2009 is the year of astronomy and Plus will be part of the celebrations!
In May 1609 Galileo Galilei received reports of "a spyglass by means of which visible objects, though very distant from the eye of the observer, were distinctly seen as if nearby." Intrigued, he set about building his own version of this curious device, and he succeeded: by the end of the year he had discovered mountains on the Moon, the moons of Jupiter and the make-up of the Milky Way. His
observations revolutionised our understanding of the Universe, and his use of the telescope marked the birth of modern astronomy — which celebrates its 400th anniversary this year.
This week both the Daily Telegraph and the Daily Mail ran stories claiming that switching off street lights could significantly increase the number of road
deaths. The stories were based on a paper published in the Cochrane Library, which considered three studies into the connection between road accidents and street lighting. However, it seems that the headlines are a typical example of misinterpretation of statistics.
As David Spiegelhalter, Professor for the Public Understanding of Risk at the University of Cambridge, writes on his website Understanding Uncertainty, the studies suffer from three major flaws: poor data, publication bias, and what's known as regression to the mean. Spiegelhalter points out that the three studies underlying the
paper were poor and conducted decades ago, with one dating from as far back as 1948 — not a very good basis for drawing conclusions about today's traffic. The term publication bias refers to the fact that studies which show dramatic results are more likely to be published than those that don't. It's quite possible that there were other studies, which found no connection between street
lights and accidents, but that no-one bothered to publish such boring results. Regression to the mean is a commonly observed effect, which results from random fluctuations. If street lights were installed on a certain road, then this is most likely because that road recently experienced a spade of accidents. Such a freak period can be purely down to chance, in which case one would expect the
accident rate to return to normal after a while. Thus the improved accident rate after the installation of lights may be purely down to chance, rather than the improved lighting.
All this doesn't of course mean that street lights are useless. It simply means that the evidence is nowhere near as sound as the newspaper headlines claim. The Daily Mail, to its credit, did consult an expert, namely Spiegelhalter, but it's probably the headline, rather than his warning, that will stick in readers' minds.
One hundred and fifty years after the publication of On the origin of species, it seems that one of Darwin's most fruitful ideas, that the course of evolution can be represented in the shape of a tree, is in need of updating. Evidence is mounting that what we should be thinking of instead is a web.
Reconstructing relationships between species from genetic information is a mathematical exercise, as well as a biological one. Darwin's tree of life, as a mathematical object, is an example of a graph, a collection of nodes connected by edges, with the special property that there's only one route between any two nodes. There are no circuits in the graph because it was assumed that genes can
only be transferred between parents and offspring. But as Plusreported last year, there is evidence that genes can also be transferred between species horizontally, for example through hybridisation or swapping of genetic material between unrelated species. An article in this week's New Scientists brings together many strands of evidence for horizontal gene transfer. According to the article, the evidence doesn't just concern strange unicellular beasts, but also humans and other mammals: it is estimated that "40 to 50 per cent of the
human genome consists of DNA imported horizontally by viruses"!
As a result, many scientists now think that a more general form of graph, a network, is what is needed to describe life. Given the potential complexity of networks, genetics may soon be in desperate need of mathematicians.
When it comes to describing natural phenomena, mathematics is amazingly — even unreasonably — effective. In this article Mario Livio looks at an example of strings and knots, taking us from the mysteries of physical matter to the most esoteric outpost of pure mathematics, and back again.
Leading European scientists have said that mathematical modelling is key to future breakthroughs in the treatment of diseases including cancer, schizophrenia and Parkinson's disease. In a science policy briefing published by the European Science Foundation, the scientists set out a detailed strategy for the application of an area called systems biology to medical research. The aim is to
improve early diagnosis, develop new therapies and drugs, and to move to a more personalised style of medicine.