Relativity and aging
NIST physicists compared a pair of the world's best atomic clocks to demonstrate that you age faster when you stand just a couple of steps higher on a staircase.
For decades it's been known in the scientific communities that time passes faster at higher elevations. And this inquisitive aspect of Dr. Albert Einstein's theories of relativity (which by-the-way, single handedly altered the notion that time runs at the same rate for everyone, everywhere in the Universe) has been previously proven by comparing clocks on the earth's surface and a high-flying rocket back in 1976, by the Smithsonian Astrophysical Observatory. And again, physicists from the National Institute of Standards and Technology (NIST) of USA have measured this very effect at a more down-to-earth scale of 33 centimeters or about 1 foot very recently! And the result of the experiment was obvious, the further away is a person from the surface of Earth, the faster the time passes for her/him on a human scale. To put it more simply, a person ages faster even when she/he stands a couple of steps higher from our planetary surface! Published in the Sept.24th issue of Science, scientists from NIST, however, explain that the difference (given that distance) is much too small for humans to perceive directly. And the research have found out that a height of that particular difference (one foot or 33 centimeters) actually resulted in a time variance of roughly a billionth of a second per year. Another aspect of the relativity that was observed by the NIST researchers was time also passes more slowly when one moves faster. This is how the research went down. This new "time dilation" experiment was performed by the scientists with the aid of a pair of world's best experimental atomic clocks. These two nearly identical clocks, which were located in different laboratories at NIST and connected by a 75-meter long optical fiber (which allowed the scientists to compare the instruments' timekeeping), are based on the "ticking" of a single aluminum ion (electrically charged atom) as it vibrates between two energy levels over million billion times per second. These aluminum clocks are also very precise and called "quantum logic clocks" since they borrow logical decision-making techniques from experimental quantum computing which makes them extremely accurate. NIST post-doctoral researcher James Chin-Wen Chou, who is also the first author of the paper, explains that the aluminum clocks can detect small relativity-based effects due to their extreme precision and high "Q factor". And this allows the clocks to reflect how reliably the ion absorbs and retains optical energy in changing from one energy level to another. Once the backdrop for experiment was all set, the NIST team focused on two scenarios of Einstein's theories of relativity. For starter, the scientists raised one of the clocks to a height of 33 centimeters or about a foot. And then, when the two clocks were subjected to unequal gravitational forces due to their different elevations above the surface of the earth, sure enough the higher clock ran faster as it experienced a smaller gravitational force. And the lower clock ran slower than the elevated one, at the rate of a 90-billionth of a second in 79 years. Secondly, when the team applied an electric magnetic field to one clock, sending the ion moving back and forth, the moving clock ran slower than the clock that was at rest. This is scientifically referred as the "twin paradox", where a 25-year-old twin sibling who travels the space near the speed of light in a duration which he perceives as only few months will return to Earth to find the other one has already reached his middle age. This "clock research" does have greater implications as NIST is planning to improve the precision of its aluminum-ion clocks so that there can be a better understanding of how time flows differently on the scale of a centimeter (half an inch) in height differences. And this could open the way for the use of atomic-clock networks as "inland tidal gauges". And such networks, NIST hoping, could vitally record the ups and downs in Earth's gravity field created by the geological shifts. And eventually this, in turn, could provide a crucially better understanding of how seismic events arise.
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