Home / Hypographies /

Heisenberg's Uncertainty Principle

Can a particle pass through two holes at the same instant? According to the Uncertainty Principle, it happens all the time.

Posted by Tormod Guldvog
13 September, 2001 04:09:08

print article
A | A | A

The Uncertainty Principle is, basically, summed up in this statement: The more precisely the position of an object is determined, the less precisely the momentum is known in this instant, and vice versa.

What does this mean? First of all, it means that if you observe a moving object, you cannot both decide at what speed it is moving, and the precise location which it is at. If you measure one of them, you can't measure the other correctly.

This implies that there is an uncertainty (hence the name of the principle) about one of the two properties.

Well, you might ask, does it really matter? Consider this: if you know that an electron is moving at a definite speed, the uncertainty principle says that you can't possibly know where it is.

And here comes the tricky part: Since you don't know where it is, it may possibly be anywhere. There is a small possibility that the electron may exists at any given point in the universe at the moment you are trying to observe it.

So strange is this phenomenon that it has led to one of the most obscure experiments in particle physics: the Double Slit experiment. By sending an electron towards a metal plate with two extremely small holes in it, the electron has been observed to travel through both holes at the same time.

Difficult concept, yes. But not very hard to understand once you check out the sources below.

Related Links

Werner Heisenberg's Uncertainty Principle
http://www.honors.unr.edu/~fenimore/wt202/close/
The page gives a simple information about Werner Heisenberg and his uncertainty principle with pictures.

Mathematical Presentation of The Uncertainty Principle
http://members.tripod.co.uk/j_champion/uncertainty/uncertainty_principle.htm
This page shows the derivation of the uncertainty principle by using mathematics (with explanations).

Heisenberg and Schr�dinger's Cat
http://www.thebigview.com/spacetime/uncertainty.html
This is an article about the differences between Heisenberg's Uncertainty Principle and, among other things, Schr�dinger's Cat.

Mathematical description of the Uncertainty Principle
http://www.treasure-troves.com/physics/UncertaintyPrinciple.html
For the more mathematically adept: here is a list of formulae related to the uncertainty principle.

Java Applet: Heisenberg's Uncertainty Principle
http://thorin.adnc.com/~topquark/quantum/heisenbergmain.html
This is a nify little applet which illustrates the uncertainty principle.

Werner Karl Heisenberg
http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Heisenberg.html
A short review of the scientific activity of W. K. Heisenberg.

People and Discoveries: Werner Heisenberg
http://www.pbs.org/wgbh/aso/databank/entries/bpheis.html
A short biography of the well known physicist.

Werner Heisenberg (1901 - 1976)
http://www.aip.org/history/heisenberg/p01.htm
This is a website about the man behind the uncertainty principle. Presented by AIP.

Werner Heisenberg and the Uncertainty Principle
http://www.aip.org/history/heisenberg/
A great introduction to Heisenberg, with lots of illustrations.

An end to uncertainty
http://www.newscientist.com/ns/19990306/anendtounc.html
A feature article in New Scientist about a theory which might refute the uncertainty principle - or not.