https://phys.org/news/2020-04-scientists-tokyo-skytree-einstein-theory.html Scientists use the Tokyo Skytree to test Einstein's theory of general relativity In another verification of the validity of Einstein's theory of general relativity, published in Nature Photonics, scientists from the RIKEN Center for Advanced Photonics and Cluster for Pioneering Research, with colleagues, have used two finely tuned optical lattice clocks, one at the base and one on the 450-meter observatory floor of Tokyo Skytree, to make new ultraprecise measurements of the time dilation effect predicted by Einstein's theory of general relativity. Einstein theorized that the warping of time-space by gravity was caused by massive objects. In line with this, time runs more slowly in a deep gravitational field than in a shallower one. This means that times runs slightly more slowly at the base of the Skytree tower than at the top. The difficulty with actually measuring the change in how quickly clocks run in different gravity field is that the difference is very small. Performing a stringent test of the theory of relativity requires either a very precise clock or a large difference in height. One of the best measurements so far has involved large and complex clocks such as those developed by the RIKEN group, which can measure a difference of around a centimeter in height. Outside the laboratory, the best tests have been taken by satellites, with altitudes that are thousands of kilometers different. Such space experiments have constrained any violation of general relativity to about 30 parts per million, a tremendously precise measurement that essentially shows Einstein to be correct. more at link............. the paper: https://www.nature.com/articles/s41566-020-0619-8 Test of general relativity by a pair of transportable optical lattice clocks: Abstract A clock at a higher altitude ticks faster than one at a lower altitude, in accordance with Einstein’s theory of general relativity. The outstanding stability and accuracy of optical clocks, at 10−18 levels, allows height differences6 of a centimetre to be measured. However, such state-of-the-art clocks have been demonstrated only in well-conditioned laboratories. Here, we demonstrate an 18-digit-precision frequency comparison in a broadcasting tower, Tokyo Skytree, by developing transportable optical lattice clocks. The tower provides the clocks with adverse conditions to test the robustness and a 450 m height difference to test the gravitational redshift at (1.4 ± 9.1) × 10−5. The result improves ground-based clock comparisons by an order of magnitude and is comparable with space experiments10,11. Our demonstration shows that optical clocks resolving centimetres are technically ready for field applications, such as monitoring spatiotemporal changes of geopotentials caused by active volcanoes or crustal deformation and for defining the geoid, which will have an immense impact on future society.
paddo A clock at a higher altitude ticks faster than one at a lower altitude, in accordance with Einstein’s theory of general relativity Is that due to two effects higher = less gravity and higher = faster (think of a tower on equator - top moving faster than bottom) Think also the old (making come back ?why) 12" record - outside edge faster than spindle edge) Outside edge will tick slower Its a strange Universe we live in Please Register or Log in to view the hidden image!
The simple fact they are in a different gravitational potential, means that gravitational time dilation will take place. This is different from time dilation caused by speed, but both effects need to be allowed for in Satellites for example. https://en.wikipedia.org/wiki/Time_dilation "Time dilation is a difference in the elapsed time measured by two clocks, either due to them having a velocity relative to each other, or by there being a gravitational potential difference between their locations" https://en.wikipedia.org/wiki/Time_dilation#Gravitational_time_dilation "Gravitational time dilation is experienced by an observer that, at a certain altitude within a gravitational potential well, finds that his local clocks measure less elapsed time than identical clocks situated at higher altitude (and which are therefore at higher gravitational potential). Gravitational time dilation is at play e.g. for ISS astronauts. While the astronauts' relative velocity slows down their time, the reduced gravitational influence at their location speeds it up, although at a lesser degree. Also, a climber's time is theoretically passing slightly faster at the top of a mountain compared to people at sea level. It has also been calculated that due to time dilation, the core of the Earth is 2.5 years younger than the crust.[32] "A clock used to time a full rotation of the earth will measure the day to be approximately an extra 10 ns/day longer for every km of altitude above the reference geoid."[33] Travel to regions of space where extreme gravitational time dilation is taking place, such as near a black hole, could yield time-shifting results analogous to those of near-lightspeed space travel" >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Yep certainly a weir and wonderful place, but by the same token, because of blokes like Newton, Darwin and Einstein, and many many others, explained by science. Please Register or Log in to view the hidden image! .
This has been done before but I can't for the life of me recall the name ...on the tip of my younger.. damn. Alex
Pound-Rebka experiment, relying on Mossbauer resonance not atomic clocks, done back in 1960: https://en.wikipedia.org/wiki/Pound–Rebka_experiment The latest RIKEN test results are consistent with GR but also with various rival theories, and it is far too insensitive to distinguish between them. It's really a good PR exercise demonstrating the technological expertise allowing such high portable clock accuracy.
Hi Q-reeus I hope you are well. Yes that's it I was getting..it's R something then Rubin..no it's not Rubin ..blank. Thanks for putting me straight much appreciated. Alex
