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Wednesday, 20 February, 2002, 15:02 GMT
Centuries-old clock puzzle solved
Researcher Matthew Bennett adjusts one of the clocks, Georgia Tech Photo - Gary Meek
The researchers recreated Huygens' design
Georgia Tech Photo - Gary Meek

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By BBC News Online's Ivan Noble
Researchers in the US think they have solved a puzzle dating back to the days of the 17th century Dutch scientist, astronomer and inventor Christiaan Huygens.

Huygens was a remarkable figure whose astronomical observations led him to try to design an accurate clock, Georgia Tech researcher Mike Schatz told BBC News Online.

He designed and built the first pendulum clock. "Da Vinci and Galileo had the idea but it was Huygens who made it work," said Dr Schatz.

While testing a pair of his clocks at sea, Huygens saw a strange phenomenon which has taken until now to explain.

Striking observation

Huygens had two clocks side by side and he found that even when they began out of sync, they soon got into a rhythm where the pendulum on one moved as if it were a mirror image of the other.

Rebuilt Huygens' clock, Georgia Tech Photo - Gary Meek
Huygens' clocks were just the right size
Georgia Tech Photo - Gary Meek

"The observation was very striking and the issue of synchronisation is big today because there's so much technology and many biological processes that depend on it," explained Dr Schatz.

"Every talk on the subject starts with Huygens' clocks and I set out to try to find out whether anyone had managed to explain their behaviour," he said.

Attempts through the centuries to recreate and explain what Huygens saw have had only partial success.

Huygens himself investigated the possibility of air currents causing the mysterious synchronisation.

Dr Schatz and his colleagues had Huygens' notes translated from their original Latin and French and set out to use modern maths to explain the curious phenomenon.

"Now, we have these more modern tools in nonlinear dynamics and chaos theory," he said.

'Serendipitous event'

In the end, their explanation showed Huygens was both lucky and conscientious.

It turns out that the pendulums only mirror each other when the conditions are just right.

The combined mass of the pendulums has to be very small compared with the combined mass of the entire clock assembly and frame - this was where Huygens was lucky.

But for the synchronisation to work, the clocks also have to run at almost the same speed.

Huygens' clocks were very accurate for their time and this is why he was probably the first person to observe the phenomenon.

"His clocks were such good timekeepers... It was a serendipitous event," said Dr Schatz. Dr Schatz and his colleagues describe their work in the scientific journal Proceedings of the Royal Society A.

See also:

12 Jul 01 | Sci/Tech
World's most precise clock developed
01 Jan 00 | Sci/Tech
Greenwich time gets online
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