Origin of the Universe: The Big Bang
It is easier to believe that there was nothing before there was something than that there was something before there was nothing.”― Julian Huxley
Complexity is difficult for our brains to comprehend and rationalise. We try to simplify complex concepts by relating them to something simpler, but the cosmos is not so simple.
Once upon a time, our Milky Way Galaxy was supposed to contain the whole known universe. But our universe now contains billions of galaxies, and its origins may be traced all the way back to the Big Bang.
The Origin of the Universe: The Big Bang
Since the early 1900s, one hypothesis for the universe's origin and fate, the Big Bang theory, has dominated the debate. The Big Bang - an explosion of space itself - was the beginning of our cosmos. Space expanded, the cosmos cooled, and the simplest elements created, starting from extraordinarily high density and temperature. Gravity brought materials together throughout time to make the earliest stars, then stars died in an explosion called Supernova, but their chemical leftovers gave birth to new generations of stars and allowed the formation of rocky planets. Life evolved to consciousness on at least one of these planets.
How Lumpy Do You Like Your Universe?
The Big Bang model, on the other hand, is not universally accepted. The hypothesis has a flaw in that it promises a smooth universe. That is, on a broad scale, the distribution of matter should be essentially the same everywhere. There should be no excessive lumpiness in the universe.
However, in 2001, scientists announced the discovery of a cluster of galaxies and quasars that spans over 125 million cubic light-years and is currently the universe's largest structure. The universe appears to have large empty gaps punctuated by tightly packed streaks of matter, rather than a uniform distribution of matter.
Proponents of the Big Bang theory insist that their idea is not flawed. They claim that stuff is attracted to clumps by gravity from massive, undetected objects in space (clouds of cold, dark matter that can't be seen with telescopes, or so-called cosmic strings). Other astronomers, who are still hesitant to believe in invisible things in order to address an incomprehensible problem, continue to cast doubt on basic components of the Big Bang theory.
Despite its flaws, most astronomers still believe the Big Bang to be the best theory we have.
The End of the Universe
Will the universe keep expanding indefinitely? Will it simply come to a halt or maybe begin to contract? The answer is determined by the amount of mass in the cosmos. If the mass of the cosmos exceeds a critical threshold, gravity should eventually prevent everything from flying away from everything else.
The cosmos will someday succumb to gravity's tremendous force and collapse back into a single point if there is enough mass—a notion known as the Big Crunch. However, if there isn't enough mass in the cosmos, it will continue to expand. In 2001, many scientists came to the conclusion that the latter option was the most likely.
In 1998, scientists discovered an even more perplexing puzzle: the cosmos appears to be speeding up as it expands, as if dragged by some sort of "antigravity" force. Other astronomers have now used a number of approaches to validate this conclusion, effectively confirming the presence of this enigmatic "dark energy."