Dec 23, 2013

Einstein's Amplifier

In 1905, Albert Einstein published the groundbreaking paper with the simple relationship: “If a body emits the energy L in the form of radiation, its mass decreases by L/V2.” That rearranges to L = mV2. Eventually we came to call energy E instead of L and the particular velocity of light, V, we now call c. E = mc2. In addition to his full-time job as a patent clerk, he cranked out six more papers in 1906 and ten more in 1907. And in his spare time in 1907, he developed an amplifier with his friends, Conrad and Paul Habicht.

The goal was to develop an instrument to study small electrical fluctuations. He thought it might be useful for experiments with his predictions concerning the equivalence of mass and energy. The concept for the amplifier was electro-mechanical. Two strips of metal acting as capacitor plates would move by each other, one inducing an opposite charge on the other. A series of strips would induce the charge ten times and then transfer to another disc. The process would be repeated until the miniscule charge (realistically, half a millivolt) was large enough to be measurable. Not an amplifier as we know it today, but an electrostatic potential multiplier.

Prototypes were built, tested and refined – mostly with Einstein’s encouragement but not too much involvement. It was called the little machine, Maschinchen. “I am astounded at the lightning speed with which you built the Maschinchen,” Einstein wrote in a letter to the Habichts. By November of 1908 it worked acceptably well. In December of 1911 it was demonstrated at the Berlin Physical Society. Your recollection is correct; the electrostatic potential multiplier was not successful. Paul Habicht built and sold a few – you can see one in the Physical Institute of the University of Tübingen.

It’s quite a stretch to say that Einstein could have been an analog engineer. He wasn’t a builder; he didn’t physically take things apart to see how they worked. He was a much better theorist. His experiments were thought experiments. But for a time, he put some thought towards engineering. The Habichts were the engineers in this story. And with persistence, they made it work. But the market went with a better solution.


“Einstein, His Life and Universe”, Walter Isaacson, 2007

“The Maschinchen”, Hans-Josef Küpper
Illustration: Dr. Torsten Hehl, Tübingen

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