Senan - The Terrifying Result of Measuring Time Perfectly

My comment:

My favourite bit was the cloud of caesium atoms and the analogy of tuning a radio. 7:37. The thing is that cloud of caesium atoms has a spatial extent: it's at least a few cms in diameter, but then we find that 33cm difference in altitude produces a measurable variation in the number of ticks. The physicist Ivette Fuentes was talking about this once. It seems there is an awkwardness here, because general relativity and quantum mechanics are being "brought into contact", but it takes a relatively long time to measure the difference in the rate of oscillation over just 33cm of altitude. Another thing that is related to this is that in practice, to know that frequency standards are indeed correct, one needs to be able to compare several independent clocks, so again the spatial resolution of clocks seems to be traded off against temporal resolution. That whole thing about needing more energy to measure time more accurately was new to me. That was a very thought-provoking video, thank you.

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See this talk at 17:29: she claims that variations in frequency have been measured over differences in altitude of a millimeter or so.  She discusses the problems this poses for theory. At 48:10 she describes an attempt to measure the gravitational self-energy of Bose-Einstein Condensates: 

How accurately could one measure differential gravitational time-dilation over an interval of only 1 or 2 seconds? 

Ivette Fuentes: Clocks in the overlap of quantum theory and relativity.

Subscribe to Appearence and Reality. 

I also found this video and made with Roger Penrose in December 2018.

Subscribe to Ivette Fuentes - Through the looking glass. 

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