Measuring particle position and velocity

[Zinite]

In a discussion of Heisenberg's Uncertainty Principle I read that we must shine light on a particle to measure its position and velocity. How does this work exactly? Does the particle cast a shadow on a wall detector? Or is its position inferred some other way?

 

[Sojourner01]

It's a thought experiment. The idea is that you have to have some kind of electromagnetic interaction with the particle in order to transmit information on its whereabouts - the precise mechanism doesn't matter - and in fact it's a slightly ropey idea, because the common interpretation of Heisenberg is that it isn't possible to measure both to arbitrary accuracy even in principle - that is, information of that precise sort cannot coexist in the same 'timeline' for want of a better word.