Birth of atomism

Print edition : May 26, 2017

THE quest of scientific inquiry is to penetrate beyond the apparent and to perceive reality. Metaphorically speculating what will result if one keeps on cutting a length of rope into two, every time a d infinitum, the Vaisheshika philosopher Kanada Kashyapa (circa 600 BCE) theorised that after a certain (very, very large) number of cuts, we should end up with tiny pieces that are indivisible— paramanu. Why? If we take two ropes, one twice the length of the other, and both can be chopped ad infinitum, what makes one smaller and the other bigger? Logically, he contended, a mountain and a molehill cannot be the same, and hence one should be composed of a lesser number of paramanu than the other. Inspired by the making of the pot, from first mixing earth and water and later adding fire, Kanada, came up with the theory that all things in the universe are cocktails of the p ancha maha-bhoota (five fundamental elements)—earth ( prithvi), water ( jal), fire ( agni), air ( vayu) and space ( akasha). Some philosophers substituted space with kaal/time.

Around the same time, in Greece, philosophers like Democritus were propounding atomism with somewhat similar logic. All these ancient philosophers were thinkers, not experimentalists, and arrived at their theories by logic and concluded that some fundamental building block—atoms—existed.

Richard Feynman famously said that he would choose “atomic hypothesis” among all others if all scientific knowledge were to be lost in a cataclysm and he was allowed to preserve one and just one idea. He said: “In that one sentence, [all things are made up of atoms], ...there is an enormous amount of information about the world if just a little imagination and thinking are applied.”

Yes, indeed, a deceptively timid idea that is intensely subversive and equalising! The idea that the same building blocks, following the same rules, made up the earth, the heavens and emperors, peasants, men, women, a cow and a pig, all living and non-living things, topples all hierarchies.

No wonder that the naturalism of the early Vaisheshika philosophy, which neither required nor relied on the concept of Ishvara to explain the working of the universe, was viewed as heretical. Insofar as attaining dharma, an intricate study of Kanada’s six padarthas and their union and dissolution, it was admonished, was like “going to the Himalayas with the resolution of going to the sea”. The early Greek atomism, too, was challenged by Christian orthodoxy. Saint Basil the Great saw atoms and God the creator as incompatible ideas.

Modern atomism

Atomism was placed on a sure footing of scientific experiments with Joseph Priestley and Antoine Lavoisier. Priestly (1733-1804) discovered oxygen as a distinct element in 1774, making air a composite substance. The discovery that water is a compound of hydrogen and oxygen was made around the 1780s by Henry Cavendish, Lavoisier (1743-1794) and others. The elemental theory of ancient Greeks and Indians was discarded and the new chemistry was born. On the basis of these developments, John Dalton (1776-1844) formulated the atomic theory in 1803, according to which atoms are indivisible. Amedeo Avogadro’s (1776-1856) work and later Dimitri Mendeleev’s (1834-1907) periodic table were attempts to improve the atomic theory.

When the scientific world was falling into a stupor, J.J. Thomson (1856-1940) upset the apple cart by discovering a particle smaller than an atom and possessing negative charge, the electron, in 1897. As atoms themselves are neutral, this implied that a component of the atom that is positively charged should exist. The world of subatomic particles was inaugurated. The gold-foil experiment of Ernest Rutherford (1871-1937) in 1911 resulted in the formulation of the nuclear atom model.

The study of cosmic rays had a shock in store for physicists. Other than the electron, the proton and the neutron, cosmic rays yielded an impressive array of new particles. One of them was a shocker; it had the same mass and other characteristics of an electron, but it was positively charged. When it, named positron, came closer to an electron, both went with a bang and vanished into pure energy, photons. Soon similar antiparticles were found for the proton, and so on. Called anti-matter, these are one of the enigmas of modern physics.

By 1936 yet another new particle, now having all the characteristics of the electron but heavier by 250 times, the meson, was discovered in cosmic rays. Cosmic rain also consisted of the Pion, the Kaon, the Lambda, the Xi and the Sigma. Accelerators, colliders, chambers and other new techniques, too, started to yield fresh subatomic particles. The Pi-zero antiproton, Omega-minus and neutrinos were discovered. The hundreds of subatomic particles gave physicists an inkling that they could not be the founding bedrock of fundamental particles.

In a crucial experiment conducted at the Stanford Linear Accelerator Centre (SLAC) in the 1960s, similar to Rutherford’s attempt to prise his way into the atom with alpha particles, high-energy electrons were bombarded and they revealed the granular nature of the proton. This gave a glimmer into the structure at the deeper level, and the idea of quarks was born.

T.V. Venkateswaran

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