[ExI] The most accurate clock ever

Brent Allsop brent.allsop at gmail.com
Mon Dec 3 01:23:00 UTC 2018

Hi John,
Very cool and interesting.
But since it seems to me, the only way to judge the accuracy of something
like a clock, is to have something to compare it to, I always wonder: how
can we objectively know it is so accurate?

On Thu, Nov 29, 2018 at 7:22 AM John Clark <johnkclark at gmail.com> wrote:

> In yesterday's issue of the journal Nature Scientists at the National
> Institute of Standards and Technology (NIST) reported they have made a
> new type of clock that is the most accurate ever, it's called a Ytterbium
> Lattice Clock. It's about 100 times better than any previous clock, if
> set at the time of the Big Bang 13.8 billion years ago today it would be
> off by less than one second.
> https://www.nature.com/articles/s41586-018-0738-2
> It's so good the main source of error is due to General Relativity, if you
> lift the clock up by just one centimeter the Earth's gravitational field is
> slightly weaker and so the clock runs noticeably faster, that may be why
> NIST is now working on a portable version of their Ytterbium Lattice Clock.
> If GPS satellites had clocks this good they'd know where they were relative
> to the Earth to within a centimeter and so could tell users on the ground
> where they were within a centimeter; and that would be more than good
> enough for jet fighters to automatically land on aircraft carriers without
> a pilot, even at night in a heavy fog in a bad storm with the deck tossing
> up and down. It would be by far the best instrument ever made to detect
> tiny changes in the gravitational field, and that would make it much
> easier to find things buried deep underground. The Earth just became more
> transparent. It might even be used to detect Gravitational Waves and Dark
> Matter.
> John K Clark
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