
Since the exact location of an electron can not
be known since the electron is constantly in
motion is it possible to tell the direction the
electron is moving? Is that direction known
theoretically or actually?

Question Date: 20120503   Answer 1:
Specifically, the exact momentum (energy) and
the exact position can't be known
simultaneously. Because something in motion will
tend to remain in motion, you can determine the
direction by knowing the momentum. (For example,
if a car has forward momentum, you know it's
moving in the forward direction.) So, you can
calculate the direction of an electron, and you
can measure it, just not with infinite
accuracy.
  Answer 2:
You are asking a question that is related to
Heisenberg's Uncertainty Principle. This
principle states that, if you know one thing
about an electron, you can't know another
thing. So, you can know the position of an
electron, but then you can't know its momentum 
how fast it is going and how heavy it is. Or,
you can know the momentum, but then you can't
know the position. I think this is a principle
of real experiments. I'm reading about it in
Wikipedia, here:
uncertainty principle
You can think about it like this: If you're
using a method to measure Exactly where the
electron is, the measurement is interacting with
the electron in some way, and so you can't know
the exact momentum of the electron. Or, if
you're using a method that measures the momentum
exactly, that measurement is interacting with
the electron in some way, so you can't know
exactly where the electron was when you measured
its momentum.
The wikipedia article gets complicated quite
quickly, so you might want to look for other
information on the subject.
Keep asking questions!
Best wishes,
  Answer 3:
There is something called the Heisenberg
Uncertainty Principle that limits what you can
know about the mass, position, energy, and time
of any particle, no matter what it is. It's
possible to know exactly where an electron is at
any given moment, but you will have no idea of
where it's going or how fast  or you know
precisely what direction it's moving in, but
have no idea where it is. This is due to a
fundamental property of physics at small scales
that is difficult to describe in layman's terms:
particles inhabit a wavelike probability
distribution of energy and position states, and
observing something alters it, so that you don't
know where it will be after you observe it.
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