Experimental gravity

The LATOR experimentAfter a few days in the abstract realms of Quantum Gravity, reading (and seeing) a bit about experimental physics today has been a refreshing experience. I picked up a couple of talks from the awesome streaming seminars collection at the Perimeter Institute for Theoretical Physics. If you search for Slava Turyshev, you’ll find an enticing talk about LATOR, and ongoing effort at JPL to test General Relativy in the PPN regime up to G^2. In the talk, Slava reviews current bounds (obtained by Solar System-based experiments) to Einstein’s theory agreement with experiment, which have improved from Edington’s one percent to 10^{-4} with the latest Doppler effect measurements from the Saturn Cassini mission. LATOR consists basically on putting in orbit two satellites (separated by 5 million kms) and observing them, using interferometers located at the International Space Station, when the Sun is passing in between (click figure on the left). The space-time curvature created by the Sun will alter the apparent position of the two space-crafts as seen from the ISS, which will be able to measure angular variations of the order of a pico-degree, thus testing GR’s predictions up to 10^{-9}. Pretty impressive. Before entering in the details of LATOR, Slava spends some time discussing the intriguing Pioneer anomaly, and i have bookmarked this article and this one to learn more about those puzzling results.

The second talk, of much lighter tone and aimed at non-specialists, was by Clifford Will and entitled Was Einstein Right? (look for it in the ‘EinsteinFest’ section of PI streaming page). He has been giving these talks about experimental checks of General Relativity for many, many years (besides studying them rigorously as part of his academic work, and publishing a couple of books), and it shows. Clifford is by now a real showman who knows how to make his talks interesting and fun for the general public. But you’ll enjoy the jokes even if you’re a specialist!

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