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SCAPA FLOW
On 14th October 1939, a British battleship HMS Royal Oak was sunk after she was hit by German U-boat U47 in Scapa Flow just off the Orkney Isles in Scotland. 833 lives were lost when the ship sank in just over ten minutes. The wreck is now designated an official war grave.

Almost 70 years on, the HMS Royal Oak is still leaking oil which could pose a threat to the coastline of Orkney and Shetland. The MOD have already launched salvage operations to remove some of the oil but they require high resolution images of the wreck in order to make sure thay have made the site secure.

Dr Martin Dean, marine archaeologist at the University of St. Andrews has been called in to do this and with the aid of Dr Chris Rowland, an expert in animation and 3D visualisation from the University of Dundee together with Dr Mark Laurence make up the ADUS (Archaeological Diving Unit Survey) Team. They have come up with some new technology that has allowed them to get some of the clearest pictures of a wreck underwater ever seen.

Using multi-beam sonar from their research vessel, recording the image over several passes and getting as close to the hull of the ship as they can - they have come up with images that can be electronically tweaked and enhanced to allow them to see the wreck in full 3D and even create ‘fly bys’ where they can virtually circle the ship and view it from any angle.

DARK MATTER
In 1933 the astronomer Fritz Zwicky tried to find the total mass of a cluster of galaxies using two methods.

Firstly he measured how bright the galaxies were that he could see, and then estimated the amount of mass necessary to burn that brightly.

Then he measured how fast the galaxies were orbiting each other, calculated how strong their mutual gravitational attraction must be to hold them together without flying off, and thus worked out how much the total mass must be to exert such a pull.

It was very clear that he could not observe nearly enough mass to account for the second figure. Either Einstein’s laws of gravity were wrong at such large distances, or something else was holding the cluster together that he could not see.

He called it "Dark Matter". But only in the early 80’s did it become reasonable to suggest that this was not just ordinary matter dimly lit or maybe obscured, but perhaps something much more exotic – something that doesn’t interact with light at all.

Sue is joined by Dr Andy Taylor of the Royal Observatory Edinburgh and Prof Gerry Gilmore of the Institute of Astronomy, Cambridge to discuss some of the recent developments in physics’ grand quest to find and identify a type – or several types - of matter that we cannot see or touch, and yet which accounts for five times more of the universe than we will ever see with our eyes.

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