I was watching some Science channel this morning. Particularly, I was watching a show about atoms and quantum theories. It was mostly a historical account of how physics has gotten to where it is today.
One of the cool things they talked about was the "Schrodinger's Cat Thought Experiment". I had read about this a few years ago in some cosmology book, maybe one by Brian Greene.
Anyway, it's a really cool thought experiment, so I thought I would share. Due to my laziness, I found a summary of it on some website:
Schrodinger's cat
Schrödinger's cat is a famous illustration of the principle in quantum theory ofsuperposition , proposed by Erwin Schrödinger in 1935. Schrödinger's cat serves to demonstrate the apparent conflict between what quantum theory tells us is true about the nature and behavior of matter on the microscopic level and what we observe to be true about the nature and behavior of matter on the macroscopic level.
Here's Schrödinger's (theoretical) experiment: We place a living cat into a steel chamber, along with a device containing a vial of hydrocyanic acid. There is, in the chamber, a very small amount of a radioactive substance. If even a single atom of the substance decays during the test period, a relay mechanism will trip a hammer, which will, in turn, break the vial and kill the cat. The observer cannot know whether or not an atom of the substance has decayed, and consequently, cannot know whether the vial has been broken, the hydrocyanic acid released, and the cat killed. Since we cannot know, the cat is both dead and alive according to quantum law, in a superposition of states. It is only when we break open the box and learn the condition of the cat that the superposition is lost, and the cat becomes one or the other (dead or alive). This situation is sometimes called quantum indeterminacy or the observer's paradox : the observation or measurement itself affects an outcome, so that the outcome as such does not exist unless the measurement is made. (That is, there is no single outcome unless it is observed.)
We know that superposition actually occurs at the subatomic level, because there are observable effects of interference, in which a single particle is demonstrated to be in multiple locations simultaneously. What that fact implies about the nature of reality on the observable level (cats, for example, as opposed to electrons) is one of the stickiest areas of quantum physics. Schrödinger himself is rumored to have said, later in life, that he wished he had never met that cat.
So, the cat's in the box, but, we don't know if it's dead or alive, so we assume both when the box is closed. Interesting, huh? What do you think?
When you apply the thought experiment above to particles in space, it gets more interesting. Basically, until we look at an atom, its everywhere. It only "somewhere" when we actually try to measure it. Interestingly enough, I can't help but think of all of the metaphysical books I read when I was younger that say that our reality is created by, you guess it... US.
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