Skip to main content

Reset your password

Please enter the e-mail address you used to register to reset your password

Note: The verification e-mail to change your password should arrive immediately. However, in some cases it takes longer. Don't forget to check your spam folder.

If you haven't received the e-mail in 24 hours, please contact customerservices@ioppublishing.org

Registration complete

Thank you for registering with Physics World
If you'd like to change your details at any time, please visit My account

Close
Home » Page 1531

Darwin’s grandson proved right over fishy physics

Darwin Year is now in full swing but the great evolutionary biologist was not the only member of the Darwin family to propose a scientific explanation for the behaviour of animals. His grandson — a British physicist, also called Charles — developed the novel idea that swimming marine life play a significant role in ocean mixing, an important process for distributing nutrients around the world’s oceans. Now, the Darwin family have yet another reason to celebrate this year, as a pair of researchers in California claim to have verified experimentally the theory of Charles Darwin Junior.

Fluid mixing processes are essential in the maintenance of global ocean circulation and they are also responsible for the transport of nutrients — a vital process in the marine ecosystem. Earth scientists have long-since agreed that this process is heavily influenced by atmospheric conditions, such as prevailing winds and heat exchange. However, for well over 100 years, some scientists have also argued that the action of fish swimming, when culminated over thousands of kilometres, could also have a part to play in the process.

Shake it like a seahorse

In the early 1950s Sir Charles Galton Darwin developed a physical model to explain how the movement of fish could be mixing the ocean. Darwin’s mechanism centred on the movement of fluid as fish swim vertically in a water column — marine animals are effectively dragging water with them as they swim up and down. As water pressure increases with depth, the swimming fish are continuously affecting the total potential energy of the fluid leading to further ambient fluid motions and eventually molecular mixing, claimed Darwin.

Partly because of inconclusive experimental results and partly because of the ongoing debates about atmospheric-ocean interaction, Darwin’s idea seemed to fall by the wayside in the mainstream research community. Fifty year later, however, Kakani Katija and John Dabiri at the California Institute of Technology say they have found firm experimental evidence to back up the idea of biogenic mixing. Enlisting the help of a team of scuba divers, the researchers captured the motion of jellyfish swimming vertically upwards from cold waters into warmer ones.

Mastigias jellyfish
In the spotlight lasers reveal motion

The major technical challenge was to capture the speed and direction of water when it is essentially transparent. By tracking the motion of particles suspended in the water, the researchers could determine how much kinetic energy an animal is injecting into the water as it swims. Particles were illuminated in a two-dimensional plane of the water and a video camera records the particle motion, in a process known as laser velocimetry. “For the divers the challenge is to control their body motions so that the camera is effectively stationary in the water, and so that the diver does not disturb the animals or the water around the animals being measured,” Dabiri told physicsworld.com.

Global mix

Another important challenge is to figure out how much Darwin’s mechanism could contribute to the overall process of ocean mixing. To do this, the researchers compare swimming efficiencies for the major marine species, with previous estimates of the total kinetic energy produced by turbulence in the wake of swimming fish. Publishing their findings in Nature, Katija and Dabiri suggest that ocean mixing due to Darwinian mixing is comparable with the global contribution of winds and tides.

“We expect to see Darwinian mixing in locations with large and dense aggregations of swimming animals that exhibit large vertical migrations. A candidate location is the Southern Ocean, where large communities of Antarctic krill perform these types of migrations,” said Dabiri.

Despite these new findings, it may still take further research for the idea to be fully accepted by the ocean science community. Eric Kunze, an ocean physicist at the University of Victoria in Canada explained that it has taken a long time to develop our current models of mixing caused by atmospheric conditions and there are still many unanswered questions. “The biological mixing mechanism appears to be even more challenging so I suspect it will be some time before we have an understanding of it,” he said.

The wider context of this research is the influence it could have on climate modelling. Amongst other effects, an increasing presence of presence of nutrients near the ocean surface could lead to algal blooms — a potential carbon sink. “An increase in one animal population can drive a decrease in another, and vice versa. Since not all animals will mix the ocean with the same efficacy, we must concern ourselves not only with the numbers of animals but also the species involved,” Dabiri told physicsworld.com.

Chamber simulates space on Earth

The cost of failure of a space mission is millions or even billions of dollars and, more importantly, could lead to loss of life. So testing spacecraft is an important part of developing new ways to travel into space. Those that carry personnel, such as the Orion capsule — part of NASA’s Constellation programme to return astronauts to the Moon — must function properly in the severe conditions of space to ensure the health and safety of the individuals on board.

The Space Power Facility (SPF) at NASA’s Glenn Research Center’s Plumbrook Station in Sandusky, Ohio, is the world’s largest space-simulation chamber used to test spacecraft. The cathedral-like chamber is 37 m tall and 30 m across, with a volume of around 23,000 m3. The facility — known as a thermal vacuum chamber — can reproduce both the temperature and pressure of space. The latter can vary from around 10–3 mbar at 50 km from Earth to 10–6 mbar at 170 km away.

Craft for testing can have a mass of up to 270 tonnes and either be built in the chamber or brought in prefabricated via two 15 ×  15 m doors and three sets of standard-gauge rail tracks. The temperature can be adjusted from –150 to 50 °C by a “thermal surface” with an area of about 1500 m2. A craft is not placed in direct contact with the surface, which means that its temperature change is due to radiation heat transfer. The temperature-controlled surface is cooled by a huge container with a million litres of liquid nitrogen and two 2.2 MW gas compressors. Infrared quartz lamps — simulating the radiation heat transfer from the Sun — are arranged around the object to be tested.

The SPF chamber can be pumped down from atmospheric pressure to high vacuum in less than 20 h using a unique technique. “Roots pumps”, which consist of two figure-of-eight-shaped lobes or impellers that rotate at 1500–3500 rpm, are first used to quickly remove the large volume of air. These work not by the principle of gas expansion and compression but by moving a volume of gas. The pumping speed is set by the internal volume of the pump multiplied by the rotational speed of the pump, so a physically bigger pump has a higher pumping speed. Evacuating the chamber is done via groups of Roots pumps in parallel, known as “stages”, which have a common inlet and a common outlet pressure. For example, a two-stage system has a first stage consisting of a group of pumps that remove air from the vacuum chamber, and exhaust it into a second stage of pumps that then pumps the chamber to a lower pressure.

At the SPF the first stage has four Roots pumps arranged in parallel and connected to the vacuum chamber through a 1.2 m diameter pipe. This stage evacuates the chamber from atmospheric pressure to 600 mbar in about 20 min. Two Roots pumps in parallel with a 60 cm inlet piping then evacuate the chamber to 390 mbar in another 20 min before two Roots pumps with 45 cm diameter inlet piping reduce the pressure to about 170 mbar after an additional 20 min. The fourth stage, consisting of two pumps with 35 cm inlet piping, reduces the pressure to 90 mbar in a further 20 min. Finally, six rotary piston pumps in parallel with 15 cm inlet piping kick in to bring the chamber to 0.0133 mbar in an additional 30 min. Rotary piston pumps use a piston to expand and compress a gas, similar to an air compressor. The fifth stage then exhausts to atmosphere.

These five stages of pumps remove 53 tonnes of air, and then they are isolated from the chamber so that the helium cyropumps can come online to remove the remaining 700 g of air. Helium cryopumps operate by freezing the air inside the vacuum chamber and then collecting it on the cold surfaces of the pumps, which are at a temperature of 15 K. When enough ice has built up on the cold surfaces, the pumps must be warmed to release the air. This type of pump can only operate under vacuum conditions. After around 70 min the chamber vacuum level is reduced to 3 ×  10–5 mbar by 10 helium cryo-pumps. The vacuum level is reduced to less than 10–7 mbar in an additional 3–10 h.

We recently tested the air-bag landing system for the Mars Exploration Rover mission by simulating the conditions that would be experienced when landing on the Martian surface. This revealed that the air bags would be torn to shreds during the actual landing of the Spirit and Opportunity rovers. Without ground testing, and overcoming these issues with the help of the SPF, the rovers would have crash-landed on Mars at a cost of around $820m.

Diamond coatings are branching out

Diamond — hard, sparkling and bright — has been revered for thousands of years as a gemstone. Nowadays it is also widely used in industry, with the first papers on “polycrystalline” diamond having been published as far back as 1911. However, it was not until 1971 that Sol Aisenberg and Ronald Chabot at Whitaker Corporation in the US discovered a new form of carbon that had the same form of bonding as diamond, but that was amorphous rather than crystalline. Created using ion-beam deposition, these thin films were coined “diamond-like carbon” (DLC) and are now used in everything from razor blades to computer hard disks.

Since then, researchers have worked hard to study the properties of DLC, which follows the contours of the surface rather than “filling in” the peaks and valleys. It is also highly smooth, its low friction arising from the relatively large proportion (65%) of diamond-like sp3 bonds between pairs of carbon atoms and the relatively small proportion (35%) of graphite-like sp2 bonds, which makes it amorphous rather than crystalline. Indeed, researchers at the Fraunhofer Institute in Germany have characterized different types of DLCs according to how they are formed and the percentage of sp2, sp3 and (sometimes) hydrogen bonds.

Another interesting feature of DLC is that it can be deposited onto substrate materials at temperatures of 200–300 °C, whereas polycrystalline materials have to be deposited at a much higher 800–1200 °C and so cannot be coated onto substrates that change phase below this temperature. Unfortunately, it is not easy to produce useful DLC films that are thicker than about 3–5 µm because the high temperatures used to make them generates stresses inside the materials, which then expand on their substrates. Now, however, Diamond Hard Surfaces Ltd has developed and patented a process for producing a material that bridges the gap between traditional DLCs and polycrystalline diamond.

The result is a hard, low-friction amorphous material, named Adamant, that can be applied in thicknesses of 40 µm and beyond, which is an order of magnitude higher than other technologies. Created using a patented plasma-assisted chemical vapour deposition (CVD) process operating at less than 100 °C, the material has a hardness of 3500–4000 on the Vickers hardness (HV) scale as a result of its very high proportion (~99%) of sp3 bonds. (The hardness of tungsten carbide, in comparison, is only 2000 HV.) The process uses ultra-high-vacuum conditions and involves splitting up carbon-containing molecules, with the resulting ions being accelerated towards the surface of a substrate on which tetrahedrally bonded carbon (i.e. diamond) is formed.

Adamant has many potential applications, particularly those where bulk materials (e.g. tungsten carbide) and coatings (e.g. hard chrome) are used in thick layers of up to 100 µm. Indeed, since Adamant is 12–15 times as wear-resistant as tungsten carbide and about twice as hard, any film made from it will last far longer than a tungsten-carbide film of the same thickness. That hardness makes the material useful for oil and gas firms that send drill bits and other moving parts long distances down underground shafts to reach the source of fuel. Adamant is also being used to make everything from long-life cam shafts for the motor-sport industry, where engines are not allowed to be opened up between races, to sharp, longer-lasting knives to cut plastic sheets as they roll off an industrial production line.

Adamant, which is transparent to infrared light, could also be used in the defence and aerospace industries. For example, the infrared light that missiles use to guide themselves to a target is usually directed through a sapphire window. Coating the sapphire with Adamant would make it much tougher and reduce the possibility of the window becoming damaged due to the abrasive effect of air rushing past. Another advantage is Adamant’s “green” credentials: it does not need much energy to be made, uses harmless precursors and does not need any energy-intensive pre- and post-processing.

Owing to the low deposition temperature, the material can be coated on a variety of substrates, such as copper, aluminium, silicon carbide, tungsten carbide, titanium and even plastics, such as polyetheretherketone. The process is scalable and our company has just completed a new facility to make Adamant in large enough quantities to satisfy customer demand. There is plenty that we do not yet know about the boundaries between amorphous carbon and polycrystalline diamond, and our company is hoping to fill that gap.

From prairie to energy frontier

Fermilab, the scientific research facility, has for the past 37 years transformed a 10-square-mile patch of the Illinois prairie into the frontier of high-energy particle physics. Fermilab, the book, is the first written history of this unique place, covering both the birth of the Fermi National Accelerator Laboratory and its journey to its current position as a world centre of “megascience”. Yet Fermilab is far from being a dry historical account. It spans the entire spectrum of what is required to establish a cutting-edge facility and perform research there — from organizational aspects and technological choices to the sociology and politics of funding and site selection. The creation of Fermilab was a far cry from the establishment of a shining light on the prairie; rather, it was a practical solution for passionate researchers, driven to do physics amid the real-world constraints of shrinking federal science budgets.

One reason that there is more to Fermilab than just a simple history is that its authors Lillian Hoddeson, Adrienne Kolb and Catherine Westfall all have a long association with the lab. Hoddeson, the Thomas M Siebel Professor of History of Science at the University of Illinois at Urbana-Champaign, was first hired by Fermilab to document its history in 1977, just five years after the lab opened. Kolb has been Fermilab’s archivist since 1983, while Westfall, currently visiting associate professor at Lyman Briggs College at Michigan State University, wrote about Fermilab’s history in her doctoral dissertation, which was directed by Hoddeson. This closeness allows the authors to give the reader a true insider’s perspective, and by “living” their story they can offer insight and commentary that go beyond the bare facts. They give a sense of the drama and understand the personalities of those involved, and their passion and fondness for Fermilab come shining through in this illuminating book.

Fermilab concentrates on the first two decades of research at the lab, when physicists were engrossed in the hunt for new particles and new interactions, as well as the underlying explanation for what they found. The book is heavily footnoted and carefully referenced, and the text is sometimes quite dense; it includes many technical details that are only relevant to those in the business of high-energy physics. However, underneath this detail is a simple, clear narrative that follows the paths of the lab’s first two directors, Robert Wilson and Leon Lederman, their unique visions for the facility and their quests to realize their dreams for its future.

The book begins in the postwar era of the 1960s, when resources for science were abundant and particle physicists were busy finding new particles. Further progress in this search — then as now — required beams of ever-increasing energy. In the field of particle physics, scientists can convert energy into mass; thus a higher-energy collider allows physicists to create more massive particles and probe deeper into the quantum universe. Fermilab was envisioned by the US high-energy physics community as the next step in that progression. However, neither the type of accelerator nor its location were unanimously agreed upon by the high-energy physics community at the time. For example, the book’s first 100 pages describe in striking detail the dramatic way in which scientific and political discussions during the 1960s led to the selection of the Weston, Illinois, site over the perhaps more obvious Lawrence Radiation Laboratory in Berkeley, California.

A second controversy surrounded the choice of Robert Rathbun Wilson, an outspoken and perhaps brash opponent of the Berkeley design, as the lab’s first director. Wilson’s credo was that “any technology that works the first time is overdesigned and thus overpriced”, and his style was to cut costs to a bare minimum. His inspirational leadership and cowboy ingenuity got Fermilab through a trying construction phase. Wilson was able to establish a working accelerator laboratory, and in so doing, he also established a culture and spirit that exists at the lab to this day.

Still, the 1970s were a difficult period for the lab. It is not enough to merely establish a new facility; one has to then use it to advance our understanding of nature. However, in the beginning Fermilab was not awash with discoveries. Important developments in physics like the discovery of weak neutral currents and the charm quark — both well within the lab’s grasp — took place at competing facilities. Wilson resigned in 1978 amid funding troubles, leaving the lab’s future in the hands of Leon Lederman, then a professor of physics at Columbia University.

Known for his keen instincts, sharp wit and strong advocacy for physics and physics education, Lederman would go on to share the 1988 Nobel Prize for Physics for his pioneering work with neutrinos. As Fermilab director, he used his considerable personal charisma to garner the political support that the lab needed to build the Energy Doubler, a new accelerator that used superconducting-magnet technology to give Fermilab an unprecedented new window into the world of quarks. This was a major scientific step forward, and one Wilson had been unable to accomplish. In 1983, the Doubler beam was commissioned, and the accelerator renamed the Tevatron.

During the Lederman era, which ended when he stepped down in 1988, experiments grew larger and more complex, as improving our understanding of the fundamental questions that govern matter required big experimental tools and, consequently, large teams of scientists. By the early 1980s, when the lab secured funding from the US Department of Energy for two new colliding-beam detectors, true large-scale science was becoming the norm. Building the Collider Detector at Fermilab (CDF) required a team of several hundred physicists; DZero, a second giant detector built across the ring from (and in competition with) CDF, needed another few hundred. In 1986 a programme of colliding proton and antiproton beams was in place, and the effort paid off: the book ends in 1995 with the joint discovery of the top quark by the CDF and DZero collaborations.

Fermilab will be of interest to anyone curious about science and science policy, as well as those who want a better understanding of what it is like to perform large-scale research in high-energy particle physics. It is particularly relevant reading now, with CERN’s Large Hadron Collider (LHC) about to restart. Many decisions facing CERN today have parallels in issues that Fermilab dealt with decades earlier — including how to commission a new accelerator safely, and the trade-offs between perfection and just making things work.

Both labs are currently involved in a decade-long search for the Higgs boson — the long-sought and perhaps final missing piece in the Standard Model of particle physics. However, Fermilab’s long-term future is currently uncertain. It will soon hand over the mantle of the “energy frontier” to CERN, leaving it without a clear mission. The lab has ambitious plans to redefine itself and to take over leadership of the “intensity frontier” — that is, to create a new accelerator complex capable of producing the high-intensity beams of particles necessary for a different “brand” of physics. However, only time will tell how Fermilab Volume II will read.

Once a physicist: Conrad C Lautenbacher Jr


What sparked your interest in physics?

I have always been fascinated with science, and when I was 12 or 13, I was fortunate to have teachers who encouraged this interest. My father also had an aptitude for science and mathematics; he was a naturally intelligent individual who left high school before graduating and became a dental technician because his family needed him to work — this was during the Great Depression. So I believe this interest is in my genes.

What led you to join the Navy?

I grew up in Philadelphia, and one of my teachers who had a son at the Naval Academy would read letters from him to the class. These letters fascinated me — they were full of adventure and excitement, with descriptions of places I had never seen. By the time I joined the Navy in 1960, students at the Naval Academy were allowed to choose a major subject, rather than focusing solely on a military and engineering curriculum, so I took every course I could in mathematics and physics. I graduated with a double major in both subjects in 1964, and then went to sea for four months on an aircraft carrier before beginning a programme leading to a PhD in applied mathematics at Harvard University.

How did you get into oceanography?

My Navy and science interests came together in the subject of fluid mechanics and I enrolled in a number of graduate-level courses in the subject. My PhD involved building tsunami models, which is an oceanographic application of this topic. In the late 1960s computers were still fairly primitive, so my model of how tsunamis run up onto islands used an IBM 7094, which required punch cards and had a memory that was probably smaller than your watch has today.

What are you working on now?

I spent many years in the Navy learning how to lead and manage large-scale operations, and I have just finished an eight-year spell as administrator of the US National Oceanic and Atmospheric Administration (NOAA), which has one of the largest research infrastructures of any single agency in the world — it even has people living at the South Pole recording atmospheric composition and investigating ozone-hole physics. Now I am working for the Computer Sciences Corporation and a subsidiary company, Antarctic Research Support, which is bidding for the next contract to support the US National Science Foundation’s work in Antarctica. Operating in Antarctica requires more than just scientists researching neutrino detection and ice-sheet mechanics — it also requires a unique and specialized support system. Antarctica has perhaps the harshest environment in the world and supply lines that stretch more than a third of the way around the Earth. Meeting the needs of daily living is an enormous challenge.

What are your views on climate change?

Whatever we do about climate change, we need to base it on sound science, which means investing in improved observing systems and obtaining climate-level data. As head of NOAA, I spent a lot of time organizing an international consortium to build a Global Earth Observation System of Systems (GEOSS) — including satellites and atmospheric-, ground- and ocean-measurement systems — so that, among other things, we can improve our understanding of climate dynamics. The models today are much better than the ones that existed a decade ago, but they are still not accurate enough to project very far into the future, and certainly not for 100 years from now. We know that the Earth has been warming, and we know that there are effects that, if extended, will cause ­significant problems. So we know enough to do something, but in my view the choice of what to do is a political question. As a scientist, I try to stay out of those kinds of debates.

What is your advice for physicists who want to tackle environmental problems?

First, work in a field associated with geosciences. For the future of the human species, we need more people who are interested in Earth sciences. The second thing is to think big. If we are going to solve the climate problem, or build a sustainable society, we need breakthrough scientific work. We have maybe a couple of generations to resolve these issues. I do not want to be negative — I am a glass-half-full person — but I do want to support the need for nations to invest more in Earth sciences and environmental education for the public. I reorganized NOAA in a way that aligned agency offices to mirror the relationships that exist among the Earth’s natural systems. It is counterproductive to isolate scientific disciplines such as meteorology, biology, geological surveying and so on — they are naturally connected by Earth systems’ dynamics. Earth scientists of all disciplines must talk to each other and break down the barriers of jargon and culture.

How do you feel your physics training has helped in your career?

Many people do not understand that physics is an important practical subject. Today’s world is highly technical. We cannot exist without the benefits of scientific discoveries — they are commonplace and everywhere around us. Physics has helped me in the same way that it helps everyone — the art of daily living requires both an appreciation and an understanding of scientific and physical processes. All of us must realize that the future of society depends on this technical world being supported properly, and also improved rapidly to reach the goal of a sustainable future for the human species.

Religion explained

When Physics World carried out a readers’ survey to mark its 20th anniversary in October 2008, in the main the editors took a light-hearted approach. They asked readers to answer nine multiple-choice questions on matters such as who inspired them to do physics, whether they mind being unpopular at parties, and what was the top physics discovery of the previous 20 years. A summary of the results appeared last year on the physicsworld.com blog (22 December 2008).

But one question was more serious: “Which of the following reflects your views on science and religion?” Readers were offered a choice of five answers (see “Readers’ view” at the end). It takes but a glance to see that this question suffers the flaws of other efforts to get hard statistics about “deep issues”. I know I cannot be too critical, given that the editors devised the survey and you (well, 505 readers) responded. Let me just say that the question must have been thought up very close to deadline. But much more revealing than the data were readers’ comments.

The matrix

I found that I could, very roughly, place each of the comments in a 2 x 2 matrix based on how readers conceive of science and religion (see figure). In the upper-left quadrant, I put respondents who regarded science as consisting of (true) beliefs about the world, and religion likewise as a set of beliefs about the world and the existence of a personal God in it. For some respondents in this quadrant, who made up perhaps two-thirds of all respondents, religious beliefs are salutary and have nothing to do with science.

But for others, religious beliefs reflect ignorance and are akin to belief in mermaids and unicorns. “Religion stems from lack of knowledge,” wrote one reader; while another said that religion has a place in human culture just as “Father Christmas and the tooth fairy” do. People in this quadrant tended to view science and religion as inevitably conflicting over issues such as evolution and cosmology.

In this quadrant I would also put respondents who said they were agnostic, viewing religion as consisting of an unproven belief in a personal God. “As a physicist,” one wrote, “I have to accept the possibility of existence of anything that can’t be disproved (yet).” Another: “I am an agnostic…there is insufficient evidence but the probability is very low.” Still another: “Never rule out anything until proved otherwise, however unlikely.” These agnostics regarded belief in a personal God as akin to belief in the Loch Ness Monster, Bigfoot or UFOs. If God is proven to exist, this may call for some behaviour modification — but until then, we are fine as we are.

In the upper-right quadrant, I assigned respondents who viewed science as belief in a set of neutral facts, and religion as an approach or stance towards the world. These people viewed religion as not consisting of beliefs — not even in a “divine administrator” — but about how we live and our principles for leading a better life, as exemplified perhaps by Buddhists, Quakers and Unitarians. Many respondents with this view of religion saw it as posing no threat to science; indeed, several cited “organized religion”, rather than religion per se, as what conflicts with science.

Others in this quadrant saw religious approaches as dangerous, as a social pestilence or plague — “the root of earthly conflicts” — while still others revealed a Marxist-like conception of religion as the opiate of the masses. “Religion has no place in science,” commented one reader, “but in practice it does have a place in human society since the masses need some sort of moral guidance that science can not supply (and shouldn’t).” Religion helps people “to develop a conscience and provides an otherwise absent comfort”, claimed another, and another said that “the masses need religion but scientists should know better”.

In the lower-left quadrant, I put respondents who saw religion as consisting of beliefs, but who saw science not as having to do with beliefs in particular theories or results — these change! — but as an approach to generating beliefs. Scientists cannot avoid inheriting some beliefs about the world, but they probe these beliefs with all available resources, and some ways of probing are better than others. Members of this group often saw science as a progressive worldview as comprehensive as religion, for inquiry is a supreme value, truth is sought in a public and objective process, and no belief is unchallengeable. Those in this quadrant tended to see science as more profound than religion. “Science is my religion,” one person wrote.

The critical point

I would assign myself — and a handful of other respondents — to the lower-right quadrant, viewing both science and religion as consisting more of approaches to the world than of sets of beliefs about it. Humans inherit fragments of knowledge about nature, and scientific inquiry is the response to the feeling that it is worth knowing more. Humans also inherit imperfect patterns of behaviour, and a religious life is the response to the feeling that we can “live better” than we do.

But it is a messy subject, for most adults know that there are better and worse ways of living. Yet in reaction to the perceived excesses and hypocrisies of organized religion, many people name that desire to live better as being “spiritual”, “humanistic” or even “secular humanistic” — reserving the term “religious” for organized schemes to live better that they themselves deem deluded or impractical.

What is fascinating about this question in the Physics World survey are not the statistics but the many different conceptions of science and religion that lie behind them.

Readers’ views

Responses to the question “Which of the following reflects your views on science and religion?”, which appeared in Physics World’s 20th-anniversary survey of October 2008. A total of 505 readers replied.

  • I am an atheist who sees no place at all for religion in the universe — 114 responses (22.6%)
  • I am a non-believer, but I think religion and science can coexist because they each deal with separate aspects of the universe — 153 responses (30.3%)
  • I am a religious person who thinks science and religion can coexist because they each deal with separate aspects of the universe — 81 responses (16.0%)
  • I am a religious person who thinks that science and religion are different ways of looking at the same thing. My faith enhances my appreciation of science — 91 responses (18.0%)
  • Other — 66 responses (13.1%)

The Earth – for physicists

The prospect of human-induced climate change has many people worried. In addition to the sheer scale of the problem, there is also the challenge of it being so complex. The Earth’s behaviour is fiendishly hard to predict in detail. Computer power is not enough: models need to be based on solid physical insights and a good understanding of the Earth’s current behaviour — and also its history.

Luckily, in the past decade we have learned a vast amount about this history. The mists of time are clearing. It seems we are not alone in passing through perilous times. The Earth has witnessed some remarkable disasters. To keep our tale brief, let us focus on four: the “big splat” about 4.55 billion years ago; the “late heavy bombardment” about 4 billion years ago; the “oxygen catastrophe” roughly 2.5 billion years ago; and the “snowball Earth” events about 850 million years ago. The details of these events — and indeed whether they even happened at all — remain controversial. They are, however, widely accepted theories. In every case there is interesting physics involved in testing these theories.

The birth of the Moon
The Sun was probably formed from the gravitational collapse of a cloud of gas and dust. Early models of star formation assumed spherical symmetry, but if you know the joke to which the punchline is “consider a spherical cow”, then you should suspect that this is a dangerous oversimplification. Indeed, angular momentum plays a major role. As such a cloud collapses gravitationally, it should form a spinning “accretion disk”.

When the centre of this disk became dense enough for its pressure to hold it up, our Sun was born as a “protostar”. This phase lasted a scant 100 000 years or so; the temperature then rose to the point where an outflow of hot gas prevented the Sun from accreting any more material. At this point the Sun became what we call a “T Tauri star”, powered only by gravitational energy as it slowly shrank. After about a further 100 million years, it became an ordinary main-sequence star as the hydrogen at its core began to undergo fusion.

Some dust circling the early Sun became hot and melted, and some of the molten droplets later froze into “chondrules” — millimetre-sized spheres of simple minerals such as pyroxene and olivine, which are mostly made of sodium, calcium, magnesium, aluminium, iron, silicon and oxygen. These chondrules are the main constituent of some of the most primitive objects that still ply their way through the solar system: stony meteorites called “chondrites”.

The dust circling the early Sun started forming lumps called “planetesimals”. As these lumps collided, they got bigger and bigger, eventually forming the asteroids and planets we see today. Some lumps melted, letting heavier metals sink to their cores while lighter material stayed on the surface. And some crashed into each other, shattering and forming chondrites and other meteorites such as iron–nickel meteorites and stony meteorites called “achondrites”.

By using radioactive-dating techniques on meteorites, researchers claim a shockingly precise knowledge of when all this happened: sometime between 4.56 and 4.55 billion years ago. So, the Earth was probably formed sometime around then — and our story officially begins at this point.

The Earth’s history is divided into four eons: Hadean, Archean, Proterozoic and Phanerozoic. When I was a child, the “Cambrian era” was as far back as my textbooks went, except for the murky “Precambrian”. But the Cambrian began just 540 million years ago. The Cambrian marks the start of the current eon, the Phanerozoic, meaning “the age of visible life”. This is when multicellular organisms took over the world, leaving fossils we find today. But we will dig much deeper: the Phanerozoic will be end of our story.

Back to the Hadean. As befits its name, this was a time when the Earth was hellishly hot. It began with an event that formed the Moon around 4.53 billion years ago. What made the Moon? The most popular current explanation is the “giant-impact theory” — sometimes called the “big splat” theory.

The idea is that another planet formed at one of the Lagrange points of Earth’s orbit. In 1772 Joseph Louis Lagrange showed that if you have a planet in a circular orbit about the Sun, then a much lighter body will stably orbit the Sun at the same distance if it lies 60° ahead or behind that planet. There are indeed many asteroids located near the Lagrange points of Jupiter, and also some at the Lagrange points of Mars and Neptune. No asteroids have been found at Earth’s Lagrange points. But according to the giant-impact theory, a planet did form at one of these points. When it attained a mass of about that of Mars, it would no longer have been stable at this location. It would have gradually drifted toward the Earth, and eventually smacked right into it! This collision could have formed the Moon.

A very bad day
A very bad day

It is a dramatic theory, but there is a strong case for it, nicely summarized by science writer Dana Mackenzie’s recent book The Big Splat, Or How Our Moon Came to Be. For example, tidal friction is making the Moon gradually recede from the Earth. We know it is now moving away at a rate of about 3.8 cm per year. Ancient sediments record the tides and show that months have been getting longer at least since Precambrian times. Extrapolating backwards we find that in the Hadean eon the Moon was very close to the Earth. Could it have been flung off from the Earth by centrifugal force, or formed near the Earth in the first place, or captured by the Earth’s gravitational field? All these theories must be considered, but the giant-impact theory seems to fit the data best. People take it so seriously that the hypothetical doomed planet that hit Earth even has a name: Theia. In Greek mythology, Theia was a female titan who gave birth to the Moon.

In 2004 the astrophysicist Robin Canup of the Southwest Research Institute in Boulder, Colorado, published some remarkable computer simulations of the big splat. To get a moon like ours to form — instead of one that is too rich in iron, or too small, or wrong in other respects — you need to choose the right initial conditions. Canup found it best to assume that Theia is slightly more massive than Mars: between 10% and 15% of the Earth’s mass. It should also start out moving slowly towards the Earth, and strike the Earth at a glancing angle.

The result is a very bad day. Theia hits the Earth and shears off a large chunk, forming a trail of shattered, molten or vaporized rock that arcs off into space. Within an hour, half the Earth’s surface is red hot, and the trail of debris stretches almost four Earth radii into space. After three to five hours, the iron core of Theia and most of the debris comes crashing down. The Earth’s entire crust and outer mantle melts. At this point, a quarter of Theia has actually vaporized.

After a day, the material that has not fallen back down has formed a ring of debris orbiting the Earth. But such a ring would not be stable: within a century, it would have collect to form the Moon we know and love. Meanwhile, Theia’s iron core would have sunk to the centre of the Earth.

The giant-impact theory is still much debated, in part because there is little direct evidence left: the oldest known rocks on Earth were formed almost half a billion years later.

The late heavy bombardment
The Archean eon begins with the formation of the first rocks that survive to this day. This happened about 4 billion years ago. Many igneous rocks, in particular basalt, must have been formed before this. In fact, the oceans may have started forming 4.2 billion years ago. But we do not see any traces of this early geology. One possible reason is that the beginning of the Archean eon was not a peaceful time.

After the Moon was formed, the Earth continued to suffer many impacts. Curiously, instead of their frequency gradually dropping off over time, it may have spiked during a period called the late heavy bombardment, which occurred some 4 to 3.8 billion years ago. A lot of large craters on the Moon date back to this period, so probably the Earth got hit too — but here, such old craters would be lost to weathering and geological activity. So, the Moon is our guide.

During the late heavy bombardment, the Moon was hit by 1700 meteors that made craters that are more than 100 km across. The Earth could easily have received 10 times as many impacts of this size, with some being much larger. To get a sense of the intensity of this pummelling, recall the meteor impact that may have killed off the dinosaurs at the end of the Cretaceous period 65 million years ago. This left a crater 180 km across. Impacts of this size would have been routine during the late heavy bombardment.

Meteor blitz
Meteor blitz

Why was this era so violent? One theory is that at around this time Jupiter and Saturn moved into a 2:1 orbital resonance (when Jupiter completes two orbits at the same time as Saturn completes just one), thereby causing a big disruption in the original population of asteroids and icy objects orbiting the Sun. In 2005 an international collaboration of planetary physicists, including Hal Levison from Southwest Research Institute — one of the people who pushed the idea that Pluto is a “dwarf planet” — published a paper about some fascinating computer simulations of the solar system (Nature 435 466). As initial conditions, they take all four gas giants to lie in circular orbits more closely spaced than they are now. By interacting with planetesimals, Saturn, Uranus and Neptune gradually migrate outwards. When Saturn reaches the point where it orbits the Sun once for every two orbits of Jupiter, the whole outer solar system destabilizes. The orbits of Neptune and Uranus become more eccentric and they throw many planetesimals out of their original orbits. Some are hurled into the inner solar system, which would explain the late heavy bombardment.

The oxygen catastrophe
It is believed that the Earth’s surface cooled enough to form a crust even before the late heavy bombardment. Meanwhile, volcanic activity would have released lots of steam, carbon dioxide and ammonia. This formed what is called the Earth’s “second atmosphere”. The Earth’s “first atmosphere”, mainly hydrogen and helium, was already lost to space. The second atmosphere was mainly carbon dioxide and water vapour, with some nitrogen but probably not much oxygen. This second atmosphere had about 100 times as much gas as today’s “third atmosphere”.

As the Earth cooled, oceans formed. They may have boiled away completely during some large impacts but then reformed. Eventually much of the carbon dioxide in the atmosphere dissolved into the seawater. This later precipitated out as carbonates, thus starting a new phase in what the geologist Robert Hazen of the Carnegie Institution of Washington’s Geophysical Laboratory and his co-workers call “mineral evolution”. This is not evolution in the Darwinian sense, just the gradual diversification of minerals over the Earth’s history. In 2008 a team of geologists led by Hazen estimated that 350 kinds of mineral could be found on Earth during the Hadean eon. But as the Earth’s history proceeds, their count keeps rising. By the end of the Archean eon it reaches 1500, thanks in part to the formation of oceans – but also thanks to the rise of plate tectonics.

The first step in plate tectonics was the formation of “cratons”: ancient, tightly knit pieces of the Earth’s crust and mantle, dozens of which survive today. For example, in the UK, south-eastern Wales and part of western England lie in the Midlands craton. While most cratons only finished forming 2.7 billion years ago, nearly all started growing earlier. Cratons are made largely of igneous rocks like granite, which are more sophisticated than basalt. Granite is formed in a variety of ways, for example by the remelting of sedimentary rock. Early granite-like rocks were probably simpler.

Cratons fit together to form the larger plates that constitute the Earth’s crust today. Indeed, plate tectonics as we know it started about three billion years ago. A key aspect of this process is the recycling of the Earth’s crust through “subduction”: oceanic plates slide under continental plates and get pushed down into the mantle. Another feature is underwater volcanism, leading to hydrothermal vents — fissures in the seafloor that spew out hot water.

It is possible that these vents played a role in the most dramatic of all Archean developments: the origin of life. Since the early Earth lacked free oxygen, the first life must have been anaerobic. Even today, many of the oldest known microbes, such as those found in hydrothermal vents, cannot tolerate the presence of oxygen. Such organisms gave rise to an active sulphur cycle and deposits of sulphate ores starting about 3.6 billion years ago. Later they made the atmosphere increasingly rich in methane.

At some point, microbes started photosynthesizing and putting oxygen into the atmosphere. It seems likely that the first plants acquired their ability to photosynthesize by symbiosis with such microbes. Indeed, the chloroplasts in plants have their own separate DNA.

It is not clear when photosynthesis began — estimates range between 3.5 and 2.6 billion years ago. One possible clue — rocks called “banded iron formations” that are made of thin layers of iron oxides alternating with iron-poor rock — started to appear at about this time. They may have formed when oxygen from the first photosynthesizing organisms reacted with iron in seawater. No-one knows for sure why the periods of iron-rich sediment come and go.

It took a long time for photosynthesis to have a significant effect on the Earth’s atmosphere — but when they did, roughly 2.5 billion years ago, the result was dramatic. After all, oxygen is highly reactive in its gaseous form, and most early life could not tolerate it. So, this episode in the Earth’s history has been dubbed the oxygen catastrophe. Luckily, evolution found a way out: now many species need oxygen.

The oxygen catastrophe marks the end of the Archean eon and the beginning of a new eon, the Proterozoic. The next billion years were dominated by something called the “intermediate ocean”: the seawater contained a lot more oxygen than before, but still much less than today.

The big chill
The big chill

Snowball Earth
Starting about 850 million years ago, something dramatic happened: episodes of runaway glaciation during which most or all the Earth was covered with ice. Advocates of the extreme version of this scenario call them “snowball Earth” events, while others argue for a mere “slushball”. Since ice reflects sunlight, making the Earth even colder, it is easy to guess how such runaway feedback might happen. The opposite sort of feedback is happening now, as melting ice makes the Earth darker and thus even warmer. The interesting questions are why this instability does not keep driving the Earth to extreme temperatures one way or another, why the snowball-Earth events started when they did, and why the Earth did not stay frozen.

Here is a currently popular answer to the last question. Ice sheets slow down the weathering of rock. This weathering is one of the main long-term processes that use up atmospheric carbon dioxide, by converting it into various carbonate minerals. On the other hand, even on an ice-covered Earth, volcanic activity would keep putting carbon dioxide into the atmosphere. So, eventually carbon dioxide would build up and the greenhouse effect would warm things up again. When the ice melted, weathering would increase and the amount of carbon dioxide in the atmosphere would drop again. However, this feedback loop is very slow. Indeed, it has been suggested that in the hot phase, as much as 13% of the atmosphere could be carbon dioxide — some 350 times more than we see today!

By the end of these glacial cycles, it is believed that oxygen had increased from 2% of the atmosphere to 15%. (Now it is 21%.) This may be why multicelled oxygen-breathing organisms date back to this time. Others argue that the “freeze–fry” cycle imposed tremendous evolutionary pressure on life and led to the rise of multicellular organisms. Both these theories could be correct. (For more details, try Gabrielle Walker’s excellent book Snowball Earth.)

The rise of multicellular organisms marks the end of the Proterozoic eon and the start of the current eon: the Phanerozoic. This is the end of our story — but of course the history of the Earth does not end here.

We are now in the Cenozoic era of the Phanerozoic eon. The Holocene era has just ended and the Anthropocene has begun, characterized by significant human impact on ecosystems and climate. By demolishing natural habitats, humans have set in motion a mass-extinction event that may rank with the end of the Cretaceous period 65 million years ago. We are also boosting atmospheric carbon-dioxide levels at an incredible rate. If the temperature rises by one more degree, then the Earth’s temperature will be the hottest it has been in 1.35 million years, before the current cycle of ice ages began. Where are we heading? Nobody knows.

However, studying the history of the Earth will put us in a better position to guess. We cannot run experiments to test the Earth’s response to different levels of greenhouse gases. Computer models are essential, but evidence from snowball Earth and other incidents in the Earth’s past are crucial checks on these models. Similarly, studying past mass-extinction events, and the Earth’s recovery from them, may provide clues about the future of biodiversity on this planet.

Threats to ultra-high-field MRI

In 2004 the European Commission (EC) adopted a directive restricting occupational exposure to electromagnetic fields. This directive (2004/40/CE), which examines the possible health risks of the electromagnetic fields from mobile phones, Wi-Fi, Bluetooth and other devices, concluded that upper limits on radiation and applied electromagnetic fields are necessary to prevent workers from suffering any undue acute health effects. But although not initially intended, the biggest impact of the directive could be on magnetic resonance imaging (MRI), which is used in hospitals worldwide to produce images of unrivalled quality of the brain and other soft tissues.

MRI involves studying how hydrogen nuclei in water molecules respond to an applied static magnetic field. When placed in a sufficiently strong field, the hydrogen nuclei absorb energy from an applied electromagnetic radio-frequency (RF) field and re-emit it in a way that reveals information about the physical and chemical properties of the tissue’s environment in the body. MRI is a powerful diagnosis tool that is much safer than techniques that use X-rays or other ionizing radiation.

A typical MRI scanner has three main components: a magnet producing a static field of typically 1–3 T; an RF-field generator with antennas or coils; and a smaller electromagnet that is switched on and off rapidly to localize the hydrogen nuclei and allow an image to be obtained. When an MRI scan is being performed in a hospital, most of the relevant staff leave the room. However, the main magnet, which is made of superconducting materials, is always on and there are a number of instances, for example when a patient is being placed in the scanner or anaesthetized, where staff members need to be present in the field. Engineers are also exposed to the main magnet’s field whenever a scanner is being installed or serviced.

Stalling progress
The problem with the exposure limits that are outlined in the directive is that they follow the recommendations of the International Commission on Non-Ionizing Radiation Protection (ICNIRP) — a non-governmental organization officially recognized by the World Health Organization — based on a precautionary approach to very limited data, most of which are not relevant to MRI. Those limits could end up preventing the technique from being used — just when European scientists are starting to lead the world in ultra-high-field (UHF) MRI magnet research. The initially proposed limits will immediately put the brakes on progress and, moreover, be a big blow to companies that make MRI scanners and magnets, such as Siemens, Philips, Bruker and Magnex. These firms could end up being unable to meet the growing global demand for clinical UHF MRI scanners, the high fields from which could boost the potential of MRI for healthcare and biomedical sciences, particularly for neurological applications.

Investigations conducted by the EC and the UK government concluded that MRI workers routinely exceed the exposure limits in the directive — despite no evidence that they experience any ill effects as a result. This fact led the EC to postpone until April 2012 the implementation in member states of the directive, which had been due to come into effect on 30 April 2008 — the idea being to allow a satisfactory solution to be found. However, in April of this year the ICNIRP published yet another report — this time setting guidelines for static magnetic fields. (The initial guidelines set by the ICNIRP addressed only time-varying electromagnetic fields of up to 300 GHz.) If included in the directive, the new guidelines would have an even greater impact on the development of MRI technology in Europe.

While I applaud the ICNIRP for putting together an outstanding review of the literature on the known or reported effects of magnetic fields in biological tissues or organisms, it should be pointed out that regulations based on current (and necessarily limited) literature might potentially prevent any progress in MRI. The problem is that the proposed guidelines state that only a worker’s limbs can be exposed to fields between 2 T and 8 T. But because the magnets that produce such fields are so much bigger than the distance between the limbs, the trunk and the head, it is difficult — if not impossible — to expose a patient’s limbs to such a field without exposing their trunk and head too. The upshot is that it will no longer be possible to build, test, validate, maintain and use biomedical magnets above 2 T in Europe.

Although the report says that exposing the head and the trunk to 2–8 T fields might be “justified for some specific work applications when the environment is controlled and appropriate work practices are implemented”, this possibility remains to be clarified within the directive. Exposure to magnetic flux densities above 8 T is not even considered, as the report says that “not enough information is available on which to base exposure limits beyond 8 T”.

There is, however, a growing worldwide demand for clinical MRI scanners operating above 3 T. These high fields can be used to image the brain, anatomically and functionally, with unsurpassed spatial and temporal resolution to detect, for example, the onset of Alzheimer’s disease. MRI with ultra-high fields also makes it possible to image molecules other than water, such as important ions, metabolites and neurotransmitters, or tracers specially designed to reveal molecular or cellular disorders.

Indeed, there are currently well over a thousand 3 T MRI scanners and more than 30 7 T clinical MRI systems in use — or about to be installed — around the world, more than half of which are in Europe. Two 9.4 T human MRI scanners are already operating in Germany, while France will soon install a 11.7 T clinical MRI system. UHF systems for biomedical research on animals are even more common, some of which have fields of over 16 T. Yet there have been no published reports of these scanners having any adverse affect on workers at those sites.

It seems that the new ICNIRP report focuses on 2 T and 8 T because reliable literature is available only up to these field strengths, and not at higher strengths. However, these upper values must not be mistakenly understood by lawmakers as real critical thresholds, but rather technical limits at a given time, thus leaving room for progress. Furthermore, the report acknowledges that “guidance is not based on time-averaged exposure because, in addition to the experience gained with the use of MRI and other static field sources world-wide over the last 20 years, mechanistic considerations indicate that any effects are likely to be acute”.

Political challenges
Although patients undergoing MRI scans are not affected by the directive, they are nonetheless also exposed to the same field strengths (or even slightly higher as they are at the centre of the magnets). The ICNIRP report points out that the exposure limits for the general public should be derived by applying a reduction of five with respect to the occupational limit, which corresponds to 0.4 T. Guidelines for patients are still in preparation.

The situation is much better in the US, where the Food and Drug Administration (FDA), which considers MRI to be a “minimal risk” procedure up to 8 T, has continuously extended its recommended limits for subject exposure over the last few years from 2 T to 4 T, and now to 8 T for anyone aged one month or older. UHF MRI can still be used on human subjects beyond this limit — indeed there are two 9.4 T MRI clinical scanners in the US with a 11.7 T system about to be installed, albeit under the approval of a local Institutional Review Committee.

Indeed, there are no reports in the literature showing that ultra-high fields have any real impact on health. Of course, electromagnetic fields could have fundamental biological effects, but the question is whether those effects can actually harm a person or their organs. So although the EC’s directive should, in principle, be welcomed, as it seeks to promote environmental protection and workers’ health and safety, the problem is that it encompasses very broad aspects of the health concerns associated with electromagnetic fields and was not intended for MRI. As a recent European Parliament resolution points out, “the use of MRI must not be threatened by directive 2004/40/EC as MRI technology is at the cutting edge of research, diagnosis and treatment of life-threatening diseases for patients in Europe”.

UHF MRI is progressing rapidly, especially in Europe — there are already sites with MRI magnets operating above 8 T, with more to come. The fact that no reports of adverse effects have been published, so far, is reassuring, but caution must, of course, be exercised when exposing people, patients or workers to ultra-high fields. The challenge for politicians and the EC over the next two years is to create regulations that are flexible enough to not only protect workers, but also allow research in the field to progress. They need to work with patient groups, healthcare professionals, trade unions, industrial MRI manufacturers and biomedical research institutions. The European Union and its member states must carry out and fund, without delay, biological and epidemiological studies on the effects of ultra-high fields on tissues and organisms. Meanwhile, in the absence of available data, we should permit tests that expose people to static fields higher than 8 T — provided that appropriate precautionary measures are taken — and ensure that these limits can be extended if current or future studies suggest it is safe to do so.

Web life: Planet SciCast

So what is the site about?
Planet SciCast is an online repository for short films about science — a bit like a science-specific, moderated version of YouTube. As of July 2009, the site hosts over 150 films on topics ranging from CERN’s Large Hadron Collider to fun things to do with treacle. New content appears on the site every few weeks, and some films include links to information about related experiments, demos and activities. The site also runs an annual competition aimed at getting more people involved in making science films, with prizes in categories like “best original score” and “best presenter”.

Can you describe a typical film?
The majority of the bite-sized movies — the maximum length is two and a half minutes — come from children and young students. Accordingly, most feature experiments that are easy to do in a classroom with common lab equipment or a few inexpensive household items. Some, like a demonstration of alkali-metal reactivity, are old stand-bys of chemistry and physics lessons. Others show an amazing degree of creativity in both their choice of topic and their presentation: a film about lasers, for example, opens with its teenage cast re-enacting a scene from the James Bond film Goldfinger before moving on to explanatory diagrams and animations.

Does this mean it is just for children?
Not at all. The site encourages contributions from parents, teachers, science communicators and researchers. Indeed, anyone with a video camera and an interest in science education is welcome to send in material, although the prize competition is only open to amateur film-makers from the UK and Ireland. Despite this limitation, competition for the 2009 best film prize in the “adults” category was fierce. The winning entry came from Andrew Hanson, a senior research scientist at the UK’s National Physical Laboratory, whose animated romp through relativity beat a tutorial on levitation, a 1950s-themed explanation of baking powder, and a film on oil and water called, er, The Immiscible Love Story.

Can you give me some highlights?
One thing that the site proves is that sometimes even extremely simple ideas can make great films. A perfect example of this is The Bernoulli Waltz, which pairs table-tennis balls suspended on a column of air with Johann Strauss’ “Blue Danube” waltz in a wordless tribute to the opening sequence of the film 2001: A Space Odyssey. Other films rely on clever word play — particularly The Geiger Müller Groove (showcasing a catchy rap about alpha, beta and gamma radiation), which won “best physics film” in 2009. Be sure to check out The Formation of Crude Oil, which illustrates the required elements — dead sea creatures, lack of oxygen, pressure and heat — in a way that is simultaneously informative, amusing and rather disturbing to lovers of stuffed toys.

How can I get involved?
In some ways, you already are: the Institute of Physics (which publishes Physics World) is one of the site’s supporters, as it sponsors both a regional competition and the SciCast Physics award. The next competition deadline is not until the end of March 2010, so there is plenty of time to brainstorm ideas for your own science film. Instructions for submitting material are available on the site, but currently you cannot submit films online.

RGA User Group offers broad appeal

The RGA User Group was originally formed to coordinate informal meetings for users and manufacturers of residual gas analysers (RGAs) to help them better understand each others needs and hence derive potential benefits. The first meeting of the group took place in 1996 in Rugby and comprised just 11 attendees. Since then the group has organized meetings approximately every 18 months. Attendance has grown steadily, culminating in the last meeting, held in March 2008 at the Culham Laboratory in Oxfordshire, which attracted more than 70 participants from industry, manufacturing and academia.

The RGA is an analytical instrument that is widely used throughout the vacuum industry. Its origins are as a diagnostic tool for measuring the partial pressures of the gases present in a vacuum chamber after it has been pumped down. However, advances in electronics and software have meant that the RGA is now revealing its true worth as a mass spectrometer, covering a variety of applications that are far removed from just measuring the quality of the vacuum.

The range of process-vacuum areas where RGAs are employed has widened to span everything from semiconductor processing to the extreme high vacuum (XHV) requirements of the latest generation of particle accelerators. The biggest benefit for users is that this range of applications has resulted in a significant market for RGAs that is filled by many different manufacturers, with the outcome that there is lots of product choice and such instruments can now be purchased at relatively low cost.

To the uninitiated, one RGA may look very much like another, but not all are the same, and this is where the group can help to enlighten users about the optimum set-ups for different vacuum processes and applications. Having an informed understanding of such intricacies is seen as a growing necessity for a large number of users, and the RGA User Group strives to address this need by providing opportunities for users, both new and old, to share their practical experiences of the instrumentation.

The user group has grown from humble beginnings to provide an established forum for the exchange of information and practical advice. It organizes workshop-style meetings with the aim of bringing industrial, academic and research-based RGA users together with equipment suppliers and manufacturers. These events are normally held at the laboratories of large UK government-research facilities. The events are free to all attendees, thanks to support from the companies attending the small exhibitions run in conjunction with the one-day meetings. The group also receives financial support from the Institute’s Vacuum Group and ASTeC, the UK’s centre of expertise for accelerator science and technology.

A typical meeting consists of eight or nine short presentations by experts from academia and industry that might cover everything from the practical aspects of using and servicing instrumentation to the latest advances in equipment miniaturization. The schedule offers attendees lots of time for networking with other users and with manufacturers, which helps to facilitate collaboration and the transfer of ideas. The meeting is usually rounded off with a tour of the facilities where the event is being held. An archive of presentations from meetings, together with other RGA User Group information, is available at rgausers.org.

The group is currently making plans for its next meeting, RGA-9, which will take place early next year. This will be another milestone in the evolution of the RGA User Group because it will form part of what it is hoped will be the first in a series of new vacuum events for the UK. Vacuum Symposium UK aims to address the needs of the vacuum community with an annual event incorporating both technical and commercial elements.

The 1st Vacuum Symposium UK (VS-1) will take place on 10–11 February 2010 at the Daresbury Laboratory in Cheshire. The meeting will be free to participants and the event will run over two days, with the RGA-9 programme forming day one and a complementary VS-1 programme running on day two. The event will include free training seminars for new vacuum users, technical talks for more-experienced attendees and a vacuum-equipment exhibition. It is hoped that the event will attract interest from across the entire UK vacuum industry and beyond. So, if you are a user of vacuum equipment, have an interest in vacuum science and technology or are a supplier/manufacturer of vacuum equipment, then this meeting is for you. Full details and registration options are available at vacuum-uk.org.

Just as RGAs offer broad appeal, so the RGA User Group looks to do the same.

Copyright © 2026 by IOP Publishing Ltd and individual contributors