Most astronomers believe that the universe began in the Big Bang about 14 billion years ago. At that time, the whole universe was in a bubble a thousand times smaller than a dizziness. It’s hotter and denser than anything we can imagine.
Then it suddenly exploded. The universe we know was born. Time, space and matter began to explode. In a matter of seconds, the universe grew from a tiny atom to a large galaxy. And it continued to grow at a fantastic pace. It is expanding today.
As the universe expanded and cooled, energy became particles of matter and counter-meter. These two opposite types of particles basically destroyed each other. But some questions persisted. More stable particles, called protons and neutrons, began to form when the Universe was one second older.
During the next three minutes, the temperature dropped below 1 billion degrees. It was now cool enough for protons and neutrons to come together to form hydrogen and helium nuclei.
300,000 years later, the Universe had cooled to about 3000 degrees. Atomic nuclei could eventually capture electrons to form atoms. The universe was filled with clouds of hydrogen and helium gas.
Planets and stars were born for hundreds of thousands of years. That is why we say that our universe was born with Big Bang.
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