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Celebrating the 1919 Eclipse at Principe
In 1919, Sir Arthur Eddington launched an expedition to the remote African island of Príncipe, to observe a total solar eclipse and prove or disprove Einstein's General Theory of Relativity. The International Year of Astronomy celebrated the anniversary of this key scientific experiment of the 20th century with a return expedition. Amidst a series of popular talks in Africa and Europe, astronomers Pedro Ferreira (University of Oxford) and Richard Massey (Royal Observatory Edinburgh), along with Oxford anthropologist Gisa Weszkalnys, installed an exhibition on the island, and an informational plaque to mark the location of Eddington's observations.

Einstein first proposed his General Theory of Relativity in 1915. It describes how any massive object, such as the Sun, creates gravity by bending space and time around it. Everything in that space is also bent: even rays of light. Consequently, distant light sources, behind the massive object, can appear in a different position than they would otherwise. The total eclipse of 29th May 1919 gave scientists the first chance to test that theory. On the day, heavy clouds over Príncipe parted minutes before the eclipse and Eddington measured the positions of stars next to the Sun. They indeed appeared shifted from the positions that he had recorded in Oxford 4 months earlier — direct evidence that our nearest star shapes the space around it.

In a parallel turn of events, a rainy tropical morning on 29 May 2009 gave way to bright sunlight for a ceremony in which president José Cassandra unveiled the IYA plaque. Excitement had built on the island during the previous week, following the talks and school visits, so several hundred people (from a population of 5000) turned out to join in the celebrations. The plaque was well received, with residents of the Roça Sundy plantation, the president and ambassadors gathering round to learn about out GR. The locals thoroughly welcomed the visitors with music, dancing and some thoroughly spectacular pineapple homebrew!