I am not sure why I thought about the electromagnetic spectrum (see below) but I did. The spectrum is awesome in its diversity. One example is the range of the wavelengths across the spectrum. The wavelength of an FM radio signal is about 3 meters. The wavelength of visible light is about .0000006 meters. The radio waves used by submarines to communicate with each other are thousands of kilometers long .
To survive you must interact with your surroundings which means you must “see” your surroundings. Why do we (and virtually all animals) “see” this tiny portion of the spectrum (the visible light portion) and not other portions? For example, why did eyes not evolve to see infrared or X-rays instead of visible light?
There are four major reasons why we see this portion of the spectrum. First, the sun produces a lot of visible light although it also produces X-rays and infrared light. Second, the intensity of the
My mother’s father ran the US Navy underwater warfare research lab in WW II. One of the problems, at the beginning of the war, was that for two submarines to communicate with each other they had to surface. This is obviously a problem when there are hostilities on the surface.
The solution was radio that used very long radio waves. The wavelengths had to be this long for them to be able to travel through large amounts of water: either depth of the ocean or distance between submerged subs.
Acoustics was an area of research for my grandfather when he was on the MIT faculty and worked at Bell Labs. You can see the cover page of a textbook he wrote in 1929. (Theresa found this book).
electromagnetic waves produced by the Sun is the highest for the visible spectrum and within that, highest for yellow. Which is why we see the sun as yellow. Third, our atmosphere largely lets visible light through unimpeded. Other types of spectra such as infrared and ultraviolet are absorbed or scattered by the atmosphere. Fourth, visible light provides you with more information about an object than infrared. Visible light would enable you to see a big hole in the ground. Infrared would not.
Hence, if we were going to pick a part of the spectrum to be used as the basis for “seeing” the visible portion is a good choice .
To add some more pictures to an already image-heavy letter, below on the left is a picture of the sun that you would see if you could only see the x-rays it was emitting. In the middle is a picture of the sky taken using gamma rays. The bright yellow line is the central plane of the Milky Way. On the right is a picture of a girl taken using infrared light; in effect you see heat. Infrared does not give you as much detail of the scene as visible light.
The visible spectrum allows us to enjoy the photos below, all of which show the many ways in which I am a very stylish fellow. On the left, the photo is of me on my walk in a snowstorm. Dressed to keep warm and to avoid being run over by a plow. In the middle, is a result of me using some free software that enables you to imagine a “new look.” I could get used to the curly hair. On the right is a photo of me taken in graduate school that shows one of my many talents.
If all you could see were infrared and x-rays, you wouldn’t be able to enjoy these fine photos of me.
Not all life forms are restricted to seeing only the visible spectrum. Bumble bees can see UV light. Mosquitos and snakes can see infrared.
It was a real pleasure to read. Great article. You’re doing great.