Big Bang Science

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 forquarks 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.
There are many ideas about what dark matter might be, ranging from exotic newparicles to black holes. One idea says that the neutrino,an abundant fundamental particle which is thought to have zero mass, actuallyhas a tiny mass. However, neutrinos generally move about the universe quicklyand are not stuck together in clumps, as they would need to be to explain the rotation of the galaxies. The most recent explanations of dark matter therefore use a combination of "hot" matter, like neutrinos, and "cold" matterlike black holes. The true answer has yet to be found. Underground experimentson dark matter are taking place now.