How well do you really know the Moon?
You see it almost every night, but the Moon still hides plenty of surprises. Six questions that go beyond the basics, each with a short explanation.
Did you know?
- The Moon's surface area is about 38 million square kilometers — roughly the size of Africa and Australia put together. Yet it is only about 1.2 percent of Earth's mass.
- The Moon has almost no atmosphere, so sounds cannot travel and the sky is black even in daytime. Temperatures swing from about 120°C in sunlight to below −130°C at night.
- A full Moon is not twice as bright as a half Moon — it is about ten times brighter. At full Moon, sunlight strikes the surface head-on, and shadows from rocks and craters almost disappear.
Earth's Moon
The Moon is Earth's only natural satellite and the brightest object in the night sky after the Sun. It is about a quarter of Earth's width, orbits at an average distance of roughly 384,000 kilometers and takes about 27 days to go around Earth. Its influence reaches far beyond its beauty: it shapes our tides, steadies Earth's tilt and has guided calendars and cultures for thousands of years.
Always the same face
The Moon spins once on its axis in the same time it takes to orbit Earth, so the same side always faces us. This is called tidal locking. Small wobbles in its orbit, known as libration, let us see about 59 percent of the surface over time, not just half.
Seas without water
The dark maria formed when lava flooded enormous craters billions of years ago. The brighter highlands are older, heavily cratered crust. Together they create the familiar 'face' that different cultures have seen as a man, a rabbit or other shapes.
Eclipses
A lunar eclipse happens when Earth passes directly between the Sun and the Moon. Because the Moon's orbit is tilted, this does not happen every month. Unlike solar eclipses, lunar eclipses are safe to watch with the naked eye.
Water on the Moon
Some craters near the Moon's poles never receive sunlight, and their floors are among the coldest places in the solar system. Spacecraft have found evidence of water ice there, which future explorers might use for drinking water, oxygen and even rocket fuel.
Exploring the far side
No one saw the far side until 1959, when a Soviet probe photographed it. Because the Moon itself blocks radio signals from Earth, landing there is difficult; the first soft landing on the far side came only in 2019, using a relay satellite to communicate.
A shrinking, quaking world
The Moon has no plate tectonics, but it is not completely still. As its interior slowly cools, it shrinks slightly, creating cliffs called scarps, and seismometers have recorded moonquakes, some lasting several minutes.