Re: If a proton is forced to touch a elctron what would happen?

Dear Kelly!

In subatomic dimensions it is not at all clear what is meant when we say `an electron touches a proton'. Electrons and protons are very much unlike little pinheads bouncing around - they behave wave-like, i.e. they can go around corners, interfere with each other like water waves etc.

The first thing you have to understand when looking at collisions between particles is that a particle is the more wave-like the lighter (in terms of mass) and slower (speed) it is. The wavelength associated with a particle is inversely proportional to its mass and its velocity, so a very slow electron has a large wavelength. Now what has the wavelength got to do with the collision? Everything! The wavelength of a particle (also called the De Broglie length) is about the dimension to which the particle can probe other structures. If a slow electron hits a proton, the proton looks (for the electron) like a point particle with no substructure, because the electron's wavelength is larger than the diameter of the proton. A slow electron would thus get scattered off a proton as if the proton were point-like.

If we crank up the electron's monentum, the process gets more involved. As you surely know, the proton has a substructure (it consists of three quarks). The more momentum the electron has, the more detail it can probe inside the proton. This is actually something that is being studied in great detail in large particle colliders: By shooting fast electrons at protons we try to unveil, as accurately as possible, the proton's structure. This goes under the name of deep inelastic scattering, DIS.

So, don't look at elementary particles as if they were tiny spheres. They are much more than that, they behave like waves that can interfere with each other (apart from the more `usual' interactions like electromagnetic attraction and repulsion). Used ingeniously, they can tell us a lot about the structure of composite particles (e.g. nucleons), like powerful microscopes.

Two other questions related to yours have already been answered in this forum:

What is the nature of an atomic collision?
How do we know about atoms &quarks & stuff when we can't see them?

A good thing to read is also The Particle Adventure, which contains a `ground-up' popularized course in particle physics.

Hope that helps,
Georg.