the oceans were inhabited by the first life forms, even before the Earth was cold enough to have oceans.

He preys steadily and calmly in the night sky, but his past is nothing like that. The moon formed about 4.5 billion years ago, when the solar system was still in its infancy and comets, meteors and asteroids collided around. It is believed that from one such collision between the Earth and a sphere the size of Mars, when the molten rocks flew into space, its cooling and merging, gave rise to the Moon as we know it today.

Its close connections with the young Earth make the Moon the most suitable and logical for research on the origin and development of our solar system and our planet. The Moon, on the other hand, has no tectonic activity to change its landscape, nor does it have rain and wind washing away ancient rocks and boulders.

All the faces of the moon

There are more than 190 species of the Moon in our solar system that surround other planets and asteroids, and our Moon is the fifth largest. Its diameter is approximately one third of the diameter of the Earth.

Every 27.3 days, the Moon makes one circle around our planet, while it also revolves once around its axis. These synchronized rotations of the celestial dance make the same side of the moon always face us.

Observed from the Earth, the surface of the Moon illuminated by the Sun alternates, creating the familiar cycle from the new moon to the crescent. This phenomenon is the result of a change in the position of the Moon in relation to the Earth and the Sun, and it takes 29.5 days to complete one lunar cycle. Although only one side of the Moon is always facing the Earth, there is no such thing as a “dark side,” as many call the side of the Moon away from our planet. Even the farthest side of the moon gets sunlight, but we don’t see it from Earth.


During the Apollo missions, astronauts brought 382 kilograms of moon rocks, sand and dust, to allow scientists to explore the surface of the moon. Based on this material, much has been learned about lunar formations and evolution. Initially, the surface of the Moon was covered with oceans of magma that gradually cooled and crystallized, with crystals of lower density reaching the surface. A large part of the lunar surface is made of glittering anorthosite stone, which we see from the Earth as glittering parts of the lunar surface.

After several billion years, this shiny surface is full of dark traces and spots. Many of these dark zones are vast expanses of lunar basalt, resembling the rocks that make up the Hawaiian Islands. These zones formed when the rocks melted, reaching the surface during the eruptions. Although everything is thought to be only visible traces of eruptions from the period we now consider ancient, some earthquakes from the Apollo mission period suggest that the Moon may not be completely geologically dead.

Beneath the lunar crust, similar to the composition of the Earth, is a mantle whose composition scientists are not yet sure. Recent research has shown that this layer is composed in part of the minerals pyroxene and olivine. In the center of the Moon there is a small core rich in iron, a little more than 482 km wide, which was discovered by the analysis of seismic waves passing through the interior of the Moon.

Wet habitat

At first it was thought that the Moon was a dry, “baked” landscape. Over time, scientists have found more and more signs that this is not true and that the Moon is wetter than previously thought. Although water in a liquid state cannot be retained on the surface of the Moon, tiny glass beads of ice from dried volcanic channels suggest that there is a surprising amount of water deep below. Interestingly, water is also released during a meteor collision with the Moon. This releases about 220 tons of water a year, which are valuable reservoirs for hydration and fuel for future human visitors or even long-term residents of the proposed lunar bases, which could serve as a starting point for further space exploration.

Life with and without the Moon

The phases of the moon provided the rhythm for generations of people who made calendars based on that. One of the most significant influences of the Moon is reflected in the tides on Earth. The moon’s gravitational field causes a water bulge to form on the nearest side of our planet, and another is created on the farthest. As the Earth rotates, the part affected by the Moon’s gravitational field moves, creating a tide every 12 hours, at any “affected” place.

The moon also calms the oscillations of the Earth’s ball while making our climate more stable. The movement of the slope of our planet directs the distribution of solar energy, which can affect the creation of the ice age. Without the Moon, the inclination of our planet would vary by as much as 85 °, which would cause a “wild” climate.

Every year the influence of the Moon gradually decreases, as it moves away from our planet into space. At the annual level, this happens by 2 cm. This is the result of the moon’s role in the tides on our planet. As our planet rotates a little faster than the Moon’s orbit, a tidal bulge rising on the side of the Earth closest to the Moon rotates directly in front of the sphere, pulling the Moon slightly accelerating its orbit and moving it away.

It is unlikely that the Moon will completely fly away from our planet. Little shining, Earth’s friend will continue to orbit the Earth for millennia to come, until its dying Sun destroys it.

Source: National Geography