Time is something we can't seem to change, no matter what we do. It marches on, minute by minute and second by second. And we use clocks to watch it progress. However, a team of scientists recently built a new clock that is so accurate that it might end our concept of time completely.

First, we have to understand that time isn't as standard as we generally think. Suppose you work in the same building as someone else, but you work on the top floor and that person works on the bottom floor. In that building, all clocks display the same time. If you have a meeting with someone at 2 p.m., it's likely that you're both working on the same perceptions of time and will meet.

However, the truth is that time doesn't really work like that. Gravity actually affects the speed of time. For example, time is moving faster at the top of a building than at the bottom of a building. If clocks were really accurate, the above meeting wouldn't happen because you and your co-worker have separate perceptions of time.

Of course, most clocks don't work like that. However, a team of researchers from the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder have built a clock that is so sensitive that it tells time differently depending on its location. If it's sitting higher up, time moves faster on the clock. If it's placed on the floor, time is moving slower.

Inside this clock is a small chamber holding strontium atoms suspended in air by laser beams. Researchers ping those beams which makes the strontium vibrate incredibly fast. This creates a clock that ticks out not just minutes or seconds, but fractions of seconds.

This clock is so accurate that it could tell time with precision for 5 billion years.

"It's about the whole, entire age of the earth," says Jun Ye, one of the scientists that built the clock. "Our aim is that we'll have a clock that, during the entire age of the universe, would not have lost a second."

Obviously, such a clock isn't useful for the real world, where we need clocks synced up so that we can make our meetings. However, a clock with that kind of sensitivity has major scientific implications.

"Scientists can make these clocks into exquisite devices for sensing a whole bunch of different things," says Tom O'Brian, of the NIST. Their extraordinary sensitivity to gravity might allow them to map the interior of the earth, or help scientists find water and other resources underground."

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