Very broadly speaking, the universe is made of three things. About 22% of it holds stuff together. This is called dark matter. Another 74% of it is pushing everything apart; this is dark energy. The last 4% is “everything else” and attends to inconsequential details like galaxies, stars, life, light, and Brad Pitt. While a fair amount is known about the last 4%, due to the successful research program known as “almost all science ever done”, very little is known about the first two.
Now, in a stunning breakthrough, we find the theory that dark matter is made of ghosts. Aside from a couple flaws*, the idea makes sense. After all, dark matter got it’s name because you can’t see it, and you can’t see ghosts either.
However, it seems to me much more likely that dark energy is made of ghosts, since dark energy provides a repulsive force and ghosts are scary.