The Four Interactions
There are four forces in the universe, some you will have come across already and some will be new:
The electromagnetic interaction causes an attractive or repulsive force between charges.
The gravitational interaction causes an attractive force between masses.
The strong nuclear interaction causes an attractive (or repulsive) force between quarks (and so hadrons).
The weak nuclear interaction does not cause a physical force, it makes particles decay. ‘Weak’ means there is a low probability that it will happen.
| Interaction/Force | Range | Relative Strength | |
|---|---|---|---|
| Strong Nuclear | ~10-15m | 1 | (1) |
| Electromagnetic | ∞ | ~10–2 | (0.01) |
| Weak Nuclear | ~10-18m | ~10–7 | (0.0000001) |
| Gravitational | ∞ | ~10–36 | (0.000000000000000000000000000000000001) |