Draft: this lesson was written with AI help and has not yet been read by a human editor.
1 What your class asks
This lesson asks you to show how mass, volume and density are related, and to determine whether an object floats, given its density, in different fluids. The museum offers two medieval accounts of how weight and displaced water were used to compare materials; the calculations and the comparison of floating and sinking in several fluids are for the class to carry out. 1
Curriculum expectations, with their official codes
- C2.2 demonstrate an understanding of the relationship between mass, volume, and density
- C2.5 determine the buoyancy of an object, given its density, in a variety of fluids
2 The lesson
What is being measured, and what could be lost?
The expectations relate three quantities. For each device you read about, write down what it measures directly, what is worked out from it, and where the measurement could go wrong.
Go deeper
Robert Hall, whose account the museum's record follows, places the balance of wisdom at Merv under Sultan Sanjar and says it was built for the treasury 2. He also passes on an older story: an earlier balance, made by al-Asfizari, was destroyed out of fear that it would expose fraud. The record treats this with care. It calls it a transmitted account, not a modern eyewitness finding 3. Afterwards al-Khazini described a similar, further refined instrument and left a substantial technical account of it 3.
Why they did it
The museum's records preserve no sentence in which al-Khazini says why he took up this work. They show three things. The balance was made for a ruler's treasury, to investigate metals and gems 4. His own preface, printed in Arabic and English, identifies Muhammad as his prophet 5. And his treatise traces a history that begins with Archimedes: he does not present himself as the first person to discover weighing, and he connects the accuracy of the balance to the contributions of those before him 3.
Often misunderstood
The balance of wisdom is sometimes presented as al-Khazini's invention from nothing. Hall credits al-Asfizari with the earlier movable pans and regards most of the fundamental theory as inherited; the museum classes al-Khazini's work as an improvement: a refined version and its calibration procedures 6. The same care applies to al-Biruni's vessel: the drawing that names it reached us through a nineteenth-century publication whose publisher acknowledges a deficient, erroneous manuscript 7.
Think about it
The story of the destroyed balance is a transmitted account, and no one today can check it. Should a historian of science still tell it, and what would have to be found for you to treat it as a fact?
Into the museum
- The balance of wisdom: how five pans turn two weighings into a judgement about a material.
- al-Khazini: what is known of his life, and what is not.
- al-Biruni's displacement vessel: the drawing, the stray drops, and the damaged manuscript it comes from.
Try this
Read about the displacement vessel and the balance of wisdom. For each, list in your own words the two weights that are compared and what the comparison tells you about the material.
3 Carry it further
Where this lesson leads in the museum.
4 Check yourself
Nothing here is marked or sent anywhere. It is for you.
In your own words: what does Al-Biruni's conical displacement and relative-density vessel have to do with this lesson?
Compare with the card
Collecting the water a stone pushes aside. The Balance of Wisdom transmits a conical vessel attributed to al-Biruni. A side tube directs the displaced water into a balance pan, and weighing that water allows a comparison of the sample's volume and weight. The record adds that drops can remain inside the tube, and that "specific gravity" here means a ratio to reference water. How would a stray drop change the result?
In your own words: what does Al-Khazini's balance of wisdom have to do with this lesson?
Compare with the card
A balance that weighs in water. Robert Hall describes al-Khazini's balance as connected with the treasury of Sultan Sanjar at Merv, in a treatise written in 515 AH/1121-1122 CE. An immersed object has a lower apparent weight because the liquid supports it, and comparing its weight in air with the loss of weight in water gives information about its density. Equal dry weights alone do not show that two objects are the same material. What else would you need to know?
I can now
Notes
- 1. Ontario Ministry of Education, The Ontario Curriculum: Science and Technology, Grades 1–8 (2022)
- 2. Al-Khazini and the balance of wisdom — Robert E. Hall, biography
- 3. Al-Khazini and the balance of wisdom — Robert E. Hall, Kitab Mizan al-Hikma
- 4. Al-Khazini and the balance of wisdom — Robert E. Hall, The Balance of Wisdom
- 5. Analysis and extracts of the Book of the Balance of Wisdom — Khanikoff, p. 3
- 6. Al-Khazini and the balance of wisdom — Robert E. Hall, Al-Khazini and the Science of Weights in Islam
- 7. Analysis and extracts of the Book of the Balance of Wisdom — Khanikoff, pp.53–54