Hubble observed that all galaxies outside our Milky Way, moving away from us, and the speed of each of them proportional to the distance from it to us. He immediately realized that this means that when something (as is now about 14 billion years ago), the whole universe was placed in a single point in space. Should be, the universe was born as a result of a grand event, which later became known as "Big Bang". To to develop a viable theory of the universe, astronomers compare mathematical models with observations at the observatory. Mathematical justification of the Big Bang theory involves a general theory of Albert Einstein's relativity and basic science material.

Today, NASA spacecraft such as the Hubble Space Telescope and Spitzer Space Telescope, are continuing to study the laws of the universe's expansion. For a long time the main goal was to to understand the universe will expand forever, or a planet one day stop, turn back, face, and the universe will collapse well in the second "Big Bang." background radiation, if we could see of the universe after a second after the Big Bang, we would see a sea of neutrons, protons, electrons, positrons, photons and neutrinos – the total temperature of 10 billion degrees. Then, after some time, the universe would cooled, neutrinos or would have become protons and electrons, or would connect with protons to form deuterium (an isotope of hydrogen). Cooling down, the universe would have reached a temperature at which the electrons would be connected with the nuclei and atom is formed.