Hello readers, Keshav this side.
This is the first part of Measuring time : What, Why and How? In this part we will talk about two major questions : what is time and what led to timekeeping. After that we will start our journey of measuring time.What is Time?
Around 400 AD, a philosopher St. Augustine stated “So what is time? If no
one asks me, I know; if I seek to explain it, I do not.” After my research, one
statement sums it up for a normal person: Time is not a real thing but it
possesses what we may call duration – Henri Bergson. This duration consists of memories which range from a heartbeat to thousand
year old temples to formation of earth 5 billion years ago. Time comes from
infinite past and goes up to infinite future.
What led to Timekeeping?
Observing time and measuring it is a crucial part of living.
Sense of dynamic surroundings is present in a human from the very beginning. It
was required to be aware about day and night while hunting, then months and
seasons while farming. With the introduction of religion, years were of a great
importance as there were rituals to be performed every year. Smaller divisions
of time like pahar and hours were required to do multiple things in a day in an
organized manner. Even smaller divisions like minute and seconds were probably
brought in as a result of competition of faster working abilities and games and
all of this starts from the sun and the moon.
Let's Begin the Journey
So we will start with time as we know it today and maintain
a relationship between what it was in the past. We will also explore some
side-lines of this path as we progress.
Time for a normal person today starts from a second to a
minute to an hour then to a day, a month, a year, a century to a millennium.
Let’s start with the day : for us a day is 24 hours and
28-31 days make a month. It is called a civil day. But the concept of day came
into existence with the appearance of noon i.e. sun over the head. This in turn
is due to rotation of earth on its own axis. These two factors were used to
measure a day in ancient times. But these both lead to a varied day length throughout the year,
sometimes longer sometimes shorter. So a mean value is used to represent these.
A mean solar day is 0.002 seconds longer than 24 hours i.e. 84000.002s whereas the rotation of earth takes about 4 minutes less than 24 hours (23h 56m
4.09s) and it is increasing irregularly because the rotation of earth is
slowing down.
For third option, if moon is used as a reference, a day is 24h 50m because moon
revolves around earth in the same direction of rotation of earth.
Sources :
The History Of Time : A Very Short Introduction by OXFORD PUBLICATIONS
Wikipedia : Time, Day
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