When the atomic second became the SI second 1967, it was of course known that atomic time
would continuously diverge from astronomical time, so periodic corrections would be needed to keep the new atomic time
scale, called Coordinated Universal Time (UTC), in step with astronomical time.
seemed a perfect wedding of nature and science, a harnessing of the unimaginable precision of the universe.
The main reason for the nearly annual adjustment we need now is a mismatch between the definition of the second in terms of atomic time
and that in terms of the average speed of the Earth's rotation.
Anyway there's Coordinated Universal Time, International Atomic Time
, GPS Time, Greenwich Mean Time and - I suspect - Public Transport Time.
Users of the service will obtain a time reading that is accurate to within one second of the atomic time
, depending on Internet delays.
To mention only a few: relativistic effects, Barycentric Dynamical Time, measurement of Atomic Time
, clock synchronization by very-long-baseline interferometry, planetary terms in nutation (used only for arc-millisecond accuracy!), the FK5 system, laser ranging, and rotation parameters for satellites of the planets.
1, 2017, UTC - based on astronomical timekeeping - will be 37 seconds behind atomic time
In 1955, the first accurate caesium atomic clock was developed, leading to the international agreed definition of the second being based on atomic time
. In 1966, the NPL developed packet-switching as a technique for transmitting long messages of data--a technique that has been important in the development of the internet.
To stop using the additional 'leap seconds' would keep us strictly on atomic time
- measured by incredibly precise reactions in caesium atoms.ut because the Earth's rotation is irregular and is slowing down by two thousandths of a second per day, this would cause us to drift slowly away from astronomical time.
The cell phone, thumb-drive flash storage, watches set to atomic time
, the iPod, digital cameras (scratch that--they're usually gizmos), pens that photograph what they're writing so a computer can store the cursive output and translate it into digital text--these all display genius and serve useful purposes.
To keep Earth time and atomic time
in sync, experts have agreed to insert a leap second every few years into the official atomic-based standard, which is called Coordinated Universal Time.