Dark Mystery No. 1: What Is Dark Matter (and Why Is There So Much)? (String Theory)

There appear to be two forms of matter in the universe: visible matter and dark matter. Scientists know dark matter exists because they can detect its gravitational effects, but they can’t currently observe dark matter directly. If extra matter weren’t there to hold galaxies together, the equations of general relativity show that they would fly apart.
Still, no one knows what the dark matter is made of. Some theorize that the dark matter may be stable superpartners of our known particles — perhaps photinos, the superpartner of the photon. String theory contains other ideas, covered in topic 14, that could explain the nature of dark matter.
But the fact is that no one knows for sure, which is disturbing because there is about five times as much dark matter as there is visible matter in the universe. So there should be a lot of it around to study — if only physicists and their scientific theories could see it for what it really is.