Moto perpetuo

It occurs to me that unbreakable copy protection is the perpetual motion of our day.

Back at the beginnings of the industrial revolution, when inventions like the steam engine and electrical generator were making new and mysterious things possible and were not widely understood, people were constantly coming up with perpetual motion schemes. And why not? If you can generate more power than hundreds of strong men and horses can produce just by burning coal, and transmit that power miles and miles away with simple metal wires, is it so implausible that some arrangement of magnets and overbalanced wheels could generate endless power from nothing?

Eventually, in the early 1800s, after commercial steam power had been around for about a century, the principle of conservation of energy came to be widely accepted and by the the middle of the century the familiar laws of thermodynamics were established, including the crucial first two:

1. You can't win (conservation of energy).
2. You can't break even (entropy increases in a closed system).

These two principles explain why perpetual motion schemes don't work. That hasn't stopped people from coming up with them, but it has stopped knowledgeable engineers and scientists from wasting time on them. It hasn't completely stopped investors from investing in them, but the long and sorry track record of such schemes probably has been a deterrent.

Why do people still bother, then? Because if it were possible, large-scale perpetual motion would do away with energy shortages forever. It woudn't necessarily make any money, infinite supply implying zero price, and an energy surplus would have drawbacks of its own, but we could probably deal with those problems when they came up. The point is that people try to prove that perpetual motion is possible because they really, really want it to be.

Anyone in the business of selling information would really, really like to be able to control the propagation of that information. You do the math.

I don't know of any specific principle of information theory that explains why this will never work, but there's a growing body of empirical evidence to that effect. Intuitively, copying bits costs much less than the price sellers would like to charge, so the protection has to come in the conversion of those bits into usable form. That runs you right in to the analog reconversion problem, of which "camming" (sneaking cameras into movie theaters) is a crude but effective example.

Clearly none of this is currently stopping people from trying to come up with copy protection schemes, or people from paying for them. The track record probably isn't quite long or sorry enough yet. I suspect it eventually will be.

Fortunately, selling bits and making them impossible to copy are two different things.

Postgraduate physics and the web

At the end of my previous post I implied that while computers and the web can be useful in learning basic physics, they're not essential. After all, the great physicists of history did very well with out them. This is all true as far as it goes, but it leaves out an important part of the picture. While classical physics is largely accessible to any careful observer with a good grounding in math, modern physics is pretty much impossible without heavy machinery.

You may or may not need billions of dollars worth of equipment to produce the results you're after, but the odds are very good you'll need a computer to sort them out. And since your collaborators might well be at other facilities far away, you'll probably want a good email connection. In fact, these days, there's all kinds of information out there, scattered all over the place. Maybe one of the major facilities should come up with a way of pulling it all together and making it accessible to the world.

Oh wait. They did.

Undergraduate physics on the web

Last month, give or take, I ran across a page of links to applets designed to demonstrate various principles of physics. The demo has long (probably always) been a staple of physics classes. I vividly remember a couple. In one, interfering laser beams were progressively filtered down to the point the detector could register individual photons landing left or right.

But the one I really remember involved the lecturer, an iron ball and a chain. The ball hung from the chain, which was anchored far up at the ceiling, centered left-to-right. At rest, the ball hung at maybe waist height. The lecturer carefully brought the ball toward the left, until it was at head height, and placed it directly against his nose. He then let go, noting that it was very important to hold completely still and not to give the ball an extra push. The ball swung slowly to the right, then back to the left. Conservation of energy being what it is, and some small amount having been dissipated by friction, the ball returned just short of its original position, to the relief of all concerned.

I doubt there's anything quite so memorable on the page I mentioned, though to be fair I've only chased a small portion of the links. As is typical with such collections, some of the links are broken, some of the apps don't work and many are a bit on the clunky side. Nonetheless, it's really great to be able to google around a bit and see a virtual demonstration with moving parts that illustrates a given principle much more effectively than mere text. This is the kind of thing that simply wasn't available to the general public a generation ago, or available at all two generations ago, and so one of the many small ways in which the web makes life just that bit better.

On the other hand, the actual physical world has always been available to all, and careful observation has always been repaid in understanding. It worked for Newton and Gallileo, so there must be something to it ...