The Moon is the most familiar object in our night sky and the only world beyond Earth that humans have ever visited. Hanging about 384,000 kilometres away, it is our constant companion, and its influence on our planet runs far deeper than the silvery light it casts on a clear night.
Where the Moon came from
The leading theory is that the Moon was born from violence. Around 4.5 billion years ago, a Mars-sized body is thought to have collided with the young Earth, blasting a huge amount of debris into orbit. Over time this material clumped together to form the Moon. This idea neatly explains why the Moon and Earth share so much in common chemically.
Master of the tides
The Moon’s gravity tugs on Earth’s oceans, creating the rhythmic rise and fall of the tides. As the Earth rotates and the Moon orbits, this gentle pull produces the two high and two low tides most coastlines experience each day. The Moon also helps stabilise the tilt of Earth’s axis, keeping our climate relatively steady over long timescales.
A changing face
The Moon appears to change shape over the course of a month, cycling through its familiar phases. This happens because we see different amounts of its sunlit side as it orbits us. The Moon also rotates at just the right rate to keep the same face turned toward Earth, which is why the far side remained a mystery until spacecraft photographed it.
Returning to the Moon
After the historic Apollo landings of the 1960s and 1970s, human exploration of the Moon paused for decades. Now interest has surged again, with new missions aiming to return astronauts to the surface and, eventually, to establish a lasting presence there. The Moon may yet become a stepping stone to the rest of the Solar System.