# Particle in Box

1. Oct 24, 2006

### somebody-nobody

The probability density at certain points for a particle in a box is zero.Does this imply that the particle cannot move across these points

2. Oct 24, 2006

### ZapperZ

Staff Emeritus
No, because by saying that, you are assuming that you CAN track the particle's trajectory every step of the way. All the probability density says is that when you make a measurement, the probability of finding the particle at the nodes is zero.

Zz.

3. Oct 24, 2006

### pibomb

Like ZapperZ said, the probability density merely defines where you can find the particle when you measure. To figure out if a particle will ever move in a spot of "zero", you should use the schrodinger equation.

4. Oct 27, 2006

### pmb_phy

Yep. The proplem is with the question itself. The OP used the term move, which is a classical idea and not a quantum one. The question is better asked regarding what the probability of finding the particle in this region and then ask what the probability of measuring the particle in this other region after the first measurement was made. If the state is an eigenstate (stationary state) the the probability density will remain constant. But we really don't speak of measuring a particle in a region of zero width (i.e. what's the probability of finding the particle at x = 2?) because that will always be zero.

Pete