Credit: ©The Royal Society
    Image number: RS.15124

    Alhazen's problem

    Date
    26 June 1669
    Creator
    Unknown, Artist
    Object type
    Archive reference number
    Manuscript page number
    p1
    Material
    Dimensions
    height (page): 205mm
    width (page): 160mm
    Subject
    Description
    This is a figure relating to Christian Huygens's treatment of Alhazen's problem, which was enclosed with his letter to Henry Oldenburg dated 26 June 1669. The problem attributed to Alhazen (the Latinized name of Ibn al-Haytham (965-1045)) is to find a point of reflection on the surface of a spherical mirror in relation to two points, the eye and the visible object.

    The diagram and text are printed using a method that Huygens claimed he had invented, making the acid bite all the way through the plate and inking over it, as with a stencil.

    Christopher Wren had come up with a similar copying method earlier in 1662.
    Object history
    C. Huygens and R. F. Slusius, 'Some letters exchanged between Monsieur Slusius and Monsier Hugenius, about a considerable optic problem (the point of reflection in a concave and convex mirror) of Alhazen', Phil. Trans., vol. 8, no. 97 (October 1673), pp. 6119-26, tab. 2, fig. 1.

    The covering letter dated 26 June 1669, ElL/H1/64, is transcribed and translated in The Correspondence of Henry Oldenburg, ed. by A. Rupert Hall and Marie Boas Hall, 13 vols (Madison: University of Wisconsin Press; London: Taylor and Francis, 1965-86), vol. 6, 42-46 (no. 1213). The editors note that the enclosure regarding the solution to Alhazen's problem, with figures printed using a 'new' method devised by Huygens himself, is no longer found in the Royal Society's archives. However, this is the enclosure that accompanied the original letter.
    Related fellows
    Christiaan Huygens (1629 - 2006, Dutch) , Natural philosopher
    Henry Oldenburg (1612 - 1677, German) , Scientific correspondent
    Associated place
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          > France
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