# Is the strong/weak force infinite like electromagnetism

1. Apr 11, 2011

### Jarfi

Electromagnetic forces go infinetly far but decrease dramatically by distance. I was wondering is the strong and weak force are Only within a certain zone with a radius or do they stretch infinetly far.

On wiki it says they have short range but it doesnt say if it ever stops completely.

2. Apr 11, 2011

### Bill_K

Jarfi, Electromagnetism and gravity are the two long-range forces. This is related to the fact that the particles that transmit their effects have mass zero. The weak force is a short-range force, which means it falls off exponentially. It is transmitted by a pair of particles, the W boson with mass around 80 GeV and the Z boson with mass 90 GeV. The range of a short-range force is related to the Compton wavelength of its particle, and can be directly calculated from the mass. All you have to do is divide the constant hc by the mass, where hc = 197.5 MeV-f. (A fermi 'f' is a unit of length, 10-13 cm and is roughly the size of an atomic nucleus.) So for the W boson we have 197.5 MeV-f/80 GeV, or about 0.0025 f. (Or about 2.5 x 10-16 cm.) Pretty small.

Last edited: Apr 11, 2011