Universe made up of 114, or so, elements

By Associate Professor Allan Blackman

This article was orignally published in the Otago Daily Times on Monday 31 December 2001.

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What is the universe made of? This must surely be one of the oldest questions posed by humankind. The ancient Greeks thought that all matter was composed of fire, air, water and earth, in varying proportion. Nowadays, we know that the universe is constructed from many fundamental building blocks. How many? Well, that’s a question we thought we knew the answer to, at least until last July.

Thanks to the pioneering work of early chemists, of whom the most famous was John Dalton (who incidentally was colourblind, which is why this condition is sometimes referred to as Daltonism) we now know that the universe is constructed of atoms, unbelievably tiny particles of matter. Chemists, and most other rational scientists, consider atoms to be the fundamental building blocks of nature. Physicists, on the other hand, believe in quarks, leptons, bosons and Santa Claus. The structure of the atom was unravelled by Ernest Rutherford who showed that atoms are composed of a positively charged nucleus surrounded by negatively charged electrons, and that atoms contain as many electrons as there are positive charges in the nucleus. It was known at this time that there were many different types of atom, each unequivocally defined by the number of positive charges in the nucleus; an atom of hydrogen always contains 1 positive charge, an atom of carbon, 6, and an atom of cobalt, 27. Each different type of atom is called an element. There are 91 different elements that occur naturally on the earth and, until around 60 years ago, absolutely everything on the planet and in the universe was made up of combinations of these elements. However, homo sapiens, being the inquisitive creature that (s)he is, wasn’t happy with only these building blocks, and in the last 60 years has actually managed to “improve” on nature by creating new elements. These are called the transuranium elements, as they contain more positive charges than the heaviest naturally occurring element, uranium. As you might expect, it’s not easy to create matter that hasn’t existed in the universe before, and the synthesis of each new element is a big scientific event – indeed, Nobel prizes have been awarded for such things. So in 1999, the scientific world got quite excited when the synthesis of an element containing 118 positive charges in the nucleus was reported by a group of scientists at the prestigious Lawrence Berkeley National Laboratory in the United States. The most remarkable thing about this report was the experiment itself – over eleven days, the researchers had detected three (yes, three!) atoms of element 118. Not only this, but these three atoms disappeared within one thousandth of a second! The Berkeley group duly published their results in a peer-reviewed journal and for a while, the universe contained 115 elements (elements 113, 115 and 117 had not yet been synthesised). However, on July 27th last year, this group retracted their claims for the synthesis of element 118 as a result of the fact that researchers elsewhere in the world were unable to reproduce their results. This was undoubtedly highly embarrassing for the Berkeley group, but is in fact a commendable example of the self-correcting nature of science – for your results to be accepted as valid, you (or others) must be able to reproduce them. In this case, replication of the results could not be easily accomplished as the necessary apparatus was only available at a handful of places in the world, and the experiment and subsequent data analysis was extremely time-consuming. This explains the two year gap between the original report and the retraction. So at the present point in time, the universe is made up of 114 elements. Doubtless, there will be more elements discovered, but after this episode you can bet that the scientists involved will ensure that their experiments are completely reproducible.

I shouldn’t really have given the physicists such a hard time above – after all, Rutherford was once famously quoted as saying “All science is either physics or stamp collecting”. The fact that he won the Nobel prize in Chemistry must have irked him immensely.