Let’s take a moment and focus on a thought experiment that many people may have heard about, but possibly don’t really understand: Schrödinger’s cat. The Schrödinger’s cat thought experiment is designed to point out a paradox that exists in previous interpretations of quantum mechanics. Understanding Schrödinger’s cat can be even more difficult since many people don’t really know quantum mechanics.
The best thing about thought experiments is that they’re designed to take extremely complex ideas and illustrate them in a easy to understand way so they’re accessible to a large number of people. A slight problem with the Schrödinger’s cat thought experiment is that the explanations of the experiment are still so damn hard to understand. I mean, just jump over to the Wikipedia entry for Schrödinger’s cat and try to get the gist of the experiment in a quick read through. Unless your brain is predisposed to reading quantum physics gobbledygook, you’ll most likely walk away muttering “huh?”
But the Schrödinger’s cat thought experiment is really cool to think about, quite important, and is actually quite easy to understand. So let’s try to whittle everything down to the basics.
A Oversimplified Way to Look at Quantum Mechanics
Alright, so let’s jump right into laying the foundations for understanding any theory in quantum mechanics! We’ll do it in such a way that would make a quantum physicist shudder, but works perfect for our specific examples today.
We’re all familiar (hopefully!) the the general laws of physics. If you throw a ball into the air it’s going to fall back down to earth. If you swing a bucket of water in circles fast enough, none of the water is going to spill out. These are physical “laws” that apply to everything that we see.
But when you get down to super tiny things, such as atoms, all of those rules change and obey the laws expressed as quantum physics. For one, when exploring quantum mechanics, the state of every particle is described as a wavelength. Which basically means that super tiny particles are always moving all around.
Not only that, but if you try to measure this movement, you get what’s called “wavefunction collapse.” Which means that as soon as you assign a mathematical number to describe these particles, the particle simply becomes the number, rather than the number describing the particle. In essence, once you observe a particle, it stops moving around. If you don’t look at it, the particle is absolutely crazy and going every which way.
The best way to think of this idea in quantum mechanics is to compare it to another thought experiment that we’re all familiar with. I’m sure you’ve been proposed the following question:
If a tree falls in a forest and no one is around to hear it, does it make a sound?
Within the interpretation of quantum mechanics we’re exploring, the answer would be that a tree falling in a forest makes a number of different, crazy sounds. But once someone hears it, the falling tree only makes one sound. The simple act of hearing the tree falling “collapses” the sound into one thing: a crash.
Schrödinger Throws in His Two Cents
The concept of wavefunction collapse sounds pretty good, and explained a lot of the inconsistencies that quantum physicists were finding in their experiments. That is, until a young man by the name of Erwin Schrödinger pops up in 1935. Schrödinger did not buy into the idea that the behavior of particles was effected by the simple act of observation. That would be like all your toys coming to life as soon as you left the room.
So, in order to explain the paradox that he saw, he came up with a thought experiment which we now call Schrödinger’s cat. It goes a little something like this:
You’ve got a solid box that, when closed, is completely opaque. You’ve also got a tiny piece of radioactive substance, a Geiger counter attached to a hammer, and a bottle of poison. The contraption is set up so that if one of the atoms on the radioactive substance decays (which might happen, but there’s an equal chance it won’t), then the hammer smashes the bottle of poison.
Then you drop a cat into the box (the cat can’t interfere with the previous setup) and seal it up. Now simply leave the box alone for an hour.
Now, according to the mathematics describing the wavefunction of the decaying particles, outcome would result in the cat being both alive and dead during the time the box is sealed.
And this, ladies and gentleman, is the paradox that Schrödinger’s cat points out. It’s as easy as that. Obviously a cat can’t be both alive and dead, that just doesn’t make logical sense. As a result, the math describing the wavefunction must be incorrect. By pointing out this flaw, Schrödinger opened the floodgates for a ton of new idea’s and interpretations. In essence, Schrödinger’s cat was the spark that lit the fire of new and even better ideas in the world of quantum mechanics.
The Schrödinger’s cat thought experiment is great, because it connections the quantum world to the physical world and allows us to imagine viewing it with our own two eyes. With a cat’s life in the balance based upon the action of a single atom, we’ve made the invisible visible. And the math just doesn’t compute.
Looking at the Big Picture
In terms of importance within quantum mechanics, the ideas expressed the Schrödinger’s cat thought experiment ranks pretty high. Since it was first proposed by Schrödinger in 1935, a good number of people have built upon the idea with additions and thoughts of their own.
One of the most interesting things about quantum mechanics is the way in which theories and interpretations are conceived. Sure there’s a ton of math and formulas to back up and support ideas, but in the end, the most popular opinion is adopted as the “truth.”
In the end, a thought experiment is nothing more than that: a thought experiment. It’s a hypothetical situation and therefore exists only in the mind. With quantum mechanics, we’re dealing with particles so small that it’s impossible to explore their properties without a potentially fallible intermediary, such as the double split experiment or thought experiments such as Schrödinger’s cat. Both of these experiments rely on the human brain for interpretation, and the mind is not always completely reliable. Scientists are able to perform tests and draw conclusions based on equations, but they’ll all be trumped once the next idea has more “proof” and becomes more popular.
But I digress, Schrödinger’s cat is a great starting point for exploring some of the ideas behind quantum mechanics. It’s one of the most important ideas this century, and has become so famous that it would be a shame not to understand the reference. And if you ever wake up to find yourself in a steel box with a Geiger counter and a hammer held just above a bottle of hydrocyanic acid, you’ll know the context of your know the context of your capture.
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