Friday, March 28, 2008
Epicycles & Electrons, Part III
Truth and utility are different. Consider a tool I learned to use while in the Navy, the maneuvering board, or moboard, pictured here. The way it works is this: you note the distance to another ship and the bearing and mark it with an X. Then, after a set number of minutes, you do it again. With this information, you can determine how close the other ship will come to you. A skilled user can determine maneuvers to increase that distance or to position your ship in some position relative to it. It is also a good way to recognize vessels on a collision course with you, Constant Bearing Decreasing Range, CBDR in Navy parlance, or stationary objects, which will present as having a reciprocal course and equal speed as own ship.
The first assumption of the moboard is that your ship is stationary. Everything moves around your ship. It is a very useful tool, and I bet many captains still require their officers to be competent with it.
Now consider Ptolemy again. Why can’t the Earth be the center of the solar system? We know that the idea of stationary (and simultaneous, btw) is arbitrary. There really is no such thing as stationary. Let’s make our convention that the Earth is the center, the Sun and the Moon revolve around the Earth, as do the planets, although obviously their orbits are distorted by the gravitational pull of the Sun. [FN1] The only reason not to do this is the math would be more complicated. There is no so-called truth about what is stationary and what is moving.
But that’s wrong, isn’t it? Although stationary is a convention, it is more true to describe the Earth as orbiting the Sun and the boat as approaching the buoy. There is a truth, perhaps a relative truth, outside of utility.
[FN1] You cannot make the Earth non-rotating. If the Sun was to be modeled as moving completely around the Earth every 24 hours, there would be forces involved that would have to go unexplained. Also, it’s speed in relation to the Earth would be a problem.