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Recently by Margaret Harris

Of physics and famine

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The Harvesters

Pieter Bruegel the Elder’s painting The Harvesters (1565) shows a scene of plenty, but
people like the peasants depicted in it would have been all too familiar with famine.
(Courtesy: The Metropolitan Museum of Art)

By Margaret Harris

Physics and medieval history don’t overlap that often. I should know: I got an undergraduate minor in medieval and renaissance studies in part because I wanted a break from doing physics. So the fact that this arXiv paper and this documentary have both come out in the past 10 days is about as unusual as – well, finding a medieval king buried in a car park.

Fascinating as the discovery of Richard III’s skeleton is, though, I’m going to write instead about the arXiv paper, which proposes something even more remarkable: a possible link between space weather and episodes of famine in late medieval Europe.

The paper focuses on the years 1590–1702, a period during which Europe’s population suffered repeatedly from famine. Over the same period, the Sun was experiencing a decades-long lull in activity, known as the Maunder minimum. Might there be a connection?

To answer this question, the paper’s authors – physicist Lev Pustilnik and economist Gregory Yom Din – begin by summarizing the evidence for a connection between space weather and local weather. Overall, this appears fairly convincing, if a bit circumstantial. For example, a 1997 study found a link between cosmic rays and cloud cover, while a 2004 paper demonstrated a similar correlation between global atmospheric circulation and level of activity in the Earth’s magnetosphere.

With the principle of a connection thus established, Pustilnik and Yom Din go on to suggest three conditions under which space weather could lead to famine:

• Local weather has to be in a “threshold state” such that it is sensitive to space weather. For example, if there is no water vapour present, clouds won’t form even if space weather is “seeding” the Earth’s atmosphere with lots of extra ions.

• Harvests must be sensitive to weather anomalies. This is more likely in areas of so-called “risk farming”, where conditions are marginal enough that a few days of bad weather can completely wipe out a crop.

• The area has to be economically isolated, such that local shortages cannot be ameliorated by buying grain from elsewhere.

To test these hypotheses, Pustilnik and Yom Din begin by comparing levels of solar activity with grain prices in 17th century England. Between 1590 and 1700, the price of grain in England and the abundance of 10Be isotopes (a proxy for solar activity) in Greenland ice cores exhibit an almost exactly inverse relationship. High prices correspond to periods of low solar activity and vice versa. Several other European markets that the authors studied also showed strong correlations between grain prices and solar activity, but in southern Europe, where crops are more likely to suffer from drought than from excess rain, prices tended to spike during solar maxima rather than minima.

Things get a bit shakier when the authors turn their attention to 19th century Iceland. In this case, famines seem to correlate with both minima and maxima in solar activity. Pustilnik and Yom Din claim this is what they expected to see, but don’t really say why; in particular, they don’t explain why the Icelandic pattern should differ so markedly from the English one.

Still, it’s an interesting study, and reading it stirred up some memories from my brief foray into medieval studies. In particular, I thought of a book called Lost Worlds whose author, a Swiss historian called Arthur Imhof, makes unusually good use of hard data in analysing what life was like for an ordinary person in early modern Europe. Might his book have something to add to the famine/space weather debate?

I skimmed my copy of Lost Worlds a couple of times before I located the bit where Imhof writes about famine. Tree-ring data and written sources from the 16th and 17th centuries, he notes, indicate a long series of harsh winters and summers with too much rain, resulting in exceptionally bad growing conditions. As a result, he adds, “our ancestors had more reason to beg for their daily bread between 1550 and 1700” than they did at almost any point before or since.

This is, of course, almost exactly the same period that Pustilnik and Yom Din studied, and it’s nice to see that Imhof’s sources corroborate their grain-price data. But Imhof wasn’t interested in climate for climate’s sake. Instead, he was trying to demonstrate that populations in areas prone to famine, plague and war became traumatized by their repeated misfortunes. You’d have to read the book to appreciate Imhof’s argument in full, but among other things, he suggests that people in these “unlucky” areas developed fatalistic attitudes to life, death and birth. These attitudes show up not only in religious beliefs, but also in data on infant and maternal mortality. For example, even in peaceful, plague-free years, more than one-third of babies born in the plague-prone and war-torn German village of Gabelbach died in infancy. In “luckier” villages, the comparable figure was one in eight.

Where does this leave us regarding space weather? Well, if we add Imhof’s conclusions to Pustilnik and Yom Din’s, it seems that the behaviour of heavenly bodies could have influenced not only the viability of medieval grain crops, but also the habits and attitudes of the people who tended them – perhaps even to the extent of determining whether their children were likely to live or die. That might not be very surprising to the peasants of 17th century Gabelbach, who lived in a more religious age (and, according to Imhof, believed fervently in astrology). But to me, it’s absolutely mind-blowing – and a whole lot more interesting than England’s “Tricky Dick” turning up in a car park.

By Margaret Harris

Last night’s awards ceremony for the 2012 Royal Society Winton Prize for Science Books highlighted the diversity of modern science writing, with six very different books competing for the prestigious £10,000 award.

Two of the shortlisted authors, James Gleick and Brian Greene, are well known in the physics community thanks to their earlier bestsellers on (respectively) chaos theory and string theory. However, they were not the only heavyweights competing, with Gleick’s book The Information and Greene’s The Hidden Reality up against Joshua Foer’s Moonwalking With Einstein; Lone Frank’s My Beautiful Genome; Stephen Pinker’s The Better Angels of Our Nature; and Nathan Wolfe’s The Viral Storm. For those of you keeping track, that’s one book about information theory; one about multiple universes; one about the science of memory; one about genomics; one on the psychology of conflict; and one on emerging infectious diseases. Whew!

The ceremony’s host, comedian Ben Miller, began by riffing on some of the year’s big scientific events, including the summer’s (probable) discovery of the Higgs boson at CERN and the recent (rumoured) discovery of methane on Mars. The biggest laugh of the evening came later, though, when Miller was interviewing Dame Jocelyn Bell Burnell, one of five judges for the award. After Miller complained that studying science at school hadn’t offered him much in the way of “social lubrication”, Bell Burnell’s response was a deadpan, “Try being a female physicist!”

The bulk of the evening, however, belonged to the shortlisted authors themselves. After reading brief passages from their books, five of the authors (Wolfe was unable to attend) joined Miller onstage for a panel discussion, fielding questions about their books and the role of science communication. For me, this was a highlight of the evening; aside from The Hidden Reality, which was on Physics World’s list of the “best physics books of 2011”, I hadn’t read any of the shortlisted books, so it was great to learn a little more about each of them.

In his speech announcing the prize, Royal Society president Sir Paul Nurse hailed the recent “renaissance” in science writing, adding that the shortlisted books were “all great contributions to that tradition”. But there could only be one winner – and it was James Gleick’s The Information, which the judges praised as an “audacious book” offering “remarkable insight” into how information is used, transmitted and stored. Gleick seemed genuinely surprised, thanking “all the very smart people who have helped me over the years” before being bundled into a live TV interview with Channel Four News.

Cartoon of a noisy magnetic system

Cartoonist Flash Rosenberg’s drawing of “noise in a magnetic system.”

By Margaret Harris at the APS March Meeting

This year’s APS meeting has been one of the biggest ever, with nearly 11,000 attendees and 54 parallel sessions. It’s impossible to capture the totality of such a huge conference, but here are a couple of snapshots.

One of the most entertaining talks I saw was given by a cartoonist, Flash Rosenberg. Rosenberg makes videos that pair her quick sketching skills with a scientific voice-over: as the scientists speak, she draws what they are saying. Rosenberg spoke during a session on communicating science to the public, and towards the end of her talk she offered to illustrate audience members’ research questions.

Understandably, several of them leaped at the chance. For the first question – “How do bubbles form in nuclear fuel?” – Rosenberg began by drawing nuclear fuel as an unhappy-looking gremlin. I wasn’t quick enough with my camera to capture the hilarious conclusion of her sketch, but another audience member has posted a video of it here (turn the sound up – it’s worth it).

I was better prepared for the second question, which was “How do you measure noise in a magnetic system?”. As you can see in the image above, Rosenberg’s idea of a noisy magnetic system is a couple whose quiet romantic dinner is being interrupted by loud music. Cute.

Crowd outside the session on Majorana fermions

An over-capacity crowd greeted Leo Kouwenhoven’s talk on Majorana fermions

By Margaret Harris

The hottest talk of the APS March Meeting so far took place yesterday, when Leo Kouwenhoven revealed that his group at TU Delft in the Netherlands may have observed Majorana fermions in one-dimensional nanowires.

Majorana fermions have a curious property – they are their own antiparticles – and particle physicists have been looking for fundamental Majorana fermions for decades. A few years ago, condensed-matter physicists got in on the act too, seeking evidence of Majorana-like behaviour in fermionic quasiparticles such as those formed by electrons in superconductors. But so far, no-one has ever found conclusive evidence that such particles exist – so if this nanowire result holds up, it would be quite the coup for Kouwenhoven and his group.

Unfortunately, Kouwenhoven’s talk was so popular that the crowd overflowed into the hallway outside, and with conference centre staff talking anxiously about fire regulations, it proved impossible for me to squeeze in (Eugenie Reich of Nature was luckier – you can read her summary here). So instead, I headed to the room next door, where Krastan Blagoev of the US National Science Foundation was delivering an inspiring talk on the kinetics of metastatic cancer.

Map of obesity rates in the US in 2004 and 2008

Obesity rates in the US in 2004 and 2008. (Courtesy: Lazaros Gallos)

By Margaret Harris at the APS March Meeting

The data on obesity are pretty unequivocal: we’re fat, and we’re getting fatter. Explanations for this trend, however, vary widely, with the blame alternately pinned on individual behaviour, genetics and the environment. In other words, it’s a race between “we eat too much”, “we’re born that way” and “it’s society’s fault”.

Now, research by Lazaros Gallos has come down strongly in favour of the third option. Gallos and his colleagues at City College of New York treated the obesity rates in some 3000 US counties as “particles” in a physical system, and calculated the correlation between pairs of “particles” as a function of the distance between them. This calculation allowed them to find out whether the obesity rate among, say, citizens of downtown Boston was correlated in any way to the rates in suburban Boston and more distant communities.

It wouldn’t have been particularly surprising if Gallos’ team had found such correlations on a small scale. The economies of Boston and its suburbs are tightly coupled, for one thing, and their demographics are also not so terribly different. But the data indicated that the size of the “obesity cities” – geographic regions with correlated obesity rates – was huge, up to 1000 km. In other words, the obesity rate of downtown Boston was strongly correlated not only with the rates in the city’s suburban hinterland, but also with rates in far-off New York City and hamlets in northern Maine.

This correlation was independent of the obesity rate itself – there are “thin cities” as well as obese ones – and also far stronger than correlations in other factors, such as the economy or population distribution, would suggest. The exception, intriguingly enough, was the food industry, which also showed tight correlations between geographically distant counties.

Gallos isn’t claiming that the food industry is causing obesity. He also doesn’t discount the importance of food choices and genetic factors: what you eat and who you are will clearly play a big role in determining whether or not you, as an individual, will become obese. However, he points out that our genes haven’t changed that much since the US obesity epidemic began in the 1980s, and neither, presumably, has our willpower. The difference, he says, is that on a societal level, increasingly large numbers of us are living in an “obese-o-genic” environment, and “the consensus is that the system makes you eat more”.

Gallos says he’ll post this research on arXiv sometime in the next few days [UPDATE 29/2/12: here’s the link to the paper]. In the meantime, I’ll be testing his hypothesis personally in the obese-o-genic environment of a major scientific conference, complete with multiple breakfasts, receptions and lunches. Pass the pastries, please!

Photo of Boston Common sign

Boston Common and the Park Street Church, part of the city’s “Freedom Trail”.

By Margaret Harris at the APS March Meeting in Boston

The American Physical Society’s March Meeting doesn’t really kick off until tomorrow morning, but with many of the 6000+ delegates arriving a day early, we’re rapidly heading towards a critical mass of physicists here in Boston. Even the good citizens of New England’s largest city are starting to notice the influx; as I was walking along the “Freedom Trail” of historic landmarks earlier today, I met a park ranger who estimated that I was 10th physicist he’d spoken to that afternoon.

Anyway, from tomorrow until Thursday I’ll be swapping sight-seeing trips for talks on a wide range of physics topics. Many of the sessions are devoted to superconductivity, which remains a popular field a quarter of a century after the famous “Woodstock of Physics” March Meeting when the first high-temperature superconductors took centre stage.

Physicists with a keen interest in graphene will face some particularly tough decisions on which talks to attend, with 39 separate sessions devoted to carbon’s newest and sexiest (well, unless you prefer diamonds or buckyballs) allotrope.

There’s also some intriguing-sounding interdisciplinary sessions on the physics of cancer and the aftermath of the Fukushima nuclear incident. And finally, I’m hoping to learn more about the latest nifty experiments in my PhD field of atomic and molecular physics.

First, though, I need to go eat some of Boston’s famous seafood…

By Margaret Harris

I went to the University of Surrey last week for a science careers evening, and as I was chatting to some students afterwards, one of them asked a fascinating question. “We’re always hearing that the UK needs more graduates in STEM fields,” she said, using the ever-present acronym for science, technology, engineering and mathematics. “But if that’s true, why are so many of us struggling to find jobs?”

I’ve been asking myself the same question for some time. As Physics World’s careers editor, I receive many upbeat press releases touting the importance of STEM disciplines in building the knowledge economy, pulling the country out of recession and so on. But I have also watched, with impotent sympathy, as some of my scientifically trained friends search in vain for jobs. So what is wrong with this picture?

Jim Al-Khalili


By Margaret Harris
One of the highlights on physicsworld.com last week was an online lecture by the University of Surrey physicist and science communicator Jim Al-Khalili, who spoke on the subject of his recent book Pathfinders: the Golden Age of Arabic Science.

If you missed the live version of Al-Khalili’s lecture “On the shoulders of eastern giants: the forgotten contributions of medieval physicists”, you can watch an archived version of the hour-long event here. Be sure to stay all the way to the end, when Al-Khalili tackles some probing questions from audience members – including one asking why these physicists’ contributions have been forgotten in the West, and another wondering why science declined in the Arabic-speaking world after the medieval period.

As usual with these question-and-answer sessions, we ran out of time long before you ran out of questions. On this occasion, several of the ones we couldn’t fit in were so interesting that we asked Al-Khalili to send us written answers so we could share them with you. Below are his replies.

Test match physics

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A cricket ball sitting in grass

A cricket ball at rest

By Margaret Harris

Late yesterday afternoon, I was pottering around with the BBC’s Test Match Special on in the background when something in the cricket commentary caught my attention. In-between the usual chatter about English bowling (good), Indian batting (bad) and the latest cakes delivered to the TMS commentary box (excellent), the conversation suddenly turned to physics – specifically, to the question of whether a ball could gain speed after nicking the edge of a bat.

The matter was raised after an Indian batsman, V V S Laxman, edged a delivery from Jimmy Anderson, an English bowler. The ball spurted off towards England’s captain, Andrew Strauss, who couldn’t quite catch it. After lamenting the missed opportunity, one of the TMS commentators suggested that Strauss might have mistimed his catch because the ball gained speed after glancing off Laxman’s bat. The commentators then spent the next several minutes talking a load of old rubbish about whether this was physically possible.

Then, shortly after 6 p.m., a secondary-school physics student, Laurence Copson, sent a message to the BBC’s online commentary team claiming that no, it wasn’t possible. “Removing all external forces on the ball, under no circumstance would the ball gain speed after a nick…as [the] bat would be slightly hitting the ball in the opposite direction,” he wrote. However, he did add a caveat: “What may be deceiving is if the batsmen swipes, catches an edge and then the ball gains top-spin and seems to reach the ground quicker than usual.”

This analysis was quickly contradicted by Rob, a university astrophysics student, who pointed out that Copson was neglecting both the elastic coefficients of ball and bat, and (more importantly) “the spin on the ball before it hits the bat which, if very fine, may accelerate the ball…in the direction of spin (like a car with its wheels spinning hitting the ground goes forward)”.

This seemed fair enough, but Rob’s parting shot – ”this is the real world, external forces on the ball can’t be discounted!” – struck me as rather snide, so I decided to do some analysis of my own.

By Margaret Harris

hands smll.jpg

Today is the day when hundreds of thousands of students across England, Wales and Northern Ireland receive the results of their A-level exams, which will determine where (and whether) they go to university in the coming academic year. The subsequent flood of exam statistics will keep education-policy experts busy for the next few days, but it’s already emerged that the number of students taking the physics A-level exam has gone up, rising 6.1% since 2010 and 19.6% over the past five years.

This is welcome news, and it’s the inspiration behind this week’s Facebook poll, which asks:

What is the main benefit of studying physics at university?

As usual, you can cast your vote on our Facebook page.

Now, as for the reasons behind the increase in physics A-level students, several commentators have cited the improving image of physics in pop culture, as evidenced by television shows like Brian Cox’s Wonders of the Universe and the US comedy The Big Bang Theory. Even the IOP’s president, Peter Knight, has suggested that the “Brian Cox effect” and publicity surrounding CERN’s Large Hadron Collider (LHC) may have helped propel physics back into the list of the 10 most popular A-level subjects for the first time since 2002.

But with all due respect to Knight, I’m personally dubious about the influence of pop culture in this case. The UK’s education system forces students to specialize early, so the current crop of A-level students will have begun narrowing down their options at least three years ago. Back then, The Big Bang Theory had only been on UK television for a few months, the LHC was still under construction and the two Wonders programmes were but gleams in Cox’s eye. So it’ll be a few years before we’ll know the true extent of their impact.

I’d place more weight on the second half of Knight’s statement, in which he noted that “Many students are also responding to calls from university leaders, businesses and the government to choose subjects which will provide the skills our country needs.” Campaigns by all these groups to boost science have been going on for years, and economic uncertainty (which, in the UK, dates back to 2007, when the bank Northern Rock collapsed) has probably made students more receptive to them. It’s worth noting that the last time the UK had so many physics students was in 2002, when the world economy was still recovering from the dot-com bust.

Anyway, regardless of the reasons behind physics’ new-found semi-popularity, we wish all students luck with their results – and those who plan to continue their physics education at university should watch this space next week, when we’ll discuss your views on the benefits of studying physics.