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YOU could be fooled into thinking this image had been digitally altered, as row upon row of apartments seem to stretch to infinity. But these are real tower blocks in Hong Kong, documented by photographer in his series Architecture of Density.

“This image is beautiful and harrowing at the same time,” says Wolf, who deliberately left the sky and ground out of frame to create the illusion of indeterminable size. “Viewed from a distance, the photograph could be mistaken for a supermarket barcode, but up close, the brutal reality of life in a megacity becomes apparent.”

The photographs in the series are numbered instead of named, reflecting the anonymity of living in one of the most densely populated places on Earth, with 7.2 million people squeezed into 1104 square kilometres. . London has 5285 per square kilometre.

The shortage of space in the city has forced Hong Kong’s buildings skyward. It now boasts the most skyscrapers of any city in the world, with 293. This photo was taken in Tseung Kwan O, one of Hong Kong’s many new developments, built on land reclaimed from the sea.

Rapid spread of disease is one complication of high density cities. Wolf began the project after the 2002 outbreak of SARS, when he realised that despite working as a photojournalist, he hadn’t documented his own vision of the city. “What I love about Hong Kong is the rapid pace of change, the unpredictability, the wonderful chaos,” says Wolf.

Architecture of Density is on display in the in London from 17 January.

This article appeared in print under the headline “Architecture of density”

Much of the world should go on a diet in 2014. More than a third of adults globally were estimated to be overweight or obese in 2008, according to a , a think tank in London. That’s a 23 per cent increase on 1980.

In the last three decades, the number of adults estimated to be obese in the developing world has almost quadrupled to 904 million, overtaking the number in rich countries.

“The most shocking thing is the degree to which obesity is now affecting developing as well as developed economies,” says Tim Lobstein of the in London. “The problems caused by overconsumption of fats and sugars are now global, not just Western, problems.”

The rise is linked to a “creeping homogenisation” of diets across the world, says the report, which says rising incomes, advertising and globalisation all play a part.

It criticises policy-makers in most countries for being slow or unwilling to tackle the problem. “We see a big gap in what governments recommend people eat as part of their nutrition campaigns and what people actually eat,” says of the ODI, a co-author. “We need governments to acknowledge the scale of the problem and start putting in place stronger steps to tackle it.”

Growing trend

Some countries have managed to go against the grain and improve diets. For example, South Koreans ate four times more fruit in 2008 than they did in 1980. The report attributes this to government health drives, which include training programmes on how to prepare low-fat meals, showing what governments can do when they act.

The report’s figures are based on extrapolated using body mass index data from 199 countries.

Given that there are very few bits of hard evidence of obesity prevalence available historically in such a wide range of countries, the authors of the report have made pretty good use of the data, says Lobstein.

Although the change is most pronounced in the developing world, the US remains the fattest country with 71 per cent of its population obese or overweight. The UK is ranked a weighty fourth with 64 per cent.

In 2006, the World Health Organization predicted that obesity in the developing world would overtake that in rich countries by 2010.

While smartphones continue to improve markedly every year, a key component seemingly left in the dust is their battery, leading some companies to build portable batteries that can hold multiple charges for smartphones. In a twist, a charger based on a hydrogen fuel cell, originally designed for use in parts of Africa without mains electricity, is to go on sale in the US. The news was announced yesterday at this year’s Consumer Electronics Show (CES) in Las Vegas.

The is made by Intelligent Energy, based in Loughborough, UK. Unlike lithium-ion battery devices, it is powered by removable hydrogen fuel canisters. It can provide five full charges for most smartphones, its makers claim, through a USB port.

Upp is not technically a battery – it combines hydrogen and air to produce energy, with water vapour as a by-product. As a result it does not need to recharge, but is instead reloaded with a fresh hydrogen canister. The detachable canisters are refillable and connected to the fuel cell with powerful magnets.

The device has an accompanying app that can organise delivery of canisters so you don’t run out of juice, as well as provide usage data. is partnering with US electronics retailer Brookstone for the release. Upp is expected to cost $199 and will go on sale early this year.

Hydrogen fuel cells are also making their way onto the market in much bigger products. At CES, Toyota , which will go on sale in 2015.

(Image: Alexandra Angelich (NRAO/AUI/NSF), NASA Hubble, NASA Chandra)

This baleful red glow is a dust factory, located at the heart of a dead star’s expanding remains.

It is the first time such an object has been glimpsed at the centre of a supernova. The red glow is newly formed dust in the cool centre of the remnant, while the blue and green part is the shockwave expanding into space.

Supernovae are extremely bright explosions that occur when massive stars die, ejecting their matter into space. This one is called supernova 1987A – its light first reached us in 1987, having travelled all the way from the Large Magellanic Cloud.

The image was created by combining data from several telescopes. The shockwave was captured by the and NASA’s , while the dust was seen by in the Atacama desert, Chile.

It has long been suspected that supernovae are the source of the dust that filled the early universe, but it was not clear that they could create enough. The huge dust cloud in supernova 1987A suggests that they can.

The results were reported at in Washington DC, and will appear in .