If a Tree Falls

If a tree falls in the forest and no one is there to hear it, does it make a sound? Everybody knows that one, but no one is quite sure where it comes from. Some attribute it to George Berkeley who, in his Treatise Concerning The Principles of Human Knowledge (1710), wrote "But, say you, surely there is nothing easier than for me to imagine trees, for instance, in a park, or books existing in a closet, and nobody by to perceive them." He didn't actually ask the question, but he identified the main issue which is about the nature of knowledge and the role played by perception and observation. It's the question I kept asking myself as I read about quantum mechanics, and the so-called problem of observation, which is at the core of its mysteries. So it wasn't too surprising when I read that Albert Einstein has pondered a version of the question when he asked a colleague, "Do you really believe the moon only exists when you look at it?" What scientists want to understand is the nature of reality, which by definition would still be reality, with or without human observation. But in the seminal experiment of atomic and subatomic science, the double slit experiment, the results changed with the 'intervention' of observation. In other words, observation seemed to be inseparable from the results, and in the 100 or so years since the science of quantum mechanics was established, it's been a 'problem' the scientists have attempted to grapple with, or avoid altogether. Why would they avoid it altogether, or alternately, as in the Copenhagen interpretation, come up with an explanation that is really more of a description and not an explanation at all? Because the 'problem of observation' takes scientists uncomfortably into the realm of philosophy.

The scientific answer to the question of a falling tree would start with the understanding that everything is made of atoms. A tree falling in the forest would disturb the atoms of the tree as well as the surrounding atmosphere and make them move faster, producing a number of effects that human being's would perceive as sound (as well as other sensations such as heat, wind, smell etc.) Sound is indistinguishable from hearing, so the only way to confirm if something makes a sound is for a human being to be present. But a falling tree, a scientist would claim, certainly creates effects whether they are observed or not. Radio waves exist, but we do not hear them unless we have a certain kind of device to capture and then process them. It would follow that imperfect measuring equipment would result in an unreliable or imperfect result. For someone who is deaf, a falling tree makes no sound, for example. Our eyes are built to receive only a certain range of colours, but we have developed measuring equipment and techniques to reveal unseen colours, like ultraviolet, that we now know exist. So the more fundamental question seems to be, how can we know what we don't know. And the answer to that is by inference, and as the famed American physicist Richard Feynman used to love talking about, increasingly the imagination, in order to arrive at an hypothesis.

But back to falling trees, and the problem of observation being a factor in determining a result. Because observation on the tiniest scale of atomic and subatomic particles is so difficult, one has to ask if developing the observational tools and techniques to make accurate observations is even realistically possible. Einstein made inferences about space/time and gravity that it took almost 100 years to confirm. For one example, we have highly sensitive clocks that can actually measure the effect of mass on the passage of time at a small scale, confirming Einstein's theory of relativity. But even now the smallest scale we measure is a micron, about 1000th of a millimeter, (although atomic collisions have been measured at 10 to the -18 centimetres.) Pretty small, but nowhere near the atomic level. So when quantum physicists say that an electron is a wave until it is observed and upon observation the wave function 'collapses' and the electron becomes a particle (the Copenhagen interpretation), maybe it's more like trees falling in forests than a statement about the fundamental nature of reality. Maybe it's about perception of reality and not reality itself. Observation does not change or determine the 'actual' result, only what we perceive as the result.