Shadowgraph
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Shadowgraph is an optical method that reveals non-uniformities in transparent media like air, water, or glass. It is related to, but simpler than, the schlieren and schlieren photography methods that
prehistoric shadowgraphy sunlight shadowgram of a martini glass "focused" shadowgram of a common firecracker explosion "Edgerton" shadowgram of the firing of an AK-47 assault rifle
Shadowgram of the turbulent plume of hot air rising from a home-barbecue gas grill.
"Edgerton" shadowgraph of bullet in flight
Shadowgram of shock waves from a supersonic bullet fired from a rifle. The shadowgraph optical technique reveals that the bullet is moving at a Mach number of about 1.9. Left- and right-running bow waves and tail waves stream back from the bullet, and its turbulent wake is also visible. To the right of the frame are seen unburned powder particles from the cartridge, themselves traveling slightly subsonic so that each of them produces a curved bow shock wave.
Robert Hooke
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Robert Hooke was an English polymath who was active as a physicist, astronomer, geologist, meteorologist, and architect. He is credited as one of the first scientists to investigate living things at m
Shadowgraph
…nearby surface by the uniform sunlight. Some aquatic predators detect their transparent prey by way of their shadows cast upon the ocean floor. It was Robert Hooke who first scientifically demonstrated the sunlight shadowgraph and Jean-Paul Marat who first used it to study fire. A modern account of shadowgraphy…
c. 1680 Portrait of a Mathematician by Mary Beale, of an unknown subject, conjectured to be Hooke or Isaac Barrow
1689 portrait of Robert Boyle by Johann Kerseboom, at Gawthorpe Hall, Lancashire
Illustration from The posthumous works of Robert Hooke... published in Acta Eruditorum, 1707
Hooke noted the shadows (a and b) cast by both the globe and the rings on each other in this drawing of Saturn.