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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! |