FEd April 1999 Newsletter - Balazs letter

April 1999



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To the Editor:

In the Fall 1998 Forum on Education Newsletter, Kenneth Heller views teaching as transforming students from their initial states to desirable final states, with some of the latter "forbidden" e.g. by energy conservation. However, "forbidden" perpetual-motion machines (PMMs) can be pedagogically helpful for understanding the "allowed" laws of physics. So can hypothetical physically-valid schemes which resemble PMMs. Their study, which may also involve many other useful concepts and techniques, could become interesting introductory-course team projects integrating science and engineering, as recently called for by many engineering deans and the National Accreditation Board for Engineering and Technology (ABET); see, e.g. the Forum on Education 1998 Summer and Spring issues.

In one example, which was actually denounced as a PMM by a Mechanical- Engineering Professor with a Ph.D. in Physics, packets of lunar material would first be "slung" electromagnetically from the moon towards earth. Their original launch kinetic energy would then be amplified gravitationally by a factor of about twenty on reaching the "edge" of the earth's atmosphere. Here their homed-in controlled horizontal multiple "impacts" with initially-slow spacecraft and orbiting generators could convert part of their kinetic energy into usable craft propulsion and electrical energy. Damaging accelerations can be prevented e.g. by pre-expanding the packets to low density, and attaching delicate payloads to the craft by long rotating tethers perpendicular to the impulse at impact. A fraction of the electrical energy could then be sent back to the moon by microwave beam, there to launch additional material and repeat the cycle, seemingly perpetually.

Eventually, of course, the moon would shrink, preserving thereby the laws of physics. But this would take hundreds of millions of years at present global energy-consumption rates.

Louis A. P. Balazs
Department of Physics
Purdue University
West Lafayette, IN 47907-1396