Science: Orkney – hot spot of the Stone Age

The Orkney Islands, off Scotland’s north coast, are famous for their wealth of Stone Age monuments. Until recently, these had been seen as the peripheral flowering – in a cold, wet and remote location – of a culture that had spread north from a more hospitable climate.

But the latest archaeological evidence, described in the journal Science this month, shows that Britain’s megalithic monuments really started on Orkney’s Mainland Island about 5,200 years ago, along with new styles of architecture and pottery. From there the innovations swept south across the British Isles, culminating hundreds of years later in Stonehenge and Avebury in Wiltshire.

“We’re looking at a fairly major transformation across Britain – the impact of a whole way of life, religious and social, which comes out of Orkney,” says Michael Parker Pearson of the Institute of Archaeology at University College London. “Orkney was a place of synthesis, where the Neolithic worlds came together.”

Although most of Orkney’s Neolithic monuments, such as the Ring of Brodgar and the Stones of Stenness, have been famous for centuries, new discoveries are coming from a vast complex of stone buildings, the Ness of Brodgar, that had been buried for millennia until excavation started less than a decade ago.

Acid attack

Global rainfall as acidic as lemon juice – caused by extreme volcanic activity, say MIT researchers – helped create the most severe mass extinction on Earth, the Great Dying 252 million years ago.

The Ness of Brodgar was built about 3200BC on the middle of a narrow isthmus dividing freshwater and saltwater lochs. It included a dozen or more buildings with outer walls up to four metres thick and inner walls incised with mysterious butterfly-like patterns. The central gathering hall, 500 sq m in area, had a cross-shaped inner sanctum.

Carbon dating of organic material found at the Ness suggests that the complex was used for about 1,000 years. Activities included feasting on a huge scale, judging from the number of cattle bones found on the site and pottery with residues of beef and dairy fats. It must have been a gigantic ceremonial centre, not only for the 10,000 or so people believed to have lived on Neolithic Orkney but probably also for outsiders who made a perilous voyage by boat from the mainland.

Archaeologists say the combination of stone circles and earth henges that is so characteristic of British Neolithic monuments – and unknown elsewhere in Europe – is seen on Orkney at least 100 years earlier than the rest of Scotland or England. The Grooved Ware style of incised pottery associated with henge monuments also appeared on Orkney before anywhere else. So did a distinctive style of housing – with a central hearth, stone beds and an area for storing household goods. But why such a remote spot became Britain’s hotbed of cultural innovation 5,000 years ago remains a mystery.

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How to prevent satellite collisions

The growing number of redundant satellites in orbit poses a threat to active spacecraft, which may collide with such “space junk”. Some collisions have already taken place: the most serious, in 2009, destroyed an active Iridium communications satellite that hit a defunct Russian military satellite.

This year, the European Space Agency (ESA) plans to test a relatively cheap and simple technique for safely “de-orbiting” satellites so that they do not hang around in space when their working life is over. Developed at Surrey Space Centre in Guildford, the technology uses a light 25 sq m “gossamer sail”. It remains furled up in a small box but when a satellite’s time is up, an operator sends a signal to unfurl the sail, which is made of a polymer called Kapton just a few thousandths of a millimetre thick.

The sail is designed to deorbit satellites in low orbits of up to 700km, where there is enough residual air to generate the drag needed to bring down the craft to an altitude where it would burn up in the atmosphere. Many communications satellites operate in such orbits, where the risk of collision with space debris is greatest; the technology would not work for satellites in far higher geostationary orbits at 36,000km.

The sail is much cheaper and lighter than existing de-orbiting technology, which uses chemical or electrical propulsion to bring down a satellite. Surrey scientists have put the sail through a series of thermal, vibration and vacuum tests. ESA plans to test it in orbit at 600km, where there is enough atmospheric drag to cause re-entry and burn-up within a few months. “The sail will be an important step in ensuring sustainable exploitation of space in the future,” says Sven Erb, ESA project manager.

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Self-healing cities

A silent road that absorbs water and heals itself is the latest in a series of inventions aimed at making cities more sustainable, writes Sarah Spickernell.

By 2030, it is predicted that five billion people – 60 per cent of the world’s population – will live in urban areas. How to manage this change is both a priority and a puzzle for scientists and engineers.

Erik Schlangen from the Delft University of Technology in the Netherlands has devised self-healing asphalt for road surfaces to try and achieve sustainability and cost effectiveness. Porous asphalt is combined with a mixture of steel-wool fibres and bitumen, which melts when a heated coil is driven over the surface by a large vehicle. Once the surface has cooled down again, the mixture resolidifies and closes any micro-cracks in the surface, preventing loose stones from escaping.

Currently applied to just four roads in the Netherlands, it is predicted that the self-healing asphalt would save the Dutch €90m per year if it was used everywhere. “The porous nature means that rainwater and noise are absorbed, while its ability to self-heal would reduce the need for repair and maintenance, resulting in fewer traffic jams and greater longevity for the roads,” says Schlangen.

But the Delft researchers are not just experimenting with asphalt. They have already conferred similar self-healing properties on concrete by impregnating it with bacterial spores. “When a crack appears, the spores wake up and multiply, converting their food into big calcite minerals. These minerals fill up the cracks and stop any leakages,” he explains.

Seeing the benefits of self-healing infrastructure in an increasingly urban environment, the rest of Europe is starting to follow in the Netherlands’ footsteps. In Britain, the universities of Cardiff, Bristol and Cambridge are all working with bacteria to create their own versions of self-healing concrete.

Other inventions that are helping us adapt to an increasingly urban and digital world include:

Amphibious architecture

A glowing, virtual cloud hovers above the Bronx River in New York. With sensors submerged in the water, the cloud reacts to changes in the river’s environmental conditions by changing colour.

E-bikes

London mayor Boris Johnson intends to introduce electrically powered bicycles to the police force this year, in the hope they will make police officers more mobile and able to enter places cars cannot.

Hello lamp post

Interactive screens have been set up on lamp posts, postboxes, bollards and bins across Bristol. These encouraged people to interact with the infrastructure around them, and they could send messages to any other screen in the city.

Easy parking

Scientists at the Massachusetts Institute of Technology have built cars that can sense available parking spaces by analysing digital traces and crowd-sourced information. It is hoped that these will reduce traffic and pollution in cities, while making drivers’ lives easier.