for thrust. In reactions between protons and antiprotons, their energy is converted largely into relativistic neutral and charged pions. The neutral pions decay almost immediately (with a lifetime of 85 attoseconds) into high-energy photons, but the charged pions decay more slowly (with a lifetime of 26 nanoseconds) and can be deflected magnetically to produce thrust. Charged pions ultimately decay into a combination of neutrinos (carrying about 22% of the energy of the charged pions) and unstable charged muons (carrying about 78% of the charged pion energy), with the muons then decaying into a combination of electrons, positrons and neutrinos (cf. muon decay; the neutrinos from this decay carry about 2/3 of the energy of the muons, meaning that from the original charged pions, the total fraction of their energy converted to neutrinos by one route or another would be about ). Weapons Antimatter has been considered as a trigger mechanism for nuclear weapons. A major obstacle is the difficulty of producing antimatter in large enough quantities, and there is no evidence that it will ever be feasible. Nonetheless, the U.S. Air Force funded studies of the physics of antimatter in the Cold War, and began considering its possible use in weapons, not just as a trigger, but as the explosive itself. See also References Further reading External links Freeview Video 'Antimatter' by the Vega Science Trust and the BBC/OU CERN Webcasts (RealPlayer required) What is Antimatter? (from the Frequently Asked Questions at the Center for Antimatter–Matter Studies) FAQ from CERN with information about antimatter aimed at the general reader, posted in response to antimatter's fictional portrayal in Angels & Demons Antimatter at Angels and Demons, CERN What is direct CP-violation? Animated illustration of antihydrogen production at CERN from the Exploratorium. Quantum field theory Fictional power sources Articles containing video clips