30/03/2022
Gravitational waves are ripples in the curvature of spacetime which travels as a wave towards their source at the speed of light, as proposed by Poincaré in 1905 (see Poincaré 1946, “The foundation of science: science and hypothesis, the values of science and method”) and predicted by Albert Einstein in 1916 (See Einstein 1916, “The foundations of the General Theory of Relativity”). Detecting gravitational waves, and analysing the information in which they carry, can allow scientists to observe the Universe in a whole new way. This month’s “What is going on in Physics?” is about a new method of detecting gravitational waves using the varying distances between the Earth and the moon.
Research from the IFAE, UAB and the University College London proposed this new method which has a measurement precision less than a centimeter. Current wave detectors do not have this preciseness.
Although predicted in 1916, the first detection of gravitational waves was in 2015. However, frequencies which current devices cannot cover could be covered by this new natural method. This could aid with the fundamental understanding of our Universe because an example of a signal currently undetectable is microhertz, which could have been produced at the dawn of the Cosmos.
Using lasers sent from observations to reflect upon the moon’s mirrors, the exact position of the moon (within a centimetre) is known. Gravitational waves constantly hit our Earth-Moon system creating small disruptions in the moon’s orbit. This means that, potentially, small disturbances by ancient gravitational waves could be detected.
This research implies that the information from other binary systems could also be used, such as pulsar binary systems. Since these are throughout the Universe, there could be hopes for finding information in the microhertz range, unveiling information from our Universe’s past.
Related papers and articles:
1. https://phys.org/news/2022-03-moon-orbit-gravitational-detector.html?fbclid=IwAR0w9BkO7mwa3HkumW4Oc4vOfZE5YyI7nklrg9ZT1i6-67wX1HLE_vcXwyA
2. https://www.innovationnewsnetwork.com/natural-gravitational-wave-detector-moons-orbit/19519/
3. https://www.ligo.caltech.edu/page/why-detect-gw
Image Description: Image 1 is of spirals coming from two spherical masses, showing gravitational waves. Image 2 shows an artistic style image of the moon near Earth. Image 3 shows four graphs which show how the moon's orbit is disturbed by gravitational waves.
