3 ms·
With very simple tools (and quite a bit of patience) it is possible to make spherical and parabolic mirrors that deviate from the true shape by (much) less than
by Sharlin 4y ago
With very simple tools (and quite a bit of patience) it is possible to make spherical and parabolic mirrors that deviate from the true shape by (much) less than one wavelength of light, which is rather impressive.
https://en.wikipedia.org/wiki/Foucault_knife-edge_test https://en.wikipedia.org/wiki/Foucault_knife-edge_test
- kragen 4y agothe candle and knife edge needed for the interferometry are indeed quite widely available in human history, but the necessary knowledge of the wavelike behavior of light is only about 200 years old