Johann Christian Andreas Doppler

Christian Doppler is known for relating the change in wavelength with movement, now known as the Doppler Effect or Doppler Shift, which he published in 1842. Dutch meteorologist Buys-Ballot used musicians sitting on a moving train to approach and recede from the observer to substantiate Doppler's theory that the frequency was higher while approaching and lower while moving away. This effect, discovered independently by Armand Fizeau in 1848 was also used to explain redshift in the light spectrum