Energy: a history of addition

In 1878, a strange parabola five meters in diameter aroused the curiosity of the public at the World Exhibition in Paris. It was in fact an immense solar reflector designed by mathematics professor Augustin Mouchot, who was multiplying experiments to produce solar heat, installations that the press of the time described as "sun machines". Even at the time, these solutions presented themselves as an alternative to coal, the supply of which remained a concern.