Most of the mass of the universe (around 95%) doesn't seem to be normal matter. It seems to be some stuff that doesn't interact with normal matter much other th

Most of the mass of the universe (around 95%) doesn't seem to be normal matter. It seems to be some stuff that doesn't interact with normal matter much other than through gravity, and this stuff is called Dark Matter. Now with regular old matter, we don't just have a ton of one type of particle; we have a whole bunch of them all interacting in different ways. This is called the Standard Model. So why should it be different for Dark Matter? What if there are just as many "dark" particles as there are "normal" ones? Then there might be a thing that's like a photon for regular matter, so lets call it a "dark photon". What would its properties be? Is there any way we could detect it? That's what they're after in the article. Personally, I think it's the answer to the Fermi Paradox: as soon as an alien civilization gets advanced enough, it converts itself into Dark Matter where there's much more interesting stuff going on. Cities the size of galaxies that we don't even notice!