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Home » Page 1843

Noisy signals strengthen human brainwaves

In many complex systems, weak periodic signals can be strengthened by noise. This happens when random peaks in the noisy signal coincide with regular peaks in the periodic signal. This stochastic – meaning ‘random’ – resonance is most effective when the noisy signal has a certain amplitude relative to the periodic signal. Scientists have already found evidence for the effect in humans, in the control of blood pressure in the brain and in the sense of touch.

In their study, Mori and Kai shone light signals into the eyes of five students while measuring their brain waves. Brain waves are electrical signals with frequencies ranging from 0.5 to 60 Hz that can be detected via electrodes attached to the scalp. So-called alpha waves have frequencies between 8 and 13 Hz, and are emitted when the brain is at rest.

The researchers shone periodic signals onto the right eyelids and noisy signals onto the left eyelids of the students as they rested, and measured the intensity of their alpha brain waves. As expected they found a sharp peak at 5 Hz, the frequency of the periodic signal. But when they increased the strength of the noise signal relative to the periodic signal, a ‘harmonic’ peak emerged in the alpha waves at 10 Hz. As the noise signal became stronger, this peak first intensified and then diminished.

Mori and Kai believe that the harmonic peak is good evidence for stochastic resonance in the visual cortex of the brain because it reaches a maximum at a particular signal-to-noise ratio. They are also confident that the effect took place in the brain – rather than in the eyes – because they placed a light-proof screen between each student’s eyes so that the signals did not interfere outside the head.

There are many natural sources of electrical noise in the brain, including electrochemical reactions and random firing of neurons, which could lead to stochastic resonance. Following their discovery, Mori and Kai speculate that the effect could play a role in complex brain functions such as perception and cognition.

Lights switch to organic LEDs

Household and commercial lamps are designed to emit a broad spectrum of light composed of many wavelengths. But LEDs typically emit light of just one wavelength, which is determined by the energy gap between the excited state and the ground state of the atoms or molecules that make up the LED.

Earlier white-light LEDs were made from a combination of atoms or molecules with different energy gaps, so that the LED emits light at many wavelengths, simulating white light. In practice, however, the different materials used in these devices degrade at different rates, so the spectrum of such white-light LEDs changes over time. This makes them unsuitable for use as lights, which must have a stable spectrum over their entire lifetime.

Duggal’s team has solved this problem by using a technique known as ‘down-conversion’ to generate light of many wavelengths. To make their device, the researchers placed an organic LED that emits blue light ‘face down’ on a glass substrate. On the other side of the glass, they deposited layers of dyed polymers that contained particles of phosphor.

When light from the LED enters the polymer layers, some of the blue photons are split – or ‘down converted’ – into two longer-wavelength photons by the phosphor particles. As the original photons and the new photons encounter subsequent polymer layers, this process is repeated again and again. When the light emerges from the device, it consists of a wide range of wavelengths – that is, it is white light.

Different white light spectra are distinguished by their ‘colour temperature’, which is the temperature at which a perfect black body would emit the same spectrum. A tungsten filament light bulb emits reddish light and has a colour temperature of around 2700 kelvin, while a ‘bluer’ metal halide lamp has a colour temperature of around 6000 kelvin.

The colour temperature of the new device can be tuned between 3000 and 6000 kelvin by changing the thickness and the number of polymer layers. Since the LED is based on light produced by just one type of molecule, Duggal and colleagues say it should be very stable and cheap to produce.

Physicists get a taste of ‘tetra-neutrons’

Studies of the interactions between nucleons — neutrons and protons — in small nuclei are crucial for theories of nuclear binding in larger nuclei. Physicists know that pairs of neutrons can exist in an ‘almost bound’ state – that is, if they interacted any more strongly, they would form a “di-neutron”. This has led to speculation that larger numbers of neutrons could form clusters, which might be found in nuclei that contain many more neutrons than protons.

Over the last 40 years, several collision experiments have been conducted to search for neutron clusters. But these experiments have been unable to tell the clusters apart from single neutrons that are also ejected in the collisions, because neither have an electric charge. Now a new technique has provided the first hints of them.

In the GANIL experiment, led by the CNRS Laboratoire de Physique Corpusculaire in Caen, neutron-rich nuclei were broken up, and the fragments were then collided with protons. The make-up of these fragments was then deduced from the energy of the recoiling protons and the time the fragments took to reach the protons.

The researchers carried out the experiment on beams of neutron-rich lithium-11, boron-15 and beryllium-14 using the UK CHARISSA and the Franco-Belgian DEMON detector arrays. An analysis of the data led by Francisco-Miguel Marqués identified six protons with energies that could be explained most easily by collisions with newly formed tetra-neutrons.

The researchers admit that other effects in their experiment could have mimicked the presence of tetra-neutrons, but believe that these account for no more than 10% of the signal. They plan to conduct similar experiments next year with better fragment detectors, a more intense beam of beryllium-14, and a beam of helium-8 nuclei, which is also expected to form tetra-neutrons.

Neutrino pioneer wins 2001 National Medal of Science

Davis began his research career at Brookhaven National Laboratory in 1948 after receiving his doctorate in physical chemistry from Yale University. He initially studied neutrinos created in the research reactor at Brookhaven, but the technology available at the time could not detect the neutrinos that physicists believed were generated by nuclear reactions in the Sun.

In the 1970s, Davis tackled this problem by developing an experiment in which solar neutrinos interacted with the chlorine nuclei in a 100 000-gallon tank of dry-cleaning fluid to produce radioactive argon. The tank was placed in a disused gold mine to protect it from the cosmic rays that had prevented scientists detecting solar neutrinos at ground level. Davis went on to confirm that the Sun produced neutrinos, but the discrepancy between the number of neutrinos expected and that observed – which became known as the solar neutrino problem – was only resolved last year.

Davis’ research took him to the University of Pennsylvania in 1984. Among other prizes, he received the 2000 Wolf Prize for his contributions to neutrino physics.


Marvin Cohen

Marvin Cohen’s career began in 1963 after he completed his PhD at the University of Chicago. After spending a year at Bell Labs, he was made a senior scientist at Lawrence Berkeley National Laboratory, a position he still holds. In 1969, he also became professor of physics at the University of California at Berkeley, and has held the post of university professor since 1995.

In the course of his career, Cohen has published nearly 600 research papers on electronic and structural effecst in semiconductors and superconductors, and has received numerous awards.

Molecular machines get light battery

Nano-scale devices based on molecular machines could play a major role in the future of electronics, medicine and communications. But a major challenge in the development of such devices is to find a suitable power source.

Now Gaub’s group has shown that light can be used to power mechanical transitions in an azobenzene polymer. This polymer is a chain-like molecule with a dangling side group, which can have one of two orientations – known as “trans” and “cis” – with respect to the main molecule. The polymer molecule is longer when the side group is in the trans position and shorter when it is in the cis position.

Chemists have long known that this molecule can be switched between its long and short states by illuminating it with light of certain wavelengths, and several chemical processes are based on this effect in bulk samples of the polymer. But Gaub and colleagues have shown that the effect can also be useful at the single molecule level.

The researchers made a sample of the polymer containing a mixture of long and short molecules, and attached a cantilever – in the form of an atomic force microscope – to one of the cis molecules. After illuminating the sample with visible violet light, the cis molecules flipped into the trans state, and the cantilever registered the force produced by the molecule as it stretched by 1.4 nm. When Gaub’s team subsequently shone higher-frequency ultraviolet light onto the polymer, a compression force was detected as the molecule contracted.

To establish whether the molecule could do mechanical work, the researchers repeated the experiment after applying loads – up to 500 pN – to the molecule using the cantilever. When they illuminated the molecule as before, they found that it continued to stretch and contract against the applied force. This allowed them to calculate that the molecule had done mechanical work as its length changed in response to light.

Although the process is currently rather inefficient, Gaub’s team is optimistic that it can be improved so that the system could operate in a real device.

Semiconductors plug terahertz gap

Semiconductor devices currently generate radiation at both ends of the electromagnetic spectrum. Oscillating circuits made up of high-speed transistors produce radiation for wireless communication at radiowave and microwave frequencies – 100 kHz and 3 GHz, respectively. At the other end of the spectrum, semiconductor lasers emit radiation at 300 THz or more, which can be used in optical fibre telecommunications.

Researchers have previously generated terahertz radiation using a laser built from lightly doped germanium. However, like other conventional semiconductor lasers, this device worked by recombining electrons in the conduction band and holes in the valence band. The frequency of the radiation was determined by the energy difference between these bands, which is an inherent property of the constituent materials.

The new laser on the other hand – known as a quantum cascade laser – was made from 1500 alternating layers of gallium arsenide and aluminium gallium arsenide, with each layer just a few nanometres thick. The quantization of electron motion perpendicular to the layers results in a series of discrete energy levels across groups of adjacent semiconductor layers known as stages. Since the spacing between energy levels depends on the thickness of the semiconductor layers, such a device could in principle emit radiation at arbitrarily long wavelengths.

By applying a potential difference across the thickness of the device, the electron energy drops in successive stages. So when an electron in the highest energy band drops to a lower energy level within that stage, it can be ‘recycled’ to the highest energy band of the stage immediately below. This process is repeated in successive stages, causing the electron to ‘cascade’ down the device in a series of steps, emitting many photons on its way.

Köhler and co-workers overcame several hurdles to create the laser. Using the quantum cascade effect, they were able to ensure that there were enough electrons in the highest energy levels for laser action. They also made a waveguide that can confine the laser’s long-wavelength radiation, and reduced optical losses arising from free electrons in the material.

Although their device only works at temperatures of a few kelvin, Köhler and co-workers believe that it could form the basis of commercial terahertz systems that would operate at higher temperatures. However, since the atmosphere absorbs radiation above 1 THz, such systems would have to operate at lower frequencies to be useful in telecommunications.

Doubt cast on “left-handed” materials

In 1967 the Russian physicist Victor Veselago predicted the existence of materials with a negative refractive index. This property arises when the electric permittivity and the magnetic permeability of a material are both negative, leading to a special solution of one of Maxwell’s equations. He speculated that these materials would refract light in the opposite direction to conventional materials – hence the name ‘left-handed’ – and could also behave as perfect lenses.

Left-handed materials do not occur naturally, but several groups have successfully made them. A number of simulations and demonstrations have shown that left-handed materials can indeed behave as perfect lenses and that ‘negative refraction’ can take place, at least for microwave wavelengths.

But Nicolas Garcia and Manuel Nieto-Vesperinas of the Consejo Superior de Investigaciones Cientificas in Madrid believe that reports of perfect lensing make false assumptions about the behaviour of radiation in left-handed materials (N Garcia and M Nieto-Vesperinas 2002 Phys. Rev. Lett. 88 207403). When light shines through an ordinary lens, a fraction of it is absorbed by the lens in the form of ‘evanescent’ – or surface – waves, leading to a distorted image.

Studies suggested that these evanescent waves could be captured and amplified in left-handed materials to form a perfect image. Now Garcia and Nieto-Vesperinas say that this is impossible in practice and that – according to their analysis of evanescent waves – the waves would need to have infinite energy for this effect to take place.

At the University of Texas at Austin, Prashant Valanju and colleagues recently concluded that earlier studies of negative refraction failed to account for both the group and phase characteristics of electromagnetic waves (P Valanju 2002 Phys. Rev. Lett. 88 187401).

They analysed the different frequency components of a signal travelling through a left-handed material, and say that although phase fronts can refract in a ‘negative’ direction, the group front of the signal always refracts in a ‘positive’ direction. According to Valanju and colleagues, negative refraction of the group front would violate the fundamental limit of the speed of light, and therefore the notion of cause and effect.

But both the Spanish and the US studies are “seriously in error”, according to John Pendry of Imperial College in London, whose previous simulations suggested that negative refraction could take place in thin sheets of silver.

He says that Garcia and Nieto-Vesperinas neglected the absorption of the signal in parts of their calculation, and that he accounted for their objections in his original work (J Pendry 2000 Phys. Rev. Lett. 85 3966). In contrast, Pendry supports the calculations made by the US team, but argues that Valanju and co-workers misinterpreted their own results, mistaking the direction of the group wave front.

If it is proved that negative refraction and perfect lensing can be achieved in left-handed materials, they could be used for a wide range of applications including high-density data storage and high-resolution optical lithography in the semiconductor industry.

Small-scale radiation check for mobile phones

Previous studies of the absorption of radio-frequency radiation in the body – and the associated increases in temperature – have detected variations on scales larger than 2 mm. This approach is adequate for studying relatively large organs in the head, such as the brain, which mostly consists of the same type of tissue.

But Van de Kamer and Lagendijk suspected that this method would not accurately map absorption in small organs like the eye and the inner ear. These contain a variety of tissues – such as bone, eye humour and muscle – that each absorb radiation to a different degree.

To test their theory, the researchers calculated the effects of a mobile phone – simulated by an antenna emitting radiation with a wavelength of 915 MHz – on a computer model of the head of a female adult. They monitored the absorption on scales of 0.4 mm, 1 mm and 2 mm, that is, with the largest ‘volume element’ over 64 times bigger than the smallest. On the largest scale, the pattern of absorption closely matched that of earlier experiments, which indicated a maximum temperature rise in the head of 0.15 K.

On the smaller scales, the results for the brain were also similar to those of previous studies, but, as predicted, the team found different levels of absorption in other parts of the head. In particular, a layer of cerebral spinal fluid around the brain was found to absorb higher levels of radiation than the rest of the brain.

The researchers say that this demonstrates the importance of establishing how small regions consisting of different tissues react to radiation. They say that this is especially important in organs that are held close to mobile phones, such as the ears.

“It is clear from our study that, for small-scale structures, high-resolution electromagnetic modelling is a necessity,” said Van de Kamer. Having demonstrated their technique, the researchers say that it could now be used at much higher resolutions.

Lasers clear leaves on the line

They cause delays, cancellations and untold frustration to rail passengers in the UK every autumn. It’s no wonder that leaves on the line have become something of a national joke, regarded by the British public as merely the latest excuse for poor railway services. The problem arises whenever leaves from trees bordering the track fall close to the rails, where they are swept up by the turbulence caused by passing trains before being crushed under the wheels of the carriages. The leaves are pounded into a hard, black, shiny Teflon-like substance that is difficult to remove, even with a sharp knife. Horse chestnuts and limes are the biggest culprits, with their leaves having the highest “squidge factor”.

The problem is exacerbated during bad weather. Crushed leaves become slippery when wet, and the poor adhesion between wheel and track makes it difficult for trains to slow down and stop. Some trains require twice the usual distance to come to a halt, and their “stopping distance” can increase by anything up to 800 m, depending on the train’s initial momentum. Leaves on the line also make it more likely that trains will overshoot signals – leading to “signals passed at danger”. And heavy-goods trains can sometimes even find it impossible to pull away on leaf-covered lines, causing delays for the rail-freight industry.

Now, however, a new Hampshire-based company set up by a former Royal Navy officer could make leaves stuck to the line a thing of the past. Malcolm Higgins founded LaserThor in November 1999 after hearing a radio report about the problems facing the railway industry. “I am no scientist or railway expert”, recalls Higgins, “but it suddenly occurred to me that lasers, which are so common nowadays, ought to be able to help.” His idea was to attach a high-power laser to a train that could then clean the tracks as it moved over them. Progress has been remarkably swift since Higgins’ initial brainwave, and – thanks to help from the Rutherford Appleton Laboratory – LaserThor hopes to have its first marketable products next year.

Cleaning the tracks

In the old days of steam trains, leaves on the line were never a problem for Britain’s railways. Trees bordering lines were regularly cut back to prevent sparks from igniting the foliage. But as diesel and electric trains gradually replaced steam engines, the trees were allowed to grow so much that they began to encroach on the line. It also became common for trees to be planted to help cut train noise.

Leaves are now such a hazard that Railtrack – the company that used to maintain the UK’s rail network before being taken over by administrators last October – spent £60m in autumn 1999 tackling the problem. The money mainly went on transporting an army of manual staff around the country to clean the rails in the early hours of the morning. Britain’s rail regulator even allows train-operating companies in the worst-hit areas to reduce the number of trains during the autumn period. South West Trains, for example, which runs commuter trains into London, regularly cuts its autumn services by up to one third to allow for potential delays.

Given the extent of the leaf problem, it is surprising that most solutions adopted by the railway industry are remarkably low-tech. Traditional methods of removing leaves include blasting the tracks with high-pressure jets of water, squirting them with a gel-like sandy material known as “sandite”, or scrubbing them with scourers. Crushed orange peel has even been tried as a possible abrasive. All of these approaches, however, are slow, unreliable and expensive.

Green light for research


Blast off

After his initial idea, Higgins wasted little time putting it into practice. He hired a lawyer to file a patent on his idea and paid for researchers at the Defence Evaluation and Research Agency in Malvern to see if rails could be cleaned with lasers without causing damage. “They said that it could be done in principle, but that it wasn’t practical for a real railway system,” recalls Higgins. “I also knew that the laser would have to work on a moving train for my idea to be viable.”

Higgins then persuaded Railtrack to look into his idea. Despite being notoriously cautious about the potential of new technology, the company’s managers were keen. They helped LaserThor to obtain the necessary safety clearance to carry out trials in autumn 2000. This was just after a damaged rail caused the Hatfield rail crash, which forced Railtrack to check almost every line in the country for similar defects, paralysing Britain’s rail network in the process. “The fact that we were allowed to run trials even when Railtrack was under so much pressure to deal with the short-term problems that arose in the wake of the crash shows how enthusiastic the company was,” says Higgins.

With help from a private investor, the Rutherford Appleton Laboratory, a government SMART award worth £40 000 and an electrical engineer called Mike Davis, the trials began in autumn 2000. The Rutherford lab provided the laser expertise, while Spectron Laser Systems of Rugby in Warwickshire lent LaserThor a pulsed neodymium yttrium aluminium garnet (Nd:YAG) laser operating at 1064 nm. The laser was installed on a carriage with electrical power provided by an on-board generator. Using a carefully designed optical set-up of lasers and mirrors that could withstand the rigours of rail travel, the laser light was directed onto the track. Each intense laser pulse can produce a series of minute explosions that blow the leaf residue off the rails, resulting in a clean track and restoring traction to passing trains.

“We found that it was entirely feasible to use lasers to remove rail contamination without damaging the track and that we could operate successfully with the train running at speeds of about 8 kilometres per hour,” says Higgins. The tests also showed that leaf residue can make or break a railway’s safety circuit, which is formed between the track, trains and the signalling equipment. “Our trials proved that high levels of leaf contaminant can cause signalling systems to miss the presence of trains on the track. Signals then have to be changed manually, which is dangerous. Lasers could also solve this problem.”

Full steam ahead

Following the success of these early trials, LaserThor then began investigating how a laser system could work on trains running at more realistic speeds of about 70 kilometres per hour. Higgins contacted the Fraunhofer Institute for Laser Technology in Aachen, Germany, who built a high-power 1 kW Nd:YAG laser that could be fitted into a 1 m3 box. The unit contains the hardware required to support the laser in the hostile railway environment, including a chiller and electrical power-control devices. The new laser system has a higher pulse rate than the original and uses fibre optics – rather than lenses and mirrors – to deliver the laser beam onto the track. The system was used in further trials last autumn.

LaserThor has also carried out lab experiments to see if exposing a railway track to intense laser light damages the track in any way. Sections of rail were exposed to a number of laser shots over a range of intensities and then sent for metallurgical analysis. The results have, happily, revealed no significant damage to the surface of the track under normal conditions. “We are well within the safety range,” says Higgins. Environmental safety checks have also been carried out to ensure that the laser ablation does not produced any harmful emissions.

One of the biggest challenges for LaserThor has been to ensure that the new system is safe enough to be operated as a “class-1” laser. The laser has to be properly shielded and fitted with fail-safe sensors that only allow the laser to work when it is properly protected. Further tests on this were carried out last autumn, with more planned for later in the year.

Moving to the market

Although LaserThor’s current system is still too big to be fitted on active passenger trains, Higgins envisages it working on “rail service vehicles” that are used to monitor the rail network. Live demonstrations to potential customers will take place this autumn, with Higgins hoping to sell his first units next year. Higgins is reluctant to say how much each laser will cost, but thinks the company can sell “up to 500 units in the first five years”. The company has also benefited from an exceptional SMART award, worth £361 000. “They are awarded only to projects that have ‘significant export potential’, which has been a huge encouragement to us,” says Higgins.

LaserThor thinks that its system could be used for more than just leaves on the line. It has found that its lasers can also remove oil, grease, ice, tyre rubber and other contaminants from tracks. It could, for example, be used on rails in rural areas, which often get coated with a film of rust when not used at weekends. Rail companies in Arizona have even expressed an interest in the system. According to Higgins, their railway lines are often coated with excess fuel dumped into the atmosphere above the Arizona desert by planes flying to Los Angeles.

LaserThor’s answer to the problem of leaves on the line sounds so simple that it seems strange that no-one has ever thought of using lasers before. “That’s what I kept asking myself,” says Higgins. “Perhaps other people had looked at the idea, but felt that the technology was not advanced enough at the time. Fortunately, I had my idea just as big developments in Nd:YAG laser technology were taking place. I suppose I just got lucky.”

Revealing the Universe: The Making of the Chandra X-ray Observatory

I first approached Revealing the Universe, which tells the story behind NASA’s Chandra X-ray astronomy mission, with a certain amount of scepticism. What I expected was another book telling us how far ahead the US and its science programme are compared with the rest of the world. It quickly became apparent, however, that I had in my hands an in-depth account of the trials and tribulations that lie behind the success of any space-science project.

From my own experience in the space industry, I can say that the long march towards Chandra’s launch in mid-1999 – with all of its technical obstacles, political intrigue and budgetary difficulties – rings very true of other missions. Wallace and Karen Tucker manage to capture this struggle well, in a style suited to the popular-science market.

The book also gives an insight into the early scientific results obtained by Chandra, providing a mouth-watering glimpse into what may be in store when the mission’s full scientific results are interpreted. Although this discussion is confined to the last few pages of the book, I have no doubt that these results will be popularized in due course by other authors. But the book’s strength is in its story of the struggle that led to Chandra’s launch.

The first part of the book reminds us that X-ray astronomy is a young science that only became possible once sounding rockets had been developed in the late 1950s to take scientific instruments beyond the atmosphere. Indeed, many of the great names associated with the birth of this branch of astronomy are still in positions of power and influence in the scientific community. The fact that the science has grown so quickly and has contributed so much to our current understanding of the universe is a tribute to these pioneers. The Chandra mission itself was named in honour of the pioneering Nobel-prize winning astrophysicist Subrahmanyan Chandraseskhar, who died in 1995.

One of the most fascinating aspects of the book is the intrigue, in-fighting and politics involved in the civilian space programme. This aspect is particularly important in the US, where funding for large projects requires approval by Congress and is subject to the whims and aspirations of the various members of the congressional committees. The rocky path to the final approval in 1988 of the Advanced X-ray Astrophysics Facility (AXAF) – as Chandra was originally known – was due as much to the marketing ability of the mission’s supporters both inside and outside NASA as it was to the mission’s scientific merits. Indeed, a final appeal to president Reagan was needed to establish AXAF as a NASA programme.

After describing the story of how the mission was approved, the authors lead us through the technical challenges in the manufacture, grinding and polishing of Chandra’s X-ray mirrors. They consist of delicate glass cylinders, mounted coaxially to form a “Woltjer-type grazing incidence assembly” – the only type of mirror that can focus particles of such high energy. The achievement of reaching the required accuracies was nothing short of a miracle with the technologies available in the late 1980s.

One aspect that the authors bring to life is the absolute dedication of the teams involved. Although their goals were almost out of reach, people were prepared to work seven days a week to ensure success. This aspect of the mission is well covered, which brings the book alive to the reader. The many pitfalls encountered – and the ingenious manner in which these were overcome – make a fascinating story in their own right.

Above all, the authors illustrate the human weaknesses involved when so many “prima donnas” are needed to realize a mission such as AXAF. They included lab technicians designing the ultimate in X-ray detectors, programme managers who had to draw together all the intricate parts into a working spacecraft, as well as the scientists who had the original vision.

The scientific instruments on AXAF are described in terms that can be understood by all. The authors manage to explain the physics of the instruments in sufficient detail while at the same time using enough analogies to everyday objects to help the reader. Their approach provides an understanding of the purpose and operation of the payload that caters for readers with a range of scientific knowledge.

The authors eventually reach the great moment where all depends on the Space Shuttle launch vehicle and its crew to put Chandra into its chosen environment high above the atmosphere. The authors capture the tensions during count down, as well as the two launch postponements. It was eventually third time lucky, as a flawless launch and orbit injection set the stage for the scientists to take over from the engineers and realize the full potential of the mission.

Even in orbit, problems were encountered, including some that had never been predicted on the ground – such is the nature of the harsh environment of space. Eventually the problems were solved and the serious business of analysing the wealth of data coming from the observatory is now under way. The early results and the illustrations from the first data are fascinating, but this is only the tip of the iceberg. The real discoveries of Chandra will be the subject of many scientific papers in years to come.

This is a riveting book in its accurate picture of the trials and tribulations in the life cycle of a large space mission. I found it particularly interesting because of my personal knowledge of many of the characters depicted, but this is certainly not a prerequisite for enjoying what is a good account of the human side of space science.

The two authors have a unique expertise – Wallace and Karen Tucker being the science spokesman and the science writer, respectively, for the Chandra X-ray Center at the Smithsonian Astrophysical Observatory. The combination results in a style that is interesting for both the layreader and the professional, making the book a “damn good read” for all those with an interest in space, science and politics.

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Revealing the Universe: The Making of the Chandra X-ray Observatory: Amazon UK/Amazon US

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