Ancient Indian Physics

In ancient India, the ideas of Physics were closely linked with theology and religion. Initially, Indian philosophers believed that the universe was composed of four elements, viz. Prathvi (earth), Jal (water), Samir (air) and Pavak (fire). The Jain philosophers then added one more element namely Akasha (ether) to it. Thus these five elements Prathvi, Jal, Samir , Pavak and Akasha were thought as the media of our senses such that the Earth of smell, Jal of taste, Samir of feel, Pavak of vision and Akasha of sound. Later on, Buddhists and the Ajivikas discarded Akasha as the element and they added-life, joy and sorrow as the elements and thus in all, seven elements were considered as the composition of universe.

Most of the ancient Indian scientists believed that all the elements other than Akasha (ether) were atomic. Pakudha Katyayana, a contemporary of Buddha, was first to plead the theory of atoms. The Jains believed and considered that all atoms (parmanu) were identical. However, it was thus thought that there were as many types of atoms as there were elements. The atoms were generally thought to be the eternal, being minutest parcticles, invisible to the eyes and completely without magnitude. A single atom has no only when they combine. Although the Indian atomic theories were qualities, but they acquire potential based on intution and logic and not on experiments, but they agree partly to some extent with the modern concept of atom.

In ancient India, Brahma Gupta had observed the theory of the attractive force of the earth; but no law of gravitation was propounded. All heavy objects fall down to earth because the earth has a nature to attract all bodies towards it. This is similar to as the water has a nature to flow. It was also observed by the Indian scientists that solids and liquids expand on heating, but it was not experimentally studied.

In the Indian ancient script Rigveda, we get the description of the following facts related to phyiscs :

(1) Agni (energy) is conserved and everlasting. This statement agrees with the modern law of conservation of energy.

(ii) Agni is produced on rubbing two pieces of stones. This statement tells us that heat is produced due to friction.

(iii) The sun has rays of seven kinds. This statement agrees with the modern concept according to which light is made up of mainly the seven colours (VIBGYOR).

(iv) In half nimesh, the motion of light is two thousand two hundred two yojana. The meaning of half nimesh is 0-1065 second and that of 1 yojana is 9 mile. Hence according to this statement,

9x2202 mile Speed of light 0.1065 second

186084.5 mile/second which is equal to nearly 2.9946579 108 metre/second. Thus it agrees with the modern value c = 2.99792458 x 108 metre/second.

(v) Each substance always attracts the other substance. This statement is analogous to the Newton's law of gravitation.

(vi) Celestial objects revolve in stationary elliptical orbits. This statement agrees with the modern Kepler's law.

After this in the following scripts of several ancient Indian scientists, we get the description of facts related to Physics.

(1) In Nyaya Kandali of Shridharacharya it is stated that on removal of deforming forces from the bodies of high density, they return back to their original state. In present day physics, this is called the property of elasticity.

(2) In Nyaya Darshan of Maharishi Kanad, it is stated that the objects which are not visible by the naked eye, can be made visible with the help of glass (lens), mica or crystal. This gives the knowledge of use of lenses.

(3) In Veg Sanskar of Maharishi Kanad, it is stated that the basic cause of increases or decrease in motion is the force. More the time for which the force is applied, more is the change in motion. Each force produces an opposite force. This is in agreement with the Newton's laws of motion.

(4) In Brahat Sanhita of Barah Mihir, it is stated that when multicoloured sun rays get decomposed by the air particles in a cloudy sky, they appear in form of a rainbow. This statement agrees with the explanation of formation of rainbow due to dispersion of light.

(5) In Arybhatta Golpadah of Aryabhatt, we find the following statements :

(i) It is due to rotational motion of earth that near the equator the fixed stars appear to move from east to west.

(ii) When earth comes in between the sun and moon, the shadow of earth covers the moon and lunar eclipse is formed.

(iii) Sun is the centre of motions of all planets.

All these facts agree with the present statements.