Arab scientists and terrestrial gravity


In physics, gravity (from Latin gravitas 'weight') is a fundamental interaction which causes mutual attraction between all things that have mass.  it determines the motion of planets, stars, galaxies, and even light.

Gravity is the force by which a planet or other body draws objects toward its center, the force of gravity keeps all of the planets in orbit around the sun.

Why do you land on the ground when you jump up instead of floating off into space?

 Why do things fall down when you throw them or drop them? 

The answer is gravity: an invisible force that pulls objects toward each other, Earth's gravity is what keeps you on the ground and what makes things fall.

The well-known beginning of Newton

Stokely talks about that day, saying: “We went to the garden, to drink tea under the shade of some apple trees, just me and him, and in the course of the conversation, he told me that in a situation like this he came up with the idea of the concept of gravity, saying:

Why does an apple always fall vertically to the ground?” Then he said to himself: “Why does it not fall sideways or rise up? It must be heading towards the center of the Earth, for surely the Earth attracted it.

Therefore, there must be attractive forces in the matter, and the sum of the attractive forces in the earth matter must be in the direction of the center of the earth, and not on any side.

Therefore, the apple falls vertically, or towards the center, and if objects attract each other, this must be proportional to their size, the apple attracts the earth, just as the earth attracts the apple.

Thus, Newton (who died in 1727 AD) became the discoverer of gravity and established its foundations and laws.

Aristotle's explanation of gravity

Aristotle believed that the universe consists of a group of circles stacked on top of each other, in the center is the circle of earth, surrounded by the circle of water, surrounded by the circle of air, and finally surrounded by the circle of fire.

Aristotle relied on this order based on the masses from heaviest to lightest,  earth is the heaviest in the center, then water, then air, then fire.

Based on these ideas, Aristotle believed that substances and molecules consisted of a mixture of the four aforementioned elements (soil, water, air, and fire), and from this standpoint he began to explain gravity.

He said that materials are not attracted to the earth as a whole, but rather they are attracted to the layer of the universe of the same type, that is, those that are composed of earth fall into the earth, those that consist of water fall into water, those that contain air fall toward the air, and those that contain water fall into water. In which there is fire, we attract towards the fire, and so on.

As for materials that consist of a mixture of four elements, Aristotle says that the proportion of the element present in the material determines the speed of its attraction toward the earth.

If it contains more soil, it will be attracted to the earth faster, and if it has a lower percentage of soil, it will be attracted to the earth at a lower speed, this is what Aristotle called the speed of natural bodies.   

Gravity and Arab physicists

If we leave Newton and his era and go back more than 7 centuries with a time machine, and go beyond Aristotle’s interpretation and delve into the heritage of Islamic civilization, we find that Muslim scholars preceded him in doing so several centuries ago, and wrote down their theories in their books that are still in our hands until now.

Abu Muhammad al-Hasan al-Hamdani

al-Hamdānī (born 893, Sanaa, Yemen—died c. 945) was an Arab geographer, poet, grammarian, historian, and astronomer whose chief fame.

From his literary production, al-Hamdānī was known as the “tongue of South Arabia.” In full: Abū Muḥammad al-Ḥasan ibn Aḥmad al-Hamdānī.

Kitab al-Jawharatayn al-ʻatīqatayn - A book describing metals known at that time, including their physical and chemical properties as well as treatment and processing (such as gold, silver, and steel), he is also considered the first person who explained gravity of Earth in a way similar to magnetic field behavior.

He referred to gravity as what attracts its iron forces from all sides.

Abu Rayhan al-Biruni

One of Al-Biruni's manuscripts in Persian


Islamic civilization was witnessing its golden age during the fourth century AH / tenth century AD, we will find a Muslim scholar living on the borders of India named Abu Al-Rayhan Al-Biruni, he says in a book of his called “The Masoudi Law”: “The people on earth are as erect as the diameters of a ball, and on them also the weights are transferred to lowest.

One of Al-Biruni’s most important works is the book “Extracting the Strings in a Circle by the Properties of the Curved Line in It,” in which he determined the length of the string of a circle.

As for the book “Al-Masoudi’s Law of Form and the Stars,” in which Al-Biruni referred to the Earth’s gravity, he included it in his theories about the universe, the Earth, calendars, distances between countries, and the movements of the sun, stars, and planets.

It was said that Sultan Masoud Al-Ghaznawi had brought three camels laden with silver to Al-Biruni when he presented him with the book “The Masoudi Law”, but Al-Biruni rejected that, saying that he served knowledge, not money.

Abd al-Rahman al-Khazini

Al-Khazini is the maker of scientific machines using the law of fluid equilibrium, leaving no doubt that he is the greatest scientist in physics. He is one of the geniuses of Islamic civilization and the pioneer of modern physics.

He was the first to talk about gravity and apply scientific methods to measure the movement of static and dynamic forces and their weights. Al-Khazni studied mathematics and philosophy at the Seljuk court, and excelled in the sciences of physics, astronomy, fluid balance, and engineering.

He invented a device to determine the specific gravity of precious stones and metals, and established ratios for them, then a device to determine the specific gravity of liquids, the results of which are close to or identical to modern ratios.

Al-Khazini recorded the ratios of specific gravity in his book Mizan al-Hikma (The balance of wisdom in Arabic language), he established the concept of gravity and addressed many problems in mechanics and fluid balancing, his measurements were distinguished by their accuracy and became a major reference for physicists and astronomers.

Al-Khazini preceded Galileo and Newton by many centuries when he explained that all parts of a body move towards the center of the Earth when they fall due to the force of gravity, and he  preceded the scientist Torricelli in pointing out that air is a substance that has weight and a lifting force like liquids, and that the weight of a body immersed in air is less than its actual weight.

Al-Khazini also believed that the difference in gravitational force was due to the distance between the falling body and the center, a conclusion that was surprisingly ahead of its time.

His book, Mizan al-Hikma (the balance of the wisdom in Arabic language), is an encyclopedia of mechanics consisting of eight books and fifty chapters, which included studies on the hydrostatic equilibrium of fluids, and covered other miscellaneous physical topics.

The book is still considered one of the most important achievements of Islamic civilization in physics,  it analyzed movement, fluid balance, and friction, it accurately described laboratory devices and machines that Al-Khazini had manufactured themselves, and explained the experimental scientific method based on quantitative calculation.

Abd al-Rahman al-Khazni died in 1130 AD and is deservedly considered the father of modern physics.


These are three Muslim physicists who lived within the Islamic civilization at different times and far apart places, and they were able, with complete merit, to explain the phenomenon of Earth’s gravity in a clear and adequate explanation hundreds of years before the well-known European Renaissance scientists.

























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