what is meanby big bang
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The Big Bang
The simplest way to explain the Big Bang Theory-- it says the universe as we know it started with a small singularity, then inflated over the next 13.8 billion years to the cosmos that we know today. The big bang is how astronomers explain the way the universe began. It is the idea that the universe began as just a single point, then expanded and stretched to grow as large as it is right now (and it could still be stretching). In 1927, an astronomer named Georges Lemaître propounded the theory of the Big Bang. He said that a very long time ago, the universe started as just a single point. He said the universe stretched and expanded to get as big as it is now, and that it could keep on stretching.
This theory explains how our universe began. About 14 billion years ago, all the matter that makes up the universe was squashed into an incredibly small space. Because the matter was so condensed, it wasn’t in any form we would recognize today. No atoms, or even particles. Suddenly, though, that matter went through a rapid inflation — an explosion, in a way. That’s the Big Bang. The result was a super-hot mass of matter, including light and charged particles such as protons and electrons. The matter cooled slowly over billions of years. As it cooled, it formed elements such as hydrogen. The matter also began to clump together into stars and planets. At the same time, the universe kept on cooling and expanding. In fact, the universe is still cooling and expanding today.
The Big Bang theory represents cosmologists' best attempts to reconstruct the 14 billion year story of the universe based on the sliver of existence visible today.
The Big Bang can also refer to the birth of the observable universe itself — the moment something changed, kickstarting the events that led to today. Cosmologists have argued for decades about the details of that fraction of a second, and the discussion continues today.
