# Interaction between solid objects

1. May 30, 2006

### Allanon

Greetings!

I've looked around in the FAQ and around the forums and couldn't find the answer to my question, so I've decided to ask. If however I did miss the answer, I apologize.

Well, it's quite elementary actually. I am wondering if it is correct to assume that no two solid objects actually touch each other, i.e. there is always a layer of space between two adjacent atoms of different objects. And if my assumption is correct, what is friction then? And what about non solid objects?

Thanks alot.

2. May 30, 2006

### pallidin

If your question involves whether or not the electrons surrounding surface atoms from two nominally colliding objects actually "touch" each other upon the event of "collision", the answer is no.
The electron fields interact and "collide", but not the actual electrons themselves. They do not collide with each other.

3. May 30, 2006

### Hootenanny

Staff Emeritus
As far as I know friction is still not fully understood. However, at the macroscoping level, friction arises from the electrostatic interactions of the nuclei at the surface.

~H

4. May 30, 2006

### pallidin

Ah, friction! It can seem counter-intuitive that friction is a "non-contact" property. But, this would depend upon your definition of "contact"
Remember, electrons have fields, and fields interact, and this interaction can be severe enough to displace the electrons(and even their associated atoms) producing the field!
So, although the electrons may not physically "contact" each other, their fields do.

Also, consider a "flat" surface. There are electrons whirling about each surface atom(which themselves are at some distance from each other), and so one might roughly and visually characterize a "flat" surface as a string of very tiny beads. Think of the outer part of the beads being the electron "cloud" surrounding each atom.
So, there are natural valleys and troughs no matter how "smooth" one makes the surface, just much less in distance from each other.

5. May 30, 2006

### Claude Bile

Friction does indeed occur at a distance, it is detectable up to about 10 nm from a surface. AFM and NSOM systems use this 'Shear-force' to regulate distance between their probes and a sample.

Claude.

6. May 31, 2006

### Allanon

Understood! Thanks.