The NIST team are on a mission of testing the equivalence principle of Einstein’s Theory of General Relativity. NIST stands for National Institute of Science and Technology. The team has made the use of the atomic clocks from across the globe for their current research study.

The findings of the research mark its presence in the journal Nature Physics. The study follows the thought experiment of great scientist Sir Einstein. Einstein’s Theory of General Relativity claims that the occupant of a windowless lift (or elevator, for our US chums) is unable to tell the difference between gravitational pull and acceleration. Further, the theory explains that every individual present within the lift would experience the same degree of gravity or what we refer as acceleration due to gravity. In addition to this, all other properties of every person in relation to every other person will remain constant and with a zero deviation.

The team of NIST concentrated on our Blue Planet for their study. They focused on Earth as a lift falling off the gravitational field of the Sun. They made use of around twelve atomic clocks spread across the world for their study and incurred the data of past fourteen years. The twelve atomic clocks were inclusive of four hydrogen microwave lasers and about eight cesium fountain clocks.

The NIST research team then compared the data based on the clock ‘ticks.’ This comparison was to show that they were in synchronization over the period.

Here the principle of the Local Position Invariance (LPI) comes into play. The LPI holds the fact that within the falling lift, the non-gravitational effects are independent of both the time and the place. Also, the researchers were successful in demonstrating the difference in the ratios of the frequencies of hydrogen and cesium clocks. This difference in rates was on account of the ‘lift’ fall within a gnat’s whiskers of the result predicted of zero – 0.00000022 plus or minus 0.00000025.

The current findings of the NIST team are about five times better than their previous attempt in the year 2007. The improvement in the present study was due to the better clocks used during the research and the improved data on Earth’s position and Earth’s velocity in space. The team plans for the future visions of the study using optical frequency-based clocks. It is believed that such watches will aid in yielding the results much closer to the zero variance.