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Essays from Our Physical World.
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Quantum Mechanics, Heisenberg Uncertainty and Free Will

Milton contends that God knew that man would sin, but He couldn’t intervene because that would be a violation of Adam and Eve’s free will.  America was founded on the principles of free will.  There’s a movie out, it’s called Free Willy.  But let me tell you about a few electrons I know and free will.  People testing back in the day got it in their heads they replicate the big screen in the microcosmic world.  Those 1920s scientists hadn’t a clue.  They tried measuring electrons with electromagnetic radiation – can you say zing! – those electrons were out of there.  Then Heisenberg and his buddies came along with their probability calculations, using equations to predict regions of space where these electrons were most likely to be found.  Probability clouds, they called it.  They didn’t stop there though; showed that a probability cloud is a special case of a more general concept, the uncertainty principle.  
Because of its wave properties, an electron in an atom can have only particular quantities of energy.  Quantum mechanics, so to speak.  In a quantum model, an electron’s wave and its probability cloud are basically aligned.  Restraining the urge to watch one electron in one place about the nucleus, the equations of quantum mechanics specify regions of space where an electron having a certain amount of energy is most likely to be found.  This is the region in which electrons orbit: an atomic orbital.  Usually, orbits are drawn to show where the electron is located ninety percent of the time.  This gives the orbital an imaginary border.  The border is arbitrary, however, for the electron may exist on either side of it.  It has a will of it’s own, I tell you.
Heisenberg showed that the more you know about an electron’s momentum, the less you can know about it’s position.  Likewise, the more you know about its energy, the less you can know when it has that energy.  That is to say, the higher accuracy you get for a particle's velocity, the less the accuracy you will get for its momentum. The more certain you are of one value, the more uncertain you are of the other.  So, you view the distinct levels of energy for an electron as the electron’s probable locations rather than exact locations.  Now that’s free will. 
I won’t kid you, the uncertainty principle is a great achievement of the human mind.  It has permanently quivered the grounds of particle physics.  The uncertainty principle is not something you notice in everyday life, like free will in the constitution – nothing quite as overt.  For example, you can weigh an automobile to find its mass, and since all automobiles have speedometers, you can calculate the momentum.  But doing so will not make the position of the car suddenly become hazy, especially if you’re inside it. So measuring the momentum of the car seems to produce no uncertainty in the car's position.  The reason you don't notice the uncertainty principle in everyday life is because of the size of Planck's constant. It's very small.  Free will, free will!