Ever wonder why the siren of a police car or a firetruck seems to change in pitch after it passes by? Well, the phenomenon is known as the Doppler Effect. The Doppler Effect explains how sound, like in the example above, or light waves are manipulated by the movement of an object in relation to a stationary object.
The Doppler Effect has confused and fascinated me since first learning about it in my junior year physics class. Admittingly, I was absent for most of the days of that particular lesson, so I left that class stumped by how the Doppler Effect truly worked and the science behind it but putting it in terms of light turned everything around.
Now the question is raised, how is my perception of light manipulated by movement? Well, turns out it all has to do with the wavelength of light waves. The visible light spectrum is composed of many different wavelengths that each dictate a different color that becomes visible, with blue and violet being the shortest wavelengths and red and orange being the longest. These wavelengths, however, can be manipulated by movement. When an object in space is traveling towards the Earth, the wavelengths of the light being emitted from that object are manipulated to be shorter than they actually are. As a result, the object appears to be bluer than it really is or known as being blueshifted. On the other side, when an object is traveling away from the Earth, the wavelengths are artificially stretched, causing the object to be redder in appearance, or known as being redshifted.
Although our perceptions of sound and light appear rigid, the manipulation that travel causes to wavelengths is a reality that, thankfully, has become far less confusing to me over time.