150th anniversary of Tyndall’s greenhouse effect

Every scientist knows that this year marks the 150th anniversary of the publication of Darwin’s ‘On the Origin of Species’, but not so many may be aware that another scientific breakthrough occurred that year. In 1859, the Irish physicist John Tyndall discovered that certain gases – carbon dioxide and water vapour in particular – absorb infra-red radiation. The discovery was established over a few short weeks, but it provided an explanation for the greenhouse effect, one of the great puzzles of science.

The Irish Times have accepted a piece I have written on Tyndall for their Irishman’s Diary slot next month. I like this column- it is a unique feature of The Irish Times, comprising an 800-word essay prominently displayed on the op-ed page, written by the house journalist 3 days a week and by a freelance writer on other days. I have written a few diaries on various Irish scientists in the past (see My Articles) and I hope one day to publish the ‘Science Diaries’ as a collection of essays.  Below is a draft of what I intend to say on Tyndall:

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John Tyndall: celebrated Irish scientist who discovered the greenhouse effect

Many readers will know that this year marks the 150^th anniversary of the publication of Darwin’s ‘On the Origin of Species’. Another breakthrough occurred in science that fateful year, this one with an Irish connection. The discovery attracted much less attention than Darwin’s theory of evolution at the time, but it has become one of the hottest topics in science today (literally).

In July 1859, the Irish physicist John Tyndall, one of the great scientists of the 19^th century, established that certain atmospheric gases absorb heat quite strongly. This innocuous-sounding discovery was established over a few short weeks, but it provided the solution to one of the great riddles of science: the famous ‘greenhouse effect’.

The greenhouse effect was first proposed by the French polymath Joseph Fourier, almost a century before Tyndall’s experiments. Fourier had wondered how the earth maintains its warm temperature, and he speculated that while heat from the sun passes easily through our atmosphere on the way to earth, heat radiated outwards by the warm earth must somehow be trapped in the atmosphere. The hypothesis was highly controversial, as it was widely assumed that gases are transparent to heat.

Tyndall, a fierce proponent of the new experimental method of science, devised a series of simple experiments to test Fourier’s hypothesis.  Working in the dusty basement of the Royal Institution in London in the summer of 1859, he soon established that, while most gases are indeed transparent to light and heat, some gases – carbon dioxide and water vapour in particular – can absorb heat energy at certain wavelengths. As traces of each gas were known to exist in the earth’s atmosphere, the puzzle of the earth’s temperature was solved.

How did an Irish scientist come to make such an important discovery? John Tyndall was born in Leighlinbridge, County Carlow in 1820, the son of an RIC officer and land agent. On completing his schooling under renowned local teacher John Conwill, he started his professional career as a surveyor for the Ordinance Survey of Ireland.  He was soon transferred to a position with the Ordinance Survey in Lancashire, England, but became interested in the new experimental sciences of physics and chemistry emerging in Germany. He moved to Germany in 1848 to study under the famous experimentalist Robert Bunsen at the University of Marburg, returning to England with a PhD in experimental science in 1851. By 1853, he had been appointed Professor of Natural Philosophy at the Royal Institution, a position previously held by the renowned scientist Micheal Faraday.

Tyndall remained at the Royal Institution for the rest of his career, making important discoveries in diverse areas of science, from magnetism to optics, from the physics of sound to the behaviour of bacteria. He is probably best known for ‘Tyndall scattering’, the scientific explanation for why the sky is blue. A keen mountaineer, he became interested in the science of glaciers and made several important discoveries concerning their behaviour. He became extremely well-known in Victorian England as a public communicator of science and was a prominent member of the ‘X Club’, an influential group of prominent scientists who defended evolution and other new scientific theories from religious dogma.

Tyndall’s verification of the greenhouse effect was accepted by the scientific establishment, but not regarded as a matter of vital importance. He and his colleagues were aware of the output of Victorian England’s factory chimneys, but no-one drew a link between this pollution and the greenhouse effect.

Nowadays, evidence has emerged that the average temperature of the earth and its oceans has been gradually rising since the industrial revolution. Despite many uncertainties, the scientific consensus is that this global warming is associated with an increase in carbon dioxide in the atmosphere, an increase that has been produced by human activities such as industry and transport. The discovery has led to concerted international efforts to agree on targets for reducing carbon emissions worldwide, a process that is only just beginning.

What would Tyndall make of today’s climate problems? Like most scientists of his era, he would probably find it difficult to grasp that humans could have such a global effect on nature. On the other hand, he would be greatly depressed by the shrinking of his beloved glaciers. Above all, he would be astonished to find that, of all the scientific discoveries he made, the work he did in the summer of 1859 has become a major preoccupation of 21^st century science.

Today, the work of this great Irish scientist is commemorated by the annual Tyndall lecture of the Institute of Physics, the Tyndall Centre for Climate Change Research in the UK, the Tyndall National Institute in Cork, Mount Tyndall in California and the Tyndall glacier in Chile.

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John Tyndall: celebrated Irish scientist who discovered the greenhouse effect

Many readers will know that this year marks the 150^th anniversary of the publication of Darwin’s ‘On the Origin of Species’. Another breakthrough occurred in science that fateful year, this one with an Irish connection. The discovery attracted much less attention than Darwin’s theory of evolution at the time, but it has become one of the hottest topics in science today (literally).

In July 1859, the Irish physicist John Tyndall, one of the great scientists of the 19^th century, established that certain atmospheric gases absorb heat quite strongly. This innocuous-sounding discovery was established over a few short weeks, but it provided the solution to one of the great riddles of science: the famous ‘greenhouse effect’.

The greenhouse effect was first proposed by the French polymath Joseph Fourier, almost a century before Tyndall’s experiments. Fourier had wondered how the earth maintains its warm temperature, and he speculated that while heat from the sun passes easily through our atmosphere on the way to earth, heat radiated outwards by the warm earth must somehow be trapped in the atmosphere. The hypothesis was highly controversial, as it was widely assumed that gases are transparent to heat.

Tyndall, a fierce proponent of the new experimental method of science, devised a series of simple experiments to test Fourier’s hypothesis. Working in the dusty basement of the Royal Institution in London in the summer of 1859, he soon established that, while most gases are indeed transparent to light and heat, some gases – carbon dioxide and water vapour in particular – can absorb heat energy at certain wavelengths. As traces of each gas were known to exist in the earth’s atmosphere, the puzzle of the earth’s temperature was solved.

How did an Irish scientist come to make such an important discovery? John Tyndall was born in Leighlinbridge, County Carlow in 1820, the son of an RIC officer and land agent. On completing his schooling under renowned local teacher John Conwill, he started his professional career as a surveyor for the Ordinance Survey of Ireland. He was soon transferred to a position with the Ordinance Survey in Lancashire, England, but became interested in the new experimental sciences of physics and chemistry emerging in Germany. He moved to Germany in 1848 to study under the famous experimentalist Robert Bunsen at the University of Marburg, returning to England with a PhD in experimental science in 1851. By 1853, he had been appointed Professor of Natural Philosophy at the Royal Institution, a position previously held by the renowned scientist Micheal Faraday.

Tyndall remained at the Royal Institution for the rest of his career, making important discoveries in diverse areas of science, from magnetism to optics, from the physics of sound to the behaviour of bacteria. He is probably best known for ‘Tyndall scattering’, the scientific explanation for why the sky is blue. A keen mountaineer, he became interested in the science of glaciers and made several important discoveries concerning their behaviour. He became extremely well-known in Victorian England as a public communicator of science and was a prominent member of the ‘X Club’, an influential group of prominent scientists who defended evolution and other new scientific theories from religious dogma.

Tyndall’s verification of the greenhouse effect was accepted by the scientific establishment, but not regarded as a matter of vital importance. He and his colleagues were aware of the output of Victorian England’s factory chimneys, but no-one drew a link between this pollution and the greenhouse effect.

Nowadays, evidence has emerged that the average temperature of the earth and its oceans has been gradually rising since the industrial revolution. Despite many uncertainties, the scientific consensus is that this global warming is associated with an increase in carbon dioxide in the atmosphere, an increase that has been produced by human activities such as industry and transport. The discovery has led to concerted international efforts to agree on targets for reducing carbon emissions worldwide, a process that is only just beginning.

What would Tyndall make of today’s climate problems? Like most scientists of his era, he would probably find it difficult to grasp that humans could have such a global effect on nature. On the other hand, he would be greatly depressed by the shrinking of his beloved glaciers. Above all, he would be astonished to find that, of all the scientific discoveries he made, the work he did in the summer of 1859 has become a major preoccupation of 21^st century science.

Today, the work of this great Irish scientist is commemorated by the annual Tyndall lecture of the Institute of Physics, the Tyndall Centre for Climate Change Research in the UK, the Tyndall National Institute in Cork, Mount Tyndall in California and the Tyndall glacier in Chile.

Dr Cormac O’Raifeartaigh is the author of the science blog ANTIMATTER

Free speech, AIDS and the HIV virus

Johnny Steinberg has a depressing article on skepticism and the HIV virus in this week’s edition of New Scientist.

The article starts with the story of Christine Maggiore, a 52-year old who died in 2008 from infections typical of AIDS. Apparently, she had tested positive for HIV 16 years ealier, but shunned anti-retroviral therapy (ART), the therapy that is known to hinder AIDS developing from the virus. Her choice, you  might say; until you read that she also denied the treatment to her infant daughter, who died of AIDs-related illnesses at age 3.

Steinberg then goes on to describe the HIV denial movement, starting with arch-skeptic Peter Duesberg. Duesberg’s work with retroviruses – the class to which HIV belongs – led him to conclude that all such viruses are essentially harmless. In fact, many scientists shared Duesberg’s skepticism of the HIV- AIDS link in the late 1980s, but support rapidly fell away as clinical evidence linking HIV to AIDs mounted. In Duesberg’s case, rather than revise his views in the face of emerging epidemiological evidence, he chose to hang on to his old theory – a position he has stuck to ever since.

Professor Peter Duesberg of the University of Berkeley

The publicity afforded to Duesberg and other skeptics has had serious consequences for society. According to the New Scientist, a recent survey suggested that 25% of the US population currently question the link between HIV and AIDS. Even more seriously, NS cites the case of South Africa, a country where AIDS has made devastating inroads. Because President Mkebe chose to believe the skeptics, he strongly resisted the use of ART therapy in South Africa – it is now estimated that over 300,000 AIDS victims died unnecessarily there.

So what is at the root of this sort of skepticism? I have to agree with Steinberg when he states that “no amount of evidence will overturn the entrenched beliefs of some”. Combine this with the tendency of the media to highlight studies that show unorthodox results and you are well on the road to the public misunderstanding of science.

Perhaps we scientists are partially to blame. It seems to me that we do a poor job of communicating the consensus position – and how it is achieved – on important issues, from global warming to the MMR vacinne. There will always be scientists who question the mainstream, even in the face of overwhelming evidence; such is human nature and we cannot censor such views in a free society. Not to mention the fact that science progresses by asking the unthinkable. Perhaps the solution is to convince the media not to allow ‘maverick’ scientists disproportionate publicity – and for the elders of science to take the communication of science to the public more seriously. In Ireland, there isn’t a single university that has a Professorship for the Public Understanding of Science..

Update

In the same issue, New Scientist have an excellent editorial on the importance of scientific heresy. There is no contradiction here – the questioning of ‘accepted science’ from within is a vital part of scientific discovery and long may it continue. It is the misrepresentation in the media of the scientific consensus on a given topic that is of concern..you can find more information on this topic on Seth Kalichman’s ’s blog denyingaids.blogspot.com

The Alchemist Cafe

I gave a talk on Wednesday evening at the Science Gallery in Trinity College Dublin, as part of the Alchemist Cafe series. It was great to be back at the Gallery, I’ve fond memories of participating in the RAW debates there last year (see blog posts on the debates here).

The Alchemist Cafe is the Irish branch of the international Cafe Scientifique movement: the idea is to get a scientist or engineer to give an informal talk on a scientific topic in a cafe/bar setting, with plenty of questions and discussion afterwards. You can find abstracts and videos of previous talks on their website above.

I gave a short spiel titled ‘The Big Bang: Fact or Fiction?”. I thought it would be fun to go over the three basic planks of evidence for the model and then discuss some modern results (from the accelerating universe to WMAP measurements of the cosmicrowave background). The rest of the session was given over to questions and discussion.

It seemed to work well, I thought the Science Gallery cafe a particularly good setting. One whole side of the cafe is a glass window onto the street and we projected the images I used onto the opposite wall, with the audience in between. It made for a nice relaxed atmosphere.

The Naughton Institute and the Science Gallery at Trinity College Dublin

Photos courtesy of The Alchemist Cafe

There were plenty of good questions, on topics as diverse as unified field theory and dark energy. I wish I’d taken note of the questions, must check with the organisers if someone did. Turnout was a big surprise – a few friends turned up at 8.05 and couldn’t get in! It’s amazing the public interest in cosmology, I guess everyone has heard of the Big Bang and Hawking’s A Brief History of Time.

All in all, it was a great experience. There will be a video of the event on the Alchemist Cafe site in a few days and I’ve uploaded the slides I used on the My Seminars page.

P.S. The Gallery is currently exhibiting INFECTIOUS, an excellent show on the spread of infectious diseases: well worth seeing and highly relevant given the news on swine flu…

Antimatter at 1

This little blog passed its first birthday a few weeks ago (a few posts go back to March 2008, but they were actually written in May!). It’s been a very useful experiment and the year certainly went by quickly…

The blog was suggested by our head of research as I’d been writing articles on science for the public in newspapers and magazines for some time. It started life as an online science diary, but I found it useful to broaden it to include posts on introductory concepts in cosmology for our students and renamed it Antimatter. During the year, it has become much more widely read than expected with about 200 hits per day. That’s about a thousand readers per post which is probably a good outreach for a teacher…

Most the traffic comes from being listed on well-known websites such as INTERACTIONS. ORG (the international particle physics website), Particle Physics Planet and the American blog NOT EVEN WRONG (thanks Peter!). I recommend all of these websites; the interactions website is a particularly useful resource as it gives a daily list of new posts on particle physics/cosmology on blogs around the world.

I note from WordPress that 112 posts have been posted on Antimatter so far; that’s an average of 2 per week which feels about right. It does take time to write the posts, but there are definite benefits for any science writer. As well as good writing practice, the blog has led to a good few public speaking engagements, newspaper profiles, magazine articles ( in Physics World) and interest from a literary agent (more on this later).

I enjoy writing the cosmology articles, but the most challenging posts are probably the lecture reviews; not many bloggers do this but I think it’s a useful service. It’s great practice to try to summarize someone’s lecture, put in appropriate links, pics and slides and send them a copy for approval, all within a matter of hours. It’s also a nice way of establishing contact with other physicists worldwide.

So I think I’ll keep posting for a while. About my only regret is the comments section – apparently a low number of comments is normal for a ‘tech” blog. Instead, readers tend to contact me by email. Which drives me mad…

Antimatter at the Royal Irish Academy

I was at a very interesting event in Dublin yesterday evening; an informal panel discussion for the public on ‘Angels, Demons and Antimatter’ hosted by the Royal Irish Academy and The Irish Times. It’s great to see the Academy hosting this sort of event as it helps to bridge the gap between science and the humanities (the ‘two cultures’ famously described by C.P. Snow).

The event was ably chaired by Dick Ahlstrom, veteran science editor ofThe Irish Times, and the panel boasted four heavy hitters from the world of particles physics: Alex Montwill, Ireland’s best-known particle physicist and renowned communicator of science: Ronan Mc Nulty, leader of the experimental particle physics group at UCD, a group that have a major involvement with the LHCb antimatter experiment at CERN: Tara Shears, lecturer in physics at Liverpool University, also heavily involved in the LHCb experiment: and Paul Bowe, the Irish physicist who is technical director of ALPHA, the anti-Hydrogen experiment at CERN.

In his introduction to the event, Dick Ahlstrom sensibly asked the audience how many had seen the film – only about a third, which confirmed my view that people are interested in particle physics for its own sake, film or no film. Tara Shears then kicked off with a pithy summary of the film, explaining that a ticking bomb made of antimatter provides the timeline of the unfolding story. Then it was over to Alex to give a brief introduction to the phenomenon of antimatter. He did this in exemplary fashion, starting with the prediction of antimatter from the Dirac equation (…“Dirac was not the sort of scientist to brush extra solutions that seemed to have no corresponding physical reality under the carpet“) and proceeding to the experimental discovery of the positron in 1932 (if you want details on the discovery of antimatter, see post here). The discussion then honed in on the nature of antimatter, how it occurs in nature and how it is produced in minicscule amounts in high-energy accelerators.

The panel then turned to one of the great mysteries of physics – why is our universe primarily made of matter and not antimatter? Ronan gave a brief overview of charge symmetry, parity symmetry, charge-parity (CP) violation and the Sakharov conditions ; these are three conditions that theory predicts must have existed in the early universe for the current asymmetry of matter and antimatter to develop.

Charge and parity operations: note that the final quadrant is not identical to the first

This led nicely to a discussion of the relevance of high-energy physics to cosmology. I was very pleased this came up, as it is not always obvious to the public that, as well as studying the fudamental nature of matter, high energy accelerators offer a direct glimpse of the very early universe by recreating the energy conditions that existed shortly after the big bang (a point that is often missed by critics of the big bang model).

Paul Bowe then discussed the production of anti-hydrogen at CERN (an atom of anti-hydrogen simply comprises an anti-electron orbiting an antiproton, see previous post on this). He gave a brief overview of the ALPHA experiment – the production of positrons, the production of antiprotons, the mixing trap etc.

Schematic of hydrogen and anti-hydrogen atom

A picture of the experiment reminded me that while I find the discoveries of particle physics fascinating, I’m happy to leave the experiments to others!

Image of ALPHA experiment

Paul also addressed a question I was asked a while ago - Do we expect the spectrum of anti-H to be the same as that of H? If I have understood correctly, the answer is yes (since the electromagnetic interaction between the anti-proton and the positron should mirror that between the proton and the electron). If not, the spectrum of anti-H will have major implications for our understanding of CP violation.

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The second part of the discussion dealt with Hollywood’s take on antimatter in Angels and Demons. It started with a clip from the film, the scene where Dr Vetra tries to explain to the destructive potential of the antimatter bomb to the authorities, advising that they evacuate the Vatican city forthwith.

Of course, the panel were quick to point out the unfeasability of the bomb, as mentioned in the post below: because of the difficulties of creating even a few atoms of antimatter in particle accelerators, it is simply not possible to create a bomb made of antimatter (or to use it as an energy source). And if such a bomb could be made, the trap container would be gigantic, not the little package portrayed in the film. However, I was pleased to hear that Tara (and I think the panel as a whole) felt Brown’s plot was acceptable cinematic license and made for a good story.

A small container for an antimatter bomb?

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In keeping with the informal nature of the event, there was a lengthy question and answer session after the panel discussion. Some interesting questions were;

1. Is it possible there is plenty of antimatter in our universe today, in the form of distant galaxies made of antimatter?

I think the answer was that this is a real possibilty, but a basic asymmetry between matter and antimatter is still implied.

2. Does the neutron have an antiparticle?

Yes, because the neutron is a composite particle – the anti-neutron is made up of anti-quarks etc). Ronan pointed out that the question Does the neutrino has an antiparticle? is much more interesting and the subject of much debate.

3. What is the relation between antimatter and dark matter?

None – dark matter is the name we give to matter that has a gravitational effect but does not interact with the electromagnetic force. However, whatever particles make up dark matter presumably have anti-particle counterparts!

4. My question: Why did Dan Brown choose to introduce the topic of antimatter to the story at all, wouldn’t TNT have done?

My own view is that he was anxious to include cutting edge science, as the relation between religion and emerging science is a major theme of the novel. However, Tara had a better answer: novelists write about what they find interesting and Brown happens to be interested in particle physics! Apparently, he even visited CERN in 1990. QED.

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All in all, this was a very interesting an informative event, a treat for anyone interested in particle physics or indeed are the public perception of physics. If there was one sour note during the evening, it was Dick Ahlstrom’s observation that “ the UCD contribution to the LHCb experiment really occurs through the back door” as Ireland is not a member of CERN. This is a sad situation that we have touched on many times before, so I’ll leave it for now. As for Dan Brown, long may he continue to include science in his bestselling novels.