Free Republic
Browse · Search
General/Chat
Topics · Post Article

To: I want the USA back

“At the quantum level, measuring a particle’s velocity changes it, and measuring a particle’s position changes it.”

Please forgive my ignorance when I ask this. I know next to nothing about quantum mechanics.

When they say that “measuring a particle’s position” changes it, is it due to the fact that some new particles are required to measure said particle?

Let me try and explain it this way. Suppose I am measuring an electric circuit. It behaves a certain way under “unobserved” conditions.

Now, let’s say that I want to “observe” a node of the circuit with an oscilloscope probe. When I measure this node, I am actually changing the conditions of the circuit as the scope probe typically has capacitance, inductance, etc. itself.

Now, let’s say I am measuring something “simple” ... like a 60Hz, 5V peak-to-peak sine wave. These new parasitics I am introducing to the system via the scope probe aren’t a big problem. They have virtually no impact on the circuit.

However, suppose I was trying to measure a high speed transceiver running at mutli-gigabit data rates. The same scope probe could cause substantial problems in that the added parasitics will cause the circuit to behave differently.

(Yes, some idiots I used to work with once “solved” a problem by adding a 10pF capacitor to a broken circuit since they saw that adding a scope probe actually made a circuit work ... sadly, that circuit failed torture testing, but that’s a whole other story).

Now, when they say that observing something on the quantum scale has an effect on the particle, is it due to conditions similar to my analogy (i.e. things like lasers/light or what have you impact the particle’s behavior), or am I way the hell off and have far too much to learn :-)?


16 posted on 02/26/2014 11:02:56 AM PST by edh (I need a better tagline)
[ Post Reply | Private Reply | To 6 | View Replies ]


To: edh; I want the USA back

Similar to how I try to explain it - the next step is to explain a photon and how it is similar to a quantum particle - we can prove it has mass and acts as a particle, but we can also prove that it is an energy wave and not a particle due to the way it acts.

Taking this to a quantum state we basically have the ability to focus in on one aspect or another of the particle - position or velocity/energy state, but only one at a time (though there have been some recent discussions on this). But once you determine the one, it means that you can’t determine the other without increased variation.

By that time people’s eye’s have glazed over and I’m getting excited and ordering my next drink - shortly thereafter if they haven’t managed to beg off to another subject they are looking for an excuse to leave ... it’s sad. ;)


21 posted on 02/26/2014 1:39:49 PM PST by reed13k (For evil to triumph it is only necessary for good men to do nothings)
[ Post Reply | Private Reply | To 16 | View Replies ]

Free Republic
Browse · Search
General/Chat
Topics · Post Article


FreeRepublic, LLC, PO BOX 9771, FRESNO, CA 93794
FreeRepublic.com is powered by software copyright 2000-2008 John Robinson