Al-ankabut as art

'Al-ankabut' literally means 'spider', but it is also the Arabic name for what is known in Latin (and now English) as a rete: the rotating part of an astrolabe which displays the sun and stars. The ankabut embodies the characteristic combination of science and artistry at the heart of this exhibition.

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The ankabut is cut and filed from a single sheet of metal. The essential elements of the structure are the off-centre zodiac circle for the sun and the pointers representing bright stars in the sky. The design of the remaining framework must ensure that it does not fall apart, but is otherwise unconstrained by the heavens or mathematics.

There is a great variety of styles in ankabut design, as well as remarkably persistent traditions. Stars can be represented figuratively, as birds and fish, or the whole surface covered in decorative engraving. The earliest instruments are plain with 'dagger' pointers, while eight centuries later Mughal Indian astrolabes are shaped and engraved as intertwining, proliferating foliage.