The Confusion of Body Parts
Imagine trying to buy cloth for a uniform. If you ask for “two arm-lengths” of cloth, whose arm should be used? Yours? The shopkeeper’s?
In ancient times, people used body parts for measurement:
- Handspan (Balisht): The distance between the tip of the thumb and the little finger when stretched.
- Cubit: Length from the elbow to the fingertips.
- Angula: The width of a finger.
- Fist: The width of a closed palm.
- Pace/Stride: The length of a step.
Why did this fail?
As Deepa and her friends discovered in the classroom activity, everyone’s body parts are of different sizes. A table might be 13 handspans long for one student but 14 handspans long for another.
Warning
Problem: Measurements using body parts differ from person to person. This causes confusion in trade, construction, and daily life. Thus, there is a need for a Standard Unit that remains the same for everyone.
Historical Context: India
India has a rich history of measurement. Ancient texts mention units like:
- Angula: Finger width.
- Dhanusa: A bow length.
- Yojana: A long distance measure.
Excavations from the Harappan Civilisation have revealed objects with ruled markings, suggesting they used precise scales thousands of years ago!
What is a Unit?
Measurement consists of two parts:
- A Number: The quantity (e.g., 5, 10, 100).
- A Unit: The fixed quantity used as a standard (e.g., metre, foot).
Example: If a table is 2 metres long, ‘2’ is the number and ‘metre’ is the unit.