Action at a distance
Action at a distance consists of affecting a distant body instantaneously. At the atomic level, this is known as "non-locality".
Examples of action at a distance in physics are:
- Newtonian gravity
- Electrostatics (before Maxwell's equations in the 1800s)
- Quantum entanglement within quantum mechanics (called "non-locality")
Some scientists have long resisted the possibility of action at at distance (non-locality), and the theory of relativity assumes that information travelling instantaneously, or faster than the speed of light, is impossible. Quantum entanglement therefore appears to violate relativity as one particle affects another instantaneously. However, no information can be encoded with the particles, so no information can be sent faster than the speed of light, in accordance with relativity.
Several theories have been developed as ways of denying action at a distance (non-locality). These include: