Einstein's fabulous century

The dance of the stars.

Last Wednesday night, Thanksgiving eve, a beautiful, full, Frost moon filled the evening sky. A luxurious carpet of stars painted a gaudy background, slowly spinning about the North Star. We were witnessing Sir Isaac Newton’s Universal Rule of Gravitation,  which determined the tracks of these myriad celestial objects based on their mutual gravitational attraction. Newton shook up the religious hierarchy in 1686 when he presented an alternative to heavenly marshalling of the skies.

Physics had supplanted the bible with a simple explanation of celestial attraction. And so we thought for well over 200 years.

But then, on November 25, 1915, Albert Einstein demolished classical physics when he presented his General Theory of Relativity, one hundred years ago. This ended our view of a static universe and opened our eyes to the spectacles of quasars, black holes, and the notion that gravity was the result of warped space-time, not a mutually attractive force. And of more practical importance, allowed us to use our GPS smartphones to navigate to the nearest Dunkin Donuts with a high degree of accuracy.

Einstein was not a gifted mathematician and relied on his friends to help him work out the difficult non-Euclidian geometry of his theory. But he was a brilliant thinker and a gifted visualizer, with an intense curiosity about how things worked. As a 16-year-old, he tried to visualize what he would see if pacing a light beam, something his high school peers couldn’t even conceive.

Einstein built his grand theory on two basic propositions:

       1. That the speed of light is constant, and;

       2. That gravity and acceleration are equivalent.

The first is based on the work of James Clerk Maxwell and others, but Einstein generalized the concept. It is very counterintuitive to us, who know that a pitcher throwing a 90 mph fastball from a 60 MPH train will deliver a 150 MPH heater to a catcher beside the tracks. But according to Einstein, a light beam launched from this train will always travel the same speed, regardless of what speed (or direction) the train is traveling.

While this is challenging to wrap our minds around, it is due to the nature of electromagnetic force (EMF) propagation. Light and heat and radio waves, all forms of EMF, traverse space by a process of alternating electric and magnetic fields, which build and alternately create further fields. The rate at which this process occurs is the speed of light, irrespective of the speed of the source. It is as if the pitcher’s fast ball would always be received by the trackside catcher at 90 MPH, regardless of the speed (or direction) of the train.

The second point was anecdotally observed by Einstein when he saw a roofer working far above the street. Imagining if the roofer were to fall, Einstein realized that he would feel no force of gravity (until impact).  It’s as if, standing on the surface of the Earth, we are experiencing a constant acceleration away from her center.

Einstein visualized this as an astronaut standing in a rocket ship at rest. As the ship fired up its engines and gently increased thrust to hover just over the Earth’s surface, the astronaut would continue to experience only her normal weight. The acceleration inside the ship is equivalent to gravity experienced outside – until it accelerates even more to rise, at which point the astronaut would feel heavier.

From all this Einstein made his great discovery – that gravity is not a force, a mutual attraction between objects as Newton posited. But rather, gravity is the result of objects (mass) warping the fabric of space-time itself. Imagine a bowling ball in the center of a suspended rubber sheet. It will cause a depression. An orange launched into that depression will tend to circle the bowling ball, much as the moon circles the earth.

Now let’s put these two ideas together. Assume a rocketship accelerating through space, its speed steadily increasing. A laser beam is pulsed from the bottom to the top of the rocket – but since light travels at a fixed rate and the detector is moving away from where it was when the beam was pulsed, it has further to go and takes a bit more time. We have already shown that acceleration is equivalent to gravity, so the same effect will occur (in reverse) when sending signals from a GPS satellite to the surface of the earth. Without accounting for this Einsteinian time dilation, our GPS positions would be off by six miles or more. Not a good recipe for finding that Dunkin.

Our world seems so familiar. We sit, and stand, with little thought that matter is 99.99% empty and that gravity is only the warping of space. It took the daydreams of a young Austrian schoolboy to reveal the true nature of the universe. Which should be inspiring to all the other daydreamers out there. Feel free to dream; revel in it. Even if you don’t discover the next theory of the universe, you will enjoy your personal journey. That’s reason enough.