Why: We all know measuring is useful. It tells us how tall we are,
how heavy we are, and how long a ladder is, and so on. But think for
a moment about why and how we measure anyway.
Why Really: Well, we measure because we need to know if a desk will fit through
the door, for example. But we can just try to get the desk through the
door without measuring. Or we can use a piece of rope to try against
the desk and the door to know. Why do we need a ruler? Or have standard
units such as Meters (or Feet), Grams (or ounces)?
Need for units:
Mostly the purpose to measure any given quantity is to communicate or
record that information. For example, you need to measure your height
from the shouder
in order to tell the clerk at a fabric store how many yards of cloth you need
to make your red Halloween cape.
This means both you and the clerk need to know how long a yard is.
A yard happens to be a well-established common unit for length and
you should have no problem using yard measures at any store here in the US.
Outside of the USA, you will find meters and centimeters for length
Different quantities (weight, length, area, volume, angle, temperature, speed,
time) need different units.
And the world has established many commonly accepted units for measuring.
Who measures anyway, you ask. Practically everyone and all the time is
Think about how we measure time. We all do it constantly.
We look at our watches to know if lunch is soon, or how long
before our favorite TV program starts.
Seconds, and minutes go by, we long for the end of a class, or for Friday.
The world is constantly and consinuously measuring time. And we wonder
how very primitive people can do without it.
See the this US Naval Observator Master Clock.