An Antimatter Bomb

In Dan Browns novel Angels and Demons, villains steal a gram of antimatter from CERN and threaten to blow up Rome. Now we know that when a substance meets antimatter, both masses disappear, turning into radiation strictly according to Einstein's formula: E = mc2. As you can see, there is a monstrous magnitude in this formula — 300,000,000 meters per second, which is the speed of light, squared. This makes antimatter much more powerful than a thermonuclear bomb. Calculations show that the annihilation of that stolen gram of antimatter would be equivalent to 430 kilotons of TNT!