Task: Text Categorization
Input (English): Different versions of this phenomenon have been experimentally tested by Ives and Stilwell on hydrogen atoms in 1938. Cherenkov radiation and verification of the absence of a medium of transmission for light are important consequences of its relativistic formulation. Johannes Stark predicted that high velocity rays of positive ions will demonstrate it, while Buys-Ballot [BOYS-ba-LOH] first verified it in 1845. First described by an Austrian scientist in 1842, FTP, name this effect that explains why a moving observer perceives a wavelength different from the source wavelength.
Output (English): Science