In 1675, Huygens and Robert Hooke invented the spiral balance spring, or the hairspring, designed to control the oscillating speed of the balance wheel. This crucial advance finally made accurate pocket watches possible. The great English clockmaker, Thomas Tompion, was one of the first to use this mechanism successfully in his pocket watches, and he adopted the minute hand which, after a variety of designs were trialled, eventually stabilised into the modern-day configuration.[40] The rack and snail striking mechanism for striking clocks, was introduced during the 17th century and had distinct advantages over the 'countwheel' (or 'locking plate') mechanism. During the 20th century there was a common misconception that Edward Barlow invented rack and snail striking. In fact, his invention was connected with a repeating mechanism employing the rack and snail.[41] The repeating clock, that chimes the number of hours (or even minutes) was invented by either Quare or Barlow in 1676. George Graham invented the deadbeat escapement for clocks in 1720.
As of the 2010s, atomic clocks are the most accurate clocks in existence. They are considerably more accurate than quartz clocks as they can be accurate to within a few seconds over thousands of years.[54] Atomic clocks were first theorized by Lord Kelvin in 1879.[55] In the 1930s the development of Magnetic resonance created practical method for doing this.[56] A prototype ammonia maser device was built in 1949 at the U.S. National Bureau of Standards (NBS, now NIST). Although it was less accurate than existing quartz clocks, it served to demonstrate the concept.[57][58][59] The first accurate atomic clock, a caesium standard based on a certain transition of the caesium-133 atom, was built by Louis Essen in 1955 at the National Physical Laboratory in the UK.[60] Calibration of the caesium standard atomic clock was carried out by the use of the astronomical time scale ephemeris time (ET).[61] As of 2013, the most stable atomic clocks are ytterbium clocks, which are stable to within less than two parts in 1 quintillion (2×10−18).[62]
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The piezoelectric properties of crystalline quartz were discovered by Jacques and Pierre Curie in 1880.[49][50] The first crystal oscillator was invented in 1917 by Alexander M. Nicholson after which, the first quartz crystal oscillator was built by Walter G. Cady in 1921.[2] In 1927 the first quartz clock was built by Warren Marrison and J. W. Horton at Bell Telephone Laboratories in Canada.[51][2] The following decades saw the development of quartz clocks as precision time measurement devices in laboratory settings—the bulky and delicate counting electronics, built with vacuum tubes, limited their practical use elsewhere. The National Bureau of Standards (now NIST) based the time standard of the United States on quartz clocks from late 1929 until the 1960s, when it changed to atomic clocks.[52] In 1969, Seiko produced the world's first quartz wristwatch, the Astron.[53] Their inherent accuracy and low cost of production resulted in the subsequent proliferation of quartz clocks and watches.[49]

In China, a striking clock was devised by the Buddhist monk and inventor Yi Xing (683–727).[5] The Chinese engineers Zhang Sixun and Su Song integrated striking clock mechanisms in astronomical clocks in the 10th and 11th centuries, respectively.[6] A striking clock outside of China was the water-powered clock tower near the Umayyad Mosque in Damascus, Syria, which struck once every hour. It was constructed by the Arab engineer al-Kaysarani in 1154. In 1235, an early monumental water-powered alarm clock that "announced the appointed hours of prayer and the time both by day and by night" was completed in the entrance hall of the Mustansiriya Madrasah in Baghdad.[7]
In a clock driven by a weight or a spring, the power is first transmitted by the main, or great, wheel. This engages with a pinion (a gear with a small number of teeth designed to mesh with a larger wheel), whose arbor (a turning rod to which gears are attached) is attached to the second wheel that, in its turn, engages with the next pinion, and so on, down through the train to the escapement. The gear ratios are such that one arbor, usually the second or third, rotates once an hour and can be used to carry the minute hand. A simple 12-to-1 gearing, known as the motion work, gives the necessary step-down ratio to drive the hour hand. The spring or weight is fitted with a mechanism so it can be rewound when necessary, and the arbor carrying the minute hand is provided with a simple slipping clutch that allows the hands to be set to the correct time.

There’s a lot of science when it comes to sleeping, and there’s never a short supply of sleep-related tests going on. One of our favorite electronic brands here on Gear Hungry has made the most effective clock (in our humble opinion), and it’s the #8 pick: Philips Wake-Up HF3505. Slow light build mimics the sunrise, and gently pulls you out of a sleep-like trance before hitting you with some serious sound. Between price, effectiveness, and the fact that we didn’t have to chase it around the room (sorry Clocky, we’re not morning people), we absolutely loved this one.

You know that feeling you get when you draw the blinds, and you didn’t expect it to be so sunny? That’s what this alarm clock does for you, except it wakes you up instead. Philips incorporated yellow-and-white light into this sunrise simulation programmable alarm clock, and this is the only alarm clock/lamp that’s certified to help you sleep better, and awake more refreshed than you ever thought possible. From America’s favorite retailer of small and budget-friendly gadgets, Philips does it again.
“This little beauty works great. I bought it when the alarm on my mobile phone began to intermittently fail me. This little travel clock is beautiful in retro seafoam green and great for travel because its bright color ensures that you will never miss picking it up from your hotel nightstand at checkout. There is a faint, pleasant ticking, the hands glow in the dark, and the nightlight button is bright when needed. The pop-up alarm button is firm and works well though I am learning not to accidentally press it and turn the alarm off when picking up the clock. Overall, a fantastic alarm clock.”