Abu-Mahmud Khujandi facts for kids
Abu Mahmud Hamid ibn al-Khidr al-Khujandi, also known as Abu Mahmood Khujandi, was a famous Muslim astronomer and mathematician. He was born around 940 AD in Khujand, a city now located in Tajikistan. Khujandi lived in the late 10th century and was an important scholar. He helped build an observatory near the city of Ray, which is close to modern-day Tehran in Iran.
Contents
Discovering the Cosmos
Building a Giant Tool
Khujandi worked at an observatory near Ray, Iran. He was supported by the Buwayhid Amirs, who were powerful rulers. In 994 AD, he built a huge instrument called a mural sextant. This was a giant tool fixed to a wall. Its purpose was to measure the Earth's axial tilt very precisely. The axial tilt is the angle at which Earth's axis is tilted as it orbits the Sun.
Earth's Changing Tilt
Khujandi measured the Earth's axial tilt to be 23 degrees, 32 minutes, and 19 seconds for the year 994 AD. He noticed something interesting. Earlier astronomers had found slightly larger values for this tilt. For example, Indian astronomers measured it as 24 degrees, and Ptolemy measured it as 23 degrees and 51 minutes.
This difference led Khujandi to an important discovery: the Earth's axial tilt is not always the same. It is actually slowly changing over time, and currently, it is decreasing. His measurement was a little bit off, by about two minutes. This was probably because his very heavy instrument settled slightly during his observations.
Exploring Mathematics
Working on Big Problems
Khujandi also made contributions to mathematics. He looked at a special part of a famous math problem called Fermat's Last Theorem. This theorem deals with equations involving powers of numbers. Khujandi tried to prove a specific case of this theorem for the number 3, but his proof was not correct.
The Law of Sines
Another important mathematical idea is the spherical law of sines. This law helps us understand the relationships between angles and sides in triangles drawn on the surface of a sphere. It is possible that Khujandi was one of the first to discover this law. However, it is not certain if he found it before other great mathematicians like Abu Nasr Mansur, Abul Wafa, or Nasir al-Din al-Tusi.
See Also
- Sextant (astronomy)#Mural sextants
