What happens when two masses touch?

  • Thread starter cowpuppy
  • Start date
  • #1
9
0

Main Question or Discussion Point

What happens when two masses touch? I mean, really touch. When I touch something, I know that the atoms in my hand are separated by some distance from the object I am touching, due to mutual repulsion by the electromagnetic force.

So, if two charge-less masses were to collide with each other, what force governs that interaction?
 

Answers and Replies

  • #2
4,662
5
  • #3
27
0
It's a question that simply cannot be answered by classical physics.

It was a big problem in the 19th Century that contemporary theory suggested that the most energetically favourable configuration of charged particle would be 'all on top of each other'.

It was only when Heisenberg came along that the 'exclusion principle' was formulated.

The idea is that these new laws predicted that two particles (like the neutral ones you mention) can never end up in the same place. As they get too close, the quantum mechanical 'degenerecy pressure' prevents them from ever 'overlapping'.

Not a great explanation, apologies.

Van der Waals forces are just one particular manifestation of classical electrostatics.

Incidentally, this degenerecy pressure is also the reason we never 'touch' anything ourselves. Classical electrostatics cannot account for that. Why would the atoms in our hand repel the atoms in the brick (or whatever)? Clasically, they would attract (due to polarisation within the atom), and then overlap, with the protons all hugging up to the electrons in a big particle soup.

Amazing to think that no-one before the beginning of the 20th century could even begin to explain why we don't fall through the floor.
 
  • #4
2,544
2
It was only when Heisenberg came along that the 'exclusion principle' was formulated.
Do you mean pauli
 
  • #5
27
0
Thanks, sorry. History a little shaky.
 
  • #6
5,601
39
The electromagnetic force still plays it's part with adjacent neutral masses "touching".....like your hand and a baseball...because the neutral masses consist of electron clouds surrounding nuclei...and the electron clouds come into first "contact"....

If they REALLY "touch" they might fission or fuse as in bombs...or form a new compound like hydrogen and oxygen to form water.....
 

Related Threads on What happens when two masses touch?

Replies
18
Views
5K
Replies
2
Views
748
Replies
15
Views
24K
  • Last Post
Replies
7
Views
2K
Replies
3
Views
533
  • Last Post
Replies
23
Views
4K
  • Last Post
Replies
12
Views
3K
Replies
1
Views
590
Replies
7
Views
1K
  • Last Post
2
Replies
43
Views
10K
Top