The Heisenberg uncertainty principle
is a statement about the way quantum objects, such as atoms and the smaller
particles inside atoms, behave. It was developed in i927 by Werner Heisenberg,
and so bears his name. The principle states that we can never know exactly
where an electron, say, is located, while at the same time knowing exactly how fast
it is moving. Either property-its speed or position -can be measured to
infinite accuracy in principle, provided we sacrifice any knowledge of the
other. This is not a shortcoming of our understanding of the workings of
nature, nor is it due to the sheer minuteness of an electron, but is simply the
way electrons are. In fact, it has nothing really to do with us at all. The electron
itself does not have a well-determined position and speed. The best we can do
is to identify a region in which the electron is likely to be moving.
Another way of stating the uncertainty principle is in terms
of energy and time. We can measure the exact energy of a particle, provided we
do not care about when it has this energy. Conversely, if we fix the time of measurement
exactly, then we give up any hope of finding out how much energy it has.
by Jim Al-Khalili, 30 Second Theory
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