History of Time Prime Time Team: Gale, Jen, and Shirley Trip Through Time • Can you measure the time of day by gazing at the sun’s shadow? • How does the flow of water aid in the measure of time? • What did the Chinese burn to tell time? • Let’s take a “Trip Through Time” to discover the answers to these ancient timekeeping secrets. Timeline 1500 – 1300 BC Sundials • Egyptians measured the time of day by using sundials. Sundials rely on the sun to tell time. These early timekeepers discovered that hours are shorter in the winter and longer in the summer. • Sundials can only be used during the day to tell time. Timeline 400 BC Water Clocks • Discovered by the Greeks these clocks measured time by observing the overflow of water from a container. • Made of two containers, water drips from the higher container to the lower container. The point at which the water is collected raises a floating device which triggers the pointer to mark the hour. • These clocks worked better than the sundial because they were able to tell time at night. • In later years these clocks were adopted by the American Indians. Timeline 980 - 1000 • Candles • The candle was used as the first alarm clock by placing a nail into the side of the candle wax, waiting for the wax to melt, and the eventually nail crashes into a pan. • The Chinese not only burned candles to mark time, but also burned incense as a measurement of time Timeline 1370 • Bells • King Charles V of France decided that all Paris church bells must ring at the same time as the Royal Palace. This stopped the ringing of bells during prayer time. • The name “Clock” originally meant “Bell.” Timeline 1400 • Mechanical Clocks • These clocks were built in Europe, using a mainspring and balance wheel. • The problem with these clocks was that they would slow down when the main spring unwound. • To eliminate this problem, a fusee, or spiral pulley, was invented. • A fusee is a cone-shaped grooved pulley used with a barrel containing the mainspring. Timeline 1500 - 1600 • Pendulum • In 1583 Galileo Galilei discovered that the rate of a pendulum swing depends on its length. • Christian Huygens invented the pendulum clock around 1656. • As the pendulum swings left to right, a wheel with teeth turns the hour and minute hands. • The second hand on the clock was developed at this time. • This clock was more accurate than any previous clock invented. Timeline 1700 • Navigation • In 1714 the British Parliament offered a cash reward to anyone that could invent an accurate clock for use at sea. • In 1759 John Harrison built a tiny pocket watch that only lost 5 seconds in 6 ½ weeks. Timeline 1800 • Inventions • The telegraph was invented in 1839. This invention allowed instant transmission of time signals. • In 1840 the first battery clock used an electrical impulse to operate the dials of a master clock. • Throughout the 1850s regional time zones were established. • Twenty-five countries accepted Greenwich, England as the Prime Meridian. Eventually, the Prime Meridian became the base of time throughout the world. Timeline 1800 • Inventions • In the early 1800’s Eli Terry mass-produced interchangeable parts for clocks. This made clocks affordable to all people. • 1886 R.W. Sears Watch Co. sold watches across America. Timeline 1900 • Modern Timepieces • In the early 1900’s women wore the wrist watch while men only used pocket watches. Because of the war, soldiers needed to tell time quickly. As a result wrist watches became a socially accepted fashion for men. • In 1928 W.A. Marrison of Bell Labs built the first quartz watch. • Quartz is a type of crystal that vibrates when you apply an electrical charge and pressure. This vibration moves the clock’s hands at a constant rate and is very precise. • Quartz was later used to make wrist watches. Timeline 1900 • Modern Inventions • In 1945 Physicist Isador Rabi experimented with building a clock using atoms. This method was known as atomic-beam magnetic resonance. • In 1949 the first atomic clock using ammonia was built. • In 1967 the first atomic clock using the cesium atom was built. Time no longer depends on astronomical bodies. • For every 1.4 million years, the clock will off by 1 second. Timeline Trivia • Daylight Savings Time/War Time • Although Ben Franklin originally had the idea in 1784, daylight savings time was not adopted in the U.S. until World War I. It was a way to save fuel needed to produce electric power. • In 1966 Congress established the Uniform Time Act. Daylight savings time was implemented throughout the nation. • ½ a billion watches are sold each year.