Forces are interactions
between the fundamental particles described on the previous page and they involve the exchange of another group of elementary particles known as bosons
. Force bosons (or exchange bosons) are emitted and absorbed by particles that are affected by the interaction. The exchange of bosons allows particles to feel
the presence of others.
The fourth force is gravity who's exchange boson
is the graviton. As far as we know, this has no observable effect in
particle physics experiments and the graviton has not yet been discovered. The
table below gives the basic properties of each force: