| Themes > Science > Physics > Elementary particle physics > An Introduction to Particle Physics > An Introduction to Particle Physics > Big Bang Science |
It is thought that the universe began around 15 billion years ago in the Big Bangand that it has been cooling down and expanding ever since. For physicists, themost interesting time was within the very first moment (within 10^-34 seconds)where the conditions were so extreme that the laws of physics as we know themtoday didn't apply. After about 0.01 seconds, the universe was cold enough for quarks to stick together, forming protons and neutrons. These formed the firsthelium nuclei after 100 seconds, but the first atoms didn't appear for 100,000years. After a few billion years stars began to form, using hydrogen and heliumto build the heavier elements that make up the familiar world around us -elements heavier than helium owe their origin to stars. The Big Bang theory correctly predicts that about 75% of all visible matter ishydrogen and about 25% helium. (All other matter accounts f or less than 1%.)Another great success of the theory is the presence of background microwaveradiation in our universe, a relic of the Big Bang. |
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