By: Prof Atta-ur-Rahman Fellow, Royal Society
What is the greatest miracle of all? We are! I am not referring just to the process of evolution, the creation of life and the billions of factors involved that must come together in mind-boggling precision and coordination for life to exist. I refer to an even more amazing process that most of us are unaware of—exploding stars and their intimate connection to us.
About 65 per cent of our body is made up of oxygen and about 18 per cent of carbon. The rest is nitrogen, and a large number of other elements in smaller quantities such as, phosphorus, iron, magnesium, calcium, etc. Where do all these atoms come from and how do they end up within us?
The process through which these atoms are created involves nuclear fusion—the fusing of smaller atoms to give larger atoms. These fusion reactions occur in the centres of hot burning stars where the temperatures are millions of degrees Centigrade, and there are huge gravitational forces that crunch atoms together to create conditions so that fusion can occur. These are nature’s kilns—super hot furnaces—where the atoms are cooked till they fuse into each other, creating the heavier elements.
The process of fusion leads to huge bursts of heat and light—the thousands of stars that we can see lighting up our skies are due to the light emitted from them by fusion reactions. This is how our sun lights up our days and warms the Earth, thereby sustaining life on it. Fusion of hydrogen atoms leads to helium and all other elements are the result of subsequent fusion reactions. The temperature of our sun at its core is about 15 million degrees Centigrade and it produces mainly helium from the fusion process.
However, when stars are about eight times the size of our sun, then the much higher gravitational forces with correspondingly greater “crunch power” result in the formation of some of the heavier elements such as carbon, nitrogen and other elements up to iron. To produce even heavier elements such as nickel, gold, and uranium requires fusion to occur at much higher energies. This happens when stars collapse (implode) and then finally explode in a huge burst of light and energy, with the emission of radiation—the supernova.
The light produced from each supernova is sufficient to temporarily illuminate an entire galaxy and it then fades away over a period of a few weeks. The luminosity in this intense explosion is greater than what our sun will produce throughout the billions of years of its existence! Such supernovae are quite common, occurring once every 50 years in a galaxy of our size. All the matter that has been synthesised in the bosoms of the stars is ejected into outer space. The stellar dust produced from the supernova explosions can later collapse to give rise to planets—such as our Earth. Indeed every single element on planet Earth was once in the centre of a burning inferno—in the bosom of a star!
Now comes the exciting part. We are what we eat. A baby grows into a man or a woman by converting what he or she eats into the various components of his/her body. All the fruits, vegetables and other edible materials are derived from the atoms and molecules present on Earth and end up in our bodies in the form of our flesh, bones and various organs. Our food items, in turn, have all arisen from the exploding star from which the Earth and the planets of our solar system were formed. This leads to an absolutely stunning conclusion: every single atom in your body was once in the centre of a burning star! All the atoms present in your fingers, skin, eyes, hair etc. were, a long, long time ago in the core of a certain star at temperatures of tens of millions of degrees centigrade!! This is fact—not a theory or fiction. From burning atoms in exploding stars we have been miraculously transformed to living, feeling human beings—the greatest miracle of all!
An attempt is being made to try to reproduce the process of nuclear fusion in the world’s largest scientific experiment, the ITER reactor in the south of France. Superconducting magnets will be used to squeeze plasma of heavy hydrogen isotopes to temperatures of 150 million degrees centigrade. The construction of the machine should be completed by 2019, and full scale experiments begin in 2026. If the experiment works, it would produce 10 times more energy than consumed by it, and we would have learned to replicate the chemistry of suns and stars to meet our energy needs from isotopes of hydrogen.