![]() Electromagnetic Radiation and the Ratio of Matter to Antimatterīy this point, the antimatter was gone, and a little matter remained. We don’t know why the early universe had a bit more matter than antimatter, but it’s a very good thing for us that it did. All the matter in the universe today-the stars, galaxies, planets, and so on-is made of the one part in a billion of matter particles left over after the antimatter was gone. Most of the original matter was gone, too, annihilated in the collisions that eliminated all the antimatter.īut there were still those one-in-a-billion particles of matter left over, with nothing to annihilate them. For every billion antiquarks and positrons, there were a billion and one quarks and electrons.īy a few seconds after the big bang, all the antiquarks and positrons were gone, and their energy had been converted to radiation. (Image: betibup33/Shutterstock)Īfter all the annihilation was done, why was there still matter? Because, before the annihilation, the early universe had slightly more matter than antimatter. The Matter in the Universe TodayĪ few seconds after the big bang, all the antiquarks and positrons were gone, and their energy had been converted to radiation. ![]() From that moment on, the observable universe has had matter, but essentially no antimatter. The positrons and electrons remained in equilibrium-with equal rates of creation and destruction-for most of the first second.īy one second, however, annihilation had begun to overtake creation even for the positrons and electrons, and by three to 10 seconds later, the positrons were gone. After roughly a tenth of a second, all of the antiprotons and antineutrons were gone. This happened first with the protons and neutrons because they are heavier and thus harder to produce than electrons and positrons. The equilibrium was broken, and annihilations began to outpace creation events. As the temperature decreased, the radiation became less intense, and creation of matter-antimatter particle pairs became less likely. However, everything in the early universe was subject to the effects of expansion and cooling. #Matter vs antimatter series#This article comes directly from content in the video series The Big Bang and Beyond: Exploring the Early Universe. The annihilation and creation processes were in equilibrium, meaning the rate at which matter and antimatter was destroyed was equal to the rate at which it was created, so the amounts of matter and antimatter remained constant. But, at the same time, that intense radiation was constantly creating new matter and antimatter. Of course, the matter and antimatter were constantly annihilating, creating high-energy radiation. So, a hundred thousandth of a second after the big bang, the universe contained protons, antiprotons, neutrons, antineutrons, electrons, and positrons. At the same time that quarks combined into protons and neutrons, antiquarks combined into antiprotons and antineutrons. When the universe was initially filled with a dense collection of elementary particles, those particles included almost identical amounts of matter and antimatter. But once we produce antimatter, it only stays around for a fraction of a second before finding its matter counterpart and annihilating. A PET scan, which stands for Positron Emission Tomography, uses antimatter to scan for activity in different regions of the brain. We produce antimatter all the time in laboratories, and even in hospitals. In the reverse process, if you concentrate high-energy radiation in a small enough region, the energy of that radiation can create a particle-antiparticle pair, such as an electron and positron or a quark and antiquark. That’s because when a particle collides with its own antiparticle, the two can annihilate and release their energy, usually in the form of electromagnetic radiation. We don’t see naturally occurring antimatter around us. Collectively, these antiparticles are called antimatter. For example, electrons have negative charge, and their antiparticles, called positrons, have positive charge. ![]() Most particles have corresponding antiparticles with the same mass but opposite charge. (Image: FlashMovie/Shutterstock) Antiparticles Why? When a particle collides with its own antiparticle, the two can annihilate and release their energy, usually in the form of electromagnetic radiation. However, after the formation of protons and neutrons, the next big change wasn’t about particles combining, instead particles were being destroyed. ![]() By Gary Felder, Smith College A hundred thousandth of a second after the big bang, the universe contained protons, antiprotons, neutrons, antineutrons, electrons, and positrons. ![]()
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