A Clock Thing

A New Atomic Generation

Contributed by Andy Page, February 17, 2003

No Time Left to Lose
By Jonathan Amos

Scientists are developing a new generation of atomic clocks which will be so accurate they will have lost only about a second by the time the world ends a few billion years from now. The clocks' technology will be used in telecommunications and experiments testing fundamental theories in physics and in probing human diseases.

Experts in the field reviewed their progress in producing the next generation of so-called optical atomic clocks at the American Association for the Advancement of Science (AAAS) annual meeting in Denver.

They expect the new super-accurate devices to be in routine use in just over a decade.

Faster ticks

Existing atomic clocks are - to the normal everyday experience - already extremely accurate.


Optical atomic clock: The first prototypes now exist

After running for more than 15 million years, these devices should lose no more than a second.

They count time based on the way caesium atoms jump back and forth between different energy levels.

These very regular jumps or "ticks" occur at microwave frequencies and are used to define the second - exactly 9,192,631,770 ticks per second to be precise.

But last year, researchers at the National Institute of Standards and Technology (Nist) in Washington DC went a step further with a clock based on the optical frequency of a single cooled mercury ion (a mercury atom with one electron stripped off).

In this device, a super-fast laser is needed to count the far more rapid jumps the mercury ion makes as it moves between energy states - producing about 1.065 quadrillion ticks per second.

"We know the clock is very stable, so now our research is focused on seeing exactly how accurate it is," Scott Diddams, a Nist researcher told the AAAS.

Experiments suggest this clock may lose only one second in 100 million years.

Faster data

Now, the trick is to take this technology still further.

The difficulty comes in counting faster and faster things, as the division between ticks becomes smaller and smaller.

Researchers are hopeful the development of laser counters will push clocks to theoretical billion-year accuracy.

According to scientists like Nist's Leo Hollberg, the new technology will allow scientists to investigate some fundamental questions about the Universe,

The clocks will be used
in disease research
whether Einstein's predictions were correct and how forces like gravity have changed during its turbulent history.

"As the Universe expands and cools from the Big Bang - do the fundamental constants, do the forces of nature evolve as the Universe cools," he said.

"There are some hints from astronomical observations that they might have in the early Universe - those constants and forces might have been different to what they are now.

"By using these clocks, we can put some constraints on that."

Super-accurate clock technology could also find a use in biology as scientists try to follow processes inside human cells, watching and timing genes as they switch on and off, which will give new insights into diseases like cancer.

There are more prosaic applications as well, speeding up telecommunications and making them more secure from hackers.

They should also improve navigation. Every satellite in the GPS system, for example, carries an atomic clock.

Nist hopes international partners will adopt the new clock standards in a decade or so.

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