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Big Bang

A diagram showing the Universe expanding during the Big Bang, and the creation of galaxiesScientists believe that the Universe began life in a single momentous event. This was an incredibly hot, dense explosion called the Big Bang, which took place about 13.7 billion years ago. It is hard to imagine that before the Big Bang, no matter or energy existed. There was no such thing as time. During this explosion, all matter, energy, space—even time itself—were created in an instant. It is said that in the first trillion-trillion-trillionth of a second of its existence, the Universe grew one hundred million times in size. It has continued to expand at an incredible rate ever since.



A history of the Universe, showing the formation of atoms, matter, stars and galaxies after the Big Bang, featured at the bottom...Read More >>A history of the Universe, showing the formation of atoms, matter, stars and galaxies after the Big Bang, featured at the bottom of the diagram. The figures give the number of years following the Big Bang.

Universe timeline

  • Millionths of a second old The first subatomic particles form.
  • One second old Protons and neutrons, the subatomic particles that form the nuclei of atoms, start to form.
  • Three minutes old The temperature drops below 1 billion °C. Protons and neutrons come together to form the nuclei of hydrogen and helium atoms.
  • 300,000 years old The first atoms, those of hydrogen and helium, are formed when atomic nuclei finally "capture" electrons.
  • 500 million years old The first galaxies and stars are formed.
  • 4 billion years old The Milky Way Galaxy starts to form.
  • 9 billion years old The Solar System comes into existence.


Formation of matter

The amount of energy actually used at the Big Bang was tiny. If converted to matter it would be the equivalent of a bag of sugar.

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