Gravitational waves cause tiny changes in the distances between objects when massive bodies accelerate—such as two black holes spiraling into each other. These waves stretch and squeeze space itself, but by the time they reach Earth, the effect is minuscule. First predicted in the early 20th century and later described in Einstein’s general theory of relativity, gravitational waves were detected in 2015 by the Laser Interferometer Gravitational-Wave Observatory (LIGO). Detecting them requires extreme precision, as the length of LIGO’s laser interferometer arms shifts by less than the width of a [[Proton|proton]] when a wave passes. [[Quantum Metrology|Quantum metrology]] helps improve the sensitivity of such measurements. Quantum effects, like shot noise in [[Laser|laser]] light, limit accuracy, but techniques such as [[Squeezed State|squeezed]] light reduce [[Heisenberg Uncertainty Principle|uncertainty]] in key aspects of the laser’s signal. Future advances, including such based on [[Entanglement|quantum entanglement]], may push sensitivity even further. >[!read]- Further Reading >- [[Interference]] >- [[Laser]] >- [[Quantum Metrology]] >- [[Squeezed State]] >[!ref]- References