Today’s observatories document every pulse and flash in the sky each night. To understand how the cosmos has changed over longer periods, scientists rely on a more tactile technology.
| Glass plates taken at the Armagh-Dunsink-Harvard Telescope in Bloemfontein, South Africa, in 1950 and 1951 were annotated by hand. |
| A photographic plate at the Neils Bohr Institute in Copenhagen captures the 1919 solar eclipse that was used to confirm Einstein’s theory of general relativity. |
| This 1934 plate of Andromeda, captured at the Oak Ridge Observatory at Harvard, was so heavily marked up because it was used to count galaxies. |