Originally posted by FabianFnas
As I see it (but I can very well be wrong on this) dark matter is everything with mass you don't see, like ordinary matter with protons and neutrons and electrons and stuff, but cold and dark. And exotic matter made up of particles that we don't know much about, like funny combinations of quarks or something made up from something unknown.
Dark matter isn't just matter that we don't see, its matter that we don't understand. For example, we generally can't see planets in other galaxies, but we can nevertheless estimate how many should be there, and what mass they are, and thus they are not
Basically we look at a galaxy, work out how much matter we think it should have based on observation and our knowledge of galaxies, then, the difference between that, and the observed gravitational attraction of that galaxy must be contributed by something as yet unknown. That unknown is the 'dark matter'.
Whereas dark energy is something completely different, like strange fields of some strange energy, with some strange properties, that interact with normal space and matter in a strange way that distorts our understanding of cosmos in large.
The concept of dark energy is the same as that of dark matter ie we have reason to think there is more energy out there, but we haven't identified what it is or where it is.
So should we discuss dark matter and dark energy in the same debate?
I don't see why not. The actual phenomena may be totally unrelated, but they still fall under the heading 'not yet fully understood large scale physics'.