IN HISTORICAL DISPLAY, TIME IS THE ESSENCE

In a single small display case holding several mechanical clocks, the Museum of Science and Industry has neatly encapsulated humanity’s progressively more complicated relationship with one of its most basic inventions–time.

The oldest timepiece is a 16th Century clock equipped with just one hand, able to mark only the passage of hours.

“That hour hand took the place of the shadow that once traveled across the face of sundials,” said Mark Hayward, the Chicago museum’s exhibit developer.

The next clock in the case, from the 17th Century, has hands for the hours and the minutes.

“After those earliest clocks the mechanization gradually improved,” Hayward said, “and people began seeing the need to break up time into ever smaller parcels.”

A 19th Century clock adds the second hand and after that come sophisticated 20th Century instruments that can measure into the tenths and hundredths of a second.

“When I was first asked to work on this exhibit,” said Hayward, “I thought, `What’s there to show? Time is like air, isn’t it? It’s just there.'”

In fact, not much is simple about time. Nobody, not even Einstein, has ever been able to define what time is.

“It is one of the simplest questions one can ask and at the same time is one of the most profound ones,” said University of Chicago cosmologist Michael Turner.

When theoretical physicists speculate about time, they sound like characters out of “The Twilight Zone,” talking about bending time and stopping time or the possibility of other times in other universes.

Opening Friday, the exhibit “Time” that Hayward designed goes from prehistory, when the passage of time was mostly measured by sunrise and sunset, to the current day, with machines that can calibrate it down to 0.0000000000000015 seconds.

Hayward used what is perhaps the world’s best collection of clocks, watches and time pieces ever assembled.

It is the collection the City of Chicago bought for $25 million in November 1999 cq from Rockford industrialist Seth Atwood. He had housed and displayed it for 28 years as the Rockford Time Museum along Interstate Highway 90.

The permanent time exhibit, free with museum admission, had been scheduled to open Dec. 31. But it ran late.

Atwood, whose family fortune came from making vacuum cleaners and from real estate, spent 30 years amassing the collection. It consists of devices that all cultures have used to measure the passage of time over the last 3,000 years, most of them original pieces.

In all, the city acquired 1,551 pieces from the Atwood collection. The museum is using 450 of them to teach several lessons about time, a relatively new concept to human society.

Ancient people thought more in terms of natural cycles–such as day and night, annual seasons, and birth, maturation and death–than in terms of periods of duration along a linear scale.

Egyptians invented the idea of hours, but ancient cultures measured their days in temporal time, meaning an hour was an elastic thing to them, changing in duration by seasons. A daylight hour was long in summer but short in winter.

The Japanese did not give up on temporal time until the 1870s, adjusting the length of their daytime and nighttime hours on their mechanical clocks every week.

“The word for clock comes from old German and English words that mean bell,” said Hayward. “That’s what the first mechanical clocks were, automated bell ringers that replaced human ringers who used to sit in the towers and watch sand hourglasses, ringing bells each time sand ran out.”

For hundreds of years, he said, people knew the time only from public clock towers. They had no clocks in their homes.

“But 400 years ago, people weren’t too concerned with time,” Hayward said. “Lateness is a modern idea. People were never late; they just got there when they got there.”

A turning point came with the invention of pendulum clocks. The earliest-surviving such clocks, accurate to one minute a day, were built by Salomon Coster in Holland in 1657. One of seven of his surviving clocks is in the exhibit.

“Pendulum technology gave birth to accurate timekeeping,” said Hayward, “and it remained the standard of timekeeping technology for 350 years, right up to 1900, which is pretty good for a technology.

“Pendulum clocks were replaced finally by quartz clocks for accuracy. And that lasted 30 years, until quartz was replaced by atomic clocks, which remain the standard today.

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“People forget that clock technology is so old and have such a long history of refinements that they remain the most efficient machines ever made. Lewis Mumford, the social historian, said clocks and watches are the machines that all other machines aspire to be.”

Precision clocks and timing devices were necessary to inventors building machines as the Industrial Revolution took off. Cheap clocks also were necessary in organizing factory systems and getting workers to their jobs at proscribed times.

The exhibit has examples of the first clocks to be mass-produced with interchangeable parts, the brilliant idea of Connecticut clockmaker Eli Terry in 1810. Mass production made clocks affordable to all.

The last portion of the exhibit leads viewers through the scientific enigma of time that physicist Albert Einstein presented with his theory of relativity.

“More than ever, there are scientific disagreements as to just what time is and does it even exist at all,” said Hayward.

“Einstein’s theory abolished the idea of absolute time and established that it is a plastic medium. He postulated that if you had a set of twins and one remained on Earth while the other was rocketed into outer space, they would experience time differently. Time stretches with acceleration, he said, so that the twin on the rocket would not age as fast as the twin left on Earth.”

Using special twin hydrogen maser clocks, one sent to space and one remaining on Earth, NASA eventually proved Einstein’s theory. One of those clocks is in the exhibit.

Today’s physicists believe time can behave in weird ways, especially on the intergalactic scale. Out there, time apparently slows and even stops near black holes and bends around stars and other large objects.

“A few believe time doesn’t exist at all,” said U. of C.’s Turner. “Others speculate that there are other times in other universes.

“But in the end, the experts really don’t know much more about time than the average person on the street. All we know is most people don’t have enough of it.”