astronomy

Khalid ibn Abd al-Malik al-Marwarrudhi

Khalid ibn Abd al-Malik al-Marwarrudhi is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Khalid ibn Abd al-Malik al-Marwarrudhi rather than just read about it. In short: Khālid ibn ʿAbd al‐Malik al‐Marwarrūdhī (Arabic: خالد بن عبدالملك المرو الروذي) was a 9th-century Baghdadi astronomer. In 827, Marwarrūdhī, together with the astronomer ʿAlī ibn ʿĪsā al-Asṭurlābī and a party of surveyors, measured the length of a meridian arc of one degree of latitude.

Key takeaways

Khalid ibn Abd al-Malik al-Marwarrudhi belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Khalid ibn Abd al-Malik al-Marwarrudhi to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Khalid ibn Abd al-Malik al-Marwarrudhi from memory before moving on to harder problems.

Reference excerpt

Khālid ibn ʿAbd al‐Malik al‐Marwarrūdhī (Arabic: خالد بن عبدالملك المرو الروذي) was a 9th-century Baghdadi astronomer. In 827, Marwarrūdhī, together with the astronomer ʿAlī ibn ʿĪsā al-Asṭurlābī and a party of surveyors, measured the length of a meridian arc of one degree of latitude. The party travelled to the Nineveh Plains in the valley of the Tigris, at 35 degrees north latitude. The measurement they obtained enabled the astronomers to obtain a value of 40,248 kilometres (25,009 mi) for the circumference of the Earth, (or, according to other sources, 41,436 kilometres (25,747 mi)). The two researchers measured in Arabian ell, and determined the geographical latitudes of the end points they used from the star altitudes in a celestial horizontal coordinate system. As it is thought that one Arabian ell represented 49.33 centimetres (19.42 in), they found the length of 1° of meridian to be 111.8 kilometres (69.5 mi), which differs from the true value by 850 metres (2,790 ft). Marwarrūdhī was chosen by the geometer Al-Abbās ibn Said al-Jawharī to organize a new observatory on Mount Qasioun. Despite encountering technical difficulties caused by the distortion of the astronomical instruments, in c. 832 he spent a year obtaining of solar and lunar observations of the Sun and the Moon. He played a role in the project c. 843/84 determine the length of the spring season by means of astronomical observations. Marwarrūdhī was the first of three generations of astronomers.

References

Sources Bolt, Marvin (2007). "Marwarrūdhī: Khālid ibn ʿAbd al‐Malik al‐Marwarrūdhī". In Thomas Hockey; et al. (eds.). The Biographical Encyclopedia of Astronomers. New York: Springer. p. 740. ISBN 978-0-387-31022-0. (PDF version) Çelebi, Kâtip (2017). Atta, M. A. (ed.). Kashf al-Zunun (in Arabic). Vol. 6. Dar Al Kotob Al Ilmiyah.

Further reading Dani, Ahmad Hasan; Bosworth, Clifford Edmund; Osimī, Muḣammad, eds. (1992). History of Civilizations of Central Asia. Vol. 4. UNESCO. ISBN 9789231036545.

Worked examples

Example 1 — a first encounter with Khalid ibn Abd al-Malik al-Marwarrudhi

Start with the simplest possible case. Write down what Khalid ibn Abd al-Malik al-Marwarrudhi claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Khalid ibn Abd al-Malik al-Marwarrudhi before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Khalid ibn Abd al-Malik al-Marwarrudhi ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Khalid ibn Abd al-Malik al-Marwarrudhi

In research: Khalid ibn Abd al-Malik al-Marwarrudhi appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Khalid ibn Abd al-Malik al-Marwarrudhi in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Khalid ibn Abd al-Malik al-Marwarrudhi is common in secondary-school and first-year university syllabi. It links to neighbouring topics 9th-century Iranian astronomers, Astronomers of the medieval Islamic world, Geodesists, so understanding it makes those chapters shorter.
In everyday life: Look for Khalid ibn Abd al-Malik al-Marwarrudhi outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Khalid ibn Abd al-Malik al-Marwarrudhi in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Khalid ibn Abd al-Malik al-Marwarrudhi means in your own words.
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Frequently asked questions

What is Khalid ibn Abd al-Malik al-Marwarrudhi in simple terms?

Why does Khalid ibn Abd al-Malik al-Marwarrudhi matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Khalid ibn Abd al-Malik al-Marwarrudhi?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Khalid ibn Abd al-Malik al-Marwarrudhi.