Tag Archives: physics

Copenhagen: at the nexus of drama, science and history

“History is what you remember as having happened, not what actually happened.” It was this thought, shared by Michael Frayn in a recent discussion with the Director of the Science Museum, that that lies at the heart of Copenhagen, the most famous work of the playwright and novelist.

Michael Frayn has a long-held interest in philosophy and the sciences, notably in his book The Human Touch: Our Part in the Creation of the Universe. However, he is best known for his Tony-award winning play, which was staged at the National Theatre in London and later on Broadway in New York.

Copenhagen is an enduring example of how the history of science can inform dramatic work, and vividly demonstrates the power of drama to explore history, bringing scholarly discussions to the attention of a wide audience.

Ian Blatchford, Director of the Science Museum, in conversation with Michael Frayn

Ian Blatchford, Director of the Science Museum (right), in conversation with playwright Michael Frayn

The play examines the uncertainties surrounding the 1941 meeting between two Nobel prize winning physicists in German-occupied Copenhagen at the height of World War II.

Physicist Werner Heisenberg, head of the German nuclear energy project, and his Danish counterpart Niels Bohr, who later worked on the Manhattan Project, discussed the possibility of building an atomic bomb.

There was no accurate record of what was said at the meeting, and there are conflicting recollections made years later in unsent letters and transcripts from Heisenberg’s internment shortly after the war at Farm Hall, a bugged house near Cambridge. As a consequence, Frayn’s dramatisation of the meeting has itself become part of the historical record.

Those listening to Michael Frayn in the audience, included his wife, the biographer Claire Tomalin, Tony award-winning director of Copenhagen, Michael Blakemore, and Niels Bohr’s great grand-daughter, Esme Dixon. Prof Jon Butterworth of University College London, science biographer Graham Farmelo, Science Museum Trustee Howard Covington, Jean M Franczyk, Director of the Museum of Science & Industry and Andrew Nahum, Principal Curator of Technology and Engineering, were also present for the fascinating discussion.

You can watch the full conversation between Michael Frayn and the Science Museum Group’s Director, Ian Blatchford, here.

JJ Thomson’s Cathode-ray tube

Rupert Cole celebrates JJ Thomson’s birthday with a look at one of the star objects in our Collider exhibition.

Holding the delicate glass cathode-ray tube in my hands, once used by the great physicist JJ Thomson, was an incredible treat, and an experience I will never forget.

I had read lots about Thomson’s famous experiments on the electron – the first subatomic particle to be discovered – but to actually see and touch his apparatus myself, to notice the blackened glass and the tube’s minute features that are omitted in books, brought the object to life. History suddenly seemed tangible.

Using more than one cathode-ray tube in 1897 for his experiments, Thomson managed to identify a particle 1,000 times smaller than the then known smallest piece of matter: a hydrogen atom. Cambridge’s Cavendish Laboratory, where Thomson spent his scientific career, also has an original tube in its collection.

Each tube was custom-made by Thomson’s talented assistant, Ebenezer Everett, a self-taught glassblower. Everett made all of Thomson’s apparatus, and was responsible for operating it – in fact, he generally forbade Thomson from touching anything delicate on the grounds that he was “exceptionally helpless with his hands”.

The quality of Everett’s glassblowing was absolutely crucial for the experiments to work.

Cathode-rays are produced when an electric current is passed through a vacuum tube. Only when almost all the air has been removed to create a high vacuum – a state that would shatter ordinary glass vessels – can the rays travel the full length of the tube without bumping into air molecules.

Thomson was able to apply electric and magnetic fields to manipulate the rays, which eventually convinced the physics world that they were composed of tiny particles, electrons, opposed to waves in the now-rejected ether.

Find out more about Thomson and the story of the first subatomic particle here, or visit the Museum to see Thomson’s cathode-ray tube in the Collider exhibition. If you’re interested in the details of how Thomson and Everett conducted their experiments visit the Cavendish Lab’s outreach page here.

A Nobel Tradition

Content Developer Rupert Cole explores the most famous science prize of all, and some of its remarkable winners. 

Today, science’s most prestigious and famous accolades will be awarded in Stockholm: the Nobel Prize.

Before we raise a toast to this years’ winners in physics, Peter Higgs and Belgian François Englert, let’s take a look back at the man behind the Prize, and some of its winners.

Alfred Nobel

A Swedish explosives pioneer who made his millions from inventing dynamite, Alfred Nobel left in his will a bequest to establish an annual prize for those who have “conferred the greatest benefit to mankind”, across five domains: physics, chemistry, physiology or medicine, literature and peace. To this end, he allocated the majority of his enormous wealth.

Alfred Nobel. Credit: Science Museum / SSPL

Alfred Nobel. Credit: Science Museum / SSPL

When Nobel’s will was read after his death in 1896, the prize caused an international controversy. Unsurprisingly, Nobel’s family were not best pleased, and vigorously opposed its establishment. It took five years before it was finally set up and the first lot awarded – the 1901 physics accolade going to Wilhelm Rontgen for his 1895 discovery of x-rays.

Paul Dirac’s maternal mortification

When the phone rang on 9 November 1933, the exceptionally gifted yet eccentric Paul Dirac was a little taken back to hear a voice from Stockholm tell him he had won the Nobel Prize.

The looming press attention, which had always surrounded the Nobels, made the reclusive Dirac consider rejecting the award, until Ernest Rutherford – JJ Thomson’s former student and successor as Cavendish professor – advised him that a “refusal will get you more publicity”.

Under different circumstances Rutherford had been similarly “startled” when he found out he was to be given a Nobel – a physicist through and through, he was awarded the 1908 Prize in Chemistry, joking his sudden “metamorphosis into a chemist” was very unexpected.

Dirac shared the 1933 physics prize with Erwin Schrödinger – famed for his eponymous equation and dead-and-alive cat – for their contributions to quantum mechanics. Each was allowed one guest at the award ceremony held at the Swedish Royal Academy of Science. Schrödinger brought his wife, Dirac brought his mother.

Quantum theorists: Wolfgang Pauli and Paul Dirac, 1938. Credit: CERN

Quantum theorists: Wolfgang Pauli and Paul Dirac, 1938. Credit: CERN

Florence Dirac did what all good mothers do: embarrass her son in every way imaginable. The first incident came at a station café in Malmo, where in this unlikely setting an impromptu press conference took place.

Dirac, who had been described by the British papers as “shy as a gazelle and modest as a Victorian maid,” was asked “did the Nobel Prize come as a surprise?” Before he could answer, Dirac’s mother butted in: “Oh no, not particularly, I have been waiting for him to receive the prize as hard as he has been working.”

The next embarrassment came when Mrs Dirac failed to wake up when the train reached Stockholm. She was ejected by a guard, who had thrown her garments and belongings out of the carriage window. The Diracs arrived late, and meekly hid from the attention of the welcoming party – who had been wondering where they were.

The third and final maternal faux pas came at Stockholm’s Grand Hotel. The pair had been booked into the finest room – the bridal suite. Mrs Dirac, displeased, demanded a room of her own, which Dirac paid for out of his own pocket. It doesn’t matter if you’ve co-founded quantum mechanics, predicted antimatter and won the Nobel Prize; mothers will be mothers.

Peter’s Pride

Like other humble laureates before him, Peter Higgs wished to duck out of the press furore surrounding the Nobel. At the time of the announcement on the 8th October there was a nail-biting delay. The cause? The Nobel committee could not get hold of Higgs, who had turned his phone off and planned to escape to the Scottish Highlands.

As Peter Higgs revealed to me at the opening of the Collider exhibition at the Science Museum, if it was not for a dodgy Volkswagen beetle or public transport, Peter would have made it to the Highlands on Nobel day. Instead, he just laid low in Edinburgh.

Peter Higgs (right) with friend Alan Walker and the personalised bottles of London Pride at Collider opening. Credit: Science Museum.

Peter Higgs (right) with friend Alan Walker and the personalised bottles of London Pride at Collider exhibition opening. Credit: Science Museum.

At the Collider launch last month, we celebrated with Higgs in the appropriate way: over a personalised bottle of London Pride ale – the same beverage he chose in favour of champagne on the flight home from CERN’s public announcement of the Higgs boson discovery. So, when Englert and Higgs receive the honour today, let’s all raise two glasses: an English Ale and a Belgian Blonde!

For more on many of the Nobel prize-winning discoveries in physics history, including those of Dirac, Englert and Higgs, visit the Collider exhibition at the Science Museum.

Celebrate the Nobel Prize at the Science Museum

Roger Highfield, Director of External Affairs at the Science Museum, celebrates the 2013 Nobel Prize for Physics ahead of the opening of our Collider exhibition next month.      

Congratulations to Briton Peter Higgs and Belgian François Englert, winners of the 2013 Nobel Prize for Physics “for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles, and which recently was confirmed through the discovery of the predicted fundamental particle, by the ATLAS and CMS experiments at CERN’s Large Hadron Collider.”

A few minutes ago, after an unusual delay, the Royal Swedish Academy of Sciences announced the winners of the physics prize in Stockholm, ending this chapter of the quest for new elementary particles, the greatest intellectual adventure to date.

Ian Blatchford, Director of the Science Museum, comments: “That it has taken decades to validate the existence of the Higgs Boson illustrates the remarkable vision of the theoretical work that Higgs, Francois Englert and others did with pen and paper half a century ago, one that launched an effort by  thousands of scientists and inspired a staggering feat of engineering in the guise of the Large Hadron Collider.

What is the Higgs? Here’s all you need to know, in just 90 seconds, from Harry Cliff, a Cambridge University physicist working on the LHCb experiment and the first Science Museum Fellow of Modern Science

Although the identity of the winners has been a closely-guarded secret, many have speculated that those who played a central role in discovery of the long-sought Higgs, notably the emeritus Edinburgh professor himself, were leading contenders for a place in history.

The Science Museum has been so confident that the Large Hadron Collider would change our view of nature that we have invested more than £1 million, and worked closely with the European Organization for Nuclear Research, CERN, to celebrate this epic undertaking with its new exhibition, Collider: step inside the world’s greatest experiment, which opens to the public on 13 November. 

Here Higgs explains how the Large Hadron Collider works during a visit to what is now Cotham School, Bristol, where he was once a pupil.

In July 2012, two separate research teams at CERN’s £5 billion Large Hadron Collider reported evidence of a new particle thought to be the Higgs boson, technically a ripple in an invisible energy field that gives most particles their mass.

This discovery represented the final piece of the Standard Model, a framework of theory developed in the late 20th century that describes the interactions of all known subatomic particles and forces, with the exception of gravity.

Nima Arkani-Hamed, a leading theoretical physicist at the Institute for Advanced Study in Princeton who will attend the launch of Collider, bet a year’s salary the Higgs will be found at the LHC.

Another speaker at the Collider launch, the world’s most famous scientist, Prof Stephen Hawking, lost a $100 bet he made against the discovery (though he is adamant that Higgs deserves the Nobel Prize).

Higgs, who refuses to gamble, told me just before the LHC powered up that he would have been puzzled and surprised if the LHC had failed in its particle quest. “If I’m wrong, I’ll be rather sad. If it is not found, I no longer understand what I think I understand.”

When Higgs was in the CERN auditorium last year to hear scientists tell the world about the discovery, he was caught reaching for a handkerchief and dabbing his eyes.  On the flight home, he celebrated this extraordinary achievement with a can of London Pride beer.

The Science Museum hoped to have the can, now deemed a piece of history Alas, Higgs had dumped it in the rubbish before we could collect it. However, the museum does possess the champagne bottle that Higgs emptied with his friends the night before the big announcement.

The champagne bottle Peter Higgs drank from, the night before the Higgs boson discovery was announced to the world. Credit: Science Museum

The champagne bottle Peter Higgs drank from, the night before the Higgs boson discovery was announced to the world. Credit: Science Museum

The modest 84-year-old  is now synonymous with the quest: the proposed particle was named the Higgs boson in 1972.

But there have been demands that the particle be renamed to acknowledge the work of others. Deciding who should share this Nobel has been further complicated because a maximum of three people only can be honoured (prompting many to question the criteria used by the Nobel committee).

The LHC, the world’s most powerful particle accelerator, is the cumulative endeavour of around ten thousand men and women from across the globe. In recognition of this the Collider exhibition will tell the behind-the-scenes story of the Higgs discovery from the viewpoint of a young PhD student given the awesome task of announcing the discovery to her colleagues (though fictional, the character is based on Mingming Yang of MIT who is attending the launch).

However, although one suggestion is to allow the two research teams who discovered the Higgs boson to share the accolade, the Nobel committee traditionally awards science prizes to individuals and not organizations (unlike the Nobel Peace Prize).

Instead, the Nobel committee honoured the theoreticians who first anticipated the existence of the Higgs.

Six scientists published the relevant papers in 1964 though, as Belgium’s Robert Brout died in 2011, there were five contenders (the Nobel Prize cannot be given posthumously).

In August 1964, François Englert from the Free University of Brussels with Brout, published their theory of particle masses. A month later, while working at Edinburgh University, Higgs published a separate paper on the topic, followed by another in October that was – crucially – the first to explicitly state the Standard Model required the existence of a new particle. In November 1964, American physicists Dick Hagen and Gerry Guralnik and British physicist Tom Kibble added to the discussion by publishing their own research on the topic.

Last week, Prof Brian Cox of Manchester University, who works at CERN, said it would be ‘odd and perverse’ not to give the Nobel to Peter Higgs, and also singled out Lyn ‘the atom’ Evans, the Welshman in charge of building the collider, as a candidate.

And the two likeliest winners were named as Peter Higgs – after whom the particle was named – and François Englert, according to a citation analysis by Thomson Reuters.

Today’s announcement marks the formal recognition of a profound advance in human understanding, the discovery of one of the keystones of what we now understand as the fundamental building blocks of nature.

Discover more about the Higgs boson and the world’s largest science experiment in our new exhibition, Collider, opening 13th November 2013.

If Particle Physics Did Parties…

With the Collider exhibition now open, Content Developer Rupert Cole explores some famous physics parties of the past. 

As it happens, Carlsberg did do particle physics. The Danish beer giant was an unlikely benefactor of the Niels Bohr Institute – one of the great centres of theoretical physics research.  

And Bohr himself even lived at the brewery’s “Honorary Residence” after winning the Nobel Prize, complete with a direct pipeline supplying free Carlsberg on tap! Just imagine what untold influence lager had on those groundbreaking discussions of quantum theory during Bohr’s thirty-year stay…

Niels Bohr’s luxury mansion at the Carlsberg Brewery, 1963. Credit: CERN

Niels Bohr’s luxury mansion at the Carlsberg Brewery, 1963. Credit: CERN

After my last blog about bubble chambers and beer, I thought, since it’s the festival season, why not go the whole hog and explore a few partying highlights from the history of physics.

The first Cavendish Laboratory Dinner, 1897

During the Christmas Holidays of 1897, the staff and students of Cambridge’s Cavendish Laboratory had a memorable dinner party at the Prince of Wales’ Hotel.

It was a “rollicking affair”. JJ Thomson, Professor of the Laboratory, was remembered by a student to be “as happy as a sand-boy”. Thomson, of course, had been very busy that year discovering the subatomic world. Another physicist, Paul Langevin, sang La Marseillaise with such fervour that a French waiter embraced him.

That night was the beginning of a Cavendish tradition: singing physics through the medium of light opera. Lyrics about atoms and ions were put to Gilbert and Sullivan tunes, long before Tom Lehrer. The next day, Thomson remarked that “he had no idea that the Laboratory held such a nest of singing birds”.

It must have been quite a noise, as the Proctors of the University came to enquire at the hotel what the “proceedings” were about. Fortunately, they did not enter the room – “being,” Thomson supposed, “impressed, and I have no doubt mystified, by the assurance of the landlord that it was a scientific gathering of research students”.

JJ Thomson and his Cavendish students, 1897. Credit: Cavendish Laboratory

JJ Thomson and his Cavendish students, 1897. Credit: Cavendish Laboratory

The first dinner was such a hoot that it became an annual occasion. The merry songs that emerged at these events were soon immortalised in regular published editions of The Post-Prandial Proceedings of the Cavendish Society.

Feynman’s entire anecdotal oeuvre

“There’s so much fun to be had”

Not many Nobel prize-winning physicists can say they’ve played the frying pan in a samba band at Rio’s Carnival; made complex calculations on napkins in strip bars; or spent a sabbatical on the Copacabana drinking themselves teetotal and seducing air-hostesses. A raconteur of almost mythic proportions, Richard Feynman had a natural aptitude for partying.

Costume parties really brought out the showman in Feynman. He was very versatile, boasting a clothing repertoire that ranged from a Ladakhi monk to God. But it was on one April Fools’ Day that Feynman surpassed himself. Sat primly on a chair, looking regally and nodding graciously to other guests, Feynman was the very image of Queen Elizabeth II – wig, white hat, green dress, purse and gloves. At the end of the evening, he performed his royal finale: a striptease!

We must unfortunately cut short of the entire Feynman backlog of anecdotes, so instead click here for a video of Feynman playing “orange juice” on the bongos.

Higgs’ champagne moment, 2012

On a Saturday night in Sicily, Peter Higgs was dining with friends when the phone rang. Fellow physicist John Ellis had called to tell Higgs to come to CERN. Swiftly, travel arrangements were made and another bottle of white ordered. History was being written.

A few evenings later, Higgs was in Ellis’ Geneva home sharing a bottle of champagne with family and friends – that day he had read a note that confirmed the particle he had predicted to exist 48 years ago had finally been found.

The following day, on 4th July 2012, CERN held a conference announcing to the world the discovery of the Higgs Boson. Emotions running high in the packed lecture hall, Higgs likened the experience to “being at a football match when the home team has won”. Fittingly then, on the Easyjet flight home to Edinburgh, he turned down more champagne in favour of a can of London Pride.

See JJ Thomson’s 1897 cathode-ray tube, Peter Higgs’ champagne bottle, and experience more great moments of discovery at Collider, a new exhibition at the Science Museum.

CERN: 60 years of not destroying the world

Ahead of November’s opening of the Collider exhibition, Content Developer Rupert Cole celebrates six decades of research at CERN, the European Organization for Nuclear Research. 

Just before the Large Hadron Collider first turned on in September 2008, there was (in some quarters) a panic that it would destroy the world.

Doomsday was all over the media. “Are we all going to die next Wednesday?” asked one headline. Even when CERN submitted a peer-reviewed safety report in an attempt to allay fears, it didn’t altogether quash the dark mutterings and comic hysteria: “Collider will not turn world to goo, promise scientists.” 

This cartoon is pinned on the wall of the theory common room at CERN. Image credit: Mike Moreau

This cartoon is pinned on the wall of the theory common room at CERN. Image credit: Mike Moreu

In case you were wondering, the LHC has subsequently proved to be completely safe, and has even found the Higgs Boson to boot.

In fact, this isn’t the first time CERN has provoked fears of world destruction. In the lead-up to the signing of CERN’s founding Convention – 60 years ago this month – the proposed organisation was greatly hindered and influenced by apocalypse anxiety.

Only, back then, it had nothing to do with micro black holes swallowing the earth or strangelet particles messing with matter. No such exotic phenomena were needed. Just the mention of the words nuclear and atomic was enough to provoke serious paranoia in the Cold-War climate.

In 1949 Denis de Rougement, a Swiss writer and influential advocate for a federal Europe, attended the European Cultural Conference — one of the early conferences in which a “European Centre for Atomic Research” was discussed. “To speak of atomic research at that time,” de Rougement reflected, “was immediately to evoke, if not the possibility of blowing up the whole world, then at least preparations for a third world war.”

The press undoubtedly subscribed to the more extreme school of thought. On the second day of the conference, all the scientists present had to be locked in a chamber for protection as they had been pestered so severely by journalists on the previous day.

In some of the initial discussions, a nuclear reactor as well as an accelerator was proposed for the European research centre. It was carefully stressed that no commercial applications would be developed and all military work scrupulously excluded.

The French, who led these early proposals, removed the director of the French Atomic Energy Commission, the communist-leaning Frederic Joliot-Curie, after J. Robert Oppenheimer (of Manhattan Project fame) stated the Americans wouldn’t support a project that included a senior figure with Soviet sympathies.

Left to right: J. Robert Oppenheimer, Isidor I. Rabi, Morton C. Mott-Smith, and Wolfgang Pauli in a boat on Lake Zurich in August 1927. Image credit: CERN

Left to right: J. Robert Oppenheimer, Isidor I. Rabi, Morton C. Mott-Smith, and Wolfgang Pauli in a boat on Lake Zurich in August 1927. Image credit: CERN

The nuclear reactor was dropped when Hungarian-American physicist Isidor I. Rabi, the so-called “father” of CERN,  stepped on the scene. Rabi, who co-founded the American research centre Brookhaven National Laboratory, put a resolution to the annual conference of UNESCO in Florence, June 1950 for a (“western”) European physics laboratory.

The fact Rabi omitted to mention a nuclear reactor was likely a political move on the part of the US, who were not keen on Soviet bits of Europe developing nuclear weapons. After much to-ing and fro-ing in the next two years, a provisional agreement was signed on 14 February 1952 by ten European states.

The next day, the signed agreement was telegrammed to Rabi, informing him of the “birth of the project you fathered in Florence”. The convention was signed on the 1st July, 1953 and CERN became an official organisation just over a year later.

Telegram sent to Isidor Rabi on 15 February, 1952 – marking the birth of CERN. Image credit: CERN.

Telegram sent to Isidor Rabi on 15 February, 1952 – marking the birth of CERN. Image credit: CERN.

For sixty years, CERN has been successfully exploring the unknown regions of the quantum world, while leaving the world we live in very much intact.

See a copy of the telegram and more in Collider: step inside the world’s greatest experiment, opening this November. Click here for further reading on the history of CERN

LHC. Camera. Action! (Part 2)

Dr. Harry Cliff, a Physicist working on the LHCb experiment and the first Science Museum Fellow of Modern Science, writes about his recent filming trip to CERN for Collider, a new Science Museum exhibition opening in November 2013. The first part can be read here

Day 2, Thursday

On the first day of the Collider exhibition team’s visit to CERN we had explored the architecture and interiors of the town-sized laboratory. Now it was time to enter its beating heart: the gigantic experiments probing the fundamental laws of the universe, and the people who make them a reality.

Our team now divided. Pippa, Finn and crew set off to the far side of the 27km LHC ring to Point 5, home of the enormous Compact Muon Solenoid (CMS) experiment. 100 metres underground, 25 metres long, 15 metres high, weighing in at 12,500 tonnes and containing enough iron to build two Eiffel Towers, CMS is one of the four huge detectors that record the particle collisions produced by the Large Hadron Collider. It is also a remarkable sight, beautiful even, its concentric layers giving it the appearance of a gigantic cybernetic eye. One member of the team said it was the most incredible thing he had ever seen, with only the Pantheon in Rome coming close to matching it.

The enormous Compact Muon Solenoid (CMS) experiment. Credit: CERN.

The enormous Compact Muon Solenoid (CMS) experiment. Credit: CERN.

CMS was photographed from every angle so that it can be recreated in a 360 immersive projection for the Collider exhibition. The CMS team were incredibly accommodating in allowing us to get our cameras as close to CMS as possible, all while they carried out vital work on the detector. We owe particular thanks to the boundlessly energetic Michael Hoch who looked after us for the day and made it all possible.

Meanwhile, 13km around the ring, in a less spectacular CERN office, our radio producer and I carried out audio interviews of LHC physicists and engineers. Each of them sharing what makes them tick as scientists and inventors. One even surprised us by dismissing the discovery of the Higgs boson as “boring”; what drives him as a scientist is seeking answers to new questions. For him the Higgs threatens to be a dead-end on the journey of discovery, rather than opening up new avenues of inquiry. Over the course of the day we interviewed five members of CERN’s international community, drawn from across Europe, representing a diverse cross section of CERN’s most important asset, its people.

Day 3, Friday

The last day might have been the most challenging. The team assembled at CERN’s custom-built TV studio to film interviews with LHC engineers against a green screen. These are the people who build and operate CERN’s experiments and they will appear as full-body projections in the exhibition, as if museum visitors have wandered into the LHC tunnel to be met by a friendly member of staff. Over dinner the night before we had shared anxieties as to how it might go. Video, unlike audio, can’t be edited to remove fumbled words or long pauses – our interviewees would have to deliver near-perfect speeches, and none of them had ever done anything like this before. In fact, neither had any of us.

Our concerns were unfounded. The engineers were naturals and by the end of the day we had recorded some brilliant interviews that should really help bring CERN to life for the visitors to the exhibition.

We returned to London that evening, exhausted but carrying a huge amount of material, covering almost every aspect of the Large Hadron Collider. For the first time I really have a sense of what this Collider exhibition will become; it’s going to be quite something to see it take shape over the next five months. If you can’t make it to Geneva to see the LHC in person, you’ll find a healthy slice of the world’s greatest experiment at South Kensington this November. 

A hundred years of the quantum atom

Alice Lighton, content developer for our Collider exhibition, writes about the history of quantum physics. Colider: step inside the world’s greatest experiment opens in November 2013 with a behind-the-scenes look at the famous CERN particle physics laboratory. 

A few years ago, a friend asked a question that took me somewhat by surprise. “Alice,” he said, “is quantum physics right, or is it just a theory?”

At the time I was in the midst of a physics degree, so my initial response was “I hope so!” Quantum physics matches up to experiment extraordinarily well – it is often called the most accurate theory ever. But the question, and subsequent conversation, made me realise how little many people know about the subject, despite its profound impact on modern life and the way we think about the universe.

This year is the centenary of the publication of one of the theories that laid the foundation for our understanding of matter in terms of quanta – packets of energy. According to quantum mechanics, light is not a wave, but lump of energy called photons. Max Planck came up with the idea at the end of the 19th Century, though he considered his light ‘quanta’ a useful model, rather than reality.

Niels Bohr

Niels Bohr, one of the founders of modern physics.

One hundred years ago, in 1913, the young Danish researcher Niels Bohr sent a paper to the Philosophical Magazine in London that used these quanta to solve a serious problem with theories about the atom. At the time, scientists thought the atom was like a solar systems; electrons orbit a nucleus of protons and neutrons. But anything that moves in a circle gradually slowly radiates energy, and so moves closer to the centre of orbit. Eventually, electrons should fall into the nucleus of the atom.

But they blatantly don’t, otherwise everything in the Universe would collapse, and we wouldn’t exist. Bohr proposed that electrons could only sit in discrete orbits or distances from the nucleus – and therefore when electrons change orbit transitions between orbits emit only emit energy in discrete packets (quanta), not gradually. The electrons therefore stay put in their orbits, and don’t fall into the nucleus of the atom.

A hydrogen atom is made from one electron orbiting a proton. Photo credit: flickr/Ludie Cochrane

Bohr was the first to show that packets of energy could successfully explain and predict the behaviour of atoms, the stuff that makes up you and me. His results were only approximately correct, but a big improvement of previous theories.

Generations of scientists have built on Bohr’s insight to understand and create the modern world. When my friend asked whether quantum physics worked, I pointed at his laptop. Computers, nanotechnology, and the Large Hadron Collider owe their existence to the physics that began with Bohr’s generation.

The CMS experiment at the Large Hadron Collider tries to work out the rules governing the sub-atomic world. Photo credit: CERN

Bohr’s original papers are clear and comprehensible, a beautiful read for physicists. The mathematics involves nothing more difficult than multiplication and division, yet the philosophical implications are immense. Max Planck never fully accepted quantum physics; neither did Albert Einstein, despite winning a Nobel Prize for his work on the subject.

Bohr also won a Nobel Prize for his quantum theory, but his work did not stop. He founded the Niels Bohr Institute, a centre of theoretical physics in Copenhagen, worked on the Manhattan Project developing the atomic bomb, and continued to make contributions to quantum mechanics.

And he has a lovely link to the exhibition I’m currently working on, about the Large Hadron Collider. Bohr was influential in the founding of CERN, the Geneva laboratory that is home to the LHC. If he had his way, the LHC would be in Denmark, but other scientists objected – Northern Europe was too cloudy, and had too few ski resorts, for Italian tastes.

LHCb VELO Modules

LHC Exhibition: From Liverpool to the LHC, via easyJet

In autumn 2013 an exhibition about the LHC will open in the Science Museum, and we’re currently scouting out objects and stories for the show. This post is the first in a series about the exhibition. Myself and Harry Cliff from the LHC exhibition team ventured to Liverpool to take a closer look at the detector that sits at the heart of the LHCb experiment.

LHCb VELO Modules

The Oliver Lodge building, home to the Universityof Liverpool particle physics department, is a typically plain post-war block. But inside, technicians and researchers constructed one of the most beautiful parts of the Large Hadron Collider (LHC): the LHCb Vertex Locator or “VELO”.

The VELO is a precision engineered piece of equipment, and we had to put on teletubby-style outfits to enter the clean room where the modules were painstakingly put together. A peek through a microscope at a spare module revealed the intricate detail in each board; hundreds of perfectly aligned connections, delicate strips of silicon and tiny computer chips.

But once assembled, the modules are surprisingly hardy. Some were taken to the LHC in Geneva in hand baggage on an easyJet flight; brave researchers drove the rest through the Channel tunnel in a hire car. Once they arrived, this incredibly intricate device was carefully put in position. It sits just millimetres from awesome power of the LHC’s proton beams, enduring high levels of radiation for years on end without missing a beat.

Most of media flurry about the LHC has concentrated on the hunt for the Higgs boson. LHCb has a different mission. As Dr Tara Shears explained, our universe is made of normal matter, not its mirror image, antimatter, and at LHCb scientists are attempting to find out where the antimatter has gone.

The LHC collides protons at near light speed. The energy of the crash creates new particles that spray out in all directions. Our host at Liverpool, Dr Girish Patel, explained that the VELO comprises 42 modules, which are lined up in pairs to form circular detectors – the proton beams travel through the hole in the centre of each pair. The pairs are lined up along the beam to record the trajectory of the new particles.

The VELO allows scientists to work out precisely where particles were created, to within a hundredth of a millimetre. It is surrounded by much larger detectors that identify what types of particle were made in each collision. LHCb is looking for a type of particle known as a bottom quark. It doesn’t detect the bottom particles directly, because they decay into other particles before they reach VELO. LHCb tracks these other particles, looking for the fingerprint of the bottom quark among the mass of data.

Thanks to everyone at Liverpool for a fascinating day, particularly Girish, Tara and Themis. For more info on the VELO, take a look at the LHCb website.

Image courtesy of CERN