Timekeeping: Technological Timeline

Discover magazine featured an article on timekeeping in their July 2000 issue. I was able to construct the following TL timeline based on what was in the article and a couple others (see references below). If you have any suggestions to add to this timeline, please .

TL Advancements
0 After decades of astronomical observations (possibly longer), stones are arranged such that the local star is observed to cycle through the monument. One cycle becomes the basis of the local year. The day is measured by the position of the primary star in the sky.
1 The first chronometers, devices able to measure the day, appear. The sundial, shadow clock, and water clock each try to offer ways to measure days without direct observance of the local star. Each relies on natural phenomena (light & gravity) to measure time. Each is accurate, at best, to 15 minutes per day.
2 The first mechanical clocks appear. Two hands denote the passage of time. One hand indicates the hour while the other the minute. In some instances, a third hand appears to mark the passage of seconds. The chiming of bells is often used to mark the passage of the hours. The cost and incredible size of these machines make them cost-prohibitive to all but institutions and aristocrats.
3 Pendulum clocks, which rely upon a planet's rotation for calibration, improve mechanical timekeeping to 1 second per month accuracy. Decreasing costs and size increase their availability to the masses.
4 The first "pocket watches" appear enabling people to carry timepieces around with them instead of relying upon structures to house them. Accuracy is sacrificed for convenience. These watches, which rely upon hairsprings and balance wheels, are accurate to within 30 seconds per week and have to be wound up regularly to ensure consistent timekeeping.
5 Pendulum clocks peak out at an accuracy of 0.3 seconds per year. The first quartz clocks are introduced. Accurate to 10 seconds per year, these devices measure the vibration of quartz crystals as electric current is passed through them.

Watches are now equipped with straps to be wrapped around appendages (arms in the case of humanoids).
6 Timekeeping takes a big leap forward thanks to advancements in physics. The ammonia clock measures resonance in ammonia molecules interacting with microwaves. Its accuracy is 1 second per 5 years. The first cesium clock, accurate to 1 second in 100 years, redefines the second as 9,192,631,770 cycles of the cesium atom's resonance frequency.

Clocks become embedded in appliances, computers, and vehicles. Their presence in society becomes ubiquitous.

Personal watches increase in accuracy. Tuning forks bring accuracy to within one minute per month. Quartz clocks are shrunk down to become watches and are accurate to 5 seconds per month. Their high price makes them unaffordable to the general public.
7 The first commercial masers appear. Accurate to 1 second per 274,000 years, masers measure hydrogen frequencies and are more stable than cesium clocks.

Watches diversify. Liquid crystal displays, alarms, chronometers, and water resistance (up to 100 meters depth or 14 atm pressure) all appear.
8 Cesium fountain clocks appear. Their accuracy is 1 second per 20 million years. High population planets become increasingly dependent upon the reliability of these clocks as global synchronization becomes crucial to staving off chaos.

Watches increase in sophistication and precision but decrease in price such that all can afford them. Quartz watches decrease in price but remain status symbols.

Advances in electronics enable watches to incorporate other functions including: thermometer, barometer, compass, and altimeter.
9 Stored-ion clocks appear. These clocks are capable of trapping atoms for indefinitely long observations. The appearance of gravitic technology enables clocks to ignore the effects of gravitational fields upon their ability to measure time.

Advances in wetware computer technology enable watches to be implanted underneath the skin for those that wish it.
10 Advances in gravitics enable researchers to develop clocks which are immune to the effects of gravity. Clocks become able to set themselves to local time in 1 planetary rotation.
11 Gravitically immune clocks appear in all vehicles which utilize gravitics.
12 With special attachments, clocks set themselves to Imperial Standard Time via astronomical observations.

1. "The Best Clock in the World ... and why we can't live without it", Discover Vol.21 No.6 (June 2000).
2. "A Walk Through Time", NIST website.
3. "Touch Screen Info Machine", Discover Vol.25 No.7 (July 2004).
4. "A Clock More Perfect Than Time", Discover Vol.17 No.12 (Dec 1996).

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