iov...@inwind.it said: > I was wondering, why we assume that Earth's rotation is slowing down, > instead that clocks are speeding up?
The quick answer is that there is a mechanism that explains why the Earth is slowing down: tidal effects. There is no corresponding way to explain why atomic clocks are speeding up. How many different timekeeping mechanisms are there that are accurate enough to notice changes in the Earth's rotation? Wikipedia says 2 ms/100 years and that it was noticed by Halley in 1695 and confirmed by Dunthorne in 1749. I assume they were using the Earth's orbit around the sun as their reference clock. http://en.wikipedia.org/wiki/Tidal_acceleration I think that's 6 parts in 1E12 so it takes a pretty good clock. (I'm frequently amazed by how good the old astronomers were.) The Wikipedia article discusses geological evidence: silt layers from 620 million years ago give a calibration on the Earth's rotation and the Moon's orbital period. http://en.wikipedia.org/wiki/Tidal_acceleration#Historical_evidence > (Speculative hint: We accept that the universe is expanding. Might this > affect the fine structure of matter, including cesium atoms? Is there any > adverse proof? What is easier to think? a) the expansion of the universe > doesn't affect at all the properties of matter. b) it might.). It's clearly easier to think that the expansion of the universe doesn't effect things. Sure, it might, and I expect a few far-out theoreticians are working on things like that. But nobody has proposed a mechanism yet, nor an experiment that would measure it. Science is all about measuring. Yes, it's fun to wave your hands about crazy ideas, but who cares if you can't come up with something to measure? I'm not really a physics wizard. There might be some gravity terms or experiments I've missed. But the universe isn't expanding very fast (at least not in the local region) so any effect will probably be very hard to measure. Maybe dark energy will distort time. -- These are my opinions, not necessarily my employer's. I hate spam. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.