Einstein's theory of relativity states that time and space are not as constant as everyday life would suggest. He suggested that the only true constant, the speed of light, meant that time can run faster or slower depending on how high you are, and how fast you are traveling.
Now researchers have demonstrated the true nature of Einstein's theory for the first time with an incredibly accurate atomic clock that is able to keep time to within one second in about 3.7 billion years - roughly the same length of time that life has existed on Earth, The Independent reported.
James Chin-Wen Chou and his colleagues from the US National Institute of Standards and Technology in Boulder, Colorado, found that when they monitored two such clocks positioned just a foot apart in height above sea level, they found that time really does run more quickly the higher you are - just as Einstein predicted.
"These precise clocks reveal the effects of gravitational pull, so if we position one clock closer to a planet, you also increase the gravitational pull and time actually runs slower than for another, similar clock positioned higher up," Chou said.
The atomic clocks used in the study are based on the tiny vibrations of aluminium atoms trapped in an electric field. These vibrations are in the same frequency range of ultraviolet light, detected by lasers, which means that the atomic timepieces are optical clocks, accurate enough to measure billionths of a second.
It means that the clocks were able to perceive the dilation of time with height above ground. For every foot above ground the clocks showed that someone would age about 90 billionths of a second faster over a 79-year lifetime, Chou said.
Besides, the scientists demonstrated that when the atomic clocks were altered in a way that mimics the effect of travelling through space, time began to slow down, as the theory of relativity says it should.