With Earth spinning more slowly, time isn’t flying as fast as before

CHalk this up as another example of an article title not really matching up with what the article concludes. It’s misleading — as the story eventually alludes — because we now use atomic time, so there is no slowing of time. The rate is the same. The explanations of the variability of earth rotation rates have implications on leap seconds, which we add to keep earth rotation time (terrestrial time) in synch with atomic time. We can’t adjust the earth, so we adjust the clocks.

GPS figures prominently in the discussion of technology enabled by atomic time, but there’s an omission in the discussion:

“If we relied on the Earth’s length of day, we could not have any of this,” says O’Brian, whose group at NIST develops, maintains and improves the supremely regular atomic clocks on which all other timekeeping ultimately is based.

GPS is actually synched with Naval Observatory time, and while USNO time and NIST’s time agree to great precision, to say “on which all other timekeeping ultimately is based” is a bit of hyperbole — it makes it sound as if others are adopting technology only after they develop it, and that the international time standard follows NIST, instead of the other way around. Timing labs around the world follow the international standard from BIPM, to whom we all contribute data. (Some of us contribute more than others. And some of us are closer in realizing the international standard.) /ChestThumping

“We have come full circle,” O’Brian says. The rotation of the Earth had long been the most accurate measure of time for humanity, but now such technologies as atomic clocks and GPS devices make it possible to measure tiny variations in Earth’s rotation. And the scientific reverberations are not just for space junkies. In a July paper in the journal Nature, for instance, researchers in England and France argued that sub-millisecond-scale variations in Earth’s rotation that occur on a 5.9-year cycle are probably linked to motions and interactions within the planet’s molten core where no one has ever been to take a look.

I think it’s pretty cool that our timekeeping is such that we can uncover evidence of processes that are redistributing mass inside the earth.