Anders Celsius, Swedish astronomer and physicist, c 1730s.
© Science Museum / Science & Society Picture Library
In 1735, Celsius (1701-1744) took part in two expeditions led by Pierre Louis Moreau de Maupertuis (1698-1759) which proved the Earth was a sphere with flattened poles and a bulging centre. In 1741, Celsius was responsible for the construction of Sweden's first observatory in Uppsala and with his asistant Olof Hiortner, discovered that the aurora borealis influenced compas needles. In 1742, using a mercury thermometer, he recommended the Celsius temperature scale which is still used today.