# How do you measure a particle's postion or momentum?

This question is about the Uncertainty Principle

$$\sigma_x \sigma_p ~\ge ~\frac{\hbar}{2}.$$

Looking at the maths, I understant why the uncertainty in the poistion increases as the uncertainty in the momentum decreases and vice versa, but I don't understand it in terms of an experiment.

For starter, how do you measure a particle's position or momentum? What is stopping me from making two simultaneous measurements, one for position and one for momentum?

(I understand that the Uncertainty Principle is a natural phenomenon, not a limitation of our technology.)

• The crux of the problem is that in order to measure the position accurately, you need to bounce low wavelength light of the particle. But to measure momentum accurately, you need low frequency light instead. – David H Mar 24 '14 at 9:35