When we make a choice, whether trivial or substantial, it seems to us that the choice makes the difference between two possible futures, and that there was nothing set in stone in advance that determined the outcome. But with the advent of classical mechanics in the seventeenth century it became possible in principle to write down equations that, in conjunction with a complete specification of the initial conditions of the universe, could allow us to predict everything that we will do – every movement we will ever make, every word we will ever speak.
These equations aren’t speculations. They are the first equations students learn in physics courses, the equations that let us calculate the motion of a pendulum and the trajectories of the planets. They are the equations that describe the laws that keep planes in the air and bridges from collapsing under the weight of cars. These equations, tested and confirmed time and again, allow us (in principle) to calculate within measurable precision the movements of every body in the universe, given enough information about its past. There are some corrections to the equations that make a difference at velocities close to the speed of light, and when we look at how things move at a very small scale (a length between ten and twenty times the diameter of a proton), but those corrections are well understood and don’t (except under very rare conditions) make a difference for the movements of things as big and slow as us.
Read Full Article »