
#1
Oct213, 03:16 PM

P: 1

Hi,
I'm sorry if I've hit the wrong subforum. Although physics is not my strong side this question has been puzzling me for some time now and from I've read so far  there's no clear answer yet. Here's the question: If we take an atom and mark it's position in space at time X and then it's position at time X+ε then how did the atom physically moved from the first to the second position? I know that I'm asking quiet a general question, so if the above is too huge to be explained(summarized), I'll be happy even with a list of fields that I should look into to find out more about the current explanations. 



#2
Oct213, 03:40 PM

Sci Advisor
P: 5,939

If it is moving, it will keep moving in the same direction and speed as long as no force is applied. If a force is applied it will change speed and/or direction accordingly. If it is not moving and no force is applied, it will stay where it is. In extreme situations, relativity and quantum theory may apply, but the above description is basic. 



#3
Oct213, 06:47 PM

P: 420

If quantum mechanics (QM) is not the issue, then, as mathman stated, it's is governed by Newton's Laws.
If you wish to consider the QM effects, then "marking" its position is a nontrivial act that will affects the path of the atom. 



#4
Oct313, 06:20 AM

P: 177

How do atoms move through space?
Joven, welcome to PF. You have asked a good question. Maybe a little too good, because the answer is that nobody knows.
The problem is known as the "source of inertia" problem. Type that into google and that will get you some interesting ideas. 



#5
Oct413, 07:40 AM

Sci Advisor
P: 1,465

According to QM, you can't mark the position of an atom at a singular point. All you can do is specify a wavefunction, with a corresponding expectation value (Interpeted as the "centre" of the wavefunction).
So the QMcorrect way to pose the question is "what causes a wavefunction to change over time". Wavefunctions can be "moved" without applying force by using a moving reference frame (or equivalently, having the atom moving at an initial constant velocity). Recall that relativity tells us that no reference frame is preferable to any other. Accelerating wavefunctions (or an accelerating reference frame) requires the application of force. Claude. 


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