Clocks driven by springs had appeared by the mid-15th century, making it possible to construct more compact mechanisms and preparing the way for the portable clock.
English spring-driven pendulum clocks were first commonly kept on a small wall bracket and later on a shelf. Many bracket clocks contained a drawer to hold the winding key. The earliest bracket clocks, made for a period after 1660, were of architectural design, with pillars at the sides and a pediment on top.
In 17th- and 18th-century France, the table clock became an object of monumental design, the best examples of which are minor works of sculpture.
The longcase clocks (also called grandfather clocks) are tall pendulum clock enclosed in a wooden case that stands upon the floor and is typically from 6 to 7.5 feet (1.8 to 2.3 m) in height. Later, the name "grandfather clock" became popular after the popular song "My Grandfather's Clock," written in 1876 by Henry Clay Work.
One of the first atomic clocks was an ammonia-controlled clock. It was built in 1949 at the National Bureau of Standards, Washington, D.C.; in this clock the frequency did not vary by more than one part in 108.
Nuclear clocks are built using two clocks. The aggregate of atoms that emit the gamma radiation of precise frequency may be called the emitter clock; the group of atoms that absorb this radiation is the absorber clock. One pair of these nuclear clocks can detect energy changes of one part in 1014, being about 1,000 times more sensitive than the best atomic clock.
The cesium clock is the most accurate type of clock yet developed. This device makes use of transitions between the spin states of the cesium nucleus and produces a frequency which is so regular that it has been adopted for establishing the time standard.
The history of clocks is fascinating, but unrelated to this problem. In this problem, you are asked to find the angle between the minute hand and the hour hand on a regular analog clock. 1 Assume that the second hand, if there were one, would be pointing straight up at the 12. Give all angles as the smallest positive angles. For example 9:00 is 90 degrees; not -90 or 270 degrees.
H:D, each on their own line, with 1 <= H <= 12 and 00 <= M <= 59. The input is terminated with the time
0:00. Note that H may be represented with 1 or 2 digits (for 1-9 or 10-12, respectively); M is always represented with 2 digits. 2
1 Ask one of the consultants to show you what this type of clock looks like, if you are not sure.
2 The input times are what you typically see on a digital clock.
12:00 9:00 8:10 0:00
0.000 90.000 175.000