Big, Bigger, Biggest Series Finale

Tuesday 13th October 8.00pm

Concluding this week is the factual series that examines the evolution of modern engineering. The final episode focuses on the technological leaps that have allowed engineers to build the largest and most advanced telescope in the world – the Large Binocular Telescope in Arizona.

Standing 3,000 metres above the Arizona desert, the two 840cm mirrors of the Large Binocular Telescope (LBT) can pick up light from stars more than nine billion light years away form Earth. “We can look at the constituent pieces of galaxies in formation,” says LBT director Dr Richard Green. The LBT represents the pinnacle of modern engineering, but it owes its existence to a number of historic advances in telescope design.

The story begins in 17th-century England when Isaac Newton invented the reflecting telescope. Thanks to his experiments into the nature of light, Newton realised that the lenses of the telescopes of his time blurred the images they captured through several points of focus. His solution was to do away with lenses altogether in favour of a 3cm mirror that reflected light from distant objects into a single point. Though Newton’s small telescope was made from ordinary household materials, it delivered the sharpest images in the world. “That telescope made people’s jaws drop in 1672,” says science historian Dr Allan Chapman. “It was more powerful than the conventional telescope of six feet long.”

In order to see deeper into space, engineers working on the Parsons telescope in Ireland in the mid-19th century needed to build a mirror considerably bigger than 3cm. Astronomer William Parsons designed a steam-powered machine to grind a mirror measuring 180cm in diameter. This was then mounted at the bottom of a 17-metre wooden tube, which was suspended from two concrete walls by chains. “When this telescope opened in 1845, it was one of the great scientific events of Victorian England,” says Dr Chapman.

At the beginning of the 20th century, powerful telescopes were picking up images of stars too far away to be resolved by the human eye. The solution was to take photographs of the night sky – but this threw up another problem. Owing to the rotation of the Earth, any image captured by a camera would become blurred. To counteract this movement, the designers of the 250cm Hooker telescope in 1906 mounted the instrument on a swivelling clockwork frame that moved in the opposite direction to the planet. As a result, the 100-ton telescope could remain locked on a single point in the sky. “You have something bigger than a locomotive moving with the accuracy of a watch,” says Dr Chapman.

Using images captured by the Hooker, Edwin Hubble came up with a revolutionary theory – that the universe was expanding. To test this principle, astronomers needed even clearer images of the night sky, for which they would have to counter the effects of light pollution. To rise above the urban glow of New York, engineers building the 510cm Hale telescope decided to locate their instrument high in the Californian mountains – some 3,000km away from the only factory capable of making such a huge mirror. Once the mirror was constructed in New York, it was transported by rail on a specially made train all the way to its new home. After completion in 1948, the Hale allowed astronomers to develop one of the most important scientific theories in history. “The Hale told us that the universe started with a big bang,” says Dr Chapman.

The last great obstacle for telescope designers came in the form of atmospheric interference. In 1990, the Hubble telescope was launched into orbit, where perfectly clear images of space could be captured at any time. However, any repairs to the Hubble’s various elements involve a shuttle launch. At the LBT, scientists believe they have hit upon the perfect solution – to use two mirrors mounted on motorised pistons to realign the light once it has made its way through the atmosphere. When the system is completed, astronomers believe they will be able to see not just the distant stars, but the planets that orbit around them.

About the author

  • BBC One
  • BBC Two
  • BBC Three
  • ITV1
  • ITV2
  • 4
  • E4
  • Film4
  • More4
  • Five
  • Fiver
  • Sky1