Friday, 31 July 2009

Madame Curie's transformation

My favourite essay in ‘The Faber Book of Science’ (edited by John Carey) is ‘Shedding Life’ by Miroslav Holub, who is a poet and immunologist. In this essay he recollects mopping up the blood of a recently shot muskrat, and he ponders on the exact nature of death. The death of an organism as a whole is generally taken to be defined as brain death or heart failure. But what about all the constituents of that organism? Holub points out that many of these; blood cells, hormones, enzymes etc., are all capable of living on for some time after the apparent death.

When Marie Curie died (in 1934) her belongings, such as her note books, were discovered to be so radioactive that they had to be deposited in lead-lined boxes. Even now, anyone who wants to look at them has to wear protective clothing.
She died of cancer, most likely caused by a lifetime of working with radioactive substances without being properly protected from the resulting radiation. Her most famous achievements were to discover new chemical elements, by virtue of the fact that they were radioactive. In making these discoveries she helped to shed light on the nature of radioactivity, and show that there are three different types; alpha, beta and gamma radiation. When an element emits or absorbs alpha or beta particles it changes into another element. This is why the study of radioactivity has been considered to be a sort of alchemy. (You can get gold from radioactive mercury, but it is very difficult).

Marie Curie worked with a uranium ore called pitchblende, exposing herself to alpha particles, and to radon gas. Both of these would have been absorbed by her body, causing damage to the cells. At an atomic level some of the alpha particles may have been absorbed by the atoms in the cells (Humans are carbon-based and so most of these atoms are carbon atoms. The process of carbon atoms absorbing alpha particles and transmuting into oxygen atoms is what happens in dying stars.)
Radon gas has a long half life but eventually decays into polonium, one of the elements Marie Curie is famous for discovering and which she named after the land of her birth; Poland. Polonium is called a ‘daughter product’ of radon as a result of this process.
Her body is interred in the Pantheon in Paris. It is still radioactive; alongside the more usual organic decay processes taking place there are also the atomic ones. She is being transmuted herself.

Sunday, 26 July 2009

Intuition about mice and quasars

‘Intuition’ (by Allegra Goodman) takes place in a cancer research lab where one of the junior workers, Cliff, thinks he’s found a virus which can cure cancer in mice. The lab is in financial trouble, so its directors are grateful for the chance to publicise these results and use them to raise funds. However, it proves impossible to replicate the results, and another post-doc, who happens to be Cliff’s ex-girlfriend, suspects him of fraud.

Some reviews of this book have suggested that it’s never made entirely clear whether Cliff has knowingly committed fraud, or if he has unwittingly made a mistake. But there is a clue quite late on, when we get a glimpse of Cliff’s reasoning;

He had not chosen to discuss every piece of data, but had run ahead with the smaller set of startling results he’d found. Still, aspects of his data were so compelling that in his mind they outweighed everything else. He had sifted out what was significant and the rest had floated off like chaff.’

From a scientific point of view, the first sentence of this quote is damning. Cliff just doesn’t seem to be a very good scientist. When you run an experiment you cannot pick and choose where your results start and end. If you start with a hundred mice, you must discuss the results of the experiment on all of those mice, not just the few that happen to show a good result. This is because there’s always the possibility that your good result happened by chance. If you spot a good looking result in a subset of your data, it may just be a random fluctuation. (That is also true of the whole dataset, of course, and should be quantified as far as possible.)

It’s bad science to select a subgroup of interesting results after the event, but it’s depressingly common. When I was an astronomer, I worked on quasars. There’s a so-called ‘controversy’ about whether or not these objects are at the incredibly large distances as implied by their redshifts, if the Big Bang model is correct. This controversy was a genuine problem when quasars were first discovered in the sixties, but has now fizzled away. Only a few ‘maverick’ astronomers, such as Halton Arp, now believe quasar redshifts aren’t cosmological. The controversy is an artefact of only choosing the data that fit the hypothesis and ignoring all the other data, in this case of looking at quasars that appear to be near to much lower redshift galaxies. Statistically this doesn’t happen any more than you would expect – but superficially it looks ‘interesting’.

One nice aspect of ‘Intuition’ is that the point of view is omniscient and no one character is particularly favoured; rare in modern literature. The reader gets to inhabit the minds of all the major characters and understand their view of the drama unfolding around them. Even so, with all this information that we are provided, it proves impossible to understand the reasons behind the characters’ actions.

This failure of the omniscient narrator to get to the truth of the matter could be read as a warning – are we deluded in hoping/expecting science to be an impartial tool for understanding the external world? Or am I confusing science with omniscience?