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I believe GPS works because of extremely small time differences between the satellites. Because of how small the time differences are, it needs to take into account gravity's effect on time. Although gravity warping time seems very far fetched in normal life, there are practical applications that we use every day that would not work if we did not know about it.

I was curious if the same applies to the uncertainty principle. Is there something that I use everyday that wouldn't work if we didn't know about the uncertainty principle? Or is it just crazy quantum mechanics?

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Yes and no. 8-)} –  Keith Thompson Feb 24 '12 at 19:08
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I'm not sure about how the uncertainty principle applies to everyday electronics, but one thing that wouldn't work without it is an electron microscope. Scanning tunneling electron microscopes are used to see things which are too small to observe with light, such as atoms.

The process they use is actually called quantum tunneling. basically, a negative charge is applied to a very fine, conductive tip, and the tip is positioned extremely closely to the surface you want to examine. Since the tip and surface don't actually touch, the charge can't transfer. However, due to the uncertainty principle, we can't really know that precisely zero electrons will transfer to the surface, and in reality there is a small probability that the charge will seemingly defy the laws of physics and "tunnel" across the gap into the surface. The probability that this happens decreases with distance, so the closer a part of the surface (such as an atom) is to the tip, the more electrons will tunnel through to it.

This only happens on a very small scale. It's theoretically possible for a basketball to run into a wall, and instead of bouncing off, tunneling through to the other side. But the more macroscopic an object is, the lower the probability of that happening.

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Note that the scanning tunneling electron microscope is a different critter than the plain old scanning electron microscope. The device you describe is the former. –  dmckee Jul 7 '11 at 14:13
    
@dmckee thank you, I corrected it. –  Carson Myers Jul 7 '11 at 17:52
    
Can a probability of a basketball "tunneling" through a wall ever reach exactly 0? If not, does this mean: The Moon can "tunnel" through the Earth (with insanely small probability)? –  sabiland Feb 27 '12 at 8:46
    
@sabiland Sure. But that probability is so small it's not even worth considering, i.e. it wouldn't happen if you watched it for the lifetime of a thousand universes. –  Carson Myers Feb 27 '12 at 18:59
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The uncertainty principle responsible for the detecting quantum level noise which is used in Hardware random number generators used sometimes for strong data encryption. These devices can generate numbers that are completely unpredictable using the photoelectric effect or other quantum phenomena.

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The Data transfer in the USB flash drives uses the principle of quantum tunneling & hence the uncertainty principle.

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Every electronic device which uses a transistor relies on this effect. –  dmckee Feb 24 '12 at 21:05
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