Any expansion or contraction of the rod caused by changes of temperature will affect the timekeeping of a pendulum; e.g., a pendulum clock with a steel rod will lose one second a day for a rise in temperature of approximately 4 °F (2.2 °C). For accurate timekeeping, the length of the pendulum must be kept as nearly constant as possible. This may be done in several ways, some of which use the differing coefficients of expansion (the amount of expansion per degree change in temperature) of different metals to obtain a cancelling-out effect. In one popular compensation method, the bob consists of a glass or metal jar containing a suitable amount of mercury. The gridiron pendulum employs rods of different metal, usually brass and steel, while in the zinc-iron tube the pendulum rod is made of concentric tubes of zinc and iron. An improved method, however, is to make the pendulum rod from a special alloy called Invar. This material has such a small coefficient of expansion that small changes of temperature have a negligible effect and can easily be compensated for if required.
Revamp the interiors of your living room with the Howard Miller Cooper Table Alarm Clock. Built for functionality and practicality, the table clock is elegant and stylishly designed to add an edge to your home. With contemporary and modern accents, the alarm clock will awaken you with its impeccable design and beauty. Crafted out of glass and metal, the table alarm clock is the perfect combination of efficiency and glamour. The top and base materials are made out of a firm aluminum frame...
For some scientific work timing of the utmost accuracy is essential. It is also necessary to have a standard of the maximum accuracy against which working clocks can be calibrated. An ideal clock would give the time to unlimited accuracy, but this is not realisable. Many physical processes, in particular including some transitions between atomic energy levels, occur at exceedingly stable frequency; counting cycles of such a process can give a very accurate and consistent time—clocks which work this way are usually called atomic clocks. Such clocks are typically large, very expensive, require a controlled environment, and are far more accurate than required for most purposes; they are typically used in a standards laboratory.

Bring your master suite into the 21st century with this essential alarm clock, offering both fashion and function for your mornings. Measuring 3.25" square, its curved frame is crafted from plastic and acrylic for a sleek, clean-lined look that's especially suited for contemporary aesthetics. This clock displays the time lit up with an LED light, powered by three AAA batteries. Plus, this piece comes backed by a one-year warranty from the manufacturer.

Acadia finish on select hardwoods and veneers is heavily distressed by scribes, and worm holes for a natural, rustic appearance — inspired by the natural yet rustic nature of reclaimed woods in beautiful patinas and burnished details. Features a multi-tiered flat top, distinctive columns with corbels frame the door. Circular spun antique nickel-finished dial with black Roman numerals, hour markers, and hands. Antique nickel-finished lyre pendulum. Quartz, battery-operated, triple-chime Harmonic movement plays choice of full Westminster or Ave Maria chimes with strike on the hour with 1/4, 1/2, and 3/4 chimes accordingly; Westminster chime and strike on the hour only; or Bim Bam chime on the hour only. Volume control and automatic nighttime chime shut-off option. Powered by two C sized batteries. One year warranty and Free Shipping

Molded by mid-century modern style, this 38" wall clock brings a bit of bold flair to any space in your home. Its generous size helps it grab glances (and compliments!) from guests, while its open and numberless design gives it a minimalist feel. Crafted from metal, this round silhouette sports a gold finish with silver-finished hands in the center for subtle contrast. Two AA batteries (not included) are required to operate.


Certainly not just for telling time, wall clocks are perfect for adding artful appeal to your kitchen wall or acting as a focal point above the living room mantel. Take this one for example: a true traditional, its Roman numeral dial is accented by a world map detailing the face. Crafted from plastic, its frame offers more of a metal-inspired look with molded trim and a bronze finish. Requires one AA battery.

An artful accent is all your need to take your entertaining space from every day to eye-catching. While low-slung sofas and a plush shag rug make a fine foundation, you can effortlessly dress it all up by centering this chic clock on the wall above. Pairing brushed aluminum metal with walnut-finished wood panels, this sunburst-inspired piece is brimming with mid-century style. Let it shine solo above an exposed light bulb lamp sitting on an end table so you can watch the time at your pre-dinner...

Bring contemporary and clean-lined looks to your walls with this understated wall clock, this perfect mix of subtle, airy looks and midcentury modern aesthetics in your space. Featuring a simple rectangular metal frame finished in antique brass and distressed gray, this clock brings a warm look to your ensemble, while its elongated Roman numerals offer an updated twist on a classic look. To clean, simply wipe with a damp cloth.


Though no longer our first pick of timepiece thanks to the smart phone, this old-fashioned clock still scores points for form. Measuring 6.25'' H x 2.5'' W x 5'' D, this compact clock’s face is encased in a metal case with a brushed nickel finish and convex glass lens, while its faded dial stays in step with vintage styling. This item is battery operated, but does not emit a loud ticking noise, so you can snooze to your heart's content.
The iHome has more in common with a sound system than an alarm clock, but this all-in-one device is perfect for anyone who’s looking to declutter their nightstand on a budget. Along with having a good alarm clock to wake you up every morning, the iHome also features Bluetooth connectivity and FM radio, meaning you’ll no longer have to deal with pesky USB chargers before you go to bed. The translucent cabinet and display changes color with the touch of a button, so you can wake up to your favorite colors.

Never squint to see what time it is again, especially when you're waking up 20 times in the middle of the night to, you know, see exactly what time it is. We love the projection feature that displays the time on your wall or ceiling for easy viewing. Plus, it'll even toss up the temperature — so you'll already know what you should wear to work before you even get out of bed.
From the 14th century, some clock towers in Western Europe were also capable of chiming at a fixed time every day; the earliest of these was described by the Florentine writer Dante Alighieri in 1319.[8] The most famous original striking clock tower still standing is possibly the one in St Mark's Clocktower in St Mark's Square, Venice. The St Mark's Clock was assembled in 1493, by the famous clockmaker Gian Carlo Rainieri from Reggio Emilia, where his father Gian Paolo Rainieri had already constructed another famous device in 1481. In 1497, Simone Campanato moulded the great bell (h. 1,56 m., diameter m. 1,27), which was put on the top of the tower where it was alternatively beaten by the Due Mori (Two Moors), two bronze statues (h. 2,60) handling a hammer.
Strong, durable, super large time display makes the model perfect for those who either want a big number clock, or for visually impaired individuals who need extra-large numerals, The red LED display on a black background, makes the contrast ideal for easy viewing. The electric power with battery backup lets you sleep with peace of mind and the extra-large snooze bar keeps nap-time within reach. This clock is a solid purchase.
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]
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]
During the 15th and 16th centuries, clockmaking flourished, particularly in the metalworking towns of Nuremberg and Augsburg, and in Blois, France. Some of the more basic table clocks have only one time-keeping hand, with the dial between the hour markers being divided into four equal parts making the clocks readable to the nearest 15 minutes. Other clocks were exhibitions of craftsmanship and skill, incorporating astronomical indicators and musical movements. The cross-beat escapement was invented in 1584 by Jost Bürgi, who also developed the remontoire. Bürgi's clocks were a great improvement in accuracy as they were correct to within a minute a day.[35][36] These clocks helped the 16th-century astronomer Tycho Brahe to observe astronomical events with much greater precision than before.[citation needed][how?]
Designed to fit anywhere in your home, the Amazon Echo Spot uses voice recognition to let you see weather forecasts, read music lyrics, listen to Audible audiobooks, and more — and it’s all hands-free. Just ask Alexa to snooze the alarm. You can even ask Alexa to control the smart home devices in your house, including lights, locks, cameras, and thermostats. Need to make a phone call and don’t want to walk across the room to your phone? Ask the Spot to make phone calls or video calls to family and friends. As you can see, the Spot has much more in common with the Echo Dot than with a traditional alarm clock, although you’ll still get the time and a sleep mode. For more, read our full review.
Marathon's Atomic alarm clock with temperature and date is packed with features. It has an ambient light sensor, which allows the auto-night light to illuminate the display when necessary. With a soft amber LED, the large digit display is easy to read at night and becomes even brighter if the Snooze/Light button is pressed. At a glance you can easily see the time, date, day and temperature. The controls on the front of the clock allow you to easily set the alarm, switch between Fahrenheit or...

A clock that looks good and runs smoothly instantly adds charm and functionality to your living space. For a fresh take on the traditional wall clock, consider this eye-catching design. Introducing Ribbonwood by Umbra Add a modern, minimalist twist to telling time. With Ribbonwood, you get a stylish piece of wall décor and a functional wall clock all-in-one. Made with natural beech wood that’s been shaped to resemble overlapping ribbons, this unique clock features contrasting hands that...
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