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The bean family, also known as the legumes, leguminoseae or papilionaceae. One of my favourite plant families. Their flowers are beautiful, very distinctive and pleasingly perky; and I like seed pods that really look like pods. There’s also something charming about the unfolding, trefoil leaves at the end of every branch, and I’m a fan of plants with tendrils.

White clover flower (or flowers, depending on where you draw the line)

On top of all that, their specially adapted root nodules house nitrogen-fixing bacteria, producing nitrogenase to draw unreactive nitrogen from the atmosphere and transform it into compounds that other plants can use. Before the Haber-Bosch process was invented we had to rely heavily on legumes and lightning to get our nitrogen fix. This is why crop rotation usually includes a phase where fields are planted with legumes.

As well as peas, the family includes all kinds of beans, lentils and peanuts. Making protein requires nitrogen, so most protein-rich plant-based foods are either legumes or the seeds of larger plants, like nut trees. Unfortunately, the seeds of legumes are also rich in oligosaccharides, complex carbohydrates that humans cannot digest, but which our gut bacteria can – producing methane and other gases. Besides the food crops, legumes also include broom, gorse, clover, vetch, laburnum and lupins.

Continue reading Fabaceae

Royal Society Summer Exhibition

I made it to the last day of this year’s Royal Society Summer Exhibition on Sunday: a fascinating collection of scientific exhibits and scientists happy to talk about them. It’s a pleasing format, especially if you’re interested in hearing scientists talk about their work – which is one of my favourite things.

I wanted to share some notes on what I learned.

Killer Fungus

Killer FungusMedical Mycology & Fungal Immunology

Apparently around a million people are killed by fungal infections every year – more than malaria. Most victims are those with compromised immune systems, including those with AIDS and transplant patients who have to take immunosuppressant drugs to prevent their bodies rejecting their new organs; one of the intriguing thing about fungal diseases is that many of them are caused by fungal organisms which live on us all the time, but hardly ever cause problems. However, the number of otherwise healthy people who are badly affected by fungal infections seems to be growing. Fungal diseases and the human immune system’s ways of responding to them are poorly understood, so far, compared with our understanding of bacterial or even viral diseases.

I have a long-standing interest in mycology in general, but like most people, I’d never given all that much thought to fungal diseases in particular.

4D Science

X-Ray Tomography

Tomography is the process of turning a series of 2D slices into a 3D image. The people from the Manchester-Harwell X-Ray Imaging Facility are pretty excited about getting to use an X-ray ’10 billion times brighter than the sun’ to extend this into the fourth dimension, showing how things like crystal structures change over time. That lets them track exactly what happens as batteries charge and discharge, or when ice cream melts and refreezes, and they had some nice little 3D-printed models to demonstrate it, as well as a Lego light-tomography machine that works by casting shadows from a model on a tiny turntable.

Antimatter Matters

Trapping Antihydrogen at CERN

Antimatter is almost exactly like normal matter except that it has the opposite electrical charge, or possibly it travels backwards in time (the two interpretations look surprisingly similar in practice). When a particle and its antiparticle collide, they annihilate, releasing a burst of energy; and when new matter is created out of a burst of energy, it comes along with antimatter, allowing the universe’s total electrical charge to be conserved.

It is puzzling that the universe as we know it consists almost entirely of matter, when matter and antimatter are usually created in exactly the same quantities. It looks as if this didn’t hold in the early universe, or somehow the antimatter was destroyed while leaving normal matter behind, which suggests that the universe is troublingly asymmetrical, and nobody knows why. This is a long-standing problem in physics, known as ‘CP violation’, and not very much progress has been made in solving it since I was studying the subject seventeen years ago.

There is currently a fiendishly difficult experiment ongoing at CERN, in which scientists are making molecules of antihydrogen by colliding antiprotons with positrons (antielectrons), and trapping them in order to study their behaviour. The experiment is so difficult because antihydrogen atoms are electrically neutral, so you can’t contain them in an electrical field; you need to use enormously powerful magnets to control them, and even then, they need to be cooled to within half a degree of absolute zero or they’ll escape.  If antihydrogen atoms turn out to behave any differently from hydrogen atoms in terms of the way they absorb and emit radiation, that will give us some valuable hints about CP violation.

Silk Acoustics

The Spider Silk Violin

One of the fun things about the 21st century is that new materials are being created all the time, with interesting properties and applications, including biomaterials incorporating things like spider silk. Luca Alessandrini is exploring the acoustic properties of some of these materials as part of his interdisciplinary research, and has created violins out of some of these novel materials.

The exhibition was a little on the crowded side, so I didn’t get to see nearly everything. Some of the things I’d have loved to get a chance to spend more time on include computational cosmology, quantum secrets of photosynthesis, morphogenesis and surgical robots. At least I have the internet…

Solar Eclipse 2015

3-1 crop of sliverOn Friday the 20th of March 2015, the moon’s shadow passed over a stretch of the northern half of planet Earth from Greenland and north Africa to Mongolia. I was in its penumbra, where it didn’t quite block all of the light from the sun. Its umbra, where it eclipsed the sun entirely, passed a few hundred miles to the north, bringing a couple of minutes of day-time night to a long strip of open sea, and the northern archipelagoes of Svalbard and the Faroe Islands.

Colander shadowMuch of Britain was covered by such thick cloud that it was impossible to really see what was going on, but we had perfect eclipse weather in Edinburgh – patchy clouds and high winds, so that there were times when the cloud cover was thick enough to look directly at the sun (though good health & safety practice recommends against it), and other times when there was enough direct sunlight to get really clear crescent shapes where there were breaks in shadows. We tried making a pinhole in cardboard, but got better results by just holding up a colander. You need to hold it far enough away that you’re viewing mostly penumbra; the effect is the same one exploited by pinhole photography.

Iridescent cloudsWe were close enough to the zone of totality that only a tiny sliver of sun remained at the maximum point of the eclipse, around 9:30 in the morning, making it about as dark as twilight – ideal for appreciating another thing that made the weather perfect. For a few minutes we had just the right kind of clouds to produce iridescent effects – thin clouds with evenly sized droplets, allowing diffraction patterns to be strongly visible. Iridescent clouds and coronas actually occur very often, but  in the daytime they’re usually too bright to be seen, while at night it’s too dark for us to fully appreciate their colours.

Projecting the eclipseAnother technique for looking at the sun indirectly is to use lenses to project an image onto a flat white surface. We tried using a macro lens-extender I normally use to take extreme macros. It projected a pleasingly clear image of the sky and its clouds, but the image of the sun was too small to be much use. We should really have used more than one lens – one to focus, one to magnify. A friend in London, also a science teacher, took the opportunity to make a projecting telescope. He reports: ‘Shame it was cloudy but under a hood you could get a clear image of buildings miles away. Kids loved it, the hood added mystery.’

Projected Eclipse by DeeAnother teacher at my school had a proper heavy-duty astronomical telescope set up to project an image of the sun about 10cm across, and 80 or so solar viewers with special film that one of the younger classes had fashioned into flimsy but effective glasses.

Scaffolding and Crescent SunThere are a few more of the pictures I took in our garden in this album. If you missed this one, the next total eclipse visible in Europe will be on the 12th of August, 2026, in northern Spain.