Water may well be everywhere, but freshwater lake ecosystems are among some of the most vulnerable on Earth. In recent decades, freshwater species have suffered double the rate of decline of land species. And nearly 50% of fresh water lakes, rivers and streams across Europe failed to meet the EU Water Framework Directive, which aimed to achieve “good ecological status” of freshwater in Europe by 2015.
Category Archives: Our Conversation
When it comes to exercise, what’s your excuse? Whether it’s lack of time, money or motivation – sometimes the lure of the sofa can just be too strong – it can be all too easy to put off that run for another day. But whatever your reason, it’s still recommended that adults aged between 19 and 64 should be getting at least 150 minutes of moderate intensity or 75 minutes of vigorous intensity exercise a week. This roughly works out at about half an hour of brisk walking or cycling five times a week. Read more
We manufacture over 300m tonnes of plastics each year for use in everything from packaging to clothing. Their resilience is great when you want a product to last. But once discarded, plastics linger in the environment, littering streets, fields and oceans alike. Every corner of our planet has been blighted by our addiction to plastic. But now we may have some help to clean up the mess in the form of bacteria that have been found slowly munching away on discarded bottles in the sludge of a recycling centre.
Plastics are polymers, long thin molecules made of repeating (monomer) building blocks. These are cross-linked to one another to build a durable, malleable mesh. Most plastics are made from carbon-based monomers, so in theory they are a good source of food for microorganisms.
But unlike natural polymers (such as cellulose in plants) plastics aren’t generally biodegradable. Bacteria and fungi co-evolved with natural materials, all the while coming up with new biochemical methods to harness the resources from dead matter. But plastics have only been around for about 70 years. So microorganisms simply haven’t had much time to evolve the necessary biochemical tool kit to latch onto the plastic fibres, break them up into the constituent parts and then utilise the resulting chemicals as a source of energy and carbon that they need to grow.
Now a team at Kyoto University have, by rummaging around in piles of waste, found a plastic munching microbe. After five years of searching through 250 samples, they isolated a bacteria that could live on poly(ethylene terephthalate) (PET), a common plastic used in bottles and clothing. They named the new species of bacteria Ideonella sakaiensis.
You may think this is the rerun of an old story, as plastic-eating microbes have already been touted as saviours of the planet. But there are several important differences here. First, previous reports were of tricky-to-cultivate fungi, where in this case the microbe is easily grown. The researchers more or less left the PET in a warm jar with the bacterial culture and some other nutrients, and a few weeks later all the plastic was gone.
Second – and the real innovation – is that the team have identified the enzymes that Ideonella sakaiensis uses to breakdown the PET. All living things contain enzymes that they use to speed up necessary chemical reactions. Some enzymes help digest our food, dismantling it into useful building blocks. Without the necessary enzymes the body can’t access certain sources of food.
For example, people who are lactose intolerant don’t have the enzyme that breaks down the lactose sugar found in dairy produce. And no human can digest cellulose, while some microbes can. Ideonella sakaiensis seems to have evolved an efficient enzyme that the bacteria produces when it is in an environment that is rich in PET.
The Kyoto researchers identified the gene in the bacteria’s DNA that is responsible for the PET-digesting enzyme. They then were able to manufacture more of the enzyme and then demonstrate that PET could be broken down with the enzyme alone.
First real recycling
This opens a whole new approach to plastic recycling and decontamination. At present, most plastic bottles are not truly recycled. Instead they are melted and reformed into other hard plastic products. Packaging companies typically prefer freshly made “virgin” plastics that are created from chemical starting materials that are usually derived from oil.
The PET-digesting enzymes offer a way to truly recycle plastic. They could be added to vats of waste, breaking all the bottles or other plastic items down into into easy-to-handle chemicals. These could then be used to make fresh plastics, producing a true recycling system.
Manufactured enzymes are already used to great effect in a wide range of everyday items. Biological washing powders contain enzymes that digest fatty stains. The enzymes known as rennet that are used to harden cheese once came from calfs’ intestines but are now manufactured using genetically engineered bacteria. Maybe we can now use a similar manufacturing method to clean up our mess.
Many of the questions I am asked regard how “true” science fiction concerning black holes might be, and whether worm holes, such as those featured in Stargate, are real or not. Invariably though, the one item that is almost assured to come up are the largely gruesome ways in which black holes might theoretically affect human beings and the Earth itself.
Mass, charge, spin
There are three properties of a black hole that are (in principle) measurable: their mass, their spin (or angular momentum) and their overall electronic charge. Indeed, these are the only three parameters that an outside observer can ever know about since all other information about anything that goes in to making up a black hole is lost. This is known as the “no hair theorem”. Put simply: no matter how hairy or complex an object you throw in to a black hole, it will get reduced down (or shaved) to its mass, charge and spin.
Of these parameters, mass is arguably the most significant. The very definition of a black hole is that it has its mass concentrated in to a vanishingly small volume – the “singularity”. And it is the mass of the black hole – and the huge gravitational forces that its mass generates – which does the “damage” to nearby objects.
One of the best known effects of a nearby black hole has the imaginative title of “Spaghettification”. In brief, if you stray too close to a black hole, then you will stretch out, just like spaghetti.
This effect is caused due to a gravitation gradient across your body. Imagine that you are headed feet first towards a black hole. Since your feet are physically closer to the black hole, they will feel a stronger gravitation pull towards it than your head will. Worse than that, your arms, by virtue of the fact that they’re not at the centre of your body, will be attracted in a slightly different (vector) direction than your head is. This will cause parts of the body toward the edges to be brought inwards. The net result is not only an elongation of the body overall, but also a thinning out (or compression) in the middle. Hence, your body or any other object, such as Earth, will start to resemble spaghetti long before it hits the centre of the black hole.
The exact point at which these forces become too much to bear will depend critically on the mass of a black hole. For an “ordinary” black hole that has been produced by the collapse of a high mass star, this could be several hundred kilometres away from the event horizon – the point beyond which no information can escape a black hole. Yet for a supermassive black hole, such as the one thought to reside at the centre of our galaxy, an object could readily sink below the event horizon before becoming spaghetti, at a distance of many tens of thousands of kilometres from its centre. For a distant observer outside the event horizon of the black hole, it would appear that we progressively slow down and then fade away over time.
Bad news for Earth
What would happen, hypothetically, if a black hole appeared out of nowhere next to Earth? The same gravitational effects that produced spaghettification would start to take effect here. The edge of the Earth closest to the black hole would feel a much stronger force than the far side. As such, the doom of the entire planet would be at hand. We would be pulled apart.
Equally, we might not even notice if a truly supermassive black hole swallowed us below its event horizon as everything would appear as it once was, at least for a small period of time. In this case, it could be some time before disaster struck. But don’t lose too much sleep, we’d have to be unfortunate to “hit” a black hole in the first place – and we might live on holographically after the crunch anyway.
Mind the radiation
Interestingly, black holes are not necessarily black. Quasars – objects at the hearts of distant galaxies powered by black holes – are supremely bright. They can readily outshine the rest of their host galaxy combined. Such radiation is generated when the black hole is feasting on new material. To be clear: this material is still outside the event horizon which is why we can still see it. Below the event horizon is where nothing, not even light, can escape. As all the matter piles up from the feast, it will glow. It is this glow that is seen when observers look at quasars.
But this is a problem for anything orbiting (or near) a black hole, as it is very hot indeed. Long before we would be spaghettified, the sheer power of this radiation would fry us.
Life around a black hole
For those who have watched Christopher Nolan’s film Interstellar, the prospect of a planet orbiting around a black hole might be an appealing one. For life to thrive, there needs to be a source of energy or a temperature difference. And a black hole can be that source. There’s a catch, though. The black hole needs to have stopped feasting on any material – or it will be emitting too much radiation to support life on any neighbouring worlds.
What life would look like on such a world (assuming its not too close to get spaghettified, of course) is another matter. The amount of power received by the planet would probably be tiny compared to what Earth receives from the Sun. And the overall environment of such a planet could be equally bizzare. Indeed, in the creation of Interstellar, Kip Thorne was consulted to ensure the accuracy of the depiction of the black hole featured. These factors do not preclude life, it just makes it a tough prospect and very hard to predict what forms it could take.
The ancient Babylonians were the first to use sophisticated geometry – a staggering 1,400 years before it was previously thought to have been developed. Sadly, these mathematical innovations were forgotten as the Babylonian civilisation collapsed and were only rediscovered this year as scientists took a close look at ancient clay tablets.
This surprising finding made me wonder about what other scientific methods that we put down to modern minds were actually discovered by ancient civilisations. So I decided to hunt down some of the most advanced uses of chemistry.
Qin Dynasty chrome plating
The mirrored shine of chrome-plated metal is almost a symbol of the modern era. A thin chrome layer coats metals and plastics in kitchens, bathrooms and cars. Credit for chrome-plating technology goes to George Sargent who published a method in 1920 that lead to the commercial plating that dominated the Art Deco period and beyond. In fact, other famous chemists including Robert Bunsen dabbled with chrome plating in the mid-19th century. But all of these may have been beaten to the shine by the metallurgists of the Qin dynasty in China some 2,000 years before chrome had even been identified in the West.
In the 1970s, razor sharp swords coated in a thin layer of chromium oxide were unearthed along with the the famous Terracotta army. The Chinese suggest that their 1st dynasty weapon smiths coated officers’ weapons to protect them from corrosion. And indeed, two millennia later the blades are untarnished. However, whether this is really the case or in fact the chromium layer slowly formed from a peculiarity of the blade’s composition and the fires that ravaged the buried terracotta army is a matter of debate.
Concrete is the mainstay of modern buildings, but ancient civilisations also used it to great effect. Concrete is a composite, meaning that it is made from two or more materials; cement is mixed with sand and gravel, which then sets into whatever structure is required. The most famous ancient concrete buildings are probably the Pantheon and Colosseum in Rome. Both are composed of fine volcanic ash mixed with lime (calcium hydroxide).
Together these make the cement, which sets and binds fist sized pieces of limestone together. This particular recipe produces a network of crystals that resist propagation of cracks, the bane of modern concrete. The result is an incredibly enduring material that is, in many ways, superior to today’s concrete. A testament to this is the majestic roof of the Pantheon, which, at 43 metres across, is still the world’s largest unreinforced concrete dome.
Carbon nanotubes are the strongest and stiffest materials known. They consist of cylinders with walls that are just one atom thick. When used within composite materials they can massively enhance the strength of an object resulting in super strong and light components, some of which you can find in wind turbines, sports gear and vehicles.
In 2006 researchers discovered that the people of Damascus were making use of nanotubes in their steel hundreds of years ago. The result was beautiful blades covered in swirling patterns. And more importantly for the soldiers of the time was the exceptional durability and the razor-sharp edges the steel held. We now know the exact composition of Damascus steel, yet modern metallurgists have failed to reproduce it so far.
William Perkin is credited with producing the first organic dye (using chemists’ meaning of the word organic – in other words, carbon-containing chemicals) when he accidentally discovered purple mauveine while trying to make quinine in 1856.
But the first synthetic pigment of any type was probably made by the Egyptians as early as 3000BC. By heating a mixture of sand, ash, calcium carbonate (possibly from shells), and a copper containing ore to temperatures of over 800°C they manufactured blue calcium copper silicate. This could be then be used in glazes to produce a stunning range of hues.
Greek atomic theory
The incredible technologies devised by craftsman and artists of ancient civilisations are astounding. Much of it can’t be bettered by modern techniques. But what separates science from skilled craft is an understanding of the underlying mechanisms involved in the making of the material. Underpinning this understanding in modern chemistry is the atomic theory often credited to John Dalton in the early 19th century. But philosophers of old also had a good crack at thinking about the nature of matter. And in fact atomism has sprung up multiple times in antiquity. Most notably from the Greek philosophers Democritus and Leucippus who speculated that everything is composed of physical, indivisible and invisible atoms back in the 5th century BC.
Editor’s note: This article was originally published on The Conversation.
By Roland Ennos, Professor of Biomechanics
In cities around the world, trees are often planted to help control temperatures and mitigate the effects of the “urban heat island”. But while trees have been called “nature’s air conditioners”, in practice, scientists often have difficulty demonstrating their cooling properties.
The most obvious way to measure the cooling effect of trees would be to compare the air temperature in parks with that in nearby streets. But this method often comes up with disappointing results: even in large, leafy parks, the daytime air temperature is usually less than 1°C cooler than in the stuffy streets, and at night the temperature in parks can actually be higher.
To explain this contradiction, we need to think more clearly about the physics of heat flows in our cities, and the scale of the measurements we are taking. Read more
By Hugo Dutel, Post-doctoral Research Fellow, Medical and Biological Engineering Research Group
Biological evolution, the changes in living organisms over time, is often considered an elusive and long process that cannot be observed during a human lifespan. But is that really the case? And is there evidence that we can see it happening right before our eyes?
Evolution is a process that occurs at a different pace in different organisms. For instance, paleontologists have shown, thanks to the fossil record, that it took a million years for whales to evolve from their land-dwelling mammalian ancestors.
But evolution can also be observed and monitored in living organisms within a human lifetime. This is true for infectious agents, such as bacteria and parasites, that can evolve extremely quickly to resist the drugs we use to fight them. But it is also the case for larger organisms, such as vertebrates – the back-boned animals. Read more