The Universe According To Albert Einstein: Relativity
Einstein’s science, and general views on humanity, have profoundly changed the way we see ourselves and the world we live in. He was not faultless, as no human is. He was an absent father and unfaithful husband. He lived in very different times, and — right or wrong from our current standards — we must analyze facts within their cultural context. Einstein epitomizes the intellectual freedom and courageous creativity that, combined with an unbeatable work ethic, defines true genius.
To shake the foundations of knowledge one needs at least two things: to believe deeply in his ideas and to have the courage to go against the established order. In the sciences, to be successful in shaking the foundations of knowledge so as to promote change, one also needs to be right.
When Einstein came into the science scene at the turn of the 20th century, physics was in crisis. The physics developed from Galileo up to 1899 had three pillars: mechanics, electromagnetism and thermodynamics, the study of heat. And the three pillars were on shaky ground, as physicists couldn’t use them to explain a series of phenomena that had been recently discovered in the lab and in the skies. New ideas were badly needed, but not much was coming forth. It was the perfect moment for a trailblazer.
First, there was trouble with light and its propagation. After a debate that lasted for centuries, people were convinced that light was a wave. (The other option, defended by Issac Newton, was that light was made of little bulletlike particles.) That being the case, and as with any other wave, light had to propagate in a material medium. Water waves, for example, travel in water; sound waves in air. Light? Well, for us to see light from distant stars, the medium had to be transparent. It also had to be very light so as not to slow down the orbits of planets. Finally, it had to be very rigid, so as to allow for the propagation of very fast waves: It was well-known by then that light traveled at about 186,000 miles per second in empty space.
What kind of medium could this be? Stumped, the greatest physicists of the 19th century came up with a wild idea: Imagine that all of space is filled with an imponderable medium called the ether. What it was, no one knew. Its sole purpose was to allow light to propagate. With hindsight, we could call it magical stuff. Even as attempts to find it failed, physicists would not let go. The alternative, having light propagating in empty space, sounded even crazier.
Enter Einstein. In 1905, he proposes his special theory of relativity, whereby he singlehandedly destroyed the notions of absolute space and time, and the need for an ether. According to the theory, now one of the greatest success stories in the history of thought, the notions of space as a rigid stage at which things just happen and of time as a steadily flowing river, are just an illusion caused by our myopic view of reality. And it’s all light’s fault.
Space would only be a rigid stage and time would only be a steady river if light could travel from Point A to Point B instantaneously. (That is if light traveled with an infinite speed.) But it doesn’t. Our illusion is corrected once we incorporate the fact that light has a finite speed of propagation, even if it’s so ridiculously high. (In fact, it is its enormous value that makes our illusions so persistent and convincing.) Once the correction is factored into our studies of motion, everything changes. An observer at rest that measures the length of a moving bus will obtain a different result from the passengers in the bus. To her, the moving bus will be shorter. If she also saw a clock attached to the bus, she would notice that the seconds pass slower for it than for the watch on her wrist. Amazed, she would conclude that moving objects shorten in the direction of their motion and that moving clocks tick slower.