COSMOS NO ENIGMA

Indian astronomers are studying 
the evolution of life on earth, says Biplab Das 

Earth has long been removed from the centre of the Universe. Man, too, has lost his privilege to be called the zenith of creation. "But the present day glamour of science owes its origin to a revolutionary event that happened when Nicolas Copernicus showed that the sun was at the centre of our planet family, debunking the church's preoccupation with a geocentric Universe," said Prof. Ramanath Cowsik, director, Indian Institute of Astrophysics, Bangalore. 

Prof. Cowsik delivered the 63rd Acharya J. C. Bose Memorial Lecture on November 30 at the Bose Institute. He described how, when earth was being 'removed' from the centre of the Universe, Galileo emerged on the scene following the footsteps of Copernicus. Prof. Cowsik spoke on 'The Ultimate Step in The Copernican Revolution: An Overview of The New Cosmology'. 

According to him, Neelkantha in Kerala had propounded the heliocentric model 20 years before Copernicus and also had proposed the concept of elliptical orbit of planets. But Galileo was the first to spot the planet Jupiter and its four moons through a telescope he himself made. 

The year Galileo died, Isaac Newton was born in England. He put forward the gravitational theory, which took a step further towards unveiling the mysteries of the Universe. 

Within a couple of centuries Charles Darwin gave the final jolt to the church's hegemony with his theory of evolution. Prof. Cowsik traced back our ancestry to fish as he showed the journey from fish to mammals aided by a graphical representation. 

He showed pictures of dinosaur and human skeletons side by side, pointing out superficial similarities between them to elucidate how mammals evolved from mammal-like reptiles. Darwin's idea convinced people beyond doubt that humans are not at the centre of creation. 

While Darwin sounded the death knell for creationism, a century later Albert Einstein proposed a theory that showed where humans beings stood in the Universe. "In a single stroke of genius, Einstein proclaimed the general theory of relativity," Prof. Cowsik said. General relativity is a theory of gravity. It predicted, among other things, that light can be deflected by gravity. This theory marked the beginning of a new era in cosmology. 

The Universe was born with a violent birth pang called Big bang and since then it has been expanding. It was Edwin Hubble who first suggested this theory. Immediately after the explosion newborn quarks coalesced into protons. "Then protons with neutrons and electrons produced neutral atoms 3,00,000 years after the Big Bang. The atoms got together to form gas clouds which eventually evolved into stars." 

Life on earth is carbon-based, but carbon is not formed on other stars, which explains why life is a rare phenomenon in the Universe. It drives home the fact that most of the stars are turned off before the formation of 
carbon." 

As a star runs out of its nuclear fuel, it is left to the mercy of gravity. If a star like sun shrinks to about the size of the earth, it will become what astronomers call a white dwarf. "In the early 1930s, Subrahmanyan Chandrasekhar made some calculations and discovered that if a star had about 50 per cent more mass than the sun, it would collapse further, ultimately giving birth to a black hole." 

Like us, a star, too, has its own life cycle. In its death throes, a star explodes violently. In this stage, the star is known as supernova. "Earth-bound telescopes captured the explosion of a supernova called SN1987A which took place in the large Magellanic Cloud, a galaxy close to our own Milky Way," said Prof. Cowsik. 

"With the help of sophisticated telescopes, astrophysicists have learnt that the Crab Nebula is actually the debris from a supernova which exploded 1,000 years ago." Apart from supernova, our Universe abounds with exploding objects, such as quasars which emit 100,000,000,000 times more radiation than a star," said Prof. Cowsik. 

In our Universe, a vacuum has the edge over matter. "Vacuum occupies 65 per cent of the total space of the Universe," Prof. Cowsik explained, "dark matter fills the 33 per cent and 2 per cent is occupied by normal matter." 

Though we are overwhelmed by the dazzling pictures of galaxies, luminous parts of the galaxies amount to only 0.003 per cent. "On the other hand, 0.02 per cent of the galaxies are constituted by the primordial particles. The halo of dark matter embedded in a galaxy reigns supreme and adds up to its enormous gravitational pull," Prof. Cowsik observed. 

According to him, India had a rich heritage in astronomical research. "Long before the present spate of astronomical studies, Meghnad Saha analysed the stellar spectra and deduced the ionisation states of atoms at varying temperatures and pressures," he said, adding that tradition is still being continued. 

An array of telescopes has been installed in Udaipur to study the sun. "From it we can learn how its influence shaped the evolution of life on earth." 

Prof. Cowsik signed off his lecture recalling a Einstein's famous quote: "The most incomprehensible thing about the universe is that it is comprehensible."