# Collision of point particles

1. Apr 27, 2006

### daniel_i_l

How can point particles collide, wouldn't the distance between them be 0 meaning that they're right on top of each other. Or, when we talk about particles colliding do we really mean the superposition of their wave functions? an explanation would be appreciated. Thanks.

2. Apr 28, 2006

### Meir Achuz

we really mean the superposition of their wave functions

3. Apr 28, 2006

### ZapperZ

Staff Emeritus
1. In many instances, these "point particles" are charge particles, such as electrons. The coulombic forces alone extends beyond the "size" (if there is such a thing) of the particle. So there does not need to be any physical contact for there to be an interaction. Strongly-correlated electron systems in condensed matter deal with this all the time.

2. Even for neutral particles such as neutrinos, at some point, the wavefunction of the particles will start to significantly overlap. When that happens, these particles will sense each other's presence and a whole set of rules starts occuring. This is what we call "interactions".

Zz.

4. Apr 29, 2006

### daniel_i_l

Thanks for the explanation.
One more thing, does modern physics have an explanation of what it means for "wavefunctions" of particles to interact. Aren't WF mathematical models that help us calculate the motion of particles statisticlly but lacking further physical meaning? (sorry for the ignorence, I havn't started learning QM yet). Thanks.

5. Apr 30, 2006

### ZapperZ

Staff Emeritus
I am not going to get into this "mathematical model" versus "physical meaning" thing that appears to have no end. I will simply say that the wavefunction has allowed us to make amazing description of the relevant system. The materials that you used in your modern electronics are understood via band theory of matter that makes use of "wavefunction overlap" to describe its behavior.

So you decide for yourself if you consider them just nothing more than "mathematical model". Come to think of it, you may also want to consider if Newton's laws and Maxwell equations are also nothing more than "mathematical models" either.

Zz.

6. Apr 30, 2006

### selfAdjoint

Staff Emeritus
Zapper, does the Compton wave length have any real meaning for an isolated particle in its rest frame? It seems to me that it only comes into play when the particle interacts, i.e. emits or absorbs something.

7. Apr 30, 2006

### ZapperZ

Staff Emeritus
I don't think I've ever associated it with anything physical. It is simply a constant, maybe can be linked to the energy gained by the electron, which is no longer in that rest frame after collision.

Zz.

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