Does the Mind Affect Quantum Mechanics?
Let's discuss one of the craziest scientific and philosophical questions raised by quantum mechanics. How is it that by simply looking at something, we cause it to change? Does the human mind, through its power to observe, control quantum mechanical systems?
First, the science. A quantum system is in no definite state until you observe or measure it. Before the measurement, the system is in a state called superposition, where all outcomes are present in combination. In lieu of a set location in space, an electron orbiting an atom is actually spread out; some percentage of it exists in one place, and some percentage in another, and another. In fact, there is a minute amount of it everywhere in the universe!
In isolation, the location, energy and momentum of a quantum system has this "slightly everywhere, yet precisely nowhere" nature. However, if you look at it, you'll see a very precise measurement of any of these properties. Your observation forces the quantum system to coalesce and take a stand at some precise value. (This is often referred to as "collapsing the wavefunction.") An orbiting electron is most likely to appear where the highest percentage of it existed before, and less likely to appear where less of it existed before.
This raises some big questions.
Does a human hand or a human mind impart some special energy by contact? Well, no. But what is it about looking at something that changes it? Why does "measurement" become such a mystical activity in quantum mechanics?
The answer illustrates a deep thought about what we do to something when we observe it. How do we see something to begin with? Light does not shoot out of our eyes to illuminate our surroundings as Plato believed. We see an object by observing how it deflects, bends, scatters or otherwise alters the travel of incoming light. Our observation is made possible by the light interacting in some way with the object.
Hold your hand in front of your face. How do you know it's there? Because light shooting towards you from the far side of your fingers is no longer reaching your eyes. The color of the skin you see is the product of some wavelengths of light interacting with your hand and bouncing off while others are instead absorbed.
What about touch? Touch is the repulsion between the electrons in your hand and the thing which you are feeling. Your skin is stopped because electrons have interactions with one another. An unfathomable number of these tiny specks belonging to your fingertip crash into the space of many more specks belonging to something else.
Hearing? Same thing. Audio waves are created and altered by interactions of atoms. Temperature is the amount of energy imparted from one bit of matter to another.
So how does this relate back to quantum mechanics? Every measurement that you can name boils down to an interaction. You poke the quantum system with something (light, a tiny probe, a thermometer, a calorimeter, a laser, etc.) and that something interacts with it. Your probe is altered by the interaction, and you look at this alteration to understand your measurement. Light is deflected, new light comes out, the thermometer level rises, your probe is pushed back.
A quantum system is in a completely uncertain state only when isolated -- i.e., interacting with nothing else. When an outside object comes into its space, the intruder interferes with the quantum system and forces it to collapse from uncertainty down to a definite spot. You can mathematically treat the impinging second system as classical or quantum in nature. Either way, the overlap of the measuring device or the spread out areas of its constituent quantum systems force the quantum system you measure to resolve.
This gives rise to astounding facts. For instance, if you take a picture of an electron, its probability cloud evaporates and leaves it at one exact place. The light that bounced off the electron to hit your camera forced the electron to appear! The resolution to this troubling idea is that if you leave the light off, no photons hit the electron. The watching camera sees nothing, the electron remains ethereal. The electron will still be forced to resolve in a lit place while watched by a camera with its lens cap on.
This is a mechanistic way to rationalize quantum trouble; philosophically, greater problems remain. Why is the position of a quantum system spread out to begin with? Why it is that the Universe is fundamentally uncertain and not deterministic? Physicists usually settle for a practical answer called shut up and calculate: we don't know why, but we can at least learn to predict how.