Experiments at high energy accelerators have found that if you start with equalĪmounts of matter and anti-matter, the interactions between them will cause a slight excess of matter to develop.Eventually matter (which initially was equal to anti-matter) came to dominate over anti-matter.The fundamental question: Why did matter (particles) eventually dominate over anti-matter (anti-particles).Photons now have too little energy to create pairs, soĮlectrons and positrons are no longer in thermal equilibrium.Universe when temperature was 1 billion K Great numbers of electrons and positrons exist in thermal equilibrium.Due to high temperature photons had enough energy to create electron-positron pairs.Very early universe (when temperature was 10 billion K) Light is free to pass through the universe as expansion of the universe changes.We've already discussed the change at about 400,000 years after the Big Bang.Matter and anti-matter can be created in pairs from energy (or electromagnetic radiation)Ĭ 2 = speed of light squared (here just a constant of proportionality)Įlectron + positron (anti-electron) -> energy A type of matter which has the same mass as normal matter, but opposite charge.Particle-antiparticle annihilation (the reverse process) is also possible pair production is the production of matter and anti-matter in pairs.In the early universe, matter and anti-matter were being created equally out of the radiation Today, it appears, dark energy dominates as the matter density has fallen.Time, eventually dominating the universe. The density of matter exceeded the density of radiation for the first The early universe was radiation dominatedĭensity of radiation exceeded density of matter.The radiation from stars and galaxies is much weaker.The radiation in the universe is a small fraction.The remaining quarter is virtually all matter (dark matter and normal matter). About 3/4 of the total mass-energy of the universe is dark energy.Today the Universe appears to be dominated by dark energy
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