system
Given the following post, respond as if you're commenting on Reddit:
human
Is there any dark matter in my room right now?
gpt
**Short answer:** Maybe. It depends what dark matter is.

**Long answer:** *Dark matter* is a bit of a catch all term. It's just meant to describe the bulk of the apparent gravitating mass in the universe which is not luminous. We don't know what it is yet. The evidence is really really good that it exists, we're just not sure what it is. 

Generally, 'dark matter' is used to refer to a presently unidentified kind of matter. For example, some people think that maybe there were just a whooole bunch of black holes floating through space, waaay more than any model for stellar evolution might predict, and since black holes don't give off light they would constitute 'dark matter'. But this isn't a favored answer for a long list of reasons. 

A more popular idea presently is that dark matter is some kind of particle. Aptly called 'particle dark matter.' This kind of dark matter would be a heavy and abundant particle which just doesn't interact with the electromagnetic force, so it doesn't give off light and it doesn't really clump into planets and stars the same way that atoms do. There are a lot of hypothetical candidates with all sorts of fun names, like sterile neutrinos, WIMPs, and axions. 

If one of these hypothetical candidates really is the dark matter, which whizzes around and could be all over the place, then there is probably some passing through your room right now, streaming through the earth like a ghost.