It is impossible to overstate the importance of what Einstein did in 1905. His work on Brownian motion provided the theoretical framework for experiments to prove that atoms were real.Hard as it might be to believe now, at the time the majority of physicists did not believe in atoms. The special theory of relativity completely changed our notions of space and time, while E=mc2 led to the remarkable conclusion that mass and energy are one and the same. And his work on the photoelectric effect was the start of a love–hate relationship with quantum mechanics that still fascinates physicists today. And 1905 was just the beginning.The general theory of relativity – his truly outstanding achievement – followed 10 years later, with its predictions for the bending of light by mass being confirmed a few years after that during the solar eclipse of 1919.
This issue marks Physics World’s main contribution to the International Year of Astronomy Astronomy can lay rightful claim to being the oldest science, with its foundations dating back even further than those of mathematics. From the ancient Babylonians who observed the regular motions of Venus to medieval Islamic scholars who had the first inklings of heliocentrism, the study of the skies has fascinated humankind. But 2009 – the International Year of Astronomy – commemorates an event central to the development of Western science: Galileo Galilei’s first observations with a telescope in 1609. This year also marks the 400th anniversary of Johannes Kepler’s Astronomia Nova, in which he outlined his laws of planetary motion. There may be more pressing scientific issues facing us today, such as the need to tackle climate change, but astronomy has several trump cards that make it worth celebrating. It has easily the best images. It is relatively simple to understand. And what can be more profound than looking at the cosmos and asking of our place in it?
Darwin was no physicist, but his approach to science will be familiar to us Charles Darwin, who was born 200 years ago, is rightly being celebrated as the founding father of modern biology with a series of events around the world this year. Just as Einstein revolutionized physics, so Darwin changed our understanding of life. He came to realize that “natural selection” could account for the huge diversity of life, with more-efficient groups – arising from random variation – always replacing less-efficient groups in a particular environment as a result of competition. After publishing his seminal book On the Origin of Species in 1859 – exactly 150 years ago – Darwin, like Einstein, became the most noted scientist of his time. But Darwin was no physicist and Physics World is not the place for an in-depth analysis of his achievements. Indeed, he had no particular interest in physics – or astronomy for that matter. Darwin did, however, approach science in a way that will be familiar to many physicists. As a result of spending five years on board the HMS Beagle from 1831 to 1836, he painstakingly obtained a welter of information about animals – notably different finches – on the Galápagos Islands off the coast of Ecuador. Darwin’s resulting theory of evolution, although not in any way mathematical, was based squarely on firm scientific evidence and careful thought. And like any good physicist, Darwin acknowledged the theory’s limitations – he could not, for example, explain exactly why natural selection came about – and was in no doubt that future observations could overturn it. As it turns out, evolution has stood the test of time and is today a thriving field of study in biology.
While Wells’ novel is a work of fiction that naturally takes some liberties with the science, the quest for invisibility has made real progress in recent years – and is the inspiration for this special issue of Physics World. Kicking off the issue is Sidney Perkowitz from Emory University (p21), who takes us on a whistle-stop tour of invisibility through the ages – from its appearance in Greek mythology to camouflaging tanks on the battlefield – before bringing us up to date with recent scientific developments. Ulf Leonhardt from the University of St Andrews then takes a light-hearted look at the top possible applications of invisibility science (p26). Hold on to your hats for invisibility cloaks, perfect lenses and the ultimate anti-wrinkle cream. Some of these applications might be years away, but primitive invisibility cloaks have already been built, with two independent groups of researchers having recently created cloaks operating with visible light that can conceal centimetre-scale objects, including a paper clip, a steel wedge and a piece of paper.
This issue of Physics World celebrates the 50th anniversary of the invention of the laser When Theodore Maiman eked out the first pulses of coherent light from a pinkruby crystal on 16 May 1960, the 32-year-old engineer-turned-physicist at Hughes Research Laboratories in the US could not have imagined that the laser would become such a workhorse of physics – and so engrained in everyday life. Within weeks, other physicists – notably those at Bell Laboratories – had reproduced Maiman’s success, with Bell Labs scientists then quickly notching up many other laser “firsts”, including the first gas lasers and the first continuously operating ruby lasers. Lasers have gone on to be one of the outstanding success stories in physics. They can cool atoms, send data, mend eyes, sharpen astronomical images and probe individual DNA molecules; they may even detect gravitational waves and trigger fusion. Hardly surprising then that, by our reckoning, some 14 physics Nobel prizes have been awarded for achievements directly related – or linked – to lasers. Indeed, despite their use in the military, lasers do not suffer from an image problem, being widely regarded as a “good thing”.
This special issue of Physics World examines the challenges in store for nuclear power From breathless early excitement at an energy source that could be “too cheap to meter” to the fear and suspicion following the accidents at Three Mile Island and Chernobyl, nuclear power has always aroused strong feelings. Some see it as the ideal carbon-free energy source – a proven technology that will play a key role in our future energy supply. Others, however, regard nuclear power as dirty, dangerous, costly and uneconomic, as our special debate makes clear (p24). And, of course, it has always had to live – fairly or unfairly – in the shadow of the nuclear bomb (p28). But there are signs that nuclear power could make a dramatic comeback. Countries such as Germany, Italy, Sweden and the UK (p26) are dusting off nuclear plans, extending the lifetime of existing plants, or reversing previous decisions to halt any new stations, which could be good news for physicists looking for a job (p60). In the short term, any new plants are most likely to be pressurized-water reactors – the most common current variety of light-water reactor (p38). But longer term, the nuclear industry is eyeing up a range of six alternative reactor designs, going under the banner generation-IV (p30). Technically fascinating, the reactors promise much, although hurdles remain before any are ever built.
This special issue of Physics World looks at how physics is helping us to understand the Earth, while our website hosts an accompanying series of video reports The devastation unleashed a year ago this month by an earthquake off the east coast of Japan was a reminder, if any were needed, of the deadly power of our planet. The magnitude-9.0 earthquake, which was one of the strongest of the modern age, triggered a huge tsunami that rose to more than 40 m in places and spread up to 10 km inland. Together, the earthquake and tsunami killed more than 15 000 people, with the rising waters doing the most damage, including crippling the Fukushima Daiichi nuclear power plant. One year on from the Japanese disaster, it is natural that this special issue of Physics World on “Physics and the Earth” should include a look at the latest advances in earthquake forecasting. While we are unlikely to ever be able to predict precisely when, where and with what magnitude particular earthquakes will strike, much can be gained from short-term “probabilistic” forecasting, which can give the odds that an earthquake above a certain size will occur within a given area and time (see pp58–63). The virtues of this kind of prediction are also underlined in a series of special video reports that you can watch at Ultimately, the best bet for combating the power of earthquakes is to ensure that buildings are as structurally sound as possible. Indeed, the Fukushima Daiichi plant safely survived last year’s earthquake;
Physics World celebrates the centenary of the discovery of superconductivity Kwik nagenoeg nul. Scrawled in a lab notebook by the Dutch low-temperature physicist Heike Kamerlingh Onnes on 8 April 1911, these words are what signalled that superconductivity . that mysterious and bizarre phenomenon of condensed-matter physics . had been discovered. Onnes, together with his colleague Gilles Holst, had found that the resistance of mercury, when chilled to a temperature of below 4.2K, fell to practically zero . the hallmark of superconductivity. Interestingly, it was only last year that the precise date of the discovery and this phrase . which means gQuick[silver] near-enough nullh . came to light, thanks to some clever detective work by Peter Kes from Leiden University, who trawled through Onnesfs many notebooks, which had been filled (often illegibly) in pencil (Physics Today September 2010 pp36.43). Researchers soon began to dream of what superconductivity could do (p18), with talk of power cables that could carry current without any losses, and later even levitating trains. Sadly, with a few honourable exceptions such as superconducting magnets (p23), there have been far fewer applications of superconductivity than from that other product of fundamental physics . the laser. Over the years, superconductivity has also baffled theorists: it was not until the mid-1930s that brothers Fritz and Heinz London made a big breakthrough in understanding how these materials work (p26). As for high-temperature superconductors (p33 and p41), theorists are still scratching their heads.