Friday, 8 July 2011

The Geiger-Marsden Experiment A.D. 1909

Manchester was the world's first industrial metropolis. In the years 1800 – 1900, its population grew from 89,000 to 1,435,000, making it the ninth largest city in the world (Chandler 1987). As the list below shows, it was also the largest city in Europe which wasn't an imperial capital:

  1. London (6,480,000)

  2. New York (4,242,000)

  3. Paris (3,330,000)

  4. Berlin (2,707,000)

  5. Chicago (1,717,000)

  6. Vienna (1,698,000)

  7. Tokyo (1,479,000)

  8. St. Petersburg (1,439,000)

  9. Manchester (1,435,000)

  10. Philadelphia (1,414,000)

The empires of Europe (Great Britain, France, Germany, Austria-Hungary and Russia) were about to enter into war with each other in the years 1914 – 1918. Manchester was never again to achieve such prominence. By contrast, the Ruhr's population grew from 766,000 (1900) to 4,900,000 making it the world's ninth biggest city in 1950. Note also that Chicago's population has increased to around the 5,000,000 mark in the same year:

  1. New York (12,463,000)

  2. London (8,860,000)

  3. Tokyo (7,000,000)

  4. Paris (5,900,000)

  5. Shanghai (5,406,000)

  6. Moscow (5,100,000)

  7. Buenos Aires (5,000,000)

  8. Chicago (4,906,000)

  9. Ruhr (4,900,000)

  10. Kolkata (4,800,000)

The 1950 list reflects a shift away from the major European powers (of whom only Britain, France and Germany remain). America and Japan have strengthened their positions. China, the Soviet Union (as Russia had then become known), Argentina and India are new additions. The lists show that whilst Manchester would keep on growing it wouldn't keep up with the expansion of other world cities. So the twenty year period between the opening of the Manchester Ship Canal and the start of the First World War can be seen as the peak of the city's global status.

This is demonstrated when we look at some of the events that were taking place in Manchester and around the world during the first half of the year 1904: On 30th January, Salford Lads Club is opened by Robert Baden-Powell; on 19th February, Winston Churchill makes an important speech on Free Trade at the Manchester Free Trade Hall (the home of the Hallé Orchestra); on 17th February, Giacomo Puccini's Madame Butterfly premieres at La Scala in Milan; on 23rd April, Billy Meredith scores the only goal of the game as Manchester City beat Bolton Wanderers 1-0 to win the FA Cup for the first time; on 4th May 1904, car manufacturer Henry Royce was introduced to motoring and aviation pioneer Charles Rolls at the Midland Hotel in Manchester.

The Suffragette movement has its origins in Manchester during this period. On 10th October 1903 the Women's Social and Political Union was founded by Emmeline Pankhurst at her house in Chorlton-on-Medlock. On 13th May 1905 Sir Edward Grey, a leading member of the Liberal Party, came to Manchester to deliver a speech at the Free Trade Hall. The event was attended by Christabel Pankhurst and Annie Kennie. They asked the speakers at the meeting if women would be allowed to vote but their questions were ignored so they created a disturbance in order to get themselves arrested. The incident achieved widespread publicity and is seen to mark the start of a long-running campaign of 'direct action' to focus attention on the issue of women's suffrage. Political progress towards a fair system of electoral representation (universal suffrage), a movement that had arguably begun in Manchester with the Peterloo Massacre of 1819, was matched by scientific progress. The story of the Manchester Physics department in the years 1900 – 1913 befits the kind of place that had pretensions of being the ninth biggest city in the world, not only a city of warehouses and commodity exchanges or a global shipping hub but one of the world's most important centres for scientific discovery.

The idea of the atom was first proposed by Manchester's John Dalton in around 1805 so it's perhaps no surprise that the city would go on to play such a hugely important role in the later stages of the development of atomic theory. J.J. Thomson was born in Cheetham Hill in 1856 and took a great interest in science as a child. He was admitted to Owens College in 1870 at the age of just fourteen before moving on to Cambridge where he became Cavendish Professor of Physics in 1884. Arthur Schuster was born in Frankfurt am Main in 1851 and moved to Manchester with his family in 1870. He also went to Owens College (Manchester) and spent five years at Cavendish (Cambridge) before returning to Owens in 1881, now Manchester University, where he was appointed Chair of Physics in 1888. [To make clear – we have Schuster (the German) at Manchester and J.J. Thomson (from Manchester) at Cambridge.] Born in 1871, Ernest Rutherford (pictured above right), moved to England from New Zealand to do postgraduate study at Cavendish (Cambridge) from 1895 – 1898, before moving to Montreal, Canada, where he was to do the work that would win him the Nobel Prize for Chemistry in 1908.

In 1897 J.J. Thomson discovered the electron (at Cavendish – where Rutherford was a postgraduate student at the time). This led him to formulate the 'plum pudding' model of the atom in 1904, where electrons were seen as being randomly distributed in a sphere of positive charge. As Chair of Physics at Manchester, Schuster established an active research department and designed a new laboratory which, when it was opened in 1900, was the fourth largest in the world and would soon become a serious rival to Cavendish. Schuster resigned in 1907 but had ensured that Rutherford would take over from him. German physicist Hans Geiger (pictured above left), born in 1882, also joined the Manchester department at this time and, in 1908, Rutherford and Geiger invented a device that would later become known as the Geiger counter (used for detecting radioactive emissions).

In 1909, Hans Geiger worked with Ernest Marsden, an undergraduate from Rishton in East Lancashire, to conduct the Geiger-Marsden experiment (or Gold foil experiment), under the supervision of Ernest Rutherford. It was the first successful attempt to probe the structure of the atom, revealing the existence of the atomic nucleus. It disproved the 1904 'plum pudding' model, devised by J.J. Thomson (the Manchester-born, Cambridge-based physicist who had discovered the electron in 1897). Rutherford's interpretation of the data from the Geiger-Marsden experiment led him to formulate the Rutherford model of the atom in 1911 which states that a very small positively charged nucleus is surrounded by electrons. This is also called the planetary model because of the way the electrons orbit the nucleus. Danish physicist Niels Bohr (pictured above centre), born in 1885, was to theorize the orbit of the electrons when he joined Rutherford's department at Manchester in 1912 (the same year Geiger moved to Berlin). Adapting Rutherford's nuclear structure to Max Planck's quantum theory, Bohr formulated the Bohr model in 1913 which was to lay the foundation for quantum mechanics.

Under Rutherford's direction, the Physics department at Manchester had made huge advances in atomic theory and Rutherford was knighted in 1914. In a poetic twist, the undergraduate who'd taken part in the experiment that had revolutionized our understanding of the nature of the atom, Ernest Marsden moved to New Zealand in 1915 (Rutherford's home country), where he'd been recommended for a Professorship in Physics at one of the universities. After four productive years at Manchester, Niels Bohr returned to Copenhagen in 1916 [and was to become one of the founders of CERN in 1954]. In 1917 Rutherford himself left the department to take over his old teacher J.J. Thomson's role at Cavendish [where, in the early 1930s, Cockroft and Walton were the first to artificially 'split' the atom, using particle accelerators]. He died in 1937 and is interred in Westminster Abbey alongside J.J. Thomson and near to Sir Isaac Newton.

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