Wednesday, July 11, 2007

Shaken by the first Limit to the reach of Science

kw: book reviews, nonfiction, science, history

The unanswered question lingers yet: When an object's position is measured, thereby disturbing its momentum, or its speed (momentum is mass times velocity) is measured, thereby disturbing its position, did those quantities have very exact values prior to the measurement, or were they uncertain to begin with? This is the biggest question that everyone tries to answer, all without satisfactory success, regarding what we call the "Heisenberg Uncertainty principle."

The development of quantum mechanics, based on experimental results and a growing body of theory that Werner Heisenberg summed up by "his" principle, are traced from the late 19th Century nearly to the present by David Lindley in Uncertainty: Einstein, Heisenberg, Bohr, and the Struggle for the Soul of Science.

Lindley has dug deep to trace the lives of all the players in the physics revolution of the "grand" era of physics from the 1870s through the 1950s, and the remaining conundrums that were only partially addressed by Bohr's formulation called the Copenhagen Convention. Considering Bohr's expertise at obfuscation, it is not surprising that most physicists let him have his way. Few could puzzle out more than a sentence or two of his musings anyway. But many agreed that there was some use to having some way to move smoothly between quantum strangeness for tiny particles and the apparent continuity of measured quantities on larger scales.

Along the way, he traces the migration of the center of scientific ferment from England, then Germany and Denmark, to the U.S. as Germany's primarily Jewish scientific establishment fled the Reich's madness in the 1930s.

The most obvious challenge to the Copenhagen Convention is "Schrödinger's cat" (Given a cat in a sealed box with a poison gas vial that has a 50% chance of being broken open, as controlled by a quantum event such as a radioactive decay during the coming hour. One hour later you open the box to see if the cat is alive or dead. But during that hour, is the cat alive or dead? Without you there to observe, how can it be known?)

The conundrum focuses on the concept of an "observer". The following thoughts are mine. An observation is, or implies, an interaction. Reversing the syllogism (sorry, Aristotle), it can be said that every interaction is an observation. For example, a common demonstration of quantum uncertainty is to shine light through a small hole onto a screen. The smaller the hole, the larger the angle the light beam is scattered through, and the larger the spot on the screen. So answer this: does the spot change size if you are not looking at it? No, because the hole itself is influencing the light.

Further, the quantum mathematics of this diffraction effect tell you that some photons that "ought" to hit the screen somehow go through the hole anyway, and that some photons that are "aimed" at the hole will instead hit the screen.

So the hole is the observer. Furthermore, because the Schrödinger Wave Equation has finite values everywhere (though very, very small most places), every particle interacts with every other particle, all the time, from the creation of any particle until its destruction...and perhaps beyond in either direction.

The whole universe is an interaction. We'll never have the math...

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