This artist's impression shows the Big Bang at point zero of the primordial universe. The Day Without Yesterday.
According to the leading physicists of the 20th and 21st century, our universe came into existence about 13.8 billion years ago as an infinitesimally small (10−20 times smaller than the diameter of a proton), unimaginably hot (1032 Kelvin) and incredibly dense concentration of pure energy.
Before this event, there was nothing - no-thing, timeless - literally, no space, eventually some quantum fluctuations - yet pretty boring.
But after the incident, the universe had no time to lose. A hundredth of a billionth of a trillionth of a trillionth of a second old, space expanded from subatomic size to the size of a ping-pong ball, almost instantaneously. And never stopped growing. Shortly after, the nucleosynthesis kicks in. During the first ten or twenty minutes in the life of our universe, the light elements hydrogen, helium, and lithium were created. But still, the universe was a pretty dark place for the next 380,000 years. Enough time for ionized atoms of hydrogen and helium to attract electrons, turning them into neutral atoms - which allowed light to travel freely for the very first time (there is a first time for everything). Space was no longer opaque! But it took another few hundred million years for the first shining stars to be born - and that dramatically changed the view of the universe. Let there be light!
Image: kk.
