Question: how does an eclipse happen

Mark Kennedy answered on 15 Nov 2016:

First of all, let me say this. Eclipses are awesome! And the main reason they’re awesome is because we’re not sure if any other planet gets eclipses like we do!

So the moon takes 28 days to orbit the Earth (which means, for 14 days a month, the moon is in between us and the Sun). Now, most of the time, when the moon is inbetween the Earth and the Sun, it doesn’t actually pass infront of the Sun – it moves above or below it.

But, every now and again, the moon will move in front of the Sun. And (and this is by pure luck) the size of the moon in the sky is just about the same as the size of the Sun in the sky, meaning the moon blocks out the whole disk of the Sun! I cannot stress enough how lucky we are that this is true!

If you were on Mars, and Phobos (which is one of the moons of mars) passed in front of the Sun, you wouldn’t get an eclipse like you would here on Earth, because the size of Phobos in the night sky is very different to the size of the Sun. And, as far as we know, no other planet in our solar system has eclipses like we do (maybe some exoplanets do, but we’re not 100%).

So the next time you see a solar eclipse, which in Ireland will be in 2021, remember – you’re looking at an event that may genuinely be unique to Earth!