Text: Every type of particle in the universe has a corresponding anti-particle that has the opposite charge. The anti-particle of the negatively charged electron has a positive charge and is called the positron, while the anti-particles of the proton and neutron are the anti-proton and anti-neutron, respectively. The anti-proton has a negative charge (opposite the proton¹s positive charge), and the anti-neutron is neutral, since the opposite charge of a neutral particle (no charge) is also neutral. Predicted in 1928 by physicist Paul Dirac, anti-particles were first detected in 1932. The early universe had nearly equal amounts of matter and antimatter, with just a slight excess of matter‹about one extra particle for every 100 million photons and particle/anti-particle pairs. Because matter and antimatter annihilate one another in a burst of electromagnetic radiation (energy in the form of particles called photons, visible light is a kind of electromagnetic radiation) the universe we see today is dominated by the extra matter that couldn¹t find antimatter with which to annihilate. http://www.pbs.org/wnet/hawking/strange/html/emc2.html

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