Standard Units of Measurement

Do you know how big is your classroom? Suppose, we want to measure the length of our classroom, what should we do?

We should get a meter scale or tape for that. We will then measure the length of our classroom and report it as - so and so meters.

But do you know how our ancestors measured lengths of objects ?? Did they have a ruler with them, the way we have now?

No, our ancestors didn't have meter scales and tapes.

Instead they measured length in other units like , , , etc. , all depending upon the lengths of our body parts as shown.

Let us know about these units used by our ancestors in detail

A is the length from the elbow to the finger tips. It was used in ancient Egypt.

"Yard" is the distance between the end of the outstretched arm and one's chin.

was commonly used to measure the length of a cloth. It is still used even today.

is the measure of length of one's foot.

And is the maximum distance between the tips of the thumb and the little finger.

So our ancestors mostly used body parts as their units for measurement of length.

Did our ancestors face any problem while measuring lengths using such units ??

Everyone's body parts are different.

The feet, hand-spans and the arm lengths are bigger or smaller in different people.

So if we measure the length of objects like tables, chairs or beds using such units, we will definitely get different readings in each measurement.

Suppose your friend Ravi measure the length of a table in hand spans and says you that the length of that table is "5 hand-spans"...

...and another friend of yours Salma, measured the length of the table and told that it is "7 hand-spans" ... whom will you believe ?

We got two different readings for measurement of the same object, because normally size of the body parts will vary among people.

So will it not be confusing ??

To avoid such confusion, scientists thought that the entire world should use common and standard units for measurement.

They came up with a standard system of units which is known as the .

According to the International System of Units (SI Units), meter is the standard unit for measuring length.

In any place of the world you go, you will see people are measuring lengths with "meter".

Time for Revision :)

Earlier people used to measure length with different units, all based on their body parts.

Currently we use a standard system of units for measurement called the International System of Units or SI Units. And SI unit of length is meter

Keep exploring :)