The Doppler effect: If you’re in your car (the dot in the ellipses to the left) and you hear an ambulance siren (the ripples on either side), you can tell it’s getting closer because the sound gets shriller, and as it passes you it gets duller

The Doppler effect: If you’re in your
car (the dot in the ellipses to the left) and you hear an ambulance
siren (the ripples on either side), you can tell it’s getting closer
because the sound gets shriller, and as it passes you it gets duller