Quantum Mechanics (and Schrödinger’s Cat) say We Are!
When I speak of “the neurosciences,” I tell people that our brains are so complex that it takes many different scientific disciplines to even begin to understand it. Then I rattle off the list, usually eliciting knowing looks and nodding heads, until I get to quantum physics.
Meow! How Can a Cat be Alive and Dead at the Same Time?
You may already be familiar with Schrödinger’s famous thought experiment. It has become the standard explanation for superposition – how quantum particles exist in multiple positions at the same time, and why quantum equations cannot predict the exact position, only the probabilities of various positions.
Measuring electrons is sort of like trying to measure a wave on the ocean. While they are in motion they are a wave of energy; the only way to get an exact measurement is to determine a single data point; but of course, the electrons/water never stay in one place, so as soon as you attempt to measure them you change their inherent nature from a curve to a single point. With me so far? This video from TEDEd might do a better job than I’m doing right now in explaining this. Image: scienceabc.com
So back to the cat. Schrödinger imagined (no cats were harmed in the making of this thought experiment) a live cat in a box with a vial of poison and radioactive particle. If a monitor (which is also in this crowded box) detects even a single radioactive particle, it shatters the vial and releases the poison, killing Mr. Whiskers. While the cat remains in the box, quantum mechanics holds that the cat is both alive and dead at the same time, because the cat exists in this cloud of probable outcomes. As soon as we open the box (or measure it), the cat’s wavelength will collapse into a single measured point – and Mr. Whiskers becomes either alive or dead. (Image: wikipedia.com)
This “explanation” is sometimes used to “clarify” Heisenberg’s Uncertainty Principle, which states that the more precisely the position of some particle is determined, the less precisely its momentum can be known, and vice versa.
How Does All This Apply to the Brain?
For starters, we can’t begin to understand a physical object without exploring the fundamental behavior of matter, so understanding physics matters. Quantum physics has very real applications for computer science, which has become a sister science of neuroscience. We use this waveform property of electrons to produce the semiconductors used in computer chips. So, it makes sense to me that exploring quantum physics may yield some understanding of our brains, the most complex object known to humankind.
The Observer Effect
So now we get into the Observer Effect, another concept from quantum physics. It would have been so much simpler if they had simply called it “the measurement effect,” because the concept states that the act of measuring something unavoidably alters it in some way. The “observer,” refers to any act or instrument of measurement – there is no need to have a human observer in the picture. Early observations of the brain required drilling holes into human skulls and extracting bits of brains, performing lobotomies to see how patient behavior changed. Today we use a wide variety of less invasive (but not completely non-invasive) techniques to study the brain. Much like capturing a wave at a moment in time will collapse it into a single data point, fMRI images and other methods of studying the brain can reduce it to a snapshot. But it is only that.
As soon as we turn away, those electrons are back to being themselves – cats who are alive and dead at the same time, trapped inside a diabolical black box.