You may have noticed there’s been a lot of interest in the moon lately, as people mark the anniversary of the moon landing.
Most of the other planets in our solar system have moons, but they all behave very differently.
Mars’ moons appear to orbit in opposite directions. Deimos rises in the east and sets in the west, like the Sun and the Earth’s moon. But Phobos appears to travel from west to east over roughly a four hour period. This is because it orbits Mars faster than Mars rotates.
Jupiter has over 70 moons. If you want, you can actually view some of the biggest with binoculars or a camera. Apps like Skyview are useful for locating the planet in the sky, and from there you can look for the four Galilean moons.
Our moon completes an orbit around Earth approximately every 28 days. It’s in synchronous rotation, which means that the moon takes about the same time to rotate on its axis as it does to orbit Earth – as a result, we only ever see the same side of the moon, the ‘near’ side. This is actually pretty unusual compared to the other planets. Another odd thing about our moon is that it is relatively large compared to the size of the planet it rotates around – about a quarter of the size.
Our moon has its own gravitational pull – not enough to affect Earth’s orbit, but enough to create Earth’s tides. Try taking note of moon phases and high/low tides – you’ll notice they’re linked.
Finally, here’s a game you can play that looks at gravity and the orbits of different planets.