Save Schrödinger’s cat – dead or alive!
I’ve always had a problem with Schrödinger’s cat. Not his actual cat, you understand (as I never met it), but his thought experiment designed to highlight the flaws of the Copenhagen interpretation of quantum mechanics. Hold on, don’t panic! There’s no reason to reach for that ‘close browser tab’-button. It’s only a little bit of quantum physics. Just like grammar is the basis of language, quantum mechanics is the basis of the universe. What’s that? You rather read about grammar instead? Why, of course; go right ahead! The Lucy’s football post is a really good one, I’ll wait for you here.
You back? Good. Anyway, I’m sure you’re already familiar with the Schrödinger’s cat paradox, but let me just recap to show off my own (limited) knowledge in quantum theory:
A cat is placed in a sealed box together with a minute amount of radioactive matter. A Geiger-meter in the box will detect if any of the radioactive atoms decay and emit radiation. The Geiger-meter is connected to a relay that will release a hammer crushing a vial containing poisonous cyanide gas. According to the Copenhagen interpretation, the likelihood of an atom actually decaying and triggering the hammer is represented by a probability waveform, and until and external observer open the box and look inside, the cat will exist in both states simultaneously – i.e. it’s both dead and alive at the same time.
Obviously, no physicists ever conducted such an experiment. They tend to leave such cruelty to us biologists. But the point here is the dual state of the whole system prior to observation: Since we haven’t observed the Geiger-meter, the atom hasn’t collapsed to a state of decayed/not-decayed yet. There seem to be some kind of ‘magical’ connection between the state of a quantum system and whether we observe it or not. If this sounds absurd, it’s because it really is, but it has been proved countless of times experimentally. Here’s an (only slightly condescending) animated video illustrating just such an experiment:
But back to my problem with Schrödinger’s cat. The idea that the cat would just sit in the box perfectly happy with being both dead and alive is obviously absurd. The cat would naturally observe first hand if the vial was crushed by the hammer (by hearing the glass of the vial being smashed, if nothing else), and would therefore collapse the quantum system to one of its probable outcomes. So, regardless of us opening the box to observe the outcome or not, the system has already collapsed and the cat is already dead or alive.
This whole magical power of the observer is all down to the concept of entanglement, and it relates to coupling systems together. By observing a quantum system, we connect our observing apparatus to it. The observing apparatus contains billions upon billions of quantum particles/waveforms, and the probability of one of them spontaneously collapsing is very high. This will trigger a chain reaction and force all other connected particles to collapse as well, including the coupled quantum system we’re trying to observe. So, by observing a quantum system we inadvertently couple it to our – already collapsed – macro-system, and forces it to collapse.
This is also the explanation for why the world doesn’t behave in that weird quantum way, but in the familiar way we’re used to, i.e. if you drop a ball you expect it to end up on the floor, not to become suspended in a probability wave until we actually observe what happened.
So, collapsing probability waveforms into particles has got nothing to do with whether we observe them or not. It’s by coupling them to a much larger system that entangle them to the already collapsed part of the universe that forces them to collapse. See? No magic. Just probability. Isn’t science awesome?