Sagnac effect
Efecto Sagnac
- Date
- 1913 · confidence high
- Place
- Paris, France
- Credited to
- Georges Sagnac
- Field
- Communication
⚠️ Disputed: the sources disagree.
What was discovered
Sagnac shows that in a rotating interferometer two beams travelling the ring in opposite directions accumulate a phase difference proportional to the rotation rate. He thought it proved the ether, but it is the basis of optical gyroscopes.
Harress observed a similar effect in Jena (1911) without interpreting it; Sagnac explained it with the ether and relativity reinterpreted it without any ether.
What it led to
- the ring laser gyroscope
- the fibre-optic gyroscope
- measuring Earth's rotation with ring lasers