January 5, 2009

The Sun Kings

Dr Stuart Clark

Report by: Mike Dryland

Dr Stuart Clark

Stuart found it very apt that he was delivering the Flamsteed’s first lecture of IYA2009, in the 150th anniversary year of the main events in his story, and in the very place which formed the centre of an important piece of the action.

In 1859 a leading Victorian astronomer, Richard Carrington, was observing and sketching a large sunspot group when he was amazed to see an intense flash of light which spread across the group. In his search later for other witnesses of this unprecedented sight, he was stunned to discover that there had been huge disturbances in the Earth’s magnetic field at the same moment when he saw the flash.

36 hours later almost the entire world was gobsmacked by an auroral display which spread way into the tropics from both north and south. Such a display had never been seen or reported before. There was global disruption of the telegraph network as power surges fried equipment and flattened operators.

The events of 1859 sparked a heated debate and search for evidence as to whether the Sun could influence the Earth in this way or if these phenomena were just coincidences. Many, especially the legendary Astronomer Royal, George Airy, refused to believe that such an influence was possible. Arguing for a link could be a reputation-threatening stance.

Stuart’s talk and excellent book take us on a tangled trail of detective work worthy of Agatha Christie. Carrington died in mysterious circumstances long before the debate was resolved. Stuart’s research found that the circumstances of Carrington’s death go some way to explaining why he is not now better known for his work… but you’ll need to get the book to read that story.

Col. Edward Sabine’s long series of magnetic observations showed that the declination of the compass (deviation from true north) varied in an 11-year cycle. Sabine was intrigued to find that his observations were in lock-step with Heinrich Schwabe’s sunspot counts which followed an identical 11-year cycle. Science had no explanation.

The debate raged through the illustrious ranks of Victorian physics — John Herschel, Michael Faraday, and many others. Total eclipses were eagerly studied and eventually photographed in the search for evidence of a mechanism that might cause a link between the Sun and the Earth’s magnetic field.

Enter E. Walter Maunder, magnetic assistant at Greenwich and antagonist of George Airy. Maunder and his wife Annie, assiduously collected and analysed years of magnetic observations. Eventually a 27-day cycle emerged — undeniably a link to the Sun’s rotation. Science could offer absolutely no explanation for the link — a clear sign that ‘new physics’ was at work. Soon the world was treated to the discoveries of cathode rays and electrons, the birth of particle, quantum, and nuclear physics.

On the way Maunder helped found the BAA and also discovered the ‘Maunder Minimum’, a 70-year period from 1645 to 1715 when very few sunspots were reported, and which coincided with the ‘little ice age’.

Today there can be no argument that the Earth is at the mercy of the Sun. A battery of satellites, including SOHO and Stereo, monitor the Sun and gives us warning of onslaughts that can fry communications and could mortally endanger astronauts who found themselves outside the protection of the Earth’s magnetic field. It is now not the fact, but the extent, of the Sun’s influence in climate change that is hotly debated.

The moral of the tale? If observations and theory disagree, don’t ignore the observations — there is the coal-face of discovery.

Stuart’s delivery is clear and entertaining. His explanations are most lucid and he makes this complex tale very accessible. The Flamsteed audience were delighted with his talk and queued up to buy all the copies of his book which Nicola had towed from Hertfordshire. A great night out for all concerned!