Double stars and trumpets on a train - the Doppler Effect
As the system is turning the emitted sine waves are compressed and expanded depending on the rotational speed and the length of the strings resulting into a vibrant sound field. Similar effects can be observed with shifted spectra of rotating double stars or galaxies. This effect was predicted in the mid 19th century by the Austrian Christian Doppler for the changing colours of rotating double star systems.
Headline of Ballot's publication of his train experiment with trumpets published 1845 in Poggendorfs Annalen.
But the proof of principle at that time was not realized with light physics, but with acoustics: Christopher Buys-Ballot installed 1845 trumpet players on a steam train in the Netherlands. In fact the approaching trumpets appeared to play at a higher pitch, whereas the pitches did sound lower by the receding band.
The Heaven's Carousel connects literally to this experiment. Instead of a brass band it uses simply loudspeakers playing sine waves.
complete record of Prélude 1 (ca. 8:50 min.)
