the birth of nuclear physics measuring rutherford’s impact...

Volume 48, Number 3, May–June 2011

The birth of nuclear physicsMeasuring Rutherford’s impact on science

Is Einstein still right? New cosmological tests of General Relativity

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A Publication of the Australian Institute of PhysicsPromoting the role of physics in research, education, industry and the community.

EDITORPeter Robertson [email protected]

ASSISTANT EDITORDr Akin [email protected]

BOOK REVIEWS EDITORDr John [email protected]

SAMPLINGS EDITORDr Don [email protected]

EDITORIAL BOARDA/Prof Brian James (Chair)

[email protected] M. A. BoxDr J. HoldsworthA/Prof R. J. SteningProf H. A. BachorProf H. Rubinsztein-DunlopProf S. Tingay

ASSOCIATE EDITOR – EDUCATIONDr Colin Taylor [email protected]

ASSOCIATE EDITORSDr John Humble [email protected] Laurence Campbell [email protected] Frederick Osman [email protected] Wen Xin Tang [email protected]

SUBMISSION GUIDELINESArticles for submission to Australian Physics should be sent in electronically.Word or rich text format are preferred. Images should not be embedded inthe document, but should be sent as high resolution attachments in JPGformat. Authors should also send a short bio and a recent photo. The Editorreserves the right to edit articles based on space requirements and editorialcontent. Contributions should be sent to the Editor.

ADVERTISINGEnquiries should be sent to the Editor.

Published six times a year.Copyright 2010 Pub. No. PP 224960 / 00008 ISSN 1837-5375

The statements made and the opinions expressed in Australian Physics donot necessarily reflect the views of the Australian Institute of Physics or itsCouncil or Committees.

PRODUCTIONControl Publications Pty LtdBox 2155 Wattletree Rd PO, VIC [email protected]

68 EditorialOur honorary Aussie Ernie

69 President’s ColumnMarc Duldig on a recentcase of unethicaladvertising

70 News & CommentNot so FASTS: Science &Technology AustraliaBig step towards the SquareKilometre ArrayDecadal Plan for Australianastronomy

72 One hundred yearsof nuclear physicsJohn Campbell traces thepath taken by ErnestRutherford and his group atthe University ofManchester that led to thediscovery of the atomic nucleus

78 Measuring Rutherford’s impact on scienceDavid Lockwood and colleagues discover that Rutherford’swork has undergone ‘scientific obliteration’, perhaps thehighest accolade that can be bestowed on a scientist

84 Is Einstein still right?Despite numerous empirical successes, General Relativity iscontinually being called into question – more so now thanperhaps ever before – as Paul Lasky reports

90 Book ReviewsAnna Binnie on ‘Mrs Perkins’s Electric Quilt and OtherIntriguing Stories of Mathematical Physics’ by Paul J. NahinMukunda Das on ‘The Quantum Story: A History in 40Moments’ by Jim BaggottLee Weissel on ‘Order, Disorder and Criticality: AdvancedProblems of Phase Transition Theory’ by Yurij Holovatch (ed.)

92 Product NewsA review of new products from Lastek, Toptica Photonics,Warsash Scientific and Coherent Scientific

Inside Back CoverPhysics conferences for 2011 and 2012

CONTENTS

CoverA portrait of Ernest Rutherford by theBelgium artist Jozef Janssens. A wartimerefugee, Janssens settled in Cambridgewhere he befriended the Rutherfords.Although unsigned and undated, theportrait is thought to have been painted in1916. Janssens also painted Rutherford’sdaughter Eileen in the same year.[Courtesy: John Campbell and theRutherford family.]

MAY–JUNE 2011 | 48(3) AUSTRALIAN PHYSICS 67

Our honoraryAussie ErnieWelcome to this particularly in-ternational issue of AustralianPhysics. The authors of our threefeature articles are all from over-seas – three from Germany, onefrom Canada and one from NewZealand (admittedly one is anAustralian postdoc).

If we were to conduct a pollto vote for the top ten physicists of the twentieth century, there islittle doubt as to who would finish in top spot. But where wouldErnest Rutherford rank in your top ten, if at all? I would certainlyput him in my top five and probably in my top three. It’s hard tothink of a better or more influential experimental physicist overthe past hundred years.

Rutherford was awarded the 1908 Nobel Prize for Chemistry(shared with Marie Curie and Henri Becquerel) but, as noted in aprevious editorial, did not win a Nobel Prize for Physics. And yet,as noted in the two articles by John Campbell and by WernerMarx, Manuel Cardona and David Lockwood, if circumstanceshad been a little different Rutherford might have been the firstscientist to have won three.

Arguably Rutherford’s greatest achievement was the discoveryof the atomic nucleus in 1911 while at the University of Manchester,one that founded a whole new branch of physics. But there wasno Nobel gong. (Manchester had its Nobel breakthrough withPatrick Blackett in 1948 and again in 2010.)

Similarly in 1919, then at Cambridge, Rutherford bombardednitrogen nuclei with alpha particles and observed the emission ofprotons, indicating that oxygen nuclei had been formed. This wasthe first controlled transmutation of atomic nuclei, fulfilling theold alchemists’ dream of changing one element into another. Forgood measure, the following year he predicted the existence andproperties of neutrons, confirmed in 1932 by his long-term col-laborator James Chadwick. Would that get a gong today?

From the sub-atomic world, our third feature article goes tocosmological scales. Just as physicists are looking for new physicsbeyond the Standard Model of the structure of matter, Paul Laskyexplains that there are clues emerging that the structure andevolution of the universe may be governed by new physics beyondGeneral Relativity.

Finally, it’s a pleasure to introduce our Samplings Editor, DonPrice from CSIRO Lindfield.

Peter Robertson

68

EDITORIALAustralian Institute of PhysicsAIP website: www.aip.org.au

AIP ExecutivePresident Dr Marc Duldig

[email protected] President Dr Robert Robinson [email protected] Dr Andrew Greentree [email protected] Dr Judith Pollard

[email protected] A/Prof Bob Loss

[email protected] Past President A/Prof Brian James

[email protected] Projects OfficersDr John Humble

[email protected] Olivia Samardzic

[email protected]

AIP ACT BranchChair Dr Anna Wilson

[email protected] Joe Hope

[email protected]

AIP NSW BranchChair Dr Graeme Melville [email protected] Dr Frederick Osman

[email protected]

AIP QLD BranchChair Dr Joel Corney

[email protected] Dr Till Weinhold [email protected]

AIP SA BranchChair Dr Scott Foster

[email protected] Dr Laurence Campbell [email protected]

AIP TAS BranchChair Dr Elizabeth Chelkowska

[email protected] Dr Stephen Newbury [email protected]

AIP VIC BranchChair Dr Andrew Stevenson [email protected] Dr Mark Boland [email protected]

AIP WA BranchChair A/Prof Marjan Zadnik [email protected] Dr Andrea Biondo [email protected]

PrintingPinnacle Print Group288 Dundas Street, Thornbury VIC 3071www.pinnacleprintgroup.com.au

AUSTRALIAN PHYSICS 48(3) | MAY–JUNE 2011


This month our Editor allocatedme a shorter column (for reasonsof space), so I am going to have alittle gripe. Not about physics orphysicists but about advertising.Many of you will have seen the ad-vertisements run by NeuroscienceAustralia that are asking for dona-tions for brain research. I am surethat everyone agrees that this researchis both necessary and worthy ofpublic support and that it is mostreasonable for Neuroscience Australiato have sought an advertising agencyto help them make the public callfor funds and to use the televisionstations’ ‘community service’ slotsto get the message out at minimalcost.

But now we come to the problem.The advertising agency chose to openwith fantastic imagery from our col-leagues the optical astronomers. Ex-cellent eye candy to attract even themost hardened cynic to view the ad.But then to call that research intoquestion, by implying it is a waste oftime, whilst smoothly changing theimagery to a scan slice of the humanbrain and telling us all that researchon the human brain is much more

relevant and should be supported, isgoing too far.

I am appalled that NeuroscienceAustralia felt that this was a reasonableapproach. Worse the AstronomicalSociety of Australia wrote to themstating that it was not in the best in-terest of any science to make suchstatements and received a reply sayingthat no one appeared to be com-plaining and they would continueto run the advertisements. I knowthat a number of other individualsand organisations raised objectionsto the advertisement.

Several people noted that thosevery brain scans that were being usedto encourage donations would nothave been possible had it not beenfor the image reconstruction workof radio astronomers who developedthe techniques of building an imagefrom an incomplete u-v plane cover-age. It would have been so muchbetter to have opened with the sameimagery and stated that thanks tothe pioneering work of astronomerswho developed the imaging tech-niques used in scanners today (thenfading to the brain scan) that we cannow view the brain while it works;

but we need funds to further under-stand the brain and to repair it whenit goes wrong.

Not that I expect anything tochange, but hopefully reading thiswill dissuade people from a similaraction in future.

Marc Duldig

PRESIDENT’S COLUMN

Unethical advertising

In our next issue…Volume 48, Number 4• ERA: Measuring the performance

of Australian physics• Searching for the highest energy

particles in nature• Teaching secondary school physics

in Kenya

INTRODUCING OUR SAMPLINGS EDITORDon Price obtained a first class Honours degree (1966) and PhD (1970) in Physics from MonashUniversity, the latter for magnetic and Mössbauer spectroscopic studies of dilute magneticalloys. Following post-doctoral work in Canada, the UK and in Canberra (ANU), he worked asa Research Engineer on the development of a medical ultrasound imaging instrument at QITin Brisbane from 1980–82. This led to an appointment as Research Scientist at CSIRO AppliedPhysics in 1982 to work on ultrasonic techniques for materials characterisation and defectdetection in engineering materials. He contributed to and led a number of strategic andindustrial projects, working extensively with international organisations such as NASA, Boeingand AEA Technology as well as a number of Australian companies. This work led to a moregeneral focus on structural health monitoring and intelligent distributed sensing systems,

utilising principles of self-organisation and information theory. At different times he held a number of Divisionalleadership positions, including Discipline Leader for Acoustics and Ultrasonics, and ultimately Chief Scientist for thethen Division of Industrial Physics. He retired in 2009 and now has an honorary appointment as Fellow in CSIROMaterials Science & Engineering, and divides his time between living in Sydney and Hobart. As Samplings Editor forAustralian Physics he would welcome any contributions or suggested items.

Not so FASTS: Science & TechnologyAustraliaAfter 26 years of supporting and promoting theimportant work of Australia’s scientists, the peak asso-ciation of scientists has evolved to become Science &Technology Australia. The new name for FASTS – theFederation of Scientific and Technological Societies –was chosen following extensive feedback from bothscientists and stakeholders and reflects a challenge forthe sector to better communicate the nation buildingwork of scientists.

Dr Cathy Foley, President of Science & TechnologyAustralia, said the nation was on the threshold of anew era in science and technology where science willbe valued and respected. “The role and value of sciencein all our lives cannot be underestimated, so it iscritical that as scientists we better communicate thecredibility of our work.”

“It is this rigorous peer review science process thatprovides decision makers with the confidence theyneed to make important decisions about our nation’sfuture. Across the board, scientific and technologicalresearch provides the foundation on which much ofthe current and future wealth and health of Australia isbuilt,” Dr Foley said.

Science & Technology Australia represents 68,000scientists and technologists, and promotes their viewson a wide range of policy issues to government, industryand the community. The organisation was formed inlate 1985, following substantial cuts to science in the1984 Federal Budget. The then Minister for Science,Barry Jones, had at the time accused the science and

technology community of being ‘wimpish’ in itslobbying and blamed the budget cuts accordingly.

Science & Technology Australia contributes to dis-cussions at the highest levels of policy making andcommunicates with the highest level of government. Ithas three formal objectives:• to encourage scientific dialogue between industry,

government, and the science and technology com-munity;

• to promote public understanding of science; and• to foster close relations between member societies.

See the new name and website for scientists at:www.sta.org.au.

Big step towards the SKA

The discovery potential of the future internationalSquare Kilometre Array (SKA) radio telescope hasbeen glimpsed following the commissioning of aworking optical fibre link between CSIRO’s Australian


NEWS & COMMENT

Decadal Plan for Australian astronomyAstronomers recently launched a plan to put Australia at the forefront of inter-national astronomy over the next five years. Compiled by the AustralianAcademy of Science’s National Committee for Astronomy, the ‘Mid-TermReview of the Australian Astronomy Decadal Plan 2006–2015’ calls for a ra-dio-quiet zone to be maintained in Western Australia and the creation of acentral international astronomical data bank linking high-performance resourcesfrom astronomy facilities around the world.

Committee chair and Fellow of the Australian Academy of Science, ProfessorElaine Sadler, said the plan sets out measures to keep Australia at the forefrontof international astronomy. “If Australia is to have a chance at attracting theSquare Kilometre Array – the most powerful radio telescope in the world – it is

essential that we preserve a radio-quiet environment in regions of Western Australia”, she said.The plan recommends Australia secures continued access to an 8-metre optical telescope – crucial infrastructure

for which the best sites are overseas. “Eight-metre telescopes are the foundation of a large part of current

Four antennas of CSIRO’s ASKAP telescope in WesternAustralia [credit: Terrace Photographers]

SKA Pathfinder (ASKAP) telescope in Western Australia,and other radio telescopes across Australia and NewZealand.

The achievement was announced at the 2011 In-ternational SKA Forum, which took place early inJuly in Banff, Canada. Six telescopes – ASKAP, threeCSIRO telescopes in NSW, a University of Tasmaniatelescope and another operated by the Auckland Uni-versity of Technology – were used together to observea radio source that may be two black holes orbitingeach other.

Data from all sites were streamed in real time toCurtin University in Perth (a node of the InternationalCentre for Radio Astronomy Research) and wereprocessed to make an image. This ability to successfullylink antennas (dishes) over large distances will be vitalfor the future $2.5 billion SKA telescope, which willhave several thousand antennas, up to 5500 km apart,working together as a single telescope. Linking antennasin such a manner allows astronomers to see distantgalaxies in more detail.

“We now have an SKA-scale network in Australiaand New Zealand: a combination of CSIRO andNBN-supported fibre and the existing AARNET andKAREN research and education networks”, said SKADirector for Australasia Dr Brian Boyle.The radio source the astronomers targeted was PKS

0637–752, a quasar that is more than 7.5 billion light-years away. This quasar emits a spectacular radio jetwith regularly spaced bright spots in it, like a string ofpearls. Some astronomers have suggested that thisstriking pattern is created by two black holes in orbit

around each other, one black hole periodically triggeringthe other to ‘feed’ and emit a burst of radiation.

“It’s a fascinating object, and we were able to zoomright into its core, seeing details just a few millionthsof a degree in scale, equivalent to looking at a 10-centpiece from a distance of 1000 km”, said CSIRO as-tronomer Dr Tasso Tzioumis. During the experimentTzioumis and fellow CSIRO astronomer Dr ChrisPhillips controlled all the telescopes over the internetfrom Sydney.

Curtin University’s Professor Steven Tingay and hisresearch team built the system used to process the tele-scope data. “Handling the terabytes of data that willstream from ASKAP is within reach, and we are on thepath to the SKA”, he said. “For an SKA built inAustralia and New Zealand, this technology will helpconnect the SKA to major radio telescopes in China,Japan, India and Korea.”


Six telescopes linked to observe the quasar PKS0637–752[credit: Carl Davies, CSIRO]

astronomical discovery”, Professor Sadler said. “Failure to retain this crucial part of our astronomical portfoliosignificantly undermines our other astronomical investments.”

Another proposal, to create an international astronomical data fabric, would open up opportunities fordiscovery by Australian researchers based on data flowing from major international telescopes, according toProfessor Sadler.

Achievements in Australian astronomy over the last five years outlined by the Review include:• Creation of major new astronomy infrastructure in WA• Dramatic upgrade and improved sensitivity to the CSIRO Australia Telescope• Australia’s partnership in an Extremely Large Telescope to be built in Chile [see AP 48(1), 23–28 (2011)]• Australia’s leading astronomers have won prestigious national and international prizes including the Malcolm

McIntosh Prize, the Shaw Prize, the Gruber Prize, the Prime Minister’s Prize for Science, and the PawseyMedal.The ‘Mid-Term Review’ was launched early in July at the Annual Conference of the Astronomical Society of

Australia held in Adelaide.

After three degrees and two years research atthe forefront of the electrical technology ofthe day, Ernest Rutherford left New Zealandon an Exhibition of 1851 Science Scholarship,

which he could have taken anywhere in the world. Hechose the Cavendish Laboratory, Cambridge University,because its director, J. J. Thomson, had written one ofthe books on advanced electricity which Rutherfordhad used to guide his research [1].This put the right man in the right place at the right

time. Initially Rutherford continued his work on thehigh-frequency magnetisation of iron, developing hisdetector of fast current pulses to measure the dielectricproperties of materials at very high frequencies and tobriefly hold the world record over which electric‘wireless’ waves were detected. Thomson, or JJ as hewas known, appreciated Rutherford’s experimental andanalytical skills and so invited him to join in his ownresearch into the nature of electrical conduction ingases at low pressures.

Within five months of Rutherford’s arrival at theCavendish, the age of new physics commenced. Röntgen’sdiscovery of X-rays and then Becquerel’s discovery ofradioactivity were announced. Rutherford used bothto ionise his gases in an attempt to learn what it wasthat was conducting the electricity in an ionised gas.Very soon he changed to trying to understand radioac-tivity, with his research determining that two types ofrays were emitted, which he named alpha and betarays. Thomson continued mainly with the ionisation of

gases. Two years after Rutherford’s arrival, Thomsoncarried out a definitive experiment which showed thatcathode rays were objects a thousand times less massivethan the lightest atom. The electronic age and the ageof sub-atomic particles had commenced, though mostlyunheralded. (Thomson’s apparatus was the basis ofglass–vacuum oscilloscopes and TV tubes for over 80years, until recently when it was replaced by LCD andplasma screens.) Rutherford was a close observer ofThomson’s discovery and became an immediate convertto, and champion of, sub-atomic objects. Beta rayswere quickly shown to be high-energy cathode rays, ie.high-speed electrons.

Rutherford had no future at Cambridge. After threeyears there as a non-Cambridge graduate, he was noteligible for a fellowship for another year so he took theMacdonald Chair of Physics at McGill University in


ERNEST RUTHERFORD and His Path to theNUCLEAR ATOMJohn Campbell

All great discoveries usually end up with one line in history. Ernest Rutherford’sdiscovery of the nuclear atom is a prime example. Yet, behind this one line is aninteresting and much more complicated pathway.

ONE HUNDRED YEARS OF NUCLEAR PHYSICS

“Alpha particles wereRutherford’s baby, havingconceived them, and theyfeatured in most of hisresearches.”


Hans Geiger returned to Germany in 1912, to the Physical–Technical Reichsanstalt in Berlin. During WorldWar I he was an artillery officer. He and Marsden served opposite each other at the Front, during which Geiger(via Niels Bohr in neutral Denmark) congratulated Marsden on his Chair. In 1927 Geiger named a sonRoland Ernst Arthur, in honour of his time at Manchester. In 1925 he became professor in Kiel, in 1929 inTübingen, and from 1936 in Berlin. He helped develop coincidence counting and studied cosmic rays. In1928 he and Muller modified the Rutherford–Geiger detector so today it is called the Geiger–Muller tube.Geiger died in 1945, not long after World War II ended.

Ernest Marsden graduated B.Sc. with First Class Honours in 1909, and was a lecturer at the University ofLondon before returning to Manchester to succeed Geiger in 1912. In 1914 he was appointed professor atVictoria University College in Wellington, New Zealand, and served in World War I, in sound ranging ofenemy guns, where he was awarded the Military Cross. From 1922 his career was in administration in NewZealand: Assistant Director of Education (1922–1926); Secretary of the new DSIR (1926–1944); scientificadvisor to the NZ Government during World War II (1941–1946); Scientific Liaison Officer in London(1947 until retirement in 1954). He died in New Zealand in 1970. It is ironic, or a sign of modern times, thatNew Zealand’s blue sky research fund, The Marsden Fund, is named for a science administrator and not forRutherford, the supreme practitioner of blue sky research.

Fig. 1. The Manchester University Physical and Electro-Technical Laboratories staff and research students in 1912. ErnestRutherford is in the centre of the second row and to his right is Arthur Schuster who stood down from his chair in naturalphilosophy in order to persuade Rutherford to return to Britain from McGill University in 1907. Hans Geiger is at far leftin the same row.Ernest Marsden is at far right in the front row. Second from the left is Harry Moseley who discovered the essential featuredistinguishing the natural elements – the atomic number. Moseley was killed three years later in WWI.

Directly behind Rutherford in the third row are May Leslie (left) who studied the diffusion of thorium and radiumemanations and Margaret White who studied the electrical properties of the atmosphere, emphasising Rutherford’ssupport of women. At far left in this row is the theoretical physicist Charles G. Darwin, named after his illustriousgrandfather. Darwin was a close collaborator of Rutherford and later followed him to Cambridge where he played asignificant role in the foundation of quantum mechanics.

William Kay, Rutherford’s assistant, is second from left in the back row. Finally, at far right in the back row is JamesChadwick who discovered the neutron exactly 20 years later. At last, there was a clear understanding of the Rutherfordnucleus.

Montreal, Canada. (Cambridge changed its rules thefollowing year.) From then on, the world centre of ra-dioactivity and particle research was wherever he wasbased.

Fuzzy beamsAt McGill, Rutherford showed that radioactivity wasthe spontaneous transmutation of radioactive atoms.For this he received the 1908 Nobel Prize in Chemistry.He also demonstrated that alpha particles were mostlikely helium atoms minus two electrons, and he datedthe age of the earth using radioactive techniques. Instudying the nature of alpha particles, by being thefirst to deflect them in magnetic and electric fields inbeautifully conceived experiments, he observed that anarrow beam of alphas in a vacuum became fuzzywhen either air was introduced into the beam or it waspassed through a thin window of mica. Alpha particleswere Rutherford’s baby, having conceived them, andthey featured in most of his researches.

Rutherford returned to England in 1907 where hewas appointed to the Langworthy Chair of Physics atthe University of Manchester. He first needed a methodof tirelessly counting alpha particles, because themethod of observing tiny flashes on a fluorescingscreen quickly caused eye strain. He was an expert onionised gases, and had been told by Townsend, his oldfriend from Cambridge days, that one alpha particle

ionised tens of thousands of atoms in a gas. So withthe assistant he had inherited, Hans Geiger, the Ruther-ford–Geiger tube was developed (with later minor im-provements by Geiger this is today known as theGeiger tube).

By this stage a number of laboratories were studyingthe scattering of beta particles from atoms. TheCavendish Laboratory claimed that the large scatteringangles were due to many consecutive small angle scat-terings inside Thomson’s ‘plum pudding’ model of theatom, the electrons being the fruit scattered throughoutthe solid sphere of positive electrification. Rutherford

did not believe this scattering was multiple, and soonce again he had to quantify the science to undo mis-taken interpretations of others.

Geiger was given the task of measuring the relativenumbers of alpha particles scattered as a function ofangle over the few degrees that Rutherford had measuredphotographically at McGill. Photography could nothowever register single particles. Nor was the Ruther-ford–Geiger detector suitable for ‘quickly’ measuringscattered particles, but one of the reasons for its devel-opment was to determine whether or not the discoveryby Crookes in 1903 of the ‘spinthariscope’ did registerone flash of light for every alpha particle which strucka fluorescing screen. Once Rutherford and Geiger hadestablished that this was the case, they were able to ac-curately measure Avogadro’s Number and standardiseradium samples.

Rutherford backscatteringGeiger used monochromatic alpha particles in a vacuumtube to impinge on a metal foil and then on a fluorescingplate forming the end of the tube. A low power micro-scope, looking at about 1 mm2 of the plate allowed thealphas to be counted. It was tiring work, waiting halfan hour for the eye to dark adapt then staring at thescreen unblinking for a minute before resting the eye.


Fig. 2. Marsden’s first large-angle scattering arrangement.AB contained radium emitting alpha particles through athin window. The alphas were scattered by a metal plate RRonto a scintillation screen S and the scintillation flasheswere observed through a low-powered microscope M. Thelead shield P blocked unscattered alphas.

“It is said that Rutherfordoften cursed and left thecounting to the youngerGeiger.”

It is said that Rutherford often cursed and left thecounting to the younger Geiger.

Another of Geiger’s duties was to train students inradioactivity techniques. It was Rutherford’s policy toinvolve undergraduates in simple researches. So whenGeiger reported to Rutherford that a young Manchurianundergraduate was ready for an investigation, Rutherfordset Ernest Marsden the task to see if he could observealpha particles reflected from metal surfaces. Thisseemed unlikely, but beta particles did reflect.

Marsden used the same detecting system as Geiger,but had the alpha source on the same side of the metalas the fluorescing screen, with a lead shield preventingalphas going directly to the screen – see Fig. 2. WilliamBragg in Adelaide, whom Rutherford had met in 1895,had reported that there were alpha rays of severaldifferent energies emitted from radium salts, one for

each member of the decay series. Rutherford couldchoose a monochromatic alpha source by allowingradium emanation (radon) to decay in the presence ofa charged plate, which became plated with the metaldecay product, and finally producing mono-energeticalphas solely from Radium C. Marsden replaced histube of radon gas with such a mono-energetic source.

When Marsden reported that he did see about onein 10,000 alphas scattered at large angles Rutherfordlater recalled his astonishment. It was as if a 15-inchnaval shell had been fired at a piece of tissue paper andit bounced back. Geiger and Marsden published theirmeasurements in June 1909 – see Fig. 3. Characteristi-cally, Rutherford’s name was not listed as an author. As

William Kaye, his laboratorysteward, stated in a memoirmany years later, Rutherfordgave full credit to his helpers.

During Rutherford’s time atManchester an extraordinarynumber of 230 papers werepublished on radioactivity. Yet,his name appears on only 37of the 200 or so for which hewas not the sole author, though

he had initiated almost all those studies. As evidenceof his helpfulness to young scientists in distant parts(perhaps recalling how his own first planned researchin New Zealand had been overwritten before he couldcomplete it) Rutherford, in March of 1911, wrote toJohn Madsen at the University of Melbourne: “I hadintended to test my theory by experiments with raysalong very similar lines to that which I understand youare doing. I shall be glad, however, to leave the matterto you if you will be able to get through the work inreasonable time.”

The nucleus unveiledErnest Marsden’s discovery remained fallow for over ayear, as he had exams to sit. Geiger continued obtainingmore accurate statistics for alpha scattering fromdifferent materials and thickness of foils. It is recorded

that one day Rutherford went into Geiger’s room toannounce that he knew what the atom looked like. ByJanuary 1911 Rutherford could write to Arthur Eve inCanada: “Among other things I have been interestingmyself in devising a new atom to explain some of thescattering results. It looks promising and we are nowcomparing the theory with experiments.”

On 7 March 1911 Rutherford presented his ideas tothe Manchester Literary and Philosophical Society. Hereported that Geiger’s experimental test of the theoryconfirmed that the alpha rays scattered through largeangles varied as cosec4φ/2, where φ is the angle of devi-ation. One conclusion was that for gold the centralcharge was about 100 units and that for different


Fig. 3. The Geiger–Marsden paper in Proc. Roy. Soc. London in 1909.

“… Rutherford later recalled his astonishment. It was as ifa 15-inch naval shell had been fired at a piece of tissuepaper and it bounced back.”

materials the number was proportional to NA2, whereN is the number of atoms per unit volume and A theatomic weight. Another conclusion was that large scat-tering (hyperbolic) paths were independent of whetherthe central charge is positive or negative.

A reporter for the Manchester Guardian wrote thatRutherford’s work “… involved a penetration of theatomic structure, and might be expected to throwsome light thereon”, before concluding that “… we

were on the threshold of an enquiry which might leadto a more definite knowledge of atomic structure” [3].

Rutherford’s talk was published in the ManchesterLiterary and Philosophical Society’s Proceedings, andmore fully in the Philosophical Magazine for May. In thelatter, Rutherford acknowledged Nagaoka’s mathematicalconsideration of a ‘Saturnian’ disc model of the atom,stating that essentially it made no difference to thescattering if the atom was a disc rather than a sphere [4].

Surprisingly, the nuclear atom created no significantscientific or public interest. Three nights later, Rutherfordaddressed the Society of Industrial Chemists on ‘Radium’without mentioning the nuclear atom. Three weekslater, when addressing the Institution of Electrical En-gineers on ‘The properties of alpha rays of radio-activematter’, he did mention that “he hoped very soon toform some reasonable view of the constitution of theatom itself.”

Sir William Ramsay, in his Presidential address tothat year’s Annual General Meeting of the British As-sociation for the Advancement of Science, never men-tioned the nuclear atom. This seems most unusualtoday when reporters and science writers would nowbe keen to mention all sorts of trivialities such as that,if the electrons in our atoms were compressed into thenuclei, a human body would be the size of a grain ofsand. Ramsay concentrated on his own discoveries,

causing Arthur Schuster, whohad stood down from thephysics chair at Manchesteron condition that it was of-fered to Rutherford, to writea letter to the editor of theManchester Guardian pointingout which of those discoverieshad been made by Ruther-ford.

An accompanying paperon p. 78 of this issue of Aus-tralian Physics [5] examinesthe citation index for Ruther-ford’s papers and concludesthat he has undergone ‘sci-entific obliteration’ – thegreatest of accolades – where-by a scientist’s work is sotaken for granted that noone any longer sees a needto cite it.


Fig. 4. Rutherford’s theory of large angle scattering from hisPhil. Mag. article of 1911.

Fig. 5. Niels Bohr and Rutherford at the Cambridge University rowing regatta in June1923. Shortly after, Bohr was offered a prestigious Royal Society professorship to workwith Rutherford at the Cavendish Laboratory, but he chose to continue developingphysics at the University of Copenhagen in Denmark.

Rutherford’s Nobel Prize in Chemistry of 1908 wastoo recent for physicists to nominate him again. It wasto be 1922 before he was next nominated, unsuccessfully.To date there have been 27 Nobel Prizes awarded forthe discovery of, or theories linking, subatomic particles,but there was never one for the nuclear atom. However,there was a related one. At the end of 1911 Rutherfordwas the guest of honour at the annual CavendishResearch Dinner, at which he was, not surprisingly, infine form. The chairman, in introducing him, statedthat Rutherford had another distinction. Of all theyoung physicists who had worked at the Cavendish,none could match him in swearing at apparatus.

Rutherford’s jovial laugh boomed aroundthe room.

A young Dane, visiting the Cavendishfor a year to continue his work on elec-trons in metals, took an immense likingto the hearty New Zealander. He resolvedto shift to Manchester and spend therest of his year working with Rutherford.And so it was that Niels Bohr receivedthe 1922 Nobel Prize for Physics for“his services in the investigation of thestructure of atoms and of the radiationemanating from them”. Bohr had placedthe electrons in stable orbits aroundRutherford’s nuclear atom.

References[1] All general information on Ernest Ruther-ford is from the book by John Campbell,‘Rutherford Scientist Supreme’ (AAS Publi-cations, Christchurch, 1999).

[2] H. Geiger and E. Marsden, ‘On a diffuse reflection ofthe α-particles’, Proc. Roy. Soc. London A82, 495–500(1909).

[3]The Manchester Guardian, 9 March 1911.[4] E. Rutherford, ‘The scattering of the α and β rays and

the structure of the atom’, Proc. Man. Liter. Phil. Soc. IV55, 18–22 (1911); E. Rutherford, ‘The scattering of theα and β rays and the structure of the atom’, Phil. Mag.Series 6 XXI, 669–88 (1911); and H. Nagaoka, Phil.Mag. 7, 445 (1904).

[5] W. Marx, M. Cardona and D. J. Lockwood, ‘Rutherford’sscientific impact from a bibliometric perspective’, Aust.Physics 48(3) 78 (2011) [this issue].


ABOUT THE AUTHORDr John Campbell is a retired condensed matter physicist from the University of Canterburyin New Zealand. He is the author of the book ‘Rutherford Scientist Supreme’ and the creatorof the website www.rutherford.org.nz. John is the co-producer of the documentary Rutherfordand was the instigator of the Rutherford Birthplace Memorial at Nelson on the South Island.He runs the Ask-A-Scientist programme; has organised firewalks throughout New Zealand;carried out marine archaeology in France, Italy and the Chatham Islands; holds several awardsfor communicating science to the public; and once came third in a gumboot throwingcompetition.

Fig. 6. Alpha scattering and the nuclearatom as depicted on the 1971 New Zealand1¢ stamp to mark the centennial ofRutherford’s birth and a Greek 100Drachma banknote from 1967.

Rutherford was awarded the Nobel Prize inChemistry in 1908 for explaining radioac-tivity as the spontaneous disintegration ofatoms, and in the process identified alpha,

beta, and gamma rays. In other equally brilliant exper-iments performed with colleagues in 1911 he determinedthe structure of the atom and thereby produced hismodel of the atom – a minute nucleus (his term) sur-rounded by a cloud of electrons [1]. Thirdly, in 1919he split the atom by converting nitrogen into oxygenusing alpha-particle bombardment to become the firsttrue alchemist.

Many of his secondary discoveries would haveresulted in fame for any other scientist. When Rutherfordfirst blew tobacco smoke into his ionisation chamberat McGill University in Montreal in 1899 and observedthe resulting change in ionisation he lead the way tothe development of the ubiquitous smoke detectoralarm systems found in our buildings today. Hepioneered the use of radioactive decay as a time markerfor determining the age of the earth and also its subse-

quent use for dating the earth’s artefacts, overcomingmuch resistance at the time from the scientific estab-lishment in the process. For more on the life and workof Rutherford, see the comprehensive biography byJohn Campbell [2].

Applying bibliometrics to the history ofscienceBibliometrics or the broader term scientometrics –both dealing with the quantitative analysis of science –has shifted from a very special subject to an issue mostrelevant to the majority of present day scientists. Ifthey are seeking a job, a promotion or tenure, theirpublication output and citation impact will possiblybe considered. Such metrics have not been establishedto replace committees of experts but to provide com-prehensible and reliable numerical data for fair assessment.Only active researchers within the same research fieldare in a position to assess the scientific quality of theircolleague’s research. However, citation based metricsprovide an objective counterweight to the peer-review


Rutherford’s Scientific Impactfrom a Bibliometric PerspectiveWerner Marx, Manuel Cardona and David J. Lockwood

In 2011 we celebrate the centenary of the publication of the ground-breakingpaper by Ernest Rutherford on the discovery of the nucleus and, hence, thebeginning of nuclear physics. Rutherford (1871–1937) was a towering figure inscientific research in the early twentieth century. His three major experimentaldiscoveries in atomic physics during that period could each have earned him aNobel Prize. However, his scientific achievements and interests went well beyondjust these notably huge advances in our knowledge of atomic physics at the time.Here we report on the impact of Rutherford’s work on scientific developmentsover the past one hundred years through an analysis of citations to hispublications.

process, which is prone to bias of many kinds (e.g.nepotism). The weakness of bibliometrics is not somuch the method itself, but the lack of backgroundinformation and understanding concerning what thedata really mean – and what they do not mean!The launching of the Web of Science (referred to

hereafter as WOS) back-files by Thomson Reuters hasextended the retrospective coverage of WOS (the mostimportant source of citation based data besides Scopusfrom Elsevier) back to 1900 [3]. There is no real needfor the evaluation of the lifeworks of the pioneers ofscience, who have long ago found their recognition bythe incorporation of their discoveries into textbooks(or even as Nobel Laureates). However, we may be in-terested to detect their traces in the databases, thedigital archives of science. Also, quantitative data onthe reception of seminal works might be of interest.Furthermore, we can illustrate some basic laws of bib-liometrics in the context of works well-known to mostscientists. Finally, we may ask whether the citationbased indicators applied to current scientists yield

meaningful results also in the case of pioneers.However, there are some caveats to searching historical

papers and counting their citations as a measure oftheir impact: the limited coverage of journals, the lim-itations of specific search fields, database errors, problemsarising from incorrect citations, and other sources oferrors resulting from the citation practice in the past[4]. Moreover, in the case of historical papers there aresome basic phenomena limiting the meaning of citationcounts as a measure of scientific impact. We enter anarea with a completely different publication and citationculture compared to the present one.

Nevertheless, Rutherford delivers an excellent examplefor applying bibliometrics to the history of science: (1)most of his papers have been published in the Philo-sophical Magazine after 1900 and hence are coveredsufficiently by WOS; (2) most of his papers are of basicimportance and are therefore cited throughout thetwentieth century; and (3) there is not only one butother major discoveries in nuclear physics, which couldeach have earned him a second Nobel Prize.


Fig. 1. Hans Geiger (left) with Ernest Rutherford in the laboratory at the University of Manchester, thought to be in 1908[credit: AIP Emilio Segre Visual Archives].

Papers, citations, and the h-indexThe multidisciplinary WOS covers 164 papers publishedby ‘our’ E. Rutherford within the time period 1900–31 (the pre-1900 publications are not covered byWOS). Additionally, some 50 papers have been publishedsince 1940 by namesakes. There are 63 out of 164papers by Rutherford that appeared in the Philosophical

Magazine. Obviously, this journal was his preferredchoice for publishing his work, starting in 1896 andending 1919. Rutherford ranks sixth in the list ofauthors having published most often in the Phil. Mag.since 1900. The 164 papers by Rutherford have garneredabout 1500 citations until the present

If we also include the citations of his books, of thepre-1900 papers (data available since 1900) and alsothe incorrect citations, we obtain altogether about

2100 citations. Compared to renowned present-dayscientists, this seems not to be overwhelming, butthese numbers are highly misleading! In the first halfof the twentieth century the number of scientists wasrelatively small. Correspondingly, the number of pub-lications was low (the publications covered per year byWOS increased by a factor of approximately hundredduring the century).

We shall speak of the period before 1960 as ‘littlescience’, whereas the period after 1960 will be referredto as ‘big science’, a transition first observed by DerekDe Solla Price [5]. It is easy to conjecture that thetransition from the period of little to big science is dueto the so-called ‘Sputnik shock’ that took place uponthe orbit of the first satellite by the Soviet Union in1957 [6]. As a reaction the Western industrial nations,especially the USA, allocated within a short timemassive funding to support related scientific researchand development. These measures resulted in a rapidincrease in the number of scientists and researchactivities followed by a dramatic increase in the numberof publications.

On average, early papers are cited less frequentlythan more recent papers. Hence, the citation numbersof early scientists are not directly comparable to thoseof present day researchers. The question arises: onaverage by what factors are contemporary papers moreoften cited than earlier papers. If we have to comparepapers and researchers from different research fields ofpresent day science, we need to take into account thefield specific average citation rates by applying nor-malisation procedures. This can be illustrated by the


“… Rutherford ranks interms of citations with MaxPlanck and Albert Einsteinas one of the maincontributors to thedevelopment of modernphysics during the earlytwentieth century.”

Table 1: The ten most frequently cited papers by Ernest Rutherford [source: Thomson Reuters WOS at 27 May 2011]

Author(s) Journal Title Citations

E. Rutherford Phil. Mag. 21, 669–88 (1911)* The scattering of α and β particles by matter and the structure of the atom 370

E. Rutherford & H. Geiger Proc. Roy. Soc. London A81, 141–61 (1908) An electrical method of counting the number of alpha-particles from radio-active substances 90

E. Rutherford Proc. Roy. Soc. London A97, 374–400 (1920) Bakerian Lecture: Nuclear constitution of atoms 68

E. Rutherford Nature 123, 313–4 (1929) Origin of actinium and age of the earth 67

E. Rutherford & C. Andrade Phil. Mag. 28, 263–73 (1914) The spectrum of the penetrating gamma rays from radium B and radium C 65

E. Rutherford Phil. Mag. 47, 277–303 (1924) The capture and loss of electrons by alpha particles 63

M. Curie, E. Rutherford et al. Rev. Mod. Phys. 3, 427–45 (1931) The radioactive constants as of 1930 – Report of the international radium-standards commission 62

E. Rutherford Phil. Mag. 47,109–63 (1899)** Uranium radiation and the electrical conduction produced by it 57

E. Rutherford Phil. Mag. 37, 581–7 (1919) Collisions of alpha particles with light atoms IV. An anomalous effect in nitrogen 55

E. Rutherford & H. Geiger Phil. Mag. 20, 698–707 (1910) The probability variations in the distribution of alpha particles 51

E. Rutherford & F. Soddy Phil. Mag. 4, 370–96 (1902) Soddy on the cause and nature of radioactivity – Part I 51

* This paper has not been included as a source record because vol. 21 of Phil. Mag. was not covered by WOS until the present [4].** Until now papers published pre-1900 are generally not covered by WOS, however, their citations since 1900 are searchable.

different average number of goals scored in differentcodes of football such as soccer and rugby. A similarproblem arises if we compare citation counts of earlypapers published in the area of little science withcitation numbers of more recent publications.

Applying our newly developed scaling method forpapers published in the period of little science meansthat the overall number of citations (500) whichRutherford received until 1931 (the year of the lastpaper covered by WOS) has to be multiplied by an ap-propriate reference multiplier: a reference multiplier of30 based on the Phil. Mag. or a reference multiplier of40 based on the Phys. Rev. [7]. This procedure resultsfor Rutherford in a present day scaled citation numberof altogether between 15,000 and 20,000 citations,which is a truly respectable citation impact.

In 2005 the so-called Hirsch or h-index was introducedby Jorge Hirsch as a combined measure of both output(in terms of papers) and impact (in terms of citations)in a single number [8]. This new bibliometric indicatorhas had a major impact on the field of researchevaluation, in part because of its simplicity and trans-parency. The h-index is defined as the number ofpapers h by an author in WOS source journals thathave had h citations or more to each individual paper.We have obtained for Rutherford an unscaled h-indexof 20. To calculate a time-adjusted h-index demandsthat all citation numbers of Rutherford papers be mul-tiplied by the appropriate reference multiplier. Thisprocedure results in a present day scaled Rutherford h-

index of between 91 and 93 (depending on a referencemultiplier of 30 or 40). For comparison, Max Planckhas an unscaled h-index of 13 and a time-adjusted oneof 95 [7].

Each paper develops its own lifespan as it is beingcited. Over time, the citations per year normally evolvefollowing a similar pattern: They generally do notincrease substantially until one year after publication.They reach a maximum after about three years, thepeak position depending somewhat on the researchdiscipline. Subsequently, as the papers are displaced bynewer ones and interest in the field wanes, their impactdecreases. Finally, most papers are barely cited or for-gotten. In contrast, the famous 1911 Rutherford paperon the discovery of the nucleus [1] belongs to therather few papers published at the beginning of thelittle science era that have been remembered throughouthalf a century and were then increasingly cited withinthe big science period.The citation ranking reveals the ten most frequently

cited Rutherford articles, as presented in Table 1 (noteof course that the citation counts are not time-adjustedin the way discussed above). Fig. 2 shows the citationhistory of the most-cited Rutherford paper [1] whichdiffers markedly from the standard pattern mentionedabove.

Rutherford also published at least seven books, butthese are generally not covered by WOS as databaserecords. However, the references assigned to bookswithin WOS journal papers are completely captured.As a result of our analysis, Rutherford’s books receivedaltogether 350 citations (17% of his overall citationimpact). Again, the present day scaled citation numberis much higher.

Informal citations and ‘scientificobliteration’Citing is afflicted to a greater or lesser extent by manydistortions which have been widely discussed in thebibliometric literature. In the case of historical papersthere are two basic phenomena limiting the meaningof citation counts as a measure of scientific impact.Firstly, seminal work is often cited by mentioning theauthor’s name or name-based items (‘informal citations’)instead of citing the full references as a footnote (‘formalcitations’) [9]. The number of ‘informal citations’ isoften many times higher than the number of referencebased citations, in particular when the name of anauthor or their contribution has become a household


Fig. 2. Time evolution of the citation history of the seminal1911 Rutherford paper on the discovery of the atomicnucleus [1]. This is a good example of a seminal paper witha long term impact, which receives an increasing number ofcitations per year along with the boom after the Sputnikshock half a century after its publication. [Source: ThomsonReuters WOS].

word. Hence, the formal citations measure only afraction of the overall impact of seminal papers or ofthe entire publications of pioneers.

As a major consequence, the overall impact of pio-neering papers cannot be entirely determined by merelycounting their citations. In the case of Rutherford themost ‘informal citations’ correspond to RutherfordBackscattering (85%). Here we pose an interesting‘Gedanken-experiment’: If for example the modernatomic model or a phenomenon related to radioactivity(his most important achievements) were to bear hisname, the number of ‘informal citations’ would bemuch higher and thus would better give a quantitativemeasure of the importance of his many fundamentalcontributions to physics.

The second phenomenon limiting the meaning ofcitation counts for Rutherford is typified by his famous1911 atomic nucleus paper [1], a prime example of‘obliteration by incorporation’, an effect first describedby the sociologist Robert Merton [10]. The process of‘obliteration’ or ‘palimpsest’ (the latter referring to apiece of parchment that is erased more than once tomake room for newer work) affects seminal worksoffering novel ideas that are rapidly absorbed into thebody of scientific knowledge. Such work is soon inte-grated into textbooks and becomes increasingly familiarwithin the scientific community.

As a result of this absorption and canonisation, theoriginal sources fail to be cited, either as full referencesor even as names or subject-specific terms. Therefore,we should not expect that the citations of the works ofRutherford could be taken as a real measure of the in-fluence of his ideas in modern science. There are nometrics for quantifying fundamentality, significance oreven elegance, which are terms falling under a completelydifferent category.

We show in Fig. 3 the time curve of the Rutherford‘informal citations’ based on the INSPEC database forPhysics, Electronics, & Computing (‘Rutherford’ ap-pearing in the titles, the abstracts or within the keywordterms). The corresponding time curve based on WOSis limited to the post-1990 literature, because theabstracts of the earlier records are not available inWOS. Besides all informal citations mentioning ‘Ruther-ford’, we have given, separately, those mentioning‘Rutherford Backscattering’ or ‘Rutherford Scattering’(RBS, RS).

Recently, a team at Harvard University has reportedthe creation of a corpus of over 5 million digitisedbooks containing ~4% of all books ever published[12]. This corpus has emerged from Google’s effort todigitise books. Computational analysis of the data hasenabled an investigation of cultural trends, quantitativelysurveying the vast terrain of a new field known as ‘cul-turomics’. The authors focused on linguistic and culturalphenomena that were reflected in the English languagebetween 1800 and 2000. The data allow carrying overthe concept of ‘informal citations’ based on searchingthe titles, abstracts and keywords of journal articles tosearching the full text of books. The search for ‘ErnestRutherford’ results in the time pattern given in Fig. 4.The distinct peak around 1905 undoubtedly corre-

sponds to the appearance of Rutherford’s first bookentitled ‘Radioactivity’ published in 1904, but the


Fig. 3. Time evolution of Rutherford ‘informal citations’based on the field-specific literature database for Physics,Electronics, & Computing (INSPEC) and on WOS. Besides allinformal citations mentioning ‘Rutherford’, separately, thosementioning ‘Rutherford backscattering’ or ‘Rutherfordscattering’ (RBS, RS) are also shown. [Source: INSPECdatabase for Physics, Electronics, & Computing under STNInternational [11] and Thomson Reuters WOS].

Fig. 4. Time evolution of the term ‘Ernest Rutherford’appearing in books searched under Books Ngram Viewer ofGoogle labs [13]. The y-axis shows the yearly percentage ofthe term ‘Ernest Rutherford’ of all equivalent termscontained in the sample of books written in English andpublished within the period 1871–2000 (after 2000 thecorpus composition undergoes subtle changes around thetime of the inception of the Google Books project) [14].

large broad peak centred around 1925 clearly demon-strates the rapid integration of his work into textbooksand the beginning of the process of its ‘obliteration’, asdiscussed above. The plot shows a remarkably steadyreference to ‘Ernest Rutherford’ long after his death in1937, confirming the lasting influence of Rutherford’swork in the scientific literature.

In conclusionRutherford’s influence on the course of science andnuclear physics in particular has been immense, as ev-idenced through our citation analysis of his publishedworks. It should be noted in this regard that he seldomco-authored papers published by his students [2], oth-erwise he would have had many more citations. As itis, Rutherford ranks in terms of citations with MaxPlanck and Albert Einstein [7] as one of the main con-tributors to the development of modern physics duringthe early twentieth century. His name lives on primarilyin the Rutherford back-scattering technique that wasdeveloped subsequent to his most important discoveryof the atomic nucleus, but was soon widely applied inmany other areas of science. This is probably unfair. Rutherford’s name should

be at least as widely quoted in the modern literatureas, for example, C. V. Raman, who was active inresearch in the same time frame as Rutherford and hadthe Raman effect named after him [9]. The process of‘scientific obliteration’ lies at fault here – Rutherford’snew ideas and discoveries, although they underpin somuch of today’s physics and chemistry, were rapidlyincorporated into our scientific knowledge and thensimply taken for granted.

References[1] E. Rutherford, ‘The scattering of the α and β rays and

the structure of the atom’, Phil. Mag. Series 6 XXI,669–88 (1911).

[2] J. A. Campbell, ‘Rutherford Scientist Supreme’(AAS Publications, Christchurch, 1999); see alsothe accompanying article by John Campbell in thisissue Aust. Phys. 48(3), 72 (2011).

[3] scientific.thomsonreuters.com/products/wos/.[4] W. Marx, ‘Special features of historical papers from

the viewpoint of bibliometrics’, J. Am. Soc. InformationSci. Technol. 62(3), 433–9 (2011).

[5] D. J. De Solla Price, ‘Little Science, Big Science’(Columbia Univ. Press, New York, 1965).

[6] P. Dickson, ‘Sputnik: The Shock of the Century’(Walker & Co, New York, 2007).

[7] W. Marx, L. Bornmann and M. Cardona, ‘Referencestandards and reference multipliers for the comparisonof the citation impact of papers published in differenttime periods’, J. Am. Soc. Information Sci. Technol.61(10), 2061–9 (2010).

[8] J. E. Hirsch, ‘An index to quantify an individual’sscientific research output’, Proc. National Acad.Sciences USA 102(46), 16569–72 (2005).

[9] W. Marx and M. Cardona, ‘The citation impactoutside references – Formal versus informal citations’Scientometrics 80(1), 1–21 (2009).

[10] R. K. Merton, ‘Social Theory and Social Structure’(The Free Press, New York, 1968).

[11] www.stn-international.de/stndatabases/databases/.[12] J. B. Michel et al., ‘Quantitative analysis of culture

using millions of digitised books’, Science 331, 176–82 (2011).

[13] ngrams.googlelabs.com.[14] www.culturomics.org/Resources/A-users-guide-to-

culturomics.[15] W. Marx, M. Cardona and D. J. Lockwood, ‘Ruther-

ford’s impact on science over the last 110 years: Abibliometric analysis’, Phys. Canada 67(1), 35–40(2011).

Werner Marx and Manuel Cardona are at the Max Planck Institutefor Solid State Research, Stuttgart, and David J. Lockwood is at theNational Research Council, Ottawa. A more detailed version of thisarticle by the same authors appeared recently in Physics in Canada[15].


“The process of ‘scientificobliteration’ lies at faulthere – Rutherford’s newideas and discoveries,although they underpin somuch of today’s physicsand chemistry, were rapidlyincorporated into ourscientific knowledge andthen simply taken forgranted.”

There are three primary reasons why onewould contemplate modifying such a suc-cessful theory. The first is the fundamentaldisagreement in theoretical foundations be-

tween Quantum Field Theory and General Relativity.The recent questioning of General Relativity is, however,borne about by more empirically tangible conceptsacting on classical, ie. non-quantum, scales. A secondrationale is as follows: despite years of increasingly

accurate laboratory and solar system based measurements,current experimental tests of gravity are far from exhaustive.It is not a question of the accuracy of measurements,but rather of the scales on which the theory has beentested. I will quantify this statement below.The third and final reason is comparatively new and

is based on possible empirical conflicts that manifestthemselves as the theoretical constructs of dark energyand dark matter. Loosely stated: there are manyunanswered questions in cosmology. These final two con-cepts, and their possible theoretical and empirical res-olutions, are examined in this article.

Why should we modify gravity?Current tests of gravity are far from exhaustive: Giventhe metric nature of General Relativity, one can calculatethe degree to which spacetime is curved around anobject, denoted by ξ [see ref. 1]. This quantity coversover fifty orders of magnitude, from the surface of thesmallest black holes, ξ ~ 10–10 cm–2, to the curvatureof the Universe as a whole, ξ ~ 10–60 cm–2. A secondquantity ε measures the potential of the gravitationalfield. The event horizon of a black hole has ε = 1,whilst moving further from such objects reduces thisvalue by up to twenty orders of magnitude.


How Right Was Einstein?Towards New Tests of General Relativity

Paul Lasky

Since its publication almost a century ago, Einstein’s theory of General Relativityhas revolutionised the way we think about space, time and the Universe as awhole. Originally based on limited empirical evidence, the intervening years havelaid witness to countless gravitational experiments that have continued to pushthe boundaries of our understanding. With each experiment has come betteragreement. Despite these vast empirical successes, Einstein’s theory of GeneralRelativity is continually being called into question – more so now than perhapsever before.

“When General Relativity isused to explain thedynamics of the Universe asa whole or the spacetimestructure of neutron starsand black holes, the validityof the theory is beingextrapolated many ordersof magnitude away fromexperimental verifications.”

Fig. 1 shows the (ε, ξ) parameter space for theentire Universe. The area highlighted in red encompassesthe region that has currently been experimentallytested. This is essentially the area of parameter spacethat our Solar System occupies, from the strongestfields at the surface of the sun, out to the furthestreaches of planetary orbits. It is therefore an under-statement to say that truly ‘strong’ and ‘weak’ fields ofgravity have not been experimentally tested. In fact,we are some 15 to 20 orders of magnitude in curvaturefrom realising the most extreme parts of the Universe.When General Relativity is used to explain the dynamicsof the Universe as a whole or the spacetime structureof neutron stars and black holes, the validity of thetheory is being extrapolated many orders of magnitudeaway from experimental verifications. Despite this,one of the supposed pillars of modern astrophysics,the standard model of cosmology, is built upon the as-sumption that General Relativity is the correct theoryof gravity on the largest scales.

Standard Model of Cosmology: The standard modelwas finalised in 1998 when two research groups dis-covered an acceleration of the Universe via Type Ia Su-pernovae (SNIa) observations [2]. SNIa are standardcandles due to almost uniform light curves that can beused to simultaneously gain information about theirdistance and redshift. The standard model has three

key assumptions: (1) General Relativity correctlydescribes gravitational interactions on cosmologicalscales and below, (2) the Universe is homogeneous,and (3) the Universe is isotropic. These assumptions,together with observations of SNIa, the cosmic microwavebackground (CMB), baryon acoustic oscillations, large-scale structure and weak lensing surveys, lead to astrange picture of the Universe. Namely, that from thetotal energy budget of the Universe, baryons composejust four percent. The remaining 96% of the Universeis ‘dark energy’ (~74%) and ‘dark matter’ (~22%). The existence of dark matter was postulated well

before the standard model of cosmology, originallybased on missing mass inferred from the rotationcurves of galaxies. The strongest candidates for darkmatter are weakly interacting massive particles that, al-though not yet directly observed, fit relatively nicelyinto simple extensions of the standard model of particlephysics. The existence and nature of dark energy is more

contentious. The simplest possibility is that dark energyis a cosmological constant. This fits all data extremelywell. It is worth noting however that a cosmologicalconstant is equivalent to the imposition of vacuumenergy. The inferred value of the cosmological constantand the theoretically derived value of vacuum energydiffer by some 120 orders of magnitude! Physical alter-natives for dark energy include models of dark fluids,and even more exotic phenomena for which the onlyobservational evidence is the concordance of observationslisted above [3].

My presentation of cosmology is biased to promotecontention. For equalities sake it should be noted thatcosmological observations do form a concordancemodel. That is, accepting the three assumptions ofGeneral Relativity, homogeneity and isotropy, all ob-servations lead to a single set of parameters describingthe Universe. If this model were wildly wrong, onewould expect tension between the datasets. But thelack of a physically viable interpretation of dark energystill motivates angst. For this reason, numerous researcherspostulate that the inference of dark energy is due toone (or more) of the three theoretical assumptionsbeing incorrect.

Research papers appear daily propounding an inho-mogeneous Universe interpretation of dark energy, allwith varying degrees of success. This would be thesimplest of all solutions to the dark energy problem asit requires no new physics. Anisotropic interpretations


Fig. 1. A parameter space quantifying the strength of gravity(adapted from [1]). The horizontal and vertical axes are thepotential of the gravitational field and curvature ofspacetime respectively.


of the Universe are harder to muster given the isotropic(to one part in 105) observations of the CMB. But forthe remainder of this article I will focus on the thirdpossibility – that General Relativity only provides anaccurate description of gravity on solar system scales,and that extrapolation to cosmological scales incorrectlydescribes the dynamics of the Universe.

What is General Relativity?The main difficulty for creating a new theory of gravitylies in the requirement to retain the vast phenomeno-logical and empirical successes of General Relativity. Itis therefore worth understanding what made GeneralRelativity successful.

General Relativity has two key ingredients: SpecialRelativity and Einstein’s Equivalence Principle. Bothof these postulates are extremely well tested and weshall not question their validity here. Einstein’s Equiv-alence Principle unequivocally leads to the interpretationthat any freely falling test body travels along geodesicsin curved, four-dimensional spacetime – ie. that gravityis a metric theory.

How does one then construct a metric theory ofgravity? The answer is remarkably simple: using a vari-ational principle approach, write down a gravity actionas some four-dimensional geometrical quantity. Rie-mannian geometry is a natural choice, and so the Ein-stein–Hilbert action describing General Relativity con-tains the simplest geometrical quantity of Riemanniangeometry – the Ricci scalar. As we are dealing with thegeometry of four dimensions, the action is an integralover the three dimensions of space plus one of time.Couple this to a matter action with an empiricallyderived coupling constant, and one has constructedGeneral Relativity. By varying this Einstein–Hilbertaction with respect to the metric results in Einstein’sfield equations.

How can we modify gravity?With a variational approach to General Relativity, onecan immediately see that to create a modified theoryof gravity relies only on changing the geometricalquantity used in the action. One of the great examplesof this comes from Einstein himself, with the famousstory about his ‘greatest blunder’. To create a stationaryUniverse, Einstein realised he needed a repulsive forceto counter gravity. He subsequently altered the Ein-stein–Hilbert action by adding a constant – the cosmo-logical constant. This, believe it or not, is the firstexample of ‘modified gravity’. Including a constant inthe action alters the way in which the geometry ofspacetime reacts to the presence of matter. Providingthis constant is small enough, it will alter the fieldequations in such a way that observations of all phe-nomena on solar system scales will not be effected.

Including a cosmological constant in the Einsteinfield equations is seldom referred to as modified gravity.However, the process outlined highlights the availabilityof further generalisations of General Relativity. For ex-ample, one can introduce any functional dependenceon the Ricci scalar in the action and create a viabletheory of gravity. Such theories, known as f(R) theories,can be designed to reproduce solar system experiments.Different functional forms will however yield differentresults on both cosmological scales and also in thestrong-field gravity regime. There is no reason to stop at the Ricci scalar. This is

but one geometrical construct inherent to Riemanniangeometry. There is a multitude of geometric objectsthat can be combined in various combinations tocreate viable theories of gravity. Many of these theorieswill have intrinsic problems such as vacuum instabilitiesthat automatically render the theory unviable. However,large classes of theories exhibit no such flaws, andvarious coupling parameters and functional forms canbe selected in such a way that all gravitational experimentsare satisfied up to experimental uncertainty.

One can also add various other types of fields to theaction such as scalar, vector and other tensor fields.This was first done in 1961 by Brans and Dicke [5],who introduced a scalar field to the intrinsic tensorfield of General Relativity and allowed a coupling con-stant to parameterise their relative strengths. Whenthis coupling constant, ω, limits to infinity, the Brans–Dicke theory reproduces General Relativity. This wasthe first time that deviations from General Relativitywere parameterised, and gave experimentalists an

“… the successful detectionof gravitational waves willlikely come from extremeevents such as the inspiral,coalescence andsubsequent ringdown of abinary black hole system.”

original way of testing the accuracy of Einstein’s theory.The current best constraints on the Brans–Dicke pa-rameter come from the Cassini–Huygens experiment,which set a value of ω > 4×104 [4, 6].The above are a small portion of the total number of

gravitational theories appearing in the literature. Ex-tremely creative physicists have developed a regularcornucopia: Einstein–Cartan theory, massive gravitons,Horava–Lifshitz theory, Finsler geometries, non-Abeliantensor fields and the list goes on. Moreover, we havefailed to mention any theory that deviates from thepremise that we live in a four-dimensional Universe.Propounded by the string theory revolution, higher-dimensional theories of gravity have been around sincethe early part of the twentieth century. The modernday inception of their idea provides the impetus forhundreds to thousands of research papers per year.

The future of experimental gravityThe large number of viable gravitational theories ispartially a consequence of the inadequate state of theempirically verified parameter space presented in Fig.1. Couple this to the unresolved questions in cosmology,such as the nature of dark energy and dark matter, andit becomes obvious that new tests of gravity are requiredin regions of the Universe that have the potential tofundamentally discern the correct theory of gravity.Fortunately, it looks certain that the next one to twodecades will provide these tests.

From Fig. 1 there are two apparent possibilities fortesting the theory of gravity – in the cosmologicalregime of weak-gravitational fields and in the strong-field regime involving the spacetime near extremelydense objects such as neutron stars and black holes.Numerous tests of gravity are being conducted in thecosmological spectrum. However, there are intrinsicdifficulties associated with such tests. In particular, it isextremely difficult to separate pure gravitational effectsfrom other physics. This is embodied in the statementthat “… cosmological observations are not ‘clean’ testsof gravitation since much ‘dirty’ astrophysics oftengoes into their interpretation” [4]. Of course, any can-didate theory of gravity must correctly explain cosmo-logical phenomena, however the shear number of can-didate theories will exclude drawing definitive conclusionsabout the worth of an individual theory of gravity overanother.

It is the other extreme of gravitational experimentsthat I believe will yield fruitful results about the theory

of gravity. In particular, by mapping the spacetimearound neutron stars and black holes we will be able todefinitively learn about pure gravitational effects.

Electromagnetic observations: Black holes in GeneralRelativity are incredibly simple beasts. This is typifiedby the ‘no-hair’ theorem, which states that any blackhole is characterised by just three quantities – mass,angular momentum and charge. Astrophysical blackholes will not possess significant charge implying thatany black hole has but two pieces of information. Thistheorem however, does not hold in most alternativetheories of gravity, where black holes can have extracharacterisations including scalar charge (due to back-ground scalar fields) and higher-order mass moments.

One of the most promising ways to map the exteriorregion of a black hole is through observations of themost central stars orbiting the supermassive black holein the centre of the Milky Way. Fig. 2 shows the orbitsof seven such stars that have been observed over fifteenyears. These orbits are determined by the geometricstructure of the spacetime around the black hole,implying the geometry can be mapped from accuratedeterminations of their orbits. Knowing the orbits oftwo stars allows us to determine both the quadrupolemoment and angular momentum of the black hole.Given that we independently know the mass, if GeneralRelativity is correct and the no-hair theorem applies,the system is over-determined. Such observations aretherefore able to accurately determine the validity of


Fig. 2. Observationally determined orbits of the closest starsto the supermassive black hole in the centre of the MilkyWay.


the no-hair theorem and hence General Relativity. There exist many more methods for determining

the structure of the spacetime around astrophysicalblack holes using photon astronomy in the near future.These include direct imaging techniques and measure-ments of accretion disk dynamics. X-ray observationsin the coming decade will provide sufficient resolutionto probe many of these facets important for discerningaccretion disk structure relevant for testing gravity.

Neutron stars also provide excellent candidates fortesting gravity. By measuring various features of atomicspectra from the surface of neutron stars, one is able todetermine compactness, radius, oblateness and frame-dragging effects. Observations on this front are still intheir infancy. It should be noted however that, as withcosmology, these systems are extremely ‘dirty’. Whilesimultaneously measuring pure gravitational effects,an incomplete knowledge of microphysics at supranucleardensities implies the equation of state of neutron starsis an extra fitting parameter. These are but a handful of possible observations

that will yield exciting results in the coming decades.There is another exciting prospect for further developingour understanding of gravity that is the topic of muchinterest – gravitational waves.

Gravitational waves: These waves are a prediction ofany metric theory of gravity. A worldwide effort is cur-rently underway to directly detect these elusive waves.These include interferometers in the US, Italy, Germanyand Japan. There is also a significant push to develop afull-scale observatory in Gingin, near Perth, atop theexisting test facility [see Aust. Phys. 47(6), 150–4(2010)]. This would have significant benefits to theworldwide community, including significantly enhanceddetection rates and directional sensitivity. In additionto interferometers, there are a number of resonant bardetectors located worldwide, and a planned space-based gravitational wave detector.

Possibly the best probes of gravity to date are indirectdetections of gravitational waves from binary pulsarsystems. In 1974 Russell Hulse and Joseph Taylor dis-covered such a system that allowed them to measurethe orbital decay with remarkable accuracy. GeneralRelativity predicts such a system should lose energythrough gravitational wave emission, implying the twoorbits should slowly coalesce. The theoretical predictionmatches the observations with astonishing accuracy(Fig. 3), thus providing the first indirect detection ofgravitational waves. Hulse and Taylor received the

Fig. 3. Orbital decay of the Hulse–Taylor pulsar system overmore than thirty years. Observations show remarkableagreement with General Relativity.

Fig. 4. Six possible gravitational wave polarisations (from[4]). General Relativity only predicts the existence of the (a)‘plus’ and (b) ‘cross’ polarisations, whilst almost all othertheories of gravity predict more modes.

Nobel Prize in 1993 for this momentous work. It isworth noting that such binary systems are still not truetests of strong gravity; neutron stars have typical massesof about one solar mass and separations on the orderof one astronomical unit, therefore placing them firmlywithin the red region of Fig. 1.

Contrary to popular belief, the successful detectionof gravitational waves does not verify General Relativityany more than any metric theory of gravity. However,observations of gravitational waves do have the potentialto discern such theories in fundamental ways. A primeexample is through their polarisation. General Relativitymay be unique in that it predicts only two polarisationsof gravitational waves – ‘cross’ and ‘plus’ modes.However, alternative theories predict up to six polari-sations (Fig. 4). A single gravitational wave detector isnot sensitive to most of these modes, however a com-bination of detectors can discern all polarisations. Thedetection of a single gravitational wave that is not ofcross or plus polarisation would immediately falsifyGeneral Relativity.

Another discerning factor between theories of gravityis the speed of propagation of gravitational waves –whose velocities are determined by the field equationsof the individual theories. General Relativity predictsgravitational waves to travel at the speed of light,however many metric theories predict different velocities.A simultaneous observation of electromagnetic andgravitational waves would yield invaluable informationabout the speed of propagation and hence the theoryof gravity.

Finally, the successful detection of gravitationalwaves will likely come from extreme events such as theinspiral, coalescence and subsequent ringdown of abinary black hole system. Specific details of the waveformthrough these phases differ between theories of gravity.Detections of such events, which are expected in thecoming decade, will yield more definitive tests ofgravity in the strongest possible regime.

ConclusionWith the multitude of alternative theories of gravity,at some point Occam’s razor must be invoked to selectthe simplest of theories that confirms all observations.Many argue that this is currently General Relativityand the standard model of cosmology, but a majorhurdle is still the lack of an adequate interpretation ofdark energy. With gravitational experiments probingsuch a small parameter space, extrapolating far beyondwhat is tested is no more aesthetically pleasing than re-modelling other physical theories to incorporate darkenergy. Perhaps the answer will not lie in observationson cosmological scales, but by probing the spacetimearound some of the most exotic objects in the Universesuch as neutron stars and black holes.

References[1] D. Psaltis, ‘Probes and tests of strong-field gravity with

observations in the electromagnetic spectrum’, LivingRev. Relativity 11, 9 (2008).

[2] A. G. Riess et al., ‘Observational evidence from supernovaefor an accelerating universe and a cosmological constant’,Astron. J. 116, 1009 (1998) [arXiv: astro-ph/9805201];S. Perlmutter et al., ‘Measurements of Omega andLambda from 42 high-redshift supernovae’, Astrophys. J.517, 565 (1999) [arXiv: astro-ph/9812133].

[3] In fact, some authors have recently argued that the onlyobservation supporting dark energy is that of the SNIa –see R. Durrer, ‘What do we really know about dark en-ergy?’, arXiv: 1103.5331 (2011).

[4] C. M. Will, ‘The confrontation between general relativityand experiment’, Living Rev. Relativity 9, 3 (2006).

[5] C. Brans and R. H. Dicke, ‘Mach’s principle and a rela-tivistic theory of gravitation’, Phys. Rev. 124, 925 (1961).

[6] B. Bertotti, L. Iess and P. Tortor, ‘A test of generalrelativity using radio links with the Cassini spacecraft’,Nature 425, 374 (2003).


ABOUT THE AUTHORPaul D. Lasky is an Alexander von Humboldt Research Fellow at the Eberhard–Karls Universityin Tübingen, Germany. Born and raised in Melbourne, he received his PhD for research on thegravitational collapse of massive stars to form black holes from Monash University’s Centrefor Stellar and Planetary Astrophysics. Paul has since published research articles on anextensive range of topics under the broad heading of gravitational physics. These include workon neutron star and black hole physics, cosmology, gravitational lensing, extragalacticastronomy and alternative theories of gravity.

Mrs Perkins’sElectric Quilt andOther IntriguingStories ofMathematicalPhysicsBy Paul J. NahinPrinceton University Press, 2009,424 pp.ISBN 978-0-691-13540-3Price US$29.95Reviewed by Anna Binnie, Sydney

This is a fun book, onethat you can take up

and put down, delve into a chapter and then go backto an earlier chapter. As the title suggests it is a patch-work of physics ideas and concepts, but not in thestandard textbook sense. It is well written with anamusing style that on occasion made me laugh outloud. Nahin shows how mathematics and physics in-teract to allow us to make sense of the world. He usesprimarily mechanics problems with a few exceptionsdelving into electric circuits and statistics. Eachchapter starts with a historical story or establishing aproblem, then solves the problem. He includes addi-tional problems which have detailed solutions at theend of the book.The book’s intended audience is upper high school

and undergraduate physics students and physicists ingeneral, and consequently most of the problems canbe solved using basic calculus or algebra, but there areexceptions. Unfortunately I feel that the book misseshis student audience unless a physics educator usessome of these problems as an enrichment exercise fortheir class and guides them through it.The book will also be of use to those involved in

physics outreach who want to demonstrate how mathsand physics work together. One of the sections attemptsto calculate how long it would take to fall into theSun, while another takes you on a random walk. I par-ticularly enjoyed the chapter on Mrs Perkins’s ElectricQuilt and was delighted to see a patchwork versionmade up by the author’s wife.

On the down side, the answers are not given in SIunits, but use miles per second or feet per secondsquared. Further, there is a chapter on Fourier transformsand Zeta functions with no explanation of what andhow they are used. His chapters on statistical physicsutilise his programs using Matlab, a program notavailable to high school or undergraduate students. Fi-

nally, there are a number of minor typographical errorsthat should have been corrected.

I really did enjoy this book despite its shortcomings.I would recommend it to anyone who enjoys physicsand as something to read on a long flight; easy andamusing reading that allows your brain to tick over ina relaxing way.

The QuantumStory: A History in40 MomentsBy Jim BaggottOxford University Press, 2011, 469pp.ISBN 978-0-19-956684-6Price US$29.95Reviewed by Mukunda Das,Australian National University,Canberra

One of the strangest ofquantum ideas is the in-distinguishability of par-ticles. In the quantum

world there are two distinct types of particles, bosonsand fermions. Bosons have a unique property: at lowtemperature, assemblies of identical bosons form asingle macroscopic wavefunction, behaving as onequantum object and manifesting as a superfluid or su-perconductor. Fermions, on the other hand, obeyFermi statistics and the ‘Pauli exclusion principle’,another special quantum property that forbids morethan one particle from sharing the same quantumstate.These two very different kinds of quantum statistics

were discovered in the mid-1920s. Today we knowthat Nature’s fundamental forces manifest a set ofintricate interactions between the two complementarytypes of quantum particles.

Quantum physics was born out of sheer necessity in1900, when a confronting puzzle was revealed in theway that objects radiate blackbody energy. With an in-spired guess, Max Planck gave a formula for blackbodyradiation that implied the existence of discrete energy‘packets’ or quanta. Planck’s packets became the cor-nerstone of all quantum hypotheses. In 1924 SatyendraNath Bose developed his statistical theory of photons,a new class of particles known as bosons. Bose gave thefirst complete justification of Planck’s hypothesis, freeof any and all gaps.


BOOK REVIEWS Compiled by John Macfarlane


The discussion above highlights the complex historicallinks in quantum theory’s origins. Those pioneeringleaps of faith, contradictions, and the final resolutions,are well documented in the works by historians ofquantum physics such as Helge Kragh, Jagdish Mehraand Helmut Rechenberg. It is difficult to present thecentury-old history of such an elusive subject, yet stillprovide a good understanding of its scope, from theinfinitesimal subatomic realm to the grandest cosmol-ogy.

Jim Baggott, a successful science writer, makes acommendable attempt in this book which is structuredaround forty pivotal moments, set in seven parts. Thefirst three parts cover philosophical aspects of quantumtheory with many interpersonal human stories.Schrödinger’s cat paradox is an example, where thestate of a cat (living or dead) is deciphered as a quantummeasurement. Parts 4 and 5 describe the rise of fieldtheory, up to the Standard Model of electro-weak in-teractions. Here one anticipates the appearance of the‘God particle’ (Higgs boson), super-symmetry andother phenomena: the apotheosis of CERN.The next six moments, in Part 6, cover Quantum

Realism – an abstract theme tracing how reality is un-derstood through our mental maps of particles, wavesand quantum measurements. The final five momentsin Part 7 trace the coming of Quantum Cosmology,and the unification of quantum theory with generalrelativity and gravity. Finally, there is mention ofcurrent efforts by high-energy and mathematicalphysicists toiling in the field of string theory, a subjectthat seems to abound in abstractions, with more looseends and less clear promise of final comprehension.

For a non-specialist these are hard topics in comingto grips with quantum physics. There is an implicationthat the quantum story is synonymous with that ofparticle physics. Such a view discounts a crucial areawithin the quantum realm, which is still probing theconsequences of indistinguishability: namely, collectiveeffects such as superconductivity and superfluidity.These underscore the truly universal applicability ofquantum theory. Despite these pitfalls, Baggott’s ‘Quan-tum Story’ is an enjoyable popular science book.

Order, Disorderand Criticality:AdvancedProblems of PhaseTransition TheoryBy Yurij Holovatch (ed.)World Scientific Press, SingaporeISBN 978-9-8127-0767-3Reviewed by Lee Weissel, WaggaWagga Christian College

This work is the secondvolume of review paperson advanced problems ofphase transitions and crit-

ical phenomena, following the success of the first volumein 2004. Broadly, the volume aims to demonstrate thatthe phase transition theory, which many believe experiencedits ‘golden age’ during the 1970s and 1980s, is far fromover and there is still a good deal of work to be done,both at the fundamental level and in respect of applica-tions.The work is not for the faint-hearted with the passion

of each of the contributors spilling out in the book. As anon-expert in this area, it did mean it was slower goingfor me, but the rewards for perseverance are there. Thetopics presented are broad in range and help capture thescope of this important field. Included in this work aretopics such as critical behaviour, critical dynamics, aspace–time approach to phase transitions, self-organisedcriticality, and exactly solvable models of phase transitionsin strongly correlated systems.

Consistent with the first volume, this book is basedon the review of lectures that were given at Lviv (Ukraine)at the Ising Lectures – a traditional annual workshop onphase transitions and critical phenomena which bringstogether scientists and other interested parties.

Although the work is designed for the experts andpostgraduate students, it is accessible to non-specialists.Chapter 3 is perhaps the best starting place as it helps toexplain some of the general premises of the field andusing Feynman’s sum over paths approach. This can feellike walking on familiar ground as the reader is broughtinto contact with new ideas, or indeed old ones presentedin new ways.The one drawback in any book based on lectures is

that a reader is tempted to ask questions either ofclarification or extension, especially in the use of some ofthe graphical representations, but alas cannot. Overall,even though primarily a technical work, the book is ex-tremely engaging.

BOOK REVIEWS Compiled by John Macfarlane

LASTEKLowest Profile 3-axisNanopositioners from MadCity Lab

The Nano-LPQ is the lowest profilehigh speed XYZ nanopositioneravailable and offers 75×75×50 µmtravel with picometer position noiseunder closed loop control. TheNano-LPQ features equal millisec-ond response times in XYZ, an in-tegrated sample holder, analog anddigital control with added scan syn-chronisation features, and compat-ibility with major image and au-

tomation software.Designed to minimise the moving

mass, lightweight sample holdersare integrated into the stage andrepresent the only moving compo-nent. This unusual design allowsthe three axes of motion to havematched resonant frequencies andstep response times. Equal 3-axisspeed is particularly useful for ap-plications like 3D particle track-ing. The Nano-LPQ uses internalposition sensors utilising proprietaryPicoQ™ technology to provide ab-solute, repeatable position meas-urement with sub-nanometer reso-lution under closed loop control.The Nano-LPQ is LabView™ and

C++ compatible and is suppliedwith Mad City Labs’ Nano-Route®3D software, for ease of use.Features:• Low profile, high speed, XYZ

motion• Built-in sample holders• Equal speeds on all three axes• Closed loop controlTypical applications:• Optical microscopy, easy to retro-fit

• Optical trapping experiments• Fluorescence imaging• Particle tracking• Single molecule spectroscopyThe Nano-LPS Series is the lowest

profile 3-axis piezo nanopositioningsystem suitable for applications suchas super resolution (SR) microscopyand force microscopy. The Nano-LPS series continues the innovativedesign approach originally intro-duced by Mad City Labs. At only20 mm tall with 83 mm wide centreaperture, the Nano-LPS series isdesigned for practical microscopyusers interested in nanoscale phe-nomena. The Nano-LPS series fea-tures up to 300 microns of motionper axis and picometer precisionunder closed loop control. The lowheight of the Nano-LPS Series allowsit to be easily integrated into existinginverted optical microscopes. Likethe related Nano-LP Series, theNano-LPS Series is ideal for de-manding microscopy applicationswhich require long range travel,fast scan rates, and three axes ofmotion.

Mad City Labs proprietary Pi-coQ™ sensors enable picometer po-sition noise with ultra high stability,which is important for demandingapplications such as SR microscopytechniques.Features:• Lowest profile 3-axis nanoposi-

tioner available• Large aperture for standard 3″

slides • 100 µm, 200 µm and 300 µm

ranges of motion (XYZ) underclosed loop control

Typical applications:• Optical microscopy, easy to retro-fit

• Optical trapping experiments• Fluorescence imaging• Alignment• Single molecule spectroscopy

Ocean Optics acquiresSandhouse Design

Ocean Optics extended its productfamily after acquiring SandhouseDesign, LLC.

Sandhouse developed a uniqueline of high-powered LED lightsources for research and spectroscopicapplications.These products have been widely

used in biotechnology, process con-trol and industrial applications.

LED Light Sources

These ergonomic andsmartly designed fibre-coupled LED lightsources are ideal for flu-

orescence, spectroscopy and generalfibre illumination applications. TheUltra LED high-power light sourcescan be operated in continuous orexternal trigger modes. Available inUV, VIS and Infrared.


PRODUCT NEWS

SIR ScanningSpectrometersThe SIR Scanning Spectrometer Se-ries from Ocean Optics providesyou a range of fibre-based spectraldata collection in a detection in-strument that is built to last andalways reliable.These SIR Scanning Spectrome-

ters feature USB 2.0-compliant in-terfaces that provide fast data trans-fers. Plus, the included softwarecan be used to control all of yourSIR spectrometer’s functions as wellas analyse data.The SIR spectrometer family in-

cludes:• SIR-1700: 400–1700 nm• SIR-2600: 0.9–2.6 µm• SIR-3400: 1.0–3.4 µm• SIR-5000: 2.0–5.0 µm• SIR-6500: 3.0–6.5 µm

Deep UV LEDs

Sandhouse Deep UV LEDs areavailable in a wide range of wave-lengths and package sizes. Thesedevices are manufactured using Al-GaN/GaN technology, which en-ables a new generation of highband-gap energy opto-electronicsdevices, able to perform down to240 nm.

LATEST NEWSFROM TOPTICAPHOTONICSMulti-Colour Systems –Multi-Laser Engines andTunable VISible Lasers

Three exciting new systems are nowavailable from Toptica:iChrome MLE-LMulti Laser Engine with up to threediode lasers and one DPSS laserfully integrated in one compactbox.• Multi-line laser with up to four

laser lines• Wavelengths diode lasers: 405,

445, 488 and 640 nm (375, 473,660, 785 nm and others on re-quest)

• Wavelengths DPSS laser: 532and 561 nm (505, 515, 594 nmand others on request)

iChrome MLE-SAll-diode Multi Laser Engine withup to four diode lasers fully inte-grated in one compact box.• Multi-line laser with up to four

diode laser lines• Available wavelengths: 405, 445,

488 and 640 nm (375, 473, 660,785 nm and others on request)

• High free-space and fibre coupledoutput power levels

Common to both MLE modelsThe individual lasers are efficientlycombined and delivered free beamor via an all-in-one PM/SM fibreoutput. The microprocessor con-trolled system enables flexible OEMintegration. High-speed analogueand digital modulations allow fastswitching of laser wavelength andintensity.

TOPTICA’s ingenious COOLAC

technology automatically aligns thesystem with a single push of a but-ton. This feature ensures a constantoptical output level even understrongly varying ambient conditionsand completely eliminates the needfor manual realignment – makingthe iChrome MLE the most ad-vanced multi-line laser system onthe market.• Single mode, polarisation main-

taining fibre output or free beamCOOLAC technology for highestcoupling efficiency, ultimate sta-bility and drop-shipment capa-bility

• Direct modulation and fastswitching between wavelengths

• True one-box solution with in-tegrated electronics

• Unique features: COOLAC, FINEand SKILL technology

• Most compact and cost effectivesolution for multicolour biopho-tonic applications

iChrome TVISOur ultrachrome picosecond laseris:• Continuously tunable in the vis-

ible range of 488–640 nm• Fibre coupled output (single-

mode)• Fully automated operation• Pure colour, narrow emission

bandwidth (<3 nm)• Perfectly suited for fluorescence

lifetime imaging microscopy(FLIM) or optical testing of com-ponentsThe iChrome TVIS laser system

is a fibre laser with the flexibility toset automatically the laser outputto any wavelength in the visible(488–640 nm). The coherent laseroutput ensures that the visible lightexhibits the best intensity noise per-formance and the use of polarisationmaintaining optical components a


PRODUCT NEWS

stable linear polarisation of the fibrecoupled output beam is achieved.The entire laser system is extremelyuser friendly: No alignment proce-dures of any optical componentsdistract the user from the main task– to produce results.

DL-RFA-SHG pro 2 Watt @589 nm, single line forsodium cooling

The new DL RFA SHG pro is anarrow-band tunable continuouswave laser for sodium cooling. Thesystem is based on a near-IR diodelaser in the successful ‘pro-design’(DL 100/pro design, 1178 nm),with a subsequent Raman fibre am-plifier (RFA) and a resonant frequencydoubling stage (SHG pro).The DL RFA SHG pro features a

spectral linewidth below 1 MHzand 20 GHz mode-hop free tuning.For system operation, no water cool-ing and no external pump is required.The power scalable approach of theDL RFA SHG pro also offers solu-tions for other high power applica-tions such as sodium LIDAR, medicaltherapy or super resolution mi-croscopy. Customised systems withhigher output powers up to 10 Ware available on request. Wavelengthsbetween 560 and 620 nm will soonbe available as customised solutions.

FemtoFiber pro – theproduct family is expanded

After the successful introduction ofthe FemtoFiber pro IR, NIR andSCIR models, TOPTICA is nowtaking the final step to also includethe remaining system variants suchas tunable visible (TVIS), tunable

near-infrared (TNIR) and tunableultra compressed pulse (UCP). Op-tions such as variable repetition rate(VAR) and a phase-locked loop LaserRepetition rate Control (LRC) byTOPTICA’s well-established PLL-electronics are rounding up theFemtoFiber pro product family.The first and fastest of the new

models, UCP, shows short pulses inthe range down to 13 fs, the fastestavailable on the market from aturnkey SAM modelocked fibre lasersystem.

The TVIS expands the super-con-tinuum generation (SCIR) by a tun-able second harmonic generationand allows transferring femtosecondpulse generation into the visiblewavelength range from 490 to 700nm.The TNIR variant finally adds a

new feature to the FemtoFiber profamily. As opposed to the TVIS, ituses the high-band continuum(>1560 nm) for second harmonicgeneration. This continuum part isa solitonic pulse and therefore needsno pulse compression. The outputwavelength can be tuned from 800to 1100 nm. This variant was notpreviously available in the FFS prod-uct family.For more information please contactLastek at [email protected] Pty LtdAdelaide University – Thebarton Campus10 Reid StThebarton, SA 5031Aus 1800 882 215; NZ 0800 441 005Tel: +61 8 8443 8668Fax: +61 8 8443 8427e-mail: [email protected]: www.lastek.com.au

WARSASHLightweight BenchtopVibration Isolation

Warsash Scientific is pleased to an-nounce a new lightweight benchtopvibration isolation system from Ki-netic Systems, Inc. Specifically de-signed for portability, the ELpF canbe easily repositioned on the bench-top, even with a load and in float.Its unique, self-contained designprovides this without causing dam-age to the vibration isolators.

An economical alternative toheavy- weight models, the Ergonom-ic Low-Profile-Format platform pro-vides vibration isolation for sensitivedevices. It features a load capacityof 100 or 300 lbs. in a lightweight,ergonomic system.The platform has a low profile

(only 3″ high), uses a small tabletop(16″×19″ standard) and weighs 40lbs., making it very portable. Er-gonomic features include gaugestilted upward for easier viewing andrecessed handles for easy carrying.

Designed for use in laboratoriesand Class 100 cleanrooms, the ELpFplatform is ideal for supportingatomic force microscopes, micro-hardness testers, analytical balances,profilometers, and audio equip-ment.

Self-levelling and active-air iso-lation give the platform low naturalfrequencies (1.75 Hz vertical, 2.0Hz horizontal) and typical isolationefficiencies of 95% (vertical) and

94 AUSTRALIAN PHYSICS 48(3) | MAY–JUNE 2011

92% (horizontal) at 10 Hz.Other tabletop sizes can be cus-

tomised per specifications. The top,which can be ordered with or with-out mounting holes, can be alu-minium plate, ferromagnetic stainlesssteel, plastic laminate, or anti-staticlaminate.For more details on this or other vibrationisolation equipment, [email protected].

Real-Time OperatingSystem for SystemsIntegration

PI (Physik Instrumente), the leadingmanufacturer of piezoceramic drivesand positioning systems, offers areal-time module as an upgrade op-tion for the host PC and also theconnection of the GCS (PI GeneralCommand Set) software drivers.The module is based on KnoppixLinux in conjunction with a pre-configured Linux real-time extension(RTAI).The use of real-time operating

systems on the host PC allows it tocommunicate with other systemcomponents, e.g. a vision system,without time delays with discretetemporal behaviour and high systemclock rate.

A library which is 100% com-patible with all other PI GCS li-braries is used for the communica-tion with the real-time system. AllPI GCS host software available forLinux can be run on this system.The real-time system running in

the real-time kernel can be used tointegrate PI interfaces and additionaldata acquisition boards for control.

Open functions to enable you toimplement your own control algo-rithms are provided. Data, such aspositions and voltages, is recordedin real time, and pre-defined tables,with positions, for example, areoutput in real time to the PI interfaceand to additional data acquisitionboards.

You can program your own real-time functions in C/C++, MAT-LAB/ SIMULINK and SCILAB.The system includes a PI GCS

server, which allows the system tobe operated as a blackbox usingTCP/IP, via a Windows computer,for example.The system can be installed on a

PC or booted directly as a liveversion from the data carrier. A freedemo version with restricted func-tionality is available.For more information on the real timeoperating software or other PIpositioning equipment, [email protected].

E-618: 3.2 kW Peak Powerfor New Piezo Amplifier

Available from Warsash Scientificis the new PI (Physik Instrumente)E-618 high power amplifier for ul-tra-high dynamics operation of PIC-MA® piezo actuators.The amplifier can output and

sink a peak current of 20 A in thevoltage range between -30 and +130V. The high bandwidth of over 15kHz makes it possible to exploitthe dynamics of the PICMA® actu-ators. This type of performance isrequired in active vibration cancel-

lation and fast valve actuation ap-plications.The E-618 also comes with a

temperature sensor input to shutdown the amplifier if the maximumallowed temperature of the piezoceramics has been exceeded. This isa valuable safety feature given theextremely high power output.The E-618 is available in several

open-loop and closed-loop versionswith analogue and digital inter-faces.For more information on these and therange of other PI products, [email protected] Scientific Pty LtdTel: +61 2 9319 0122Fax: +61 2 9318 2192Web: www.warsash.com.au

New Sensors ImprovePrecision of S-340 Tip/TiltMirror

Warsash Scientific is pleased to an-nounce the release of the new S-340 piezo tip/tilt mirror platformfrom PI (Physik Instrumente),equipped with new high-resolutionstrain gauge sensors.The S-340 now achieves a reso-

lution of 20 nrad at angles of 2mrad about both orthogonal axes.This large mirror platform is used

for optics with diameters of up to100 mm (4 inches) and achieves aresonant frequency of 900 Hz for amirror of 50 mm diameter.The S-340 can be operated by

the new, low-cost E-616 controller.Together, they form a compact,high-performance solution for beamcontrol and image stabilisation as

95MAY–JUNE 2011 | 48(3) AUSTRALIAN PHYSICS

employed in astronomy, laser ma-chining or optical metrology, forexample.For more information on the S-340 Tip/TiltMirror platform or other Positioningequipment from PI, [email protected].

COHERENTQuantel release newdual-pulse later forPIV studies

Quantel has released EverGreen, anew dual-pulse Nd:YAG laser forPIV (particle imaging velocimetry)studies.

EverGreenincorporatesdual laser cavi-ties and com-mon harmonic

generation to produce two preciselyoverlapping beams. The lasers areintegrated onto a commonmonoblock platform to guaranteeperfect alignment and uniform lightsheets. The power supplies and tim-ing electronics are also integratedinto a single housing. The EverGreensystem requires no specialised in-stallation and no adjustments ofany kind. Pulse energies of 70 mJ,145 mJ and 200 mJ are available.EverGreen is an ideal choice for awide range of PIV applications andthe simplified operation allows theresearcher to concentrate on flowfieldresults rather than the laser.For further information please contactPaul Wardill on [email protected] Scientific116 Sir Donald Bradman DriveHilton, SA 5033Tel: +61 8 8150 5200Fax: +61 8 8352 2020Web: www.coherent.com.au

Brilliant Q-SwitchedNd:YAG Lasers

The Brilliant laser from Quantelfeatures a compact and reliableNd:YAG oscillator of medium en-ergy (up to 850 mJ at 1064 nm)with a full range of “plug and play”harmonic options (up to a 5th har-monic generator) as well as OPO’sfor tunable output. With over 1000units installed worldwide, the Bril-liant laser is a proven scientificworkhorse offering exceptional sta-bility, reliability and ease of use.For further information please contactPaul Wardill on [email protected] Scientific116 Sir Donald Bradman DriveHilton, SA 5033Tel: +61 8 8150 5200Fax: +61 8 8352 2020Web: www.coherent.com.au

Verdi G Series expanded to10 Watts of 532 nm outputpower

New! Photonics West announcesrelease of the Coherent Verdi G10DPSS-OPSL laser, the latest additionin the field-proven Verdi G productline with an output power of 10 W(532 nm CW). Featuring Coherent’snext-generation of economical op-tically pumped semiconductor laser(OPSL) technology it offers a sig-nificantly smaller footprint, low-noise output and power-independentbeam quality for higher power ap-plications.For further information please contactPaul Wardill on [email protected] Scientific116 Sir Donald Bradman DriveHilton, SA 5033Tel: +61 8 8150 5200Fax: +61 8 8352 2020Web: www.coherent.com.au

96 AUSTRALIAN PHYSICS 48(3) | MAY–JUNE 2011

12 – 13 August 2011Summer School on Functional Imaging in Radiotherapy:Australasian College of Physical Scientists & Engineers inMedicineDarwin, NT

14 – 18 August 2011Engineering and Physical Sciences in Medicine and theAustralian Biomedical Engineering ConferenceDarwin Convention and Exhibition Centre, NT

28 August – 1 September 2011IQEC/CLEO Pacific Rim 2011Sydney, NSW

16 – 19 October 2011Australian Radiation Protection Society ConferenceMelbourne, VIC

30 November – 2 December 2011Solomonoff 85th Memorial ConferenceMelbourne, VIC

31 January – 3 February 2012Thirty-sixth Annual Condensed Matter & Materials MeetingCharles Sturt University, Wagga Wagga, NSW

25 February 2012Queensland Astronomy Education Conference (QAEC)Brisbane, QLD

4 – 11 July 2012Thirty-sixth International Conference on High EnergyPhysics, ICHEP2012Melbourne Convention and Exhibition Centre, VIC

5 – 10 August 2012Nuclei in the Cosmos 2012Cairns Convention Centre, QLD

18 – 23 November 2012Fifteenth International Conference on Small-angleScattering, SAS 2012Sydney, NSW

CONFERENCES IN AUSTRALIA 2011–2012

C O N F E R E N C Erisk perceptions: safety & security

we invite you to attend the

register now to attend the conference

www.arps.org.au

The 2011 ARPS Conference promises to be an exciting event with emphasis on the conference theme of Risk Perceptions: Safety and Security. The conference program will explore this theme and will include presentations from an interesting array of speakers, enjoyable social functions, pre conference workshops and a post conference Technical Tour.

program at a glance keynote speakers

C O N F E R E N C E

16-19 October 2011Crown Promenade HotelMelbourne

AUSTRALASIAN RADIATION PROTECTION SOCIETYwww.arps.org.au

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97MAY–JUNE 2011 | 48(3) AUSTRALIAN PHYSICS

High PerformanceNd:YAG &

Tuneable LasersNanosecond Nd:YAG lasers

Dye lasers & solid state OPO's

Multipulse lasers

Phone

Fax

Frecall

(08) 8150 5200

(08) 8352 2020

1800 202 030

116 Sir Donald Bradman Drive, Hilton SA 5033

www.coherent.com.au

the birth of nuclear physics measuring rutherford’s impact...

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