“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,” Dr. Chou noted in his study. “No one has seen such effects before with clocks, which is why we wanted to see if these effects are there.”
“We would say our results agree with Einstein’s theory—we weren’t expecting any discrepancies and we didn’t find any,” he added.
More than a century ago, Albert Einstein proposed that time is a relative concept. Instead, he proposed that the only true constant was the speed of light, and that time could change depending on how high you are and how fast you are traveling. He suspected that the higher you live above sea level, the faster you should age. Now, scientists have used the world’s most accurate clock to show just how right the legendary genius really was.
For the first time, scientists have demonstrated the true nature of Einstein’s theory using an accurate atomic clock. The machine is able to keep time to within one second in about 3.7 billion years—the same length of time that life has existed on Earth.
When James Chin-Wen Chou and his colleagues from the US National Institute of Standards and Technology in Colorado 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.
The atomic clocks are based on tiny vibrations of aluminum atoms trapped in an electric feed. While an ion clock works with a single atom, this clock allows you to manipulate thousands of atoms at a faster speed, giving scientists the ability to measure the frequency of atomic clocks to 17 digits accurately. The vibrations are in the same frequency range as ultraviolet light, meaning that the atomic clocks are optical clocks—accurate enough to measure billionths of a second and to keep time accurately for millions of years. These amazing clocks revealed that for every foot above sea level, someone would age about 90 billionths of a second faster of a 79-year lifetime.
The study also revealed that one the atomic clocks were altered in a way to mimic the effects of traveling through space, time began to slow down. Essentially, this was the first practical demonstration of the “twin paradox,” or the idea that an identical twin sibling who travels through space in a rocket will age more slowly than the other twin living on Earth.
The experiment, first published in Science, is stunning proof of how time is not what we perceive it to be. Einstein called the moment he realized that gravity and acceleration were the same thing “the happiest thought of [his] life.” 100 years later, his findings stand strong.