* Comets vary greatly in size. Some are only a few miles across, while others can be tens of miles wide.

* The Moon is about 2,159 miles in diameter.

So, some comets are bigger than the moon, while others are much smaller.

It's important to remember that comets also have a coma, which is a cloud of gas and dust that surrounds the nucleus. This coma can be much larger than the nucleus itself, but it's not solid matter.

Here's a good way to think about it:

* The nucleus of a comet is like the solid rock of the comet.

* The coma is like the atmosphere around the nucleus.

So, while a comet's coma might be larger than the Moon, the solid nucleus is usually much smaller.