Back To Past :History Of Physics

Elements of what became physics were drawn primarily from the fields of astronomy, optics, and mechanics, which were methodologically united through the study of geometry. These mathematical disciplines began in Antiquity with the Babylonians and with Hellenistic writers such as Archimedes and Ptolemy. Meanwhile, philosophy, including what was called “physics”, focused on explanatory (rather than descriptive) schemes, largely developed around the Aristotelian idea of the four types of “causes”.

The move towards a rational understanding of nature began at least since the Archaic Period in Greece (650 BCE – 480 BCE) with the Pre-Socratic philosophers. The philosopher Thales (7th and 6 centuries BCE), dubbed "the Father of Science" for refusing to accept various supernatural, religious or mythological explanations for natural phenomena, proclaimed that every event had a natural cause.Leucippus (first half of 5th century BCE), developed the theory of atomism — the idea that everything is composed entirely of various imperishable, indivisible elements called atoms. This was elaborated in great detail by Democritus.

Aristotle (Greek: Ἀριστοτέλης, Aristotélēs) (384 BCE – 322 BCE), a student of Plato, promoted the concept that observation of physical phenomena could ultimately lead to the discovery of the natural laws governing them. He wrote the first work which refers to that line of study as "Physics" (Aristotle's Physics). During the classical period in Greece (6th, 5th and 4th centuries BCE) and in Hellenistic times, natural philosophy slowly developed into an exciting and contentious field of study.

Early in Classical Greece, that the earth is a sphere ("round"), was generally known by all, and around 240 BCE, Eratosthenes (276 BCE - 194 BCE) accurately estimated its circumference. In contrast to Aristotle's geocentric views, Aristarchus of Samos (Greek: Ἀρίσταρχος; 310 BCE – ca. 230 BCE) presented an explicit argument for a heliocentric model of the solar system, placing the Sun, not the Earth, at the centre. Seleucus of Seleucia, a follower of the heliocentric theory of Aristarchus, stated that the Earth rotated around its own axis, which in turn revolved around the Sun. Though the arguments he used were lost, Plutarch stated that Seleucus was the first to prove the heliocentric system through reasoning.

In the 3rd century BCE, the Greek mathematician Archimedes laid the foundations of hydrostatics, statics and the explanation of the principle of the lever. In his work On Floating Bodies, around 250 BCE, Archimedes develops the law of buoyancy, also known as Archimedes' Principle. The astronomer Ptolemy wrote the Almagest, a comprehensive astronomical text that formed the basis of much later science.

Much of the accumulated knowledge of the ancient world was lost. Even of the works of the better known thinkers, few fragments survived. Although he wrote at least fourteen books, almost nothing of Hipparchus' direct work survived. Of the 150 reputed Aristotelian works, only 30 exist, and some of those are "little more than lecture notes". Though reinterpreted to fit theological concerns, both Jewish and Islamic scholarship preserved and developed some of the ancient knowledge that would otherwise have been lost.

The Islamic Abbasid caliphs gathered many classic works of antiquity and had them translated into Arabic. Islamic philosophers such as Al-Kindi (Alkindus), Al-Farabi (Alpharabius), Avicenna (Ibn Sina) and Averroes (Ibn Rushd) reinterpreted Greek though in the context of their religion. Important contributions were made by Ibn al-Haytham and Abū Rayhān Bīrūnī before eventually passing on to Western Europe where they were studied by scholars such as Roger Bacon and Witelo.

Awareness of ancient works re-entered the West through translations from Arabic to Latin. Their re-introduction, combined with Judeo-Islamic theological commentaries, had a great influence on Medieval philosophers such as Thomas Aquinas. Scholastic European scholars, who sought to reconcile the philosophy of the ancient classical philosophers with Judeo-Christian theology, proclaimed Aristotle the greatest thinker of the ancient world. In cases where they didn't directly contradict the Bible, Aristotelian physics became the foundation for the physical explanations of the European Churches.

Based on Aristotelian physics, Scholastic physics described things as moving according to their essential nature. Celestial objects were described as moving in circles, because perfect circular motion was considered an innate property of objects that existed in the uncorrupted realm of the celestial spheres. The theory of impetus, the ancestor to the concepts of inertia and momentum, was developed along similar lines by medieval philosophers such as John Philoponus, Avicenna and Jean Buridan. Motions below the lunar sphere were seen as imperfect, and thus could not be expected to exhibit consistent motion. More idealized motion in the “sublunary” realm could only be achieved through artifice, and prior to the 17th century, many did not view artificial experiments as a valid means of learning about the natural world. Physical explanations in the sublunary realm revolved around tendencies. Stones contained the element earth, and earthy objects tended to move in a straight line toward the centre of the earth (and the universe in the Aristotelian geocentric view) unless otherwise prevented from doing so.


Important physical and mathematical traditions also existed in ancient Chinese and Indian sciences. In Indian philosophy, Kanada of the Vaisheshika school proposed the theory of atomism during the 1st millennium BCE,and it was further elaborated on by the Buddhist atomists Dharmakirti and Dignāga during the 1st millennium CE.In Indian astronomy, Aryabhata's Aryabhatiya (499 CE) proposed the Earth's rotation, while Nilakantha Somayaji (1444–1544) of the Kerala school of astronomy and mathematics proposed a semi-heliocentric model resembling the Tychonic system. In Chinese philosophy, Mozi (c. 470-390 BCE) proposed a concept similar to inertia, while in optics, Shen Kuo (1031–1095 CE) independently developed a camera obscura. The study of magnetism in China dates back to the 4th century BCE (in the Book of the Devil Valley Master),eventually leading to the invention of the compass.