Prime meridian (planets)

So, you know how when you draw a picture, you sometimes make a line to divide it in half? That's kind of what the prime meridian is, but for the whole world (or a planet).

The prime meridian is a very important line that goes from the North Pole to the South Pole on Earth, and from one side of a planet to the other on other planets. It helps us figure out where different places are on the planet, kind of like a map.

People decided to use this line as a starting point to measure longitudes, which are like imaginary lines that run from north to south around the world (or planets). So, just like you might say your house is a certain number of blocks east of the main street, people can figure out how far east or west a place is from the prime meridian.

So, the prime meridian is a big imaginary line that helps us figure out where places are on a planet. It's kind of like a starting point so we can figure out how far away other places are from it.