In the Blink of an Eye

Astronomer Clyde Tombaugh looks through the instrument he used to discover the planet Pluto at Lowell Observatory in Arizona in 1930. He put two photographic plates of the sky, which were taken several nights apart, into the machine, which then "blinked" back and forth between the two images. When one of the little points of light moved between the images, Tombaugh realized he had discovered a new planet. Tombaugh was born 100 years ago. [Credit: Lowell Observatory]