Dark matter is one of the most elusive and puzzling entities in our Universe today. We have plenty of indirect evidence for it, but one of the the “holy grail” questions in physics right now is to figure out exactly what its particle nature truly is.
It ought to exist in a halo around our galaxy, and if it interacts with normal matter at all — even weakly — it should leave a signal that changes slightly over the course of the year. So what to make of the DAMA results, which has seen exactly that for more than a decade now?
Believe it or not, we may have finally explained these results without the need for dark matter at all! Go read the whole thing.