Re: [asa] writing equations - a request

A general response:

All the criticisms of the Chinese launderers' attempt to cut their heating bill have some validity. Whether or not they get to the heart of the matter is another question & depends to a certain extent on whether one is oriented more to theory or practice. The practically oriented point out that there are no point irons or ironing boards, no perfect reflectors, that energy is needed to do whatever it is that irons do when they smooth out wrinkles in real cloth &c. In other problems they would be inclined to argue that there are no weightless ropes or frictionless pulleys, that there is no material which could serve as the lens for Heisenberg's gamma ray microscope, & that no one will ever drive a car powered by a Carnot (pronounced car-no!) engine.

All true. But (the theorists reply) to argue in this way keeps us from getting at the fundamental issues which are involved when those idealizations are introduced - Newton's laws, the uncertainty principle or the laws of thermodynamics.

& speaking of the laws of thermo, yes, what the Chinese laundry comes up against is the 2d law. But if we're satisfied just with citing the 2d law we again don't the fullest insight into the problem.

In geometric optics there is a "brightness theorem" that says that if an image is formed in the same medium as that in which the object is located, & if losses are negligible (N.B.) then the brightness of the image equals the brightness of the object. But geometric optics is only an approximation to wave optics. Light can't really be focussed to a point because of diffraction - one of the things that puts a limit on measurement with the aforementioned gamma ray microscope. & if you trace out the details you find that this is where the 2d law manifests itself.

I really should apologize for playing "Guess what I'm thinking" but hope this hasn't been an entirely useless exercise.

Shalom
George
http://web.raex.com/~gmurphy/

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Received on Fri Jul 21 11:30:14 2006