I'm Not Sure

How much wood would a woodchuck chuck if a woodchuck could chuck wood?

I don't know, but if a scientist tried to answer it, I'm sure there would be a highly precise number, in grams of course. One of the hallmarks of science is the quest for precision and certainty. The ideal experiment starts with a precise set of initial circumstances, from which there flows an inevitable and certain result.

Of course, nature pays little heed to human ideals.

The science of quantum mechanics accurately describes the behavior of the smallest things we can observe. It is the basis of many modern technologies including lasers, medical imaging techniques, and computer components.

Early in the development of quantum mechanics, an unusual fact was deciphered from its mathematical equations. This mathematical relation, called the Uncertainty Principle, has gotten physicists' and philosophers' undergarments in a wad ever since. It's a cosmic wedgie played by the universal prankster.

In essence, the uncertainty principle says that knowing the precise state of anything is impossible; by making the measurement of some property more precise, one automatically makes the measurement of a related property less precise. This is not due to limitations of equipment, but to the very nature of the universe.

Take the lowly electron as an example. The more precisely one measures where it is, the less precisely one can know how fast it's going, and vice versa. In the extreme, if one could measure with absolute precision an electron's location, then it would be impossible for one to know anything at all about its speed. Similarly, the more precisely one knows an electron's energy, the less precisely one can know the time at which it had that energy.

One clue to this strange behavior is that any measurement is an interaction with what is being measured. Looking at something under a microscope involves bouncing light off the object. At the extremely tiny scale of quantum mechanics, even one particle of light changes the state of what's being looked at. The effect of the measuring equipment cannot itself be measured with precision, for the same reasons, meaning that there will always be some uncertainty in measurements.

The uncertainty principle does not make measurement impossible, but simply says that measurement of related properties, even by perfect equipment, will always have a margin of error.

At the level of quantum mechanics, nature is described not in words but in mathematical formulas. Physicists routinely discover equations that accurately explain some observed natural process, without having any idea of what the equation "means" in practical terms.

There is often more than one plausible interpretation for any given equation. Scientists often debate alternative interpretations for decades before reaching a rough consensus on which one is most likely "right" -- and for many equations the debates still rage.

As an example, there is a mathematical equation called the "wave function" that describes what we know about electrons. The wave function describes an electron over a region of space -- quite conflicting with the particle behavior of electrons. One early interpretation was that the wave function described the density of the electron's charge or matter spread through space, but this was later rejected. A more accepted interpretation says that the wave function describes the probability of finding the electron particle at any given point within the region.

In other words, by today's interpretations, quantum mechanics cannot tell us an exact location for a particle, but can only give probabilities for various possibile locations. Scientific predictions boil down to something like, "More than likely, if we look for the electron it will be found near here, but there is always a chance that it will be found somewhere else."

The "uncertainty principle" and the statistical nature of modern science challenge fundamental aspects of science itself.

If every observation affects the system being observed, then separating observer from observed is impossible.

If no measurement can ever be absolutely precise, and science can only make statistical predictions, then experiments are repeatable only to an approximation, and predictions are testable only to an approximation. While a theory can say what will usually happen in most cases, there will be many cases where it is observed in exceptions rather than the rule.

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