Search results
Results from the WOW.Com Content Network
International Atomic Time. International Atomic Time (abbreviated TAI, from its French name temps atomique international [1]) is a high-precision atomic coordinate time standard based on the notional passage of proper time on Earth's geoid. [2] TAI is a weighted average of the time kept by over 450 atomic clocks in over 80 national laboratories ...
Time standards. An atomic clock is based on a system of atoms which may be in one of two possible energy states. A group of atoms in one state is prepared, then subjected to microwave radiation. If the radiation is of the correct frequency, a number of atoms will transition to the other energy state.
NIST-F1, source of the official time of the United States. NIST-F1 is a cesium fountain clock, a type of atomic clock, in the National Institute of Standards and Technology (NIST) in Boulder, Colorado, and serves as the United States' primary time and frequency standard. The clock took less than four years to test and build, and was developed ...
NIST physicists Steve Jefferts (foreground) and Tom Heavner with the NIST-F2 cesium fountain atomic clock, a civilian time standard for the United States. NIST-F2 is a caesium fountain atomic clock that, along with NIST-F1, serves as the United States ' primary time and frequency standard. [1] NIST-F2 was brought online on 3 April 2014.
The Hafele–Keating experiment was a test of the theory of relativity. In 1971, [1] Joseph C. Hafele, a physicist, and Richard E. Keating, an astronomer, took four caesium -beam atomic clocks aboard commercial airliners. They flew twice around the world, first eastward, then westward, and compared the clocks in motion to stationary clocks at ...
International Atomic Time (TAI) was set equal to UT2 at 1 January 1958 0:00:00. At that time, ΔT was already about 32.18 seconds. The difference between Terrestrial Time (TT) (the successor to ephemeris time) and atomic time was later defined as follows: 1977 January 1.000 3725 TT = 1977 January 1.000 0000 TAI, i.e. TT − TAI = 32.184 seconds
NIST. March 2010. WWVB is a time signal radio station near Fort Collins, Colorado and is operated by the National Institute of Standards and Technology (NIST). [1] Most radio-controlled clocks in North America [2] use WWVB's transmissions to set the correct time.
Universal Time. Universal Time ( UT or UT1) is a time standard based on Earth's rotation. [1] While originally it was mean solar time at 0° longitude, precise measurements of the Sun are difficult. Therefore, UT1 is computed from a measure of the Earth's angle with respect to the International Celestial Reference Frame (ICRF), called the Earth ...