Help and hindrance

We consider how new technology can make it harder to understand new science.

Last week we looked at the telegraph as an instance of digitally-coded communication.  This week we ponder how the physics of the invention pointed to new science, while the actual use made the new science harder to understand.

Throughout the nineteenth century physics was triumphantly Newtonian.  The laws of motion and gravity that Newton had formulated two centuries before seemed to be borne out in every instance where they could be clearly tested.  Indeed, no serious competitors appeared until the very end of the century (when Max Planck introduced the quantum theory); but there were signs of strain before then, if you looked closely enough.

One feature of the Newtonian formulation is that the laws of physics, that is the equations you use to work out what’s going to happen, don’t depend on your velocity.  As long as you’re going in one direction at a constant speed, everything looks the same: you calculate the same force, acceleration and all that.  This is often convenient, allowing you to choose a frame of reference where the numbers are easy to deal with.

But about mid-century Maxwell unified the equations of electricity and magnetism, which describe what’s happening in telegraphs.  They assert, in part, that the magnetic force on a particle depends on its velocity.  In particular, you can choose a frame of reference where there is no magnetic force at all; but it appears in other frames.  In retrospect, this should have been deeply troubling.  It was only resolved in Special Relativity, which Einstein published in 1905.  But the Maxwell equations worked, and supported the network of telegraphs that covered much of the world by the latter half of the 1800s, so there were no loud objections raised.

One point of difference between Newtonian and Relativistic physics is the idea of “now.”  Newton assumes that there is an absolute time, so we can talk about what’s happening everywhere at this particular “now.”  For Einstein, “now” depends on where you are and how fast you’re moving; even in principle you can’t say anything about an event over there until light has had time to get from there to here.  Your knowledge is constrained by the speed of your messenger.

This would not have seemed strange to a pre-telegraphic world.  Sitting in London, although you knew in theory that a “now” situation existed in Bombay (as it was then), you knew you couldn’t know what it was until a message arrived by ship; maybe four or six or eight weeks.  Knowledge being constrained by the speed of the messenger was familiar, if frustrating.

But once the submarine cables were laid and everything was connected, you could know what was happening in India in hardly more time than was required to walk to the next office in Whitehall.  The Newtonian “now” had materialized.

So the physics of the telegraph demanded the abolition of “now,” just when its function had made the idea apparently quite real.  We are savoring the irony of an invention that looks backward and forward at the same time.