Johannes Stark won the physics Nobel Prize in 1919 for "for his discovery of the Doppler effect in canal rays and the splitting of spectral lines in electric fields. Johannes Stark contributed to a variety of areas in physics. His most known has to do with the splitting, and shifting, of spectral lines in electric fields, called the Stark effect. This effect arises because in the electric field, the nuclei are pulled one way and the electrons the other, shifting or splitting energy levels. A canal ray is a beam of positively charged ions from an anode. Doppler effects are ones of frequency shifts due to relative motion between the frequency source and the detector.