Physics in Ancient India5
According to Kanada, an object appears to be heavy under water than it does in air. This was because the density of atoms in water is more than in air. Further, he also stated that the additional density in water, takes on part of the weight of an object. As a result of this, we feel only a part of its total weight. However, in air, the lesser density of atoms results in a lesser part of an object's weight being picked by air. Due to this, we feel the object to be heavier in air than what is was when under the water.
In saying this, in a very elementary but important way, Kanada foreshadowed Archimedes. The reason being that according to Archimedes theory', a body immersed in a fluid is subject to an upward force equal in magnitude to the weight of the fluid it displaces. Kanada's idea also had shades of relativity in it which was propounded by Einstein in our times.
Kanada observed that an inherent urge made one Parmanu combine with another. This was his his ideas on atom. When two Parmanu belonging to one class of substance combined, a dwinuka (binary molecule) was the result. This dwinuka had properties similar to the two parents Parmanu. In the material universe, according to him, Parmanu belonging to different classes of substances combine in different combinations. This gave us a variety of dwinuka, which in other words means different types of substances.
Besides this, Kanada also put forth the idea of chemical changes occurring because of various factors. He claimed that variation in temperature could bring about such changes.
He cited the examples of blackening of a new earthen pot and the ripening of fruit to illustrate the chemical change in substances brought about by the heat. Thus according to Kanada all substances, all matter that existed in the universe was formed of Parmanu (atoms).
The variations in the matter reflected the peculiarity of the Parmanu which constituted that particular matter, the variety of combinations between different types of Parmanu and the effect on them of variation in temperature.
These Indian ideas about atom and atomic physics were probably transmitted to the west. This wcould have been done during the contacts created between India and the west by the invasion of Alexander. The Greeks invaded north-western India in around 330 B C. Along with Alexander; came Greek philosophers like Aristotle. Aristotle is reported to have been Alexander's mentor.
Scholars like Aristotle would surely have keenly studied the sciences of the lands which the Greek armies overran. Even after Alexander's departure, massive trade and diplomatic relations existed between Indians and Greeks who had settled in Asia.This way perhaps, Indian ideas could have travelled westwards where they were developed further.
Some scholars even go to the extent of saying that in Kanada's lifetime itself some Greek scholars had visited India. At that time, through a debate with the great philosopher had been exposed to Indian ideas about atom. The possibility of such a meeting is remote. This is because Kanada lived in the 6th century B.C. and the Greeks came into India only in the 4th century B.C. But nevertheless it remains a fact that Indian ideas about atom are the oldest.
It is only after the 4th century B.C., after the Greeks had come in contact with India. This can be traced through references to the idea of an atom in Greek science. Thus it is quite possible that the Greeks borrowed the ideas about atom from Indian philosophers in the 4th century B.C. But the credit of developing these ideas further, goes to the Greeks and other western philosophers.