All atoms are either fermions — particles that have a spin quantum number of 1/2, 3/2, 5/2 and so on — or bosons, which have integer quantum numbers for spin. Fermions obey the Pauli exclusion principle, which means that two identical fermions cannot occupy the same quantum state. Therefore, if a Fermi gas could be cooled to absolute zero, the atoms would fill up all the available energy levels up to a level known as the Fermi temperature. If all or most of these levels are occupied the gas is said to be degenerate.
The Pauli exclusion principle prevents identical atoms from approaching each other too closely. However, if the atoms can be placed in different internal states, then the exclusion principle does not apply. Thomas and co-workers therefore cooled a gas in which half of the lithium-6 atoms were in the lowest hyperfine state, and half were in the second lowest hyperfine state. Atoms in different internal states can be made to approach each other unusually closely in the presence of an applied magnetic field.
Physicists have predicted that a Fermi gas of atoms could become superfluid — in other words, it could flow without friction — at temperatures lower than the Fermi temperature. In a superfluid, atoms at relatively long distances from one another are “locked” together and behave as a single quantum system. If lithium-6 is a superfluid, Thomas says it is a special type of superfluid that would be analogous to a very high-temperature superconductor.
“The very strong attraction in our atomic system leads to a particularly strong locking together of pairs of atoms. It is in this way that our atoms behave as a superconductor,” Thomas told PhysicsWeb. Superconductivity — the flow of currents without resistance — arises from the locking together of pairs of electrons.
The team now hopes to unambiguously determine that they have observed superfluid behaviour in their system. They also plan to perform further experiments to study the general behaviour of strongly interacting Fermi gases. “This, we feel is a much broader and ultimately more important area of investigation,” says Thomas.
Neutrinos are one of the fundamental particles of matter. They are similar to electrons but are electrically neutral and are not therefore affected by electromagnetic forces. They can pass through large distances in matter without hindrance and are thus very difficult to detect. Three types — or “flavours” — of neutrino are known, the electron, muon and tau neutrinos. Anti-neutrinos are the anti-particle equivalents of neutrinos and can be created in fission reactions in nuclear power plants.
The current research was performed at the Kamioka Liquid scintillator Neutrino Detector (KamLAND), which is located in an old mine near Toyamu in Japan. The detector comprises a balloon 13 metres in diameter that contains about a 1000 tonnes of liquid scintillator. It identifies anti-neutrinos by counting the number of telltale flashes of light that are produced when anti-neutrinos collide with protons in the liquid.
The researchers recorded anti-neutrino events produced by electron anti-neutrinos from Japanese and South Korean nuclear reactors. The team, which consists of 92 scientists, detected 54 electron anti-neutrino events over a period of 145 days as opposed to the approximately 86 predicted by the Standard Model of particle physics– which assumes that neutrinos and anti-neutrinos have no mass and therefore do not oscillate.
These results confirm earlier work — at the Sudbury Neutrino Observatory and Super-Kamiokande — that also provided strong evidence for neutrino oscillation. The KamLAND researchers are now certain that the “solar neutrino problem” — the fact that fewer neutrinos are observed from the Sun than predicted — is indeed due to neutrino oscillation and not because of some interaction the neutrinos may have had with the Sun’s magnetic field, as some researchers suggested.
“The main result is that we now have the mechanism for oscillations firmly in hand,” Giorgio Gratta, the co-spokesperson for the US collaboration told Physics Web. The researchers have now turned their attention to the “mixing angle” — a quantity that is related to physics beyond the Standard Model and determines just how the neutrinos oscillate. The mixing angle is important as neutrinos with a large mixing angle are much less affected by matter than those with a small mixing angle. KamLAND has ruled out small mixing angles — in the context of two-flavour neutrino oscillations.
Theoretical physicists hope that this new information will help refine the Standard Model. “[It] needs to be updated to include neutrinos masses and mixing, ” says Gratta.
“The government is to be congratulated,” says Ian Halliday, chief executive of the Particle Physics and Astronomy Research Council (PPARC). “This much-needed investment in fundamental physics will enable our physicists and astronomers to build on their high international standing, and engage in new collaborative international programmes.”
PPARC will see its overall budget rise from £256m in 2003/4 to £291m in 2005/6. It will get a further £31.6m over this period to continue its e-science programme, and will receive £5.4m for R&D in new accelerators as part of a joint programme with the Council for the Central Laboratory of the Research Councils. In addition, PPARC has been allocated £9m to carry out research relating to gravitational wave detection and planetary exploration.
The Engineering and Physical Sciences Research Council, meanwhile, will see its core budget increase by £26.8m for on-going expenditure and by £17.4m for capital expenditure. It will also get extra money for a number of programmes involving collaboration with other research councils, including £8m for research on renewable energy and £7m for a new energy research centre, as well as £60m to continue the basic technology programme, £18m for e-science and £15.6m for post-genomics and proteomics.
As announced in July, the research councils will also get an extra £100m from 2005/6 to increase the pay of post-doctoral researchers and PhD students, and an extra £120m a year from 2005/6 to fund some of the “indirect” costs of university research. The spending review also allocates £500m a year by 2004/5 for university infrastructure costs, provides a doubling of funding for large facilities to £205m by 2005/6 and includes £114m for the commercialization of scientific research by 2005/6.
Proxima Centauri is a very low-mass star that — together with the double-star Alpha Centauri — forms a triple stellar system in the constellation of Centaurus. Proxima Centauri is about half as hot as the Sun and about 150 times fainter, which has made it difficult to measure its size — until now.
Ségransen and co-workers used interferometric measurement data – obtained last year — from the Very Large Telescope Interferometer (VLTI) and the VLT Interferometer Commissioning Instrument (VINCI) at the Paranal Observatory in Chile. Optical interferometry combines the light from multiple telescopes so that they behave as a single, much larger telescope. The interference between the different light waves can be used to eliminate glare from bright stars or to measure distances and angles precisely.
The VLTI was used with two large VLT telescopes that provide the image sharpness needed to resolve small stellar disks like that of Proxima Centaur. These telescopes are large enough to observe objects that are fainter than those normally studied by interferometric measurements. The researchers analyzed the observational data using improved software and a novel technique called “wavelet analysis” to overcome the effects of turbulence from the Earth’s atmosphere on their measurements.
The team found that Proxima Centauri’s diameter – and mass — is about one-seventh that of the Sun. It is about one and half times bigger than Jupiter, but is 150 times more massive. Proxima Centauri lies in the critical transition region between stars and brown dwarfs – stars that are not heavy enough to sustain fusion in their cores.
The group now hopes to measure even smaller extra-solar objects with the VLTI.
Caesium atoms are the basis of atomic clocks – on which global time standards depend – and they also play a key role in several metrological applications, including measurements of the fine-structure constant and the electric dipole moment of the electron. Physicists are therefore keen to know more about the quantum behaviour of caesium atoms.
In a Bose-Einstein condensate, certain quantum properties of the constituent atoms are evident on a macroscopic scale. This happens because all of the atoms occupy the same quantum state and can therefore be described by a single wavefunction. Although physicists can condense alkali atoms such as sodium and rubidium with relative ease, the unusual quantum properties of caesium atoms have defeated all previous attempts at condensation.
To tackle this problem, the Innsbruck team first trapped around 20 million atoms in the focus of two lasers. These lasers induced a dipole moment in the atoms, which attracted them to the intense electric field of the focus. By reducing the power of the lasers, the most energetic atoms were allowed to escape, which reduced the temperature of the remaining atoms. This technique is known as evaporative cooling.
But when Grimm and co-workers tried to chill the atoms further, they found that this cooling technique only worked when they also applied a carefully chosen magnetic field. When the temperature of the atoms fell to 160 nK, the researchers switched off the lasers to reveal a condensate that contained around 20 000 atoms. It lasted for 15 seconds.
By adjusting the applied magnetic field, the researchers found that they could sensitively control the attractive and repulsive interactions between the caesium atoms. Grimm and colleagues now suggest that their technique could be used to create molecular condensates, and that single atoms extracted from a caesium condensate could form the basis of a new, super-accurate atomic clock. They also hope that the high sensitivity of caesium atoms to magnetic fields could allow physicists to probe the properties of Bose-Einstein condensates in the greatest detail yet.
Gamma-ray bursts (GRBs) are extremely energetic flashes of radiation detected about twice a day from somewhere in the universe. They were discovered in 1967 by US military satellites and observed systematically by NASA’s Compton Gamma Ray Observatory from 1991 onwards. But it was not until the launch of the Italian/Dutch BeppoSAX satellite in 1996 that scientists were able to accurately locate GRBs.
In 1997, researchers working on the BeppoSAX project discovered that GRBs emit X-rays for several days, and astronomers at the University of Amsterdam confirmed that the bursts also emit at optical wavelengths. These observations led to the discovery that GRBs originate in very distant galaxies.
Then, in 1998, astronomers at the University of Amsterdam observed a GRB that took place at the same time as a stellar explosion. It was subsequently discovered that a significant fraction of gamma-ray bursts are related to very powerful stellar explosions known as hypernovae. Exactly how such GRBs are created remains a mystery, however, and the nature of the remaining bursts is unknown.
Lars Fugger of Aarhus University Hospital in Copenhagen and co-workers in Denmark, Sweden, the UK and the US shared the prize for their work on the immunological basis of multiple sclerosis. The winners were selected from a short list of ten by a panel of eminent academics and industrialists. Altogether there were 108 entries for the prize, which recognizes outstanding research made possible by European collaboration.
One of the most common ways of making polymers is from vinyl monomers — small molecules containing carbon-carbon double bonds — in a process called free radical polymerization. At present, the “initiators” used in such reactions are organic peroxides, which are hazardous and environmentally unfriendly. Now, Kuijpers and co-workers propose using ultrasound in a technique that could reduce the use of such chemicals.
Ultrasound waves cause bubbles to form in liquid carbon dioxide. These bubbles — a few tens of microns in size — then expand and collapse violently. This “cavitation” generates tiny pockets of very high temperature and pressure, which can then create excited states in a molecule, break chemical bonds and form radicals in the polymerization process.
To initiate the growth of a cavitation bubble, a pressure above a certain threshold must be applied. However, pressurizing a liquid raises this threshold and prevents bubbles from forming. The advantage of liquid carbon dioxide is that it has high vapour pressure, which effectively counteracts the hydrostatic pressure – the pressure needed to keep the carbon dioxide in its liquid state. This means that the threshold pressure is decreased and bubbles can form.
When liquid carbon dioxide is mixed with the polymer it acts as an “antisolvent” that makes the polymer insoluble in the high-pressure liquid gas. In this way, the polymer precipitates out of solution without the need for a solvent. Cavitation also enables the polymer chain to be broken at specific sites so that a desired molecular weight of polymer can be obtained. Another advantage of this technique is that turning off the electrical supply can stop a polymerisation reaction that proceeds too quickly. This control is not possible with any other methods currently used.
Stock markets rely on “positive feedback”, which means that if traders start to sell, other investors, big and small, follow suit. If traders buy, then investors begin to buy too. This leads to waves of behaviour — or “herding” — that reinforce a bull or a bear market. If this herding is left unchecked, it can cause runaway effects if a bullish bubble bursts — a “crash”. A drawn-out bear market however, leads to an “anti-bubble ” phase — a period of decline following a market peak.
Didier Sornette and Wei-Xing Zhou, who are based at the University of California at Los Angeles, have now identified an anti-bubble in the US stock market index. The researchers analyzed the markets using the statistical physics of critical phase transitions and identified two main signatures of criticality. The first appears in the increase (for a bull phase) or decrease (for a bear phase) of the price up to the end of the speculative bubble or anti-bubble. The second appears in the modulations –the “ups” and “downs” — of this increase or decrease. The current increase observed in the market index is simply an “up” in the overall downward trend, according to Sornette.
The researchers found that there was a clear similarity in the behaviour of the US market index from 1996 to August 2002 and of Japan’s Nikkei index from 1985 to 1992. They saw a similar anti-bubble in the Nikkei index at the beginning of the 1990’s — which marked the beginning of a decade of decline for Japan. They attribute the decay of the US market index since August 2000 to herding behaviour.
The researchers are, however, unable to predict how the market will behave after 2004 because it may depart from the anti-bubble regime and have additional non-linear effects.
After studying physics at Manchester University, Derek Robinson joined the Atomic Energy Research Establishment, Harwell — the forerunner of the UKAEA — in 1965. He began by carrying out fundamental studies of plasma turbulence at Harwell’s ZETA fusion experiment. In 1968 he spent a year working with scientists on the T3 tokamak at the Kurchatov Institute in Moscow, where he performed seminal work on the theory of instabilities in plasmas. This work helped to convince a previously sceptical community that the tokamak device was the way forward for fusion.
In 1970 Robinson joined the UKAEA’s Culham laboratory, and began carrying out research on a range of other magnetic-confinement devices. He was a driving force behind Culham’s experimental fusion programme, including the COMPASS tokamak experiment and then the START and MAST spherical tokamak devices. Robinson also collaborated extensively with fusion scientists from many countries, including Japan, China, Korea and Brazil.
In 1990 Robinson was appointed UK member to the Joint European Torus (JET) project at Culham, and six years later became a member of its board. He was elected fellow of the Royal Society in 1994, and became fusion director at UKAEA in 1996. Robinson, who was a fellow of the Institute of Physics, was also actively involved in the design of the International Thermonuclear Experimental Reactor (ITER).
“Derek’s untimely death is a great sadness and loss for all his colleagues at Culham and the wider international fusion community,” said Jack Connor, head of theory at Culham. “Derek committed his life to fusion and the fact that fusion research finds itself in such a positive position is in no small measure to his untiring and effective efforts at both the political and scientific levels. His enthusiasm for the physics of fusion was apparent to all he met.”
Physicists in Russia also mourned the loss of a well-liked colleague. “Derek Robinson was highly respected in Russia ever since his visit in 1968,” said Evgeny Velikhov, president of the Kurchatov Institute. “His measurements of the electron temperature profiles in the T-3 plasma led to the beginning of active research on tokamaks all over the world. Derek was known for his brilliant scientific research and bright personality. He was an extremely friendly, charming, clever and intelligent person, who will be remembered by all who met him.”
TODAY the Georgian terrace of College Square East in Belfast is little more than a clutter of shopfronts looking out over congested traffic and a crowded city skyline. But this unsuspecting set of buildings contains the birthplace of arguably the most important scientist of the Victorian age. For it was here on 26 June 1824 that William Thomson – later Lord Kelvin – was born.
Thomson was a leading figure in the creation of thermodynamics, he researched problems as diverse as the age of the Earth and the design of the nautical compass, and was intimately involved in the laying of the first transatlantic telegraph cable. He also corresponded with an array of other important scientists such as George Fitzgerald, Hermann von Helmholtz, James Joule, James Clerk Maxwell and George Gabriel Stokes.
Thomson was educated at Glasgow and Cambridge universities, and from 1846 until 1899 was professor of natural philosophy at Glasgow. He was elected a fellow of the Royal Society in 1851, knighted in 1866 and elevated to the peerage as Lord Kelvin in 1892. He died at his home near Largs in Ayrshire, Scotland, on 17 December 1907 at the age of 83 after a long and successful life.
Family matters
William’s father – James Thomson – was the largely self-taught son of a Ballynahinch farmer. The elder Thomson had studied hard and advanced far, becoming professor of mathematics at the Belfast Academical Institution. Today the institution is a school, but at the time it was a combination of school and “university college”. William’s father wrote a number of successful textbooks on arithmetic, calculus and trigonometry, which brought in a comfortable income for the family.
Gone home His house, now demolished, lies just to the right of a present-day electronics shop.
When Thomson was born, just two houses of the College Square East terrace stood. Beyond them – apart from the school where his father taught – there lay only “the open plain with its blue encircling hills”, as his sister later described them. Thomson’s early life in Belfast appears to have been as idyllic as the scenery that his home looked out onto. His family was a close and affectionate one, and there were many friends. Family summer holidays included stays in the coastal towns and villages around the waters of Belfast Lough; Donaghadee, Bangor and Carrickfergus were all backdrops to happy childhood memories.
In May 1830, however, the family circle was ruptured when William’s mother died. Shortly afterwards the family moved to Scotland, where Thomson’s father had been appointed professor of mathematics at Glasgow University. In 1834 Thomson, who was aged just 10, and his brother James, 12, both matriculated at the university. Such an early start to one’s academic career might seem unusual, but it was not quite as remarkable as it might at first appear – at the time the usual minimum age for matriculation at Glasgow was 14.
William regularly came first in the class in mathematics and natural philosophy, with James second. Thomson’s prodigious ability in mathematics had been evident from an early age, and it was obvious that he should go on to study at Cambridge after finishing at Glasgow. However, it was feared that if he graduated from Glasgow, he might not be able to subsequently enrol as an undergraduate at Cambridge. So although both boys passed their BA examinations at Glasgow in May 1839 – and both achieved their MA the following year – on each occasion only James graduated. Thomson would occasionally designate himself as BATAIAP (Bachelor of Arts To All Intents and Purposes).
From Glasgow to Cambridge
In October 1841 the 17-year-old Thomson entered St Peter’s College (Peterhouse), Cambridge, as a “pensioner” – in other words as a student who paid his own way. The formal tutoring in mathematics in his first year was of a very low level compared with what Thomson already knew. Indeed, by the time he reached Cambridge, Thomson had already published a paper in the Cambridge Mathematical Journal, in which he defended the mathematical rigour of Fourier series against the erroneous criticisms of Philip Kelland, a mathematician at Edinburgh University. During his time as an undergraduate he wrote a further 10 papers and was quickly tipped to be the “senior wrangler” (the student who would come first in the final mathematics examinations).
While Thomson was at Cambridge every member of his family regularly wrote to him. His father, who was footing all the bills, often advised him on the wise use of money and time. Yearly college maintenance fees alone came to £230, which would probably have accounted for as much as one-third of his father’s annual income. Thomson’s letters to his father often contained detailed lists of all expenditure. If writing to ask for extra money, he would sometimes include a mathematical theorem for possible use in exams to soften his father up.
Letter writer Thomson communicated extensively with the most famous physicists of the Victorian age, including Maxwell, Joule and von Helmholtz. He exchanged over 650 letters with George Gabriel Stokes alone.
In one early letter to his father, Thomson outlined how he planned to spend his days at Cambridge. His intention was to rise at 5 a.m. and light his fire; read until 8:15 a.m.; attend his daily lecture; read until 1 p.m.; exercise until 4 p.m.; attend chapel until 7 p.m.; read until 8:30 p.m.; and finally go to bed at 9 p.m. As Thomson’s modern biographers point out, it is doubtful whether he actually adhered strictly to this timetable, but it does illustrate his lifelong desire to minimize wasted time (see Smith and Wise in further reading).
Thomson took part in many other activities at Cambridge besides studying. He rowed, becoming an excellent oarsman. He played the cornet and helped to establish the university’s music society. He also walked, skated and swam. Of all these activities it was Thomson’s rowing that his father disapproved of the most, fearing that it would bring his son into loose company, which would “ruin [Thomson] forever” with wine parties and time wasting.
Thomson’s final exams – the Senate House examinations – began on New Year’s Day 1845 and went on until 7 January. There were 12 papers, with morning papers lasting two and a half hours and afternoon papers three hours. The final result depended on both the quantity and quality of the answers to the questions. The exams were the toughest mathematical racecourse in the land, with the competitors trained like thoroughbreds to answer questions at top speed, and to use all possible short cuts to reach the answers.
To universal surprise Thomson came not first but second, behind one Stephen Parkinson of St John’s College. The family was disappointed, but justice was eventually done when Thomson came first in the Smith’s prize examination at the end of January. The papers for this exam were more suited to Thomson’s abilities, containing as they did more problem-solving questions and less of the bookwork that characterized the Senate House papers. Even though Thomson had come second in the Senate House examinations, the comments around Cambridge showed that he was by far the greater mind. As one examiner commented to a colleague: “You and I are just about fit to mend [Thomson’s] pens.” These successes meant that Thomson was elected a fellow of St Peter’s in June 1845 at the age of 21.
The death of William Meikleham
While Thomson was studying at Cambridge, events were taking place in Glasgow that would define his future career. At the start of Thomson’s first year at Cambridge in 1841, William Meikleham – who was then professor of natural philosophy at Glasgow – fell ill and was not expected to return to his teaching post. It was the duty of Thomson’s father – in his role as professor of mathematics – to begin thinking about Meikleham’s replacement. His father wanted someone of Cambridge calibre, but who would also teach well and have sympathy with the broad, non-hierarchical Scottish education system.
Initially, Thomson’s father wanted to secure a fellowship for his son at either Cambridge or Trinity College Dublin. But as 1842 came and went – with still no obvious candidate for the Glasgow chair having been found – the elder Thomson began to realize that William, then only 18, could be in the running. Once the idea settled itself in his mind, he began a careful – and at times surreptitious – campaign to have his son appointed to the chair.
Thomson’s mathematical ability was not in doubt, but he needed experimental experience if he was to be in contention for the post. His father therefore advised him to pick up all the experience he could at Cambridge. So it was that Thomson attended lecture courses on experimental natural philosophy, practical astronomy and astronomical instruments. Part of the manoeuvring for the Glasgow post included a trip to Paris after Thomson graduated in 1845. There he attended lectures on chemistry and physics at the Sorbonne, and – on the advice of one of his father’s colleagues – bought and studied French texts. He also met eminent scientists like Augustin Cauchy and Jean Biot, and worked for a time in the laboratory of Regnault, who was professor of natural philosophy at the Collège de France.
Rather conveniently, Meikleham died on 6 May 1846, just after Thomson had finished his course at Cambridge. His illness had been in the background of Thomson’s thoughts for some time. In a letter to his father in 1844 he wrote, in a somewhat macabre passage: “Sorry to hear about Dr Meikleham’s precarious state. I have now got so near to the end of my Cambridge course that even on my own account I should be very sorry not to get completing it. For the project we have, it is certainly much to be wished that he should live till after the commencement of next session.” Thomson was obviously concerned that he would not be able to apply for the job at Glasgow if Meikleham died while he was still studying at Cambridge.
From the moment Meikleham died, Thomson and his father’s covert manoeuvrings turned to overt action. They arranged for a long list of testimonials to be written by the master and fellows of St Peter’s, the Cambridge examiners, George Boole, Arthur Cayley, Augustus de Morgan, Sir William Rowan Hamilton, Victor Regnault, George Gabriel Stokes and others. Thomson’s father wanted maximum impact; he arranged for the testimonials to be printed and had a preference towards them being gilt-edged. The printing would be done in Glasgow, and he would do the checking.
All was wreathed with success when, on 11 September 1846, Thomson was unanimously elected – at the age of just 22 – to the chair of natural philosophy at Glasgow. He held the post until 1899, and was not tempted away even by the Cavendish chair at Cambridge, which was offered to him on three separate occasions in the 1870s and 1880s.
Bound for Scotland
Thomson gave his first lecture as professor at Glasgow on 4 November 1846, in which he provided an introductory survey of the physical sciences for students enrolled on the natural-philosophy course. However, in a letter to Stokes, Thomson admitted that he thought the lecture had been a failure. He had written everything down and was concerned that he had read it too fast. But this did not prevent Thomson from using the same manuscript the next year, and indeed every subsequent year – with various accretions, corrections and amendments – for the next half century. Students at Glasgow became devoted to their famous professor, although his quicksilver mind – which saw connections and analogies across the discipline – left many of them floundering, particularly when he introduced these off the cuff into lectures.
Thomson’s enthusiasm and drive transformed the natural-philosophy course at Glasgow from a broad-brush survey to a thorough coverage of selected topics, with emphasis on modern developments. In his first five years, he swept away much of the old equipment, spending £550 on new apparatus. Given the considerable underinvestment in the previous few years, this was not a lavish amount but it did underline his new approach. He involved good students in experimental research, and at one point even extended his kingdom by stealth, taking over vacant college rooms without permission and only asking the faculty after the event if it would ratify his actions.
Thomson had a strong relationship with another physicist of Irish origin – George Gabriel Stokes. The pair had met at Cambridge and remained firm friends for the rest of their lives, exchanging over 650 letters. Much of this correspondence dealt with their research in mathematics and physics. Their minds complemented each other, and in some cases their thoughts melded so that neither knew – nor cared – who had come up with an idea first. Perhaps the most famous example of this is Stokes’ theorem in vector calculus, which allows us to convert line integrals into surface integrals and vice versa. The theorem in fact first appears in a letter from Thomson to Stokes, which suggests that it should really be called “Thomson’s theorem”.
Heated discussions
In 1847 Thomson came across James Joule from Manchester at a meeting of the British Association (BA) in Oxford. For the previous four years Joule had been claiming at BA meetings that heat was not – as was supposed at the time – a substance (“caloric”) that moved between materials. Joule argued that heat was in fact due to the vibration of a material’s atomic constituents. By studying the way in which a gas shrunk in volume as it was cooled, Joule suggested that no substance could be colder than a temperature of &min;284 °C. He had also demonstrated the equivalence of work and heat by carrying out experiments to determine the equivalent amount of mechanical work need to warm a pound of water by 1 °F. He had even suggested that the temperature of water at the bottom of a waterfall should be higher than at the top.
Joule’s talks at the BA were greeted with the silence of apathy and incredulity. But things changed at the 1847 meeting in Oxford, because Thomson was sitting in the audience. He became fascinated by what Joule had to say. He asked questions from the floor and provoked a lively debate, but assumed that Joule must be wrong. In a letter to his brother after the meeting was over, Thomson wrote: “I enclose Joule’s papers, which will astonish you. I have only had time to glance through them as yet. I think at present some great flaws must be found.”
But Joule was not wrong, and Thomson – through careful thought – came to agree with him. Along the way, he connected Joule’s work with that of Carnot on heat engines. In doing so, he devised a more fundamental way of defining the absolute zero of temperature, independent of any particular material substance. It is for this reason that the fundamental unit of temperature was later called the Kelvin – the name Thomson adopted after being made a Lord in 1892. Thomson also saw the idea of conservation of energy as a great unifying principle in science, and introduced the ideas of “statical” and “dynamical” energy – or what we now call potential and kinetic energy.
It is difficult to disentangle Thomson’s work on heat and the conservation of energy from that of other scientists of the time, including Clausius, Helmholtz, Joule, Liebig and Rankine. All of them can take some of the credit for the first and second laws of thermodynamics – ideas that are so important to modern science that each contributor should be held in high regard.
The age of the Earth
In June 1851, just before his 27th birthday, Thomson’s scientific achievements were recognized when he was elected a fellow of the Royal Society. In September of the following year Thomson married his second cousin Margaret Crum. He proposed to her after being rejected three times by his former girlfriend Sabrina Smith; his last proposal to her came in April 1852 – just three months before his proposal to Margaret!
At the time Thomson was extremely highly regarded as a pure scientist, but he became perhaps even more famous as a result of his applications of science. In December 1856 the Atlantic Telegraph Company was formed, with Thomson on the board of directors. The company’s aim was to lay a telegraph cable along the full length of the 3000 mile seabed between Europe and North America. The project captured the public’s interest and, during the mid-1850s, Thomson became a well known public figure.
The first attempt at laying a cable in 1857 was, however, a failure, and it was not until the fifth try in 1866 that the company succeeded. The Times called the link between Valentia in Ireland and Newfoundland no less than “the most wonderful achievement of this victorious century”. Thomson spent months at sea on the project, and became intimately and enthusiastically involved with the practicalities. Along with others involved in the project, Thomson was knighted in November 1866 at the age of 42.
Thomson’s views on the thermal history of the Earth also became extremely well known. His interest in this topic began in 1844, while he was still a Cambridge undergraduate. It was a topic that he returned to repeatedly, and which led him into conflict with other scientists such as John Tyndall, Thomas Huxley and Charles Darwin. The tone of the debate was not advanced by Darwin describing Thomson as an “odious spectre”, nor by Huxley promoting evolutionary theory as an alternative to religious belief with evangelical fervour.
Young at heart Thomson spent 53 years as professor of natural philosophy at Glasgow University, but after resigning his chair in 1899 he immediately re-registered as a research student so that he could carry on studying.
Thomson was a Christian, but he was not concerned with defending a literal interpretation of the Genesis narratives and he was happy to speculate that life came to Earth via a meteor. He did, however, want to defend and promote good science. He believed that geology and evolutionary biology were weak subjects when placed against the rigours of mathematically based natural philosophy. Indeed, many physicists did not even believe that geology and biology were sciences at all.
To evaluate the age of the Earth, Thomson used the methods of his beloved Fourier to calculate how long it had taken the planet to cool from a molten state to its current temperature. Thomson had greatly admired Fourier’s book The Analytical Theory of Heat, which he had read at the age of just 16. In some ways the book set the agenda for many aspects of his life’s research. The mathematical description of heat flow linked his work on thermodynamics, the cooling of the Earth and even the flow of electrical signals through telegraph wires.
In each case, Thomson attempted to cast the problem in terms that could be solved using Fourier’s methods. In the case of electrical signals through telegraph wires, however, Thomson’s reliance on Fourier’s approach initially lead him astray. The equation he initially proposed had the beautiful property that it was a direct analogue to Fourier’s equation for heat diffusion. However, it was also wrong, as it completely ignored self-inductance.
To the chagrin of the biologists and geologists, Thomson’s calculations for the age of the Earth did not allow enough time for evolution to occur. In 1862 he estimated the Earth to be 100 million years old, but by 1899 he had revised this figure down to 20–40 million years. The biologists and geologists, however, suggested figures of up to 100 times greater than this.
The discrepancy between the theories was not resolved until the beginning of the 20th century, when Ernest Rutherford realized that radioactivity provides the Earth with an internal heating mechanism that opposes – and thus slows down – the cooling. This process makes the Earth older than was originally envisaged; current estimates suggest that the planet is at least 4600 million years old. But given that radioactivity was not discovered until Thomson was in his seventies, he can be forgiven for not using it in research begun in his twenties!
Sailing in new directions
On 17 June 1870 tragedy struck Thomson when his wife Margaret died, although she had been ill for virtually the whole of her married life. Three months after her death Thomson bought a 126 ton sailing boat, Lalla Rookh. This provided a diversion from his bereavement and he would spend much time aboard the boat pursuing his research. It also offered a change of scene from familiar places that were perhaps haunted by the memory of his wife.
Time spent on Lalla Rookh opened up Thomson’s interest in navigation. He designed and patented a new compass that was more stable than existing ones and compensated for the effect of the iron hull of modern ships. Initially the Admiralty was sceptical, with one committee concluding that it was “too flimsy [and] sure to be fragile”. Thomson’s response was to throw his compass across the committee room; it remained intact. A probably apocryphal addition to this story claims that Thomson then threw the Admiralty’s standard-issue compass across the room. It, so the story goes, did not survive the impact. The Navy was finally convinced of the soundness of the new compass and by 1888 had adopted it as standard on all Admiralty ships. Thomson also invented a mechanical tide predictor, and developed a new sounding machine that allowed depths to be determined quickly and, more importantly, without having to stop the ship.
Thomson’s continuing work on laying submarine telegraph cables took him to Madeira in 1873. A fault on one of the cables, however, forced the ship on which he was aboard to remain off the coast of the island for some 16 days. During this time Thomson was entertained by the island’s wealthiest landowner, Mr Charles Blandy. Thomson sailed back to Madeira on Lalla Rookh the following May, and proposed to Mr Blandy’s second daughter, Fanny, who was then 36. She accepted and they were married on Thomson’s 50th birthday in 1874.
Soon after his second marriage, Thomson and his wife built a new home, Netherhall, at Largs near Glasgow. It was largely designed by Thomson himself and was in the Scottish baronial style, complete with peacocks for the grounds supplied by James Clerk Maxwell. True to Thomson’s love of inventions and progress, Netherhall was one of the first houses in the area to be fitted with electric light.
In 1884 Thomson and Fanny went to North America. The BA was holding meetings that year in Montreal, and Thomson was to give a series of 20 lectures at Johns Hopkins University in Baltimore. His discursive style of lecturing with frequent digressions into other issues – a trait that some of his students in Glasgow found positively confusing – was considered “delightful” by the North Americans. The Baltimore lectures were interactive and spontaneous, with Thomson not speaking from notes. Indeed Lord Rayleigh – who was in the audience alongside men like Michelson and Morley – noticed that many of the morning lectures were based on questions that had been raised by the group over breakfast. Thomson spoke on subjects such as the nature of the atom, the wave nature of light and the existence of the ether – even going so far as to calculate its mass per cubic kilometre.
The scale of Kelvin’s achievements
In 1892, aged 68, Thomson was raised to the peerage, becoming Baron Kelvin of Largs, taking his title from the river Kelvin that flows by Glasgow University on its way to the River Clyde. Four years later Thomson’s 50th jubilee as professor at Glasgow was celebrated in grand style. The affair lasted three days, with greetings from Queen Victoria, her eldest son Albert Edward, who was then Prince of Wales, and a wide range of academics, scientific societies and engineers.
Thomson resigned his chair in 1899 after 53 years as professor of natural philosophy at Glasgow, but, true to his inquisitive and enthusiastic character, promptly enrolled himself as a research student. He thus made himself one of the youngest and oldest students in the university’s history.
Thomson died at his home on 17 December 1907. His mastery of mathematics and his thoroughness as an experimentalist, coupled with his lifelong enthusiasm and curiosity, meant that he contributed to virtually every problem to which he turned his attention – whether thermodynamics or telegraph cables. He had been the “king” of Victorian physics and it is perhaps fitting that he now lies buried in Westminster Abbey near to Sir Isaac Newton.
This article is an edited version of a chapter in the book Physicists of Ireland: Passion and Precision edited by Mark McCartney and Andrew Whitaker (2002 Institute of Physics Publishing)
