Ever since I started learning about waves in physics, for sound first then light, I have wondered about their similarities and differences and how they affect our senses. I have always loved music, especially playing with it. At times I would think, "since sound is a wave and light is a wave, could there be a visual representation of a simple song incorporating simple notes and their harmonics?" Of course, there is much more to music than simple notes and harmonics, but this is mainly what I'm interested in discussing. We can transmit a sound signal through a laser and have it returned to sound, but that's not really what I mean. I'm talking more about how music or even simple notes can affect us based on how we perceive it. What "Music" is to people.
One problem is the range of our hearing is very different from the range of our seeing. Humans have a range of about 20 to 20,000 Hz for sound and a musical note, say middle "C" on a piano would correspond to a frequency of 261.63 Hz, it's octave (the next "C" over) has a frequency of 523.26 Hz. All other notes fall in between these frequencies and their corresponding octaves are 2x greater for higher pitch sounds and 1/2x smaller for lower pitch sounds. So then the next octave for "C" would be 1046.52 Hz and so on. As we can see, we get a good amount of octaves for each musical note in this range of 20 to 20,000 Hz, but can we do this with light?
The picture above shows the electromagnetic spectrum and that tiny portion titled "The Visible Spectrum" is all that we can sense with our eyes. It is shown in wavelength but this corresponds to about 405-790 THz. These frequencies are much higher than those of sound, which I'm pretty sure has more to do with their specific properties that differentiate them (like their speed and traveling mediums). So can we think about light like sound in terms of frequencies and octaves? If we take a color like red, which has a frequency range of about 405-480 THz, and try to find its octave or next harmonic, we would double this frequency. This gives us a range of 810-960 THz which is out of our "Visible Spectrum". We would not be able to see the next octave for the color red and neither would we for any higher frequency colors since red is the lowest of all the colors we can see. You could say we are a bit deprived in the abilities of our eyes, but we owe that to our sun which peaks at these frequencies and we simply evolved to make the best use of the light coming down to us.
So what does this mean? Well, I guess it means we can't see light the way we hear music, at least not with our own eyes. Luckily for us, we are very smart and have created technologies to detect the other parts of the electromagnetic spectrum. This is very useful in space since there is light of different frequencies going around for us to detect. With the help of Chandra for x-rays, Hubble for ultraviolet and visible, Spitzer for some infrared and Herschel for infrared and microwaves (along with other technologies) we can look into space and detect a much larger portion of the electromagnetic spectrum than with our eyes. These telescopes can take what they detect in higher and lower frequency ranges and turn it into something we can actually see. This means we can, in a way, see light the way we hear music. I think this is something really amazing. Humans have always found a way to expand on their abilities, this is just one example of that. Now I wonder if it would be of any interest to science or people in general try to make devices that expand our hearing range (dog whistle?).
Beautiful "Music" to my eyes
4 points. you ever use the visualizer on iTunes. A friend of mine wrote that software and sold it to Apple. He's an engineer that liked music.
ReplyDeleteI never have until you mentioned it now, and it looks great, much better than the windows media player visualizer. I completely forgot about visualizers, they are an awesome intersection of the senses.
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