One of the more fascinating books I’m currently reading is Stephen Hawking’s A Brief History of Time. It’s actually light reading for a theoretical physics book, meaning that he doesn’t lose you at any point, nor does he bore/frustrate his readers with lots of obscure math, so thus far, I’m happy with it.

A quick synopsis of the first chapter: For anyone who wasn’t paying attention in history, the ancient Greeks knew that the world was round - it wasn’t discovered to be so by Christopher Columbus - but according to the Aristotle/Ptolemy model, the earth stood stationary at the center of the universe with eight spheres surrounding it. So you had the earth. and then you had a sphere a little bit bigger than the earth that held both the earth sphere and the moon. and then you had a sphere a little bigger than that that held the earth sphere, the moon sphere and mercury. and as you went further from the earth, you traveled into the spheres of Venus, the sun, Mars, Jupiter, and Saturn, until you got to the final all encompassing sphere which held all other spheres and was where the stars resided.

Copernicus’ Heliocentric Universe
Of Course today, we know that model isn’t accurate. In 1514, Copernicus proposed that the sun was the stationary object and all other objects revolved around it. Galileo and Kepler publicly supported it and eventually contributed to the world accepting that objects could revolve around other objects that weren’t the earth and they followed elliptical paths instead of circular paths.

Newton and Gravity
Enter Newton in 1687 and his law of universal gravitation which said that each body in the universe was attracted towards every other body by a force. That force was stronger when the bodies had greater masses and when they were closer together. Gravity is what causes the moon to orbit the earth and the planets to orbit the sun. That led to Newton’s theory that the stars must be moving because if they remained stationary, eventually they’d fall in on themselves. His method of solving this dilemma was to propose that stars are distributed uniformly over an infinite space. In an infinite universe, every point can be regarded as the center because every point has an infinite number of stars in any direction away from it.

Many people put forth arguments against this infinite universe problem, specifically, if every point was infinite and static, the entire sky, even at night, should be as bright as the sun. Another argument was that the light from distant stars would be dimmed because stars closer to them would absorb the light. This would then make that matter hotter until they glowed as brightly as stars. The only way to avoid the conclusion that the entire sky should be as bright as the sun was to believe that at one point the universe had a beginning.

The Big Bang Theory
And so in 1929, Edwin Hubble proposed the Big Bang theory because in his studies, he observed that galaxies are moving away from each other, or in other words, the universe isn’t static, but expanding. Therefore, there must have been one time when the universe was infinitesimally small and infinitely dense. Time would not exist before the big bang, which was the point in time when the universe started expanding because any event before it would not effect what is currently happening. Therefore time is only relevant from the beginning of the universe onward.

Towards A Unified Theory of Everything
The goal of scientific theory is to come up with one unified theory that explains the entirely of everything. As of now, there are currently two partial theories that seem to be inconsistent with each other. The first is Einstein’s general theory of relativity which works rather well on a larger scale. The second is quantum mechanics, which works rather well on extremely small scales. Physicists are trying to combine the two partial theories into a unified quantum theory of gravity.