Planets and moons
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Moon. (2023). In Q-files Encyclopedia, Space, Planets and moons. Retrieved from
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"Moon." Space, Planets and moons, Q-files Encyclopedia, 4 Apr. 2023.
https://www.q-files.com/space/planets-and-moons/moon.
Accessed 19 Mar. 2024.
Moon 2023. Space, Planets and moons. Retrieved 19 March 2024, from
https://www.q-files.com/space/planets-and-moons/moon
Space, Planets and moons, s.v. "Moon," accessed March 19, 2024.
https://www.q-files.com/space/planets-and-moons/moon
Moon
The Moon, our nearest neighbour in space, is neither a star nor a planet. It is a ball of rock that travels around Earth, taking about 27 days to complete the circle. The same side of Earth's Moon always faces the Earth, because the Moon is "tidally locked" to Earth: Earth's gravitational pull holds it in place. This means that the Moon takes the same time to spin on its own axis as it does to orbit Earth. In turn, its gravitational pull, along with that of the Sun, causes tides on Earth. The Moon is the brightest object in the night sky as seen from Earth, although the light it “shines” is actually reflected from the Sun. The Moon is so far the only other world in the Solar System that human beings have set foot on.
Formation of the Moon
This diagram shows the sequence of events in the formation of the Moon. Soon after the Earth had formed, 4.5 billion years ago, a planet (1) the size of Mars (sometimes called Theia) collided with it and exploded (2). The impact “splashed” vast amounts of debris into space, surrounding the Earth. Some of the fragments collected in orbit round the Earth, the surface of which was molten due to other, smaller impacts (3). The Earth’s surface later cooled. (4). The orbiting fragments compacted together to form the Moon (5, 6).
Landscape
With neither air nor liquid water, it is impossible for any living thing to exist on the Moon. The totally barren lunar landscape is pitted with craters—about 300,000 of them wider than one kilometre (0.6 mile) on the near side alone—blasted out by asteroids and comets crashing to its surface billions of years ago. Scattered debris has left streaks radiating from some craters. Because there are no winds on the Moon, these streaks have remained ever since. The Moon also has wide, smooth lava plains which early astronomers, without being able to study them through telescopes, mistook for seas. They are still called by the Latin name for sea, mare. Nearly all of these areas of ancient lava flows are found on the near side of the Moon, with only a very few scattered patches on the far side.
Phases of the Moon
The shape of the Moon appears to change from one night to the next. This happens because our view of the sunlit part changes as the Moon orbits the Earth. When it lies roughly between the Sun and the Earth, the face pointed towards us is turned away from the Sun so we cannot see the Moon at all: this is called a New Moon (1). When the Moon lies on the far side of the Sun from us, the whole of the face we see is lit by the Sun: a Full Moon (5). In between, the Moon passes through crescent (2), quarter (3) and gibbous (4) phases, and back again (6–8).
Lunar eclipse
Sometimes, the Moon lies in exactly the same direction as the Sun, and so blots out our view of the Sun completely. This event is called a total solar eclipse. On other occasions, when Earth lies directly between the Sun and the Moon, Earth casts its shadow on the Moon. This is called a lunar eclipse. The Moon turns a rosy colour, giving it the nickname: blood moon. Unlike a solar eclipse, which can only be viewed from a small area, a lunar eclipse may be viewed from anywhere on Earth at night. A solar eclipse lasts for only a few minutes, while a lunar eclipse lasts for a few hours.
Composition
The Moon's internal structure is similar to that of Earth's, although its crust is thicker and not divided into tectonic plates. Beneath the crust there is a rocky mantle. At its centre is an iron-rich core, liquid on the outside, solid on the inside. The core is only about 20% the size of the Moon, compared to about 50% in the case of the Earth's core.
Factfile
Average diameter: 3476 km (2159 miles)
Average distance from Earth: 384,600 km (239,000 miles)
Day: 29.5 days
Surface temperature: -155 to +105°C (-247 to 220°F)
Atmosphere: none
Consultant: Mike Goldsmith