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

How to empty the ketchup bottle every time

FOR anyone (and that is almost everyone) who has shaken and thumped a bottle of ketchup to squeeze the last dollop out of it, or flattened and then rolled up a tube of toothpaste to eject one final squirt onto their brush, help may soon be at hand. For more than a decade Kripa Varanasi and his colleagues at the Massachusetts Institute of Technology (MIT) have been creating and studying slippery surfaces for use in industrial equipment such as steam turbines and desalination plants.

More recently, they have found ways to apply their ideas to create internal coatings for containers so that their contents will flow out easily and completely, with no shaking, thumping or squeezing. And now they think they have discovered a way to adapt these super-slippery coatings to steer liquids across flat surfaces, opening up the possibility of pumping fluids around without the need for pipes.

The lotus position

Dr Varanasi’s work started with what are known as super-hydrophobic water-shedding surfaces, a classic natural example of which is a lotus leaf. It repels water so effectively that droplets simply tumble off. The reason is that the leaf’s surface is covered with microscopic structures which contain air pockets. This reduces the surface tension that would otherwise cause a water droplet to cling on. By coating the condensing areas used in…Continue reading
Source: Economist

Big bomber is watching

Source: Economist

Retired jet engines could help clear smog

TO LAND at Indira Gandhi Airport is to descend from clear skies to brown ones. Delhi’s air is toxic. According to the World Health Organisation, India’s capital has the most polluted atmosphere of all the world’s big cities. The government is trying to introduce rules that will curb emissions—allowing private cars to be driven only on alternate days, for example, and enforcing better emissions standards for all vehicles. But implementing these ideas, even if that can be done successfully, will change things only slowly. A quick fix would help. And Moshe Alamaro, a researcher at the Massachusetts Institute of Technology, thinks he has one.

His idea is to take a jet engine, put it next to one of India’s dirty coal-fired power plants, point its exhaust nozzle at the sky and then switch it on. His hope is that the jet’s exhaust will disrupt a meteorological phenomenon known as “inversion”, in which a layer of warm air settles over cooler air, trapping it, and that the rising stream of exhaust will carry off the tiny particles of matter that smog is composed of.

Inversion exacerbates air pollution in Delhi and in many other…Continue reading
Source: Economist

Why research papers have so many authors

ONE thing that determines how quickly a researcher climbs the academic ladder is his publication record. The quality of this clearly matters—but so does its quantity. A long list of papers attached to a job application tends to impress appointment committees, and the resulting pressure to churn out a steady stream of articles in peer-reviewed journals often leads to the splitting of results from a single study into several “minimum publishable units”, to the unnecessary duplication of studies and to the favouring of work that is scientifically trivial but easy to publish.

There is another way to pad publication lists: co-authoring. Say you write one paper a year. If you team up with a colleague doing similar work and write two half-papers instead, both parties end up with their names on twice as many papers, but with no increase in workload. Find a third researcher to join in and you can get your name on three papers a year. And so on.

To investigate the matter, The Economist reviewed data on more than 34m research papers published between 1996 and 2015 in peer-reviewed journals and conference proceedings. These were drawn from Scopus, the world’s biggest catalogue of abstracts and citations of papers, which is owned by RELX Group, a publisher and information company.

<div class="content-image-float-290…Continue reading
Source: Economist

Award

On October 23rd Natasha Loder, our health-care correspondent, was named Science Commentator of the Year in the 2016 Comment Awards, an annual set of prizes for British journalists.

Source: Economist

How to take pictures of exoplanets

IN THE quarter of a century since the first extrasolar planets were discovered, astronomers have turned up more than 3,500 others. They are a diverse bunch. Some are baking-hot gas giants that zoom around their host stars in days. Some are entirely covered by oceans dozens of kilometres deep. Some would tax even a science-fiction writer’s imagination. One, 55 Cancri e, seems to have a graphite surface and a diamond mantle. At least, that is what astronomers think. They cannot be sure, because the two main ways exoplanets are detected—by measuring the wobble their gravity causes in their host stars, or by noting the slight decline in a star’s brightness as a planet passes in front of it—yield little detail. Using them, astronomers can infer such basics as a planet’s size, mass and orbit. Occasionally, they can interrogate starlight that has traversed a planet’s atmosphere about the chemistry of its air. All else is informed conjecture.

What would help is the ability to take pictures of planets directly. Such images could let astronomers deduce a world’s surface temperature, analyse what that surface is made from and even—if the world were…Continue reading
Source: Economist

Has a British engineer broken the laws of physics?

Any reaction?

ROCKETS are spectacular examples of Isaac Newton’s third law of motion: that to every action there is an equal and opposite reaction. Throwing hot gas out of its engines at high speed (the action) thrusts a rocket off its launch pad and into space (the reaction). But having to carry the propellants needed to create the gas (the reaction mass) is a pain, for at any given moment during a flight the action has to propel not only the rocket itself, but also all of the remaining, unburnt propellant. Most of the effort expended in a rocket launch is therefore directed towards lifting propellant rather than payload. As a result, even the most modern rockets start off with a mass that is more than 90% propellant.

The fantasy of rocket scientists is therefore an engine that needs no propellant. And that is what Roger Shawyer, a British aerospace engineer, claims to have invented. In his view, his EMDrive (the “EM” stands for “electromagnetic”) converts electrical energy straight into thrust, with no need for reaction mass. The only trouble is, that should be impossible.

An EMDrive (see picture) is a…Continue reading
Source: Economist

Snapping planets

Source: Economist

Fijian ants grow their own homes

HUMANS began planting crops about 10,000 years ago. Ants have been at it rather longer. Leafcutters, the best known myrmicine agriculturalists, belong to a line of insects that has been running fungus farms based on chopped-up vegetable matter for 50m years. By that yardstick even Philidris nagasau, a species of Fijian ant, is a newcomer to farming. It started cultivating plants only about 3m years ago. What distinguishes it is that it is growing not only food, but also homes. It was already known that P. nagasau lives in epiphytes (plants that grows upon other plants) called Squamellaria. But as Guillaume Chomicki and Susanne Renner of the University of Munich describe in this week’s Nature Plants, it also sows and nurtures them.

Dr Chomicki and Dr Renner discovered, in the course of study of the six species of Fijian Squamellaria, that P. nagasau worker ants harvest seeds from their epiphytic homes, carry them away, and then insert them into cracks in the bark of suitable trees. That done, they patrol the sites of the plantings to keep away herbivores, and also fertilise the seedlings as they…Continue reading
Source: Economist