What is time:
Time in physics and philosophy (time as a physical phenomenon),
Time in psychology (our sense of passing time),
Time in mathematics and engineering (the time that we measure and use to regulate our lives).
History of time :
The measurement of time began with the invention of sundials in ancient Egypt some time prior to 1500 B.C. However, the time the Egyptians measured was not the same as the time today's clocks measure. For the Egyptians, and indeed for a further three millennia, the basic unit of time was the period of daylight. The Egyptians broke the period from sunrise to sunset into twelve equal parts, giving us the forerunner of today's hours.
The need for a way to measure time independently of the sun eventually gave rise to various devices, most notably sandglasses, waterclocks, and candles. The first two of these utilized the flow of some substance to measure time, the latter the steady fall in the height of the candle.
sundial an instrument showing the time by the shadow of a pointer cast by the sun on to a plate marked with the hours of the day.
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| Sundial |
The most precise timekeeping device of the ancient world was the water clock.
The hourglass uses the flow of sand to measure the flow of time. They were used in navigation. Ferdinand Magellan used 18 glasses on each ship for his circumnavigation of the globe
Incense sticks and candles were, and are, commonly used to measure time in temples and churches across the globe
Great advances in accurate time-keeping were made by Galileo Galilei and especially christiaan huygens with the invention of pendulum-driven clocks along with the invention of the minute hand by Jost Burgi
The most accurate timekeeping devices are atomic clocks.
Atomic clocks use the frequency of electronic transitions in certain atoms to measure the second.
GPS in coordination with the Network time protocol can be used to synchronize timekeeping systems across the globe.
Measurement of time:
when we travel from one place to another we will calculate the time and speed.
This is way to calculate the time
When we measure the speed of a car, we seem to be measuring speed with
something abstract called time; we are actually just comparing a known motion (of the sun)
with an unknown motion of the car
History of calendar
Artifacts from the old stone age suggest that the moon was used to reckon time as early as 6,000 years ago.
Lunar calendar were among the first to appear, with years of either 12 or 13 lunar months (either 354 or 384 days).
solar calendar is a calendar whose dates indicate the season or almost equivalently the apparent position of the sun relative to the stars.
A lunar calendar is a calendar based on the monthly cycles of the Moon's phases ,In solar calendar annual cycles are based only directly on the solar year.
Living by the clock
Today, we live our lives according to clock. We start our day by an alarm clock, we listen to the radio at a particular time, we travel to and from work at a certain time of day, we attend meetings that start and finish at predetermined times, we eat our meals according to the clock, not simply when we feel hungry, and the clock tells us when to go to a movie, to a concert, to the theater, or to watch our favorite television program. Indeed, not only are most of our daily activities regulated by the clock, they are often ruled down to the precise minute. This way of living is very recent. Not only does it depend on the uniform system of worldwide time measurement, it also requires that each one of us carries on our person a reliable means to keep track of time.
