Scientists in Singapore Build a Clock That Loses One Second Every 55 Billion Years

SINGAPORE — Scientists at the National University of Singapore have built a pair of atomic clocks so accurate that they would lose just one second in the entire history of the universe, plus a little, a result the team published in the journal Nature that has left physicists describing the work as “the most precise clock comparison ever made” and timekeeping professionals describing it as “a problem for us now, but only in about 54 billion years.”

The clocks use an atom of lutetium, a rare, unglamorous element best known to most people as the green color in certain fireworks and the ingredient in certain kinds of high-end laser surgery. Each clock traps a single lutetium ion in a cage of electric fields and watches it vibrate. The vibration, measured over 200 hours, turned out to be identical on both clocks to a precision of about 5.7 parts in 10 to the 19th power, which the team converted, for the benefit of readers, into one second of disagreement over 55 billion years.

For context, the universe is about 13.8 billion years old. That means the clocks are so in agreement that, if you started them at the Big Bang, they would still be pointing at essentially the same second by the time the universe has finished. They have about four billion years of margin left before they would be considered “off by a bit.”

"They would still be pointing at essentially the same second."

Why this matters, the team explains, is that the best clocks are not just for telling time. A clock precise enough to feel a change in gravity is a telescope pointed at the ground, because gravity, as Einstein was the first to note and physicists have been noting ever since, bends time. The stronger the gravity, the slower the clock. A clock this accurate can map the flow of gravity around the Earth the way a surveyor maps a field, which is useful for geology, for tracking sea level, and for the small number of researchers who are looking for dark matter the way one looks for a needle in a haystack that is also, incidentally, the entire planet.

The practical consequence for the rest of humanity is smaller but real. Navigation systems, financial markets that trade in microseconds, and the entire internet infrastructure that relies on synchronized time all lean on atomic clocks, and a better clock is a better version of all of it. The team said the design is a candidate for a future international standard of time, which would make Singapore, a country the size of one of the smaller U.S. counties, the unofficial timekeeper of the world.

At press time, the two clocks were still ticking, still in agreement, and still, in the words of the lead researcher, “not doing anything we told them not to.” The team’s next goal is a clock that loses one second every 150 billion years, which would make the universe, on current physics, too small to test the difference. They are, the team said, “very excited about the math.”