While the effects are there at even small differences in elevation or speed, "people won't notice a difference" in their day-to-day lives. ©iStockphoto.com
- Time dilation, an effect of relativity, takes place during everyday activities.
- Time flows slower at higher velocities and faster when at a higher elevation, even a foot higher.
Anyone looking to defer the effects of aging, at least for a split-second, may want to think about driving fast cars at low elevations, according to scientists from the National Institutes of Standards and Technology (NIST).
New experiments have proven that time dilation, a phenomenon predicted by Einstein's theories of relativity where time flows faster or slower depending on speed and gravity, occurs during ordinary events like riding a bike or climbing the stairs.
"We demonstrated that with our incredibly accurate clocks, just going up a step or two, we can see the effects of time dilation," said James Chou, a co-author of the new Science article.
While the effects are there at even small differences in elevation or speed, "people won't notice a difference" in their day-to-day lives.
Movies and television often interpret this phenomenon as one person being shot into space at nearly the speed of light and returning with only minimal aging, while the Earth-bound counterpart grows old.
A consequence of Einstein's 1905 theories of relativity, time dilation wasn't definitely proven for many years.
In one particularly famous demonstration in 1971, scientists equipped commercial jets with atomic clocks and flew them around the world. When the aircraft landed, the clocks on the aircraft and the clocks on the ground did not match up. This demonstrated that the time dilation predicted by Einstein indeed happened.
"People have measured time dilation before," said Vladan Vuletic, a professor of physics at the Massachusetts Institute of Technology who was not involved in the research. "But it's impressive that it can be measured over such small distances."
The new experiments used more mundane methods -- and much more precise clocks -- to test the theory.
The NIST scientists used aluminum ions that act like the second hand, ticktocking between two energy levels over a million-billion times per second. The two clocks are some of the most accurate in existence.
In the first experiment, the scientists offset the two clocks by roughly one foot in elevation to test gravity's effect of the flow of time. In the second experiment, since they couldn't send the clocks around the world at a high speed, the scientists made one clock's ion oscillate faster than the other, several meters per second faster, to test the effect of speed on time dilation.
In both experiments, time flowed differently. Time flowed faster in the clock at a higher elevation, as predicted. Similarly, time flowed slower in the clock where the ions moved faster.
The difference in the clocks was very small, but given the distances involved were significant. If two people somehow managed to live 79 years exactly one foot apart in elevation, the difference in time would only amount to 83 billionths of a second.
One foot is not very far apart, however. What if the distance between two people was much larger, say a person standing on top of the Empire State Building and another one on Fifth Avenue?
"Even over a lifetime it wouldn't come to a second's worth of difference," said Chou.