Time capsules

OXYGEN makes up a fifth of the atmosphere (20.9%, to be precise), but that has not always been so. For the first 2 billion years of Earth’s existence, before photosynthetic organisms became common, there was no chemically uncombined oxygen in the air at all. Even after that, the gas remained scarce for hundreds of millions of years. By 575m years ago, however—which was when animals whose dimensions are measured in centimetres rather than microns appear—there must have been enough oxygen around to support their respiration. The usual guess is that the gas’s levels began to rise about 700m years ago. But a guess it is.

Now, Nigel Blamey of Brock University, in Ontario, Canada, has brought some evidence to bear on the question. His study, just published in Geology, is the first to measure directly the composition of samples of air from this ancient time. They were trapped in rock salt from the Officer Basin in south-western Australia, laid down by the evaporation of seawater between 830m and 800m years ago.

Previous estimates of oxygen’s past abundance have been made indirectly. In particular, the gas’s…Continue reading
Source: Economist

Breathtaking

SMOKING a whole packet of cigarettes in a day once or twice a year would certainly make someone feel ill, but probably would not kill him. Smoking even one cigarette every day for decades, though, might do so. That is the difference between acute and chronic exposure, and it is a difference most people understand. What they may not understand is that the same thing applies to air pollution.

On a day-to-day basis, the forecasts most cities offer turn red only when pollution levels rise to a point where they will cause immediate discomfort. That makes sense, for it lets people such as asthmatics take appropriate action. But it might also lead the unwary to assume, if most days in the place he inhabits are green, that the air he is breathing is basically safe. This may well not be the case. In London, for example, a study published last year by researchers at King’s College suggested air pollution shortens the city’s inhabitants’ lives by nine to 16 months.

To investigate the matter, The Economist crunched a year’s worth of data collected from May 2015 onwards in 15 big cities. They were gathered…Continue reading
Source: Economist

On a roll

MAKING things with 3D printers is an idea that is being adopted by manufacturers to produce goods ranging from false teeth to jet engines. Conventional printing, though, has not remained idle. Machines that have their origins in the high-speed rotary presses that apply words and images to large reels of paper, like the ones which turn out the physical versions of this newspaper, have started making other things as well.

The extent of this transformation can be seen at a factory in Accrington, a town in one of Britain’s former industrial heartlands, Lancashire. Here, Emerson & Renwick, founded in 1918, has expanded beyond its formative business of making wallpaper-printing equipment. The latest piece of kit to which the finishing touches are being added is part of the firm’s Genesis range. It is about the size of a shipping container and is designed to coat and print electrical devices. Like a conventional printer it does so on long rolls of material, called webs. Then, just as printed pages are cut by guillotines from such webs for binding into newspapers, magazines or books, these printed items are cut out and used in products ranging from solar…Continue reading
Source: Economist

When AI meets reality

Source: Economist

People may be more honest than psychologists thought

“IN THE state of nature, profit is the measure of right,” wrote Thomas Hobbes, a philosopher with a dim view of human nature. Hobbes’s fellow-thinkers have spent centuries pondering whether humans tend to be self-serving or are more inclined to straight-dealing. (Obviously, people exhibit both kinds of behaviour. The question is which comes most easily.)

So far, most experiments have tended to favour the first idea—that humans are dishonest by default when it serves their self-interest. In one study led by Shaul Shalvi at the University of Amsterdam, for example, participants were told to roll a die secretly three times and write down the results of the first roll. They would then receive 10 times that number in Israeli New Shekels. The researchers found that people who were asked to report their die roll within 20 seconds tended to report higher numbers than those who were given no time limit (though both groups reported higher numbers, on average, than would be expected if they were being truthful).

Now, though, the waters have been muddied by a new study…Continue reading
Source: Economist

Rallying the troops

VETERANS of the war on AIDS wear the medal stamped “Durban” with pride. It was in that city, in 2000, that the most effective of the International AIDS Conferences was held. The field’s bigwigs agreed that everything possible should be done to make the antiretroviral (ARV) drugs that had been invented a few years earlier available to all who needed them, and began to create the institutions that would distribute them.

In retrospect, it sounds an obvious thing to do. But in those days ARVs were costly, and ways of getting them to people in poor countries nearly non-existent. The ramp-up therefore took time, and deaths from AIDS continued to rise. According to UNAIDS, the United Nations agency charged with combating the disease, they peaked at 2m a year in 2005. Since then, though, they have almost halved, to around 1.1m a year. That is fewer than the 1.5m who die from viral hepatitis, a fact that would have astonished the delegates to Durban in 2000.