Relativity

Is everything relative? And relative to what?

With the beautiful theories and laws of Galileo, Kepler and Newton, the universe relied on a fixed spatial grid, and events were organised on a fixed timeframe. Light was understood to travel through an ether — a medium for electromagnetic waves, and for all matter in the universe. When Albert A. Michelson and Edward W. Morley tried to measure the differences in light speed depending on the direction it was measured, they found none: light always has the same speed! It became the most famous “failed” experiment in physics.

When Einstein found a way to extend classical physics into special relativity in 1905, integrating the light-speed constant, it came as a shock: there is no such thing as a fixed space grid or a fixed timeframe — everything is relative, even the simultaneity of events. So on one hand, light always has the same speed, a universal constant, no matter which reference frame it’s observed from; but on the other hand, the same event does not happen at the same “time” for two observers moving relative to each other at high speed. Reality is shaking…

A few years later, Einstein was able to add gravity into a general theory of relativity, making space-time more and more fuzzy. It is “deformed” by mass, which is equivalent to energy — leading to discoveries such as the presence of mysterious black holes, and, more recently, the need for dark matter and dark energy to explain the movement of cosmic objects and the acceleration of the universe’s expansion.

Let’s take a black hole: at its surface, its “horizon”, time is… stopping. And yet, as demonstrated by Stephen Hawking, energy — or “information” — is still escaping from a black hole, whose destiny is to shrink and be reduced to something we don’t understand. Scientists like Carlo Rovelli propose that a black hole will collapse into a singularity he calls a “white hole”, where time reverses! But trying to merge two contradictory theories — general relativity, where the world is continuous, and quantum physics, where everything comes in pieces — seems like a dead end. Even string theory, which tries to reconcile the two, remains unproven.

All of this feels like an incomplete theory… Or an incomplete set-up by its creator?

Suppose a programmer creates a simulation: it would have limited resources. They would first set up reasonable rules — three dimensions of space, a timeframe, some gravitational laws. Information needs to stay locally limited for the simulation to run, hence the speed-of-light limit. And then it runs, and simulated agents like Newton work out the rules — everything goes well. But because the rules are contradictory, things start to get confused: the simulation creates black holes and inconsistent phenomena, and its human agents get more and more confused trying to uncover the underlying laws.

So let’s hope the creator doesn’t decide to stop the simulation now, and let’s just enjoy the game.

Sources

A Brief History of Time — Stephen Hawking