This is not my definition, it is taken from a man named Suresh, who defined it in a way that i was thinking, but couldn't explain.
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The concept of time is related to motion, or change. Moreover, time is
related to how things changes with respect to each other.
For example, we see the sun go up and down every day. We see the
seasons change. Now, it is possible to relate the number of times the
sun goes up and down, the number of counts it takes the moon to go
from full moon to new moon.
In a way, we can relate
Counts of sun moving up and down = (Constant of Exchange) * (Number
of count for moon to go from full moon to new moon)
Now, ofcourse, this is something very similar to the concept of money.
Money, a dollar bill, by itself, does not hold any value. However,
there are standards of exchange setup by people that say that
you need 1 dollar to buy a soda pop
you need to work 1 hour to earn 5.00
and you need to 200 dollars to buy a TV.
Now, suppose we look at a transcation between the amount of work you
do, and amount of money spent to buy the TV, we can relate number of
hours we were at a job to buy the TV
1 TV = 40 hours of work
From the point of an external observer, i could say that you worked 40
hours to buy a TV. Or, i can introduce the concept of money and say
You spent 40 hours working at a job that pay 5.00$/hour. And you
bought a TV that was worth $200 dollars. Now, by introducing money, we
have acheived a notion of independence between 40 hours spent on work
and a $200 TV.
By introducing money, i can alienate the 40 hours of work you did,
from the TV you bought. Similarly, by introducing the concept of
time, I can alienate the counts of sun goin up and down and the
changes of the moon.
1 Day = Sun going up and down
15 Days = Moon going from Full Moon to new moon.
Similarly, a clock or watch, does the same thing.
For example, suppose after 200 clicks of the clock, you have typed 1
page. Now, if played a song and it ended after 30 clicks. Now, the
concept of time, provides a way to keep an notion of indepedence
between these arbitary events.
We arbitrarily choose a unit for time. For example, we can say that 1
second = 1 click of the clock. From that, i can say, it took be 200
seconds to type 1 page, 30 seconds to play the song.
Now, if i want to relate amount of songs, i can play, to the number of
pages, you can type. We can do that. Just as the way, we can relate 1
TV = 40 hours of work, by getting ride of the concept of money.
Now, a unit of a second is a standard. It is based on speed of light
and counts of decay of a cessium atom [ i think, i read this a while
ago].