Photon torpedoes are a standard ship-based weapon armed with an antimatter warhead. The antimatter wave destroys countless parallel universes. When a matter and corresponding antimatter particle meet, they annihilate each other. Experiments to compare the gravitational behavior of matter and antimatter are currently being developed. The biggest limiting factor in the large-scale production of antimatter is the availability of antiprotons. The highest density sources of energy aside from antimatter are fusion and fission. The presence of remaining matter, and absence of detectable remaining antimatter, is called baryon asymmetry. The AMS measures cosmic rays to look for evidence of dark matter and antimatter. Another evil equivalent exists in the Antimatter Universe called Deadeye. These bursts can be explained by the annihilation of matter and antimatter microcomets. The process by which this inequality between matter and antimatter particles developed is called baryogenesis. Antihydrogen is the only type of antimatter atom to have been produced . It is not yet understood why the universe has more matter than antimatter. This resulted in the predominance of matter over antimatter in the present universe. Antihydrogen () is the antimatter counterpart to hydrogen.