How clean is solar power?

THAT solar panels do not emit greenhouse gases such as carbon dioxide when they are generating electricity is without question. This is why they are beloved of many who worry about the climate-altering potential of such gases. Sceptics, though, observe that a lot of energy is needed to make a solar panel in the first place. In particular, melting and purifying the silicon that these panels employ to capture and transduce sunlight needs a lot of heat. Silicon’s melting point, 1,414°C, is only 124°C less than that of iron.

Silicon is melted in electric furnaces and, at the moment, most electricity is produced by burning fossil fuels. That does emit carbon dioxide. So, when a new solar panel is put to work it starts with a “carbon debt” that, from a greenhouse-gas-saving point of view, has to be paid back before that panel becomes part of the solution, rather than part of the problem. Observing this, some sceptics have gone so far as to suggest that if the motive for installing solar panels is environmental (which is often, though not always, the case), they are pretty-much useless.

Wilfried van Sark, of Utrecht University in the Netherlands, and his colleagues…Continue reading
Source: Economist

An atlas of where proteins are found in cells

ONE of the most important concepts in biology is compartmentalisation. Different organs do different jobs within bodies. Different tissues do different jobs within organs. Different cells within tissues, likewise. And within cells, different organelles—as subcellular components such as nuclei, mitochondria and Golgi bodies are known—are also specialised for particular functions. Each of these levels of organisation has, over the years, been catalogued in what have come to be known as atlases, beginning in 1543 with Andreas Vesalius’s “De Humani Corporis Fabrica” (On the Fabric of the Human Body), the founding text of modern anatomy.

The latest level of detail is to look at different proteins within organelles. Proteins are the molecules that do most of the work within a cell. They range from things like actin and myosin, which collaborate to flex muscle cells—and thus the muscles of which those cells are part—to the enzymes of the Krebs cycle, which disassemble glucose to release the energy therein. The Cell Atlas, a database launched on December 4th at a meeting of the American Society of Cell Biology, records which proteins are found in which…Continue reading
Source: Economist

New fossils illuminate the route that led ultimately to human beings

ONE of the most important steps on the journey to Homo sapiens was that made by the first fish to crawl onto dry land. It was both a metaphorical and a literal step, but knowing exactly when it happened is tricky. It depends, for one thing, on the definition of “dry land”. Scrambling over the mud from one pool to another, assisted by fins that had evolved to walk along the seabed in the way modern coelacanths do, was probably going on by 385m years ago. 

By 375m years ago, the descendants of these first-footers had evolved four limbs clearly recognisable as legs. They were no longer fish, but “tetrapods”. Their legs, though, could have as many as eight digits each, and do not look capable of supporting an animal properly when it was out of the water. Some might thus argue that even by this stage, the step onto dry land had not been truly made.

All of these events occurred during a period called the Devonian when, though the oceans teamed with organisms no less varied than today’s, life on the continents was just getting going. Vascular plants (those bigger than mosses and liverworts) had evolved only…Continue reading
Source: Economist

Ancient eclipses show how days are getting shorter

AS THE well-known Australian philosopher, Kylie Minogue, once pointed out, it can be a source of comfort to remember that, no matter what else is happening, the world still turns. Unfortunately, things are not quite so simple. Thanks to the moon’s gravitational tug, the speed at which Earth spins has been slowing since the satellite’s birth about 4.5bn years ago. Physicists can calculate from first principles how big the effect should be. It turns out that the moon should be adding about 2.3 milliseconds to the length of the day with each century that passes. This means, for instance, that 100m years ago, when dinosaurs ruled Earth, a day was nearer 23 than 24 hours.

But that 2.3 milliseconds is only an average. Geological events within Earth can speed the process up, or slow it down. Tracking changes in day length over time is thus of interest. And that requires data. Thanks to the development of super-accurate atomic clocks in the 1950s, and to laser range-finding equipment left on the moon by the Apollo astronauts, researchers have plenty of such data from the past half-century. But more information is always welcome. And extra data are exactly what a team led by Leslie…Continue reading
Source: Economist

Ancient eclipses show how days are getting longer

AS THE well-known Australian philosopher, Kylie Minogue, once pointed out, it can be a source of comfort to remember that, no matter what else is happening, the world still turns. Unfortunately, things are not quite so simple. Thanks to the moon’s gravitational tug, the speed at which Earth spins has been slowing since the satellite’s birth about 4.5bn years ago. Physicists can calculate from first principles how big the effect should be. It turns out that the moon should be adding about 2.3 milliseconds to the length of the day with each century that passes. This means, for instance, that 100m years ago, when dinosaurs ruled Earth, a day was nearer 23 than 24 hours.

But that 2.3 milliseconds is only an average. Geological events within Earth can speed the process up, or slow it down. Tracking changes in day length over time is thus of interest. And that requires data. Thanks to the development of super-accurate atomic clocks in the 1950s, and to laser range-finding equipment left on the moon by the Apollo astronauts, researchers have plenty of such data from the past half-century. But more information is always welcome. And extra data are exactly what a team led by Leslie…Continue reading
Source: Economist

A dinosaur’s tail preserved in amber

Who was a pretty boy, then?

TWO decades ago palaeontologists were astonished to discover impressions of feathers in rock around the petrified bones of dinosaurs that had clearly, from the anatomy those bones displayed, been unable to fly when they were alive. Astonishment turned to delight with the subsequent discovery of exquisitely preserved examples of these feathers in the petrified tree resin known as amber. Now, a team led by Xing Lida at the China University of Geosciences, in Beijing, and Ryan McKellar at the Royal Saskatchewan Museum, in Regina, has uncovered something even more impressive. As they report in Current Biology, they have found, again preserved in amber, part of a dinosaur’s feathered tail.

Their fossil comes from the Hukawng valley amber mines in northern Myanmar, already famous for many spectacular specimens of life dating from 99m years ago, during the mid-Cretaceous period. The tail in question was once attached to a carnivorous dinosaur from a group known as the coelurosaurs, the most famous member of which is Tyrannosaurus. The coelurosaur here,…Continue reading
Source: Economist

The Breakthrough prizes attempt to upstage the Nobels

IN 2012 the world of science was stirred by an announcement that nine physicists would each receive the eye-popping sum of $3m for their contributions to such arcane fields as string theory and inflationary cosmology. They were the first winners of Breakthrough prizes—a set of now-annual awards given to the brains behind important recent advances in basic research. The Breakthroughs are both inspired by, and intended to outdo, those willed into existence at the beginning of the 20th century by Alfred Nobel.

Like Nobel, Yuri Milner, the prizes’ creator, is a scientist-turned-businessman (he is a former physicist who has made his fortune as a venture capitalist). Unlike Nobel, however, he has not created an exclusive brand. Anyone with a few million dollars burning a hole in his or her back pocket can join in. The initial awards for physics, for example, were followed by equally munificent prizes in life sciences and mathematics. These were paid for in part by Anne…Continue reading
Source: Economist

Machines are learning to find concealed weapons in X-ray scans

Prettier than an x-ray

EVERY day more than 8,000 containers flow through the Port of Rotterdam. But only a fraction are selected to pass through a giant x-ray machine to check for illicit contents. The machine, made by Rapiscan, an American firm, can capture images as the containers move along a track at 15kph (9.3mph). But it takes time for a human to inspect each scan for anything suspicious—and in particular for small metallic objects that might be weapons. (Imagine searching an image of a room three metres by 14 metres crammed to the ceiling with goods.) To increase this inspection rate would require a small army of people.

A group of computer scientists at University College London (UCL), led by Lewis Griffin, may soon speed up the process by employing artificial intelligence. Dr Griffin is being sponsored by Rapiscan to create software that uses machine-learning techniques to scan the x-ray images. Thomas Rogers, a member of the UCL team, estimates that it takes a human operator about ten minutes to examine each X-ray. The UCL system can do it in 3.5 seconds.

Dr Griffin’s team trained its system on…Continue reading
Source: Economist

Why disrupted body clocks trigger liver cancer

DRINKING too much and eating too much are both good ways of getting liver cancer. But there is a third. The disrupted circadian rhythms caused by working shifts or crossing time zones also seem to induce the disease. Precisely how and why meddling with day and night cycles has such a dire effect on the liver remains an enigma, but a study just published in Cancer Cell by Loning Fu and David Moore at the Baylor College of Medicine, in Texas, sheds some light on the matter.

Among the liver’s many jobs is making bile, a substance secreted into the intestine to break down the fats and oils in food. One of bile’s main components is bile acid, a derivative of cholesterol. Dr Fu and Dr Moore knew from their previous research that disrupting the circadian rhythms of mice causes the rodents’ livers to overproduce this substance. They also knew that liver cancer commonly appears in mice engineered to lack certain genes required for the management of day-night cycles. This led them to suspect a link between liver cancer and too much bile acid. To take a closer look, they set up an experiment.

Working with a team of colleagues, the two researchers…Continue reading
Source: Economist

Bombs that can recognise their targets are back in fashion

IT IS easy to forget, given the ubiquity of satellite-navigation devices in cars and mobile phones, that the Global Positioning System (GPS) of orbiting satellites on which they rely was originally—and, indeed, remains—a military technology. The system is, for instance, relied upon by the JDAM (joint direct-attack munition) kits that America’s air force attaches to its free-fall bombs to turn them into smart weapons that can be guided with precision to their targets. 

But JDAM and similar systems work only when they can receive signals from GPS satellites. And such signals are weak—approximately as powerful as a standard television transmission would be if the transmitter were five times as far away as the Moon is. They are thus easily jammed. For obvious reasons, details of the capabilities of jammers are hard to come by, but a Russian system called Pole-21, for instance, may be able to suppress GPS signals as much as 80km (50 miles) away.

One way to get around this—and to guide weapons automatically to their targets without relying on satellites—is to give weapons a map. That has been done in the past. The cruise-missile…Continue reading
Source: Economist