Space exploration began with the launch of Sputnik and Astrophysics was born as the application of physics to the phenomena observed by Astronomy, which etymologically means laws of the stars.
There are 2759 entries in this glossary.| Term | Definition |
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| Foucault Knife-Edge Test |
A technique for testing the accuracy with which the surface of a mirror or lens is figured. It was introduced by J. B. L. Foucault 1819-68 in 1851. The method utilizes the fact that a knife-edge moved slowly across the focal plane will cause the image of a beam of light to darken uniformly only if the imaging surface is perfectly spherical: any depressed or raised areas on the lens or mirror cause light and dark zones to appear in the image as the test is carried out.
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