An illuminating journey to the sun

By Stuart Nathan

All life on Earth – with the exception of some weird creatures huddled around geothermal vents deep in the ocean – depends on the sun. It props up every food chain, providing the fuel for plants to grow. Until the middle of the 20th century, every joule of energy that humans used was derived from it, either directly or through burning the fossilised remains of plants and animals. Today, scientists are trying to generate energy by mimicking the chemical processes that happen in the sun.

An exhibition at the Science Museum in London about humanity’s relationship with the sun is appropriately illuminating. “The Sun: Living with Our Star” starts with anthropology, noting how ancient civilisations thousands of miles apart worshipped its rays in similar ways. It was typical, for instance, to depict the god of the sun traversing the sky in a vehicle – although some societies portrayed him more stylishly than others. The chariot of the Hindu god Surya was pulled by seven mares, each a different colour of the rainbow, while the Egyptian god Ra had to make do with a boat.

Other displays chart the development of solar power, which, the curators point out, has a long history. During the siege of Syracuse (213-212BC), Archimedes is said to have invented a giant mirror which deflected the sun’s rays onto the sails of Roman boats, setting fire to them. Around 30AD, the emperor Tiberius commissioned the world’s first greenhouses so that he could enjoy his favourite salad vegetables, cucumber-like melons from the Middle East.

One of the quirkier exhibits is a solar panel that President Jimmy Carter had installed at the White House in 1979. Ronald Reagan, keener on the oil industry than renewable energy, had it removed soon after taking office in 1981. The exhibition culminates with a huge projection of the roiling surface of the sun, obtained by the latest orbital observatories – a mesmerising end to an enlightening visit.

Danish sun chariot (1,400BC)

This is a replica of a sculpture found on Trundholm Moor in Denmark. It is believed to have been used in rituals aimed at keeping the sun on its course. In Scandinavian mythology the sun was mounted in a chariot drawn by two horses called Árvakr and Alsviðr, which had bellows fixed under their shoulders to cool them down. The chariot was perpetually chased by a monstrous wolf called Skoll, prophesied to catch them at the end of the world.

The first orrery (1712)

Orreries are mechanical models that demonstrate the movement of the planets around the sun. This ornate example includes the orbits of only the Earth and Moon. Although planetary models had been around since ancient times, this is believed to be the first called an orrery, after the man who commissioned it, Charles Boyle, fourth Earl of Orrery. It was made by a London clockmaker, George Graham.

Portable sundial (1566)

You might think that the advantage of carting around a sundial as opposed to wearing a watch is that it wouldn’t need to be adjusted as one travelled through different time zones. However, unlike mechanical clocks, which need to be recalibrated with changes in longitude, sundials need to be adjusted according to latitude, because of the changes to the apparent angle of the sun. This one includes six interchangeable plates to keep the instrument accurate as its owner travelled around Europe.

Sunspot painting by James Nasmyth (1860)

James Nasmyth was a 19th-century industrialist who is best known for inventing the steam hammer. After he retired, he became interested in astronomy and designed and built his own telescopes. He was the first person to observe the granular texture of the surface of the sun, which he said looked like willow leaves, and meticulously document it in paintings. Much later, scientists would determine that these “sunspots” were cooler areas, caused by changes in the sun’s magnetic field.

ST-25 tokamak

The sun, like all stars, generates its energy by nuclear fusion: its immense gravity crushes hydrogen gas so much that the nuclei of hydrogen atoms merge to form helium, releasing enormous amounts of heat. Scientists have been trying to replicate this process since the 1940s, with much of their efforts focused on doughnut-shaped devices called tokomaks. This small prototype was built by Tokamak Energy, a British company which describes its mission as “striving to harness the significant potential of fusion power to deliver an abundant, safe and cost-effective source of clean energy to the world.” At the moment, this device doesn’t perform fusion – it’s used instead to investigate the behaviour of hydrogen plasma. Fusion isn’t expected to be a practical reality for generating electricity until around 2060.

The Sun: Living with Our Star Science Museum, London, until May 6th