We know that red mercury makes the manufacturing of nuclear bombs much, much easier. We don't exactly know how it manages to do this, but that's only because red mercury, as far as we know, doesn't exist.
In the swinging 1970s, the design for nuclear bombs at the time required two explosions. A primary explosion was caused by material that could undergo fission splitting its atoms. That explosion squeezed a secondary material, which underwent fusion, melding its atoms together and causing the actual boom.
Fissionable material is hard to come by; the odd isotope of an element that is prone to fission would have to be strained from many that aren't prone to fusion. The difference between the two isotopes could be nothing more than one neutron, so the process takes years of work with expensive and huge equipment. Red mercury could separate fissionable isotopes quickly and easily.
Or perhaps red mercury just meant you needed a great deal less fissionable material for the primary explosion in the first place. Or perhaps red mercury was an explosive all on its own, and cut out the need for fissionable material. And then there are the people who heard that it was a kind of spray-on material that made the bombs stealthy and guided warheads to their target.
The rumors continue to this day. Some, like the one that claims red mercury was a chemical that acts as both stealth technology and a missile guidance system, aren't given much credence, but others have at least the backing of credible sources. Samuel Cohen, a well-respected scientist who did work on new innovations in nuclear bombs, believed that red mercury was a chemical that, when compressed, produced the explosive force of fissionable material and so eliminated the need for an outer layer on a bomb. Other scientists claim that this is impossible. Perhaps the most credible rumor is the one that takes some of the mystery out of red mercury. It might have been a nickname or a code name for Lithium-6, which helps put a bang into fissionable material. In that case it would just be a new, cooler name, for an already-known substance.
Most intriguingly, there's a rumor that various law enforcement agencies just invented red mercury so they could catch potential terrorists trying to acquire the wonder material. In the early 1990s, ex-Soviet conmen selling red mercury were caught, along with their clients. Technically they were selling red mercury — it was regular mercury dyed with nail polish.
Do you think red mercury exists? And if so, how much are you charging?