Origin of the Universe

The Big Bang model principally states that the portion of the Universe that we can see today once was infinitesimally small. The four principal forces – gravitation, electromagnetism, the weak force and the strong force – were bound together. About 13.7 billion years ago, a violent event started and within a fraction of a second, the four forces became distinct and the Universe expanded by many hundred billion times. This was the start of the Big Bang, the birth of the Universe.

The temperature rose to an unimaginable level. Photons were emitted and under the extreme temperature and pressure were compressed to protons, neutrons and electrons, the building blocks of atoms. All this happened in the first second. Then the temperature dropped, in the first second from a trillion degrees to ten billion degrees.

Three minutes later, the temperature had fallen to a billion degrees, at which time protons and neutrons were pressed into the first atomic nuclei. But the Universe was still just a soup of extremely hot elementary particles.

The temperature continued to drop. After 300,000 years, it fell to 3000 degrees. Then free electrons and nuclei combined to form the first hydrogen and helium atoms. And the Universe became transparent.

The Universe has expanded rapidly since the Big Bang. Recently, scientists have found that the Universe is expanding aster and faster. From a small point in nothing, the Universe has become enormous, and perhaps infinite.