The Big Bang Theory

 

The most popular theory of our universe's origin centers on a cosmic cataclysm unmatched in all of history - the Big Bang. The Big Bang Theory is (aside from a long-running TV sitcom) the leading scientific theory of our universe's origin. Scientists believe the entire vastness of the observable universe, including all of its matter and radiation, was compressed into a hot, dense mass just a few millimeters across. This nearly incomprehensible state is theorized to have existed for just a fraction of the first second of time.

Below: artist impression of the Big Bang, image via The Guardian

Then about 13.7 billion years ago, space expanded very quickly - a cosmic cataclysm unmatched in all of history—the Big Bang. Scientists can't be sure exactly how the universe evolved after the big bang. Many believe that as time passed and matter cooled, more diverse kinds of atoms began to form, and they eventually condensed into the stars and galaxies of our present universe.
Below (left) Starburst iron sculpture, from epoca in San Francisco. Circa 1970's.
Below (right) Rare quartz and silvered metal brutalist style illuminating sculpture by Marc D'Haenens, Belgium, circa 1970 - from Milord Antiques.

It was Georges Lemaître, a Belgian priest,  who first noted (in 1927) that an expanding universe could be traced back in time to an originating single point. The idea subsequently received major boosts by Edwin Hubble's observations that galaxies are speeding away from us in all directions, and from the discovery of cosmic microwave radiation by Arno Penzias and Robert Wilson. 
Below: From Henry Saywell, “Vessel”, 2018 by British artist Tom Kemp

The glow of cosmic microwave background radiation, which is found throughout the universe, is thought to be a tangible remnant of leftover light from the big bang. The radiation is akin to that used to transmit TV signals via antennas. But it is the oldest radiation known and may hold many secrets about the universe's earliest moments. 
Below, from Modernism: “Grasswood”, 2012, by Natalie ARNOLDI, oil on canvas