Exploring the Invisible: Humans and the Electromagnetic Spectrum
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Chapter 1: The Limits of Human Perception
Have you ever paused to admire a rainbow? The vivid hues stretching across the sky can be captivating, even if just for a fleeting moment.
In late summer 2020, as the anticipation of autumn loomed and the ongoing pandemic weighed heavily, I was treated to one of the most brilliant rainbows I had ever witnessed, which certainly brightened my day. I believe rainbows represent one of nature's most stunning spectacles, with each color from the visible light spectrum vividly displayed against a cloudy backdrop. As someone with partial sight, I genuinely appreciate the spectrum of colors I can perceive.
Yet, it’s crucial to note, as I often emphasize during my lessons, that the human eye is capable of detecting only 0.0035% of the electromagnetic spectrum. The small segment we can see is referred to as 'visible light,' while we remain largely unaware of the vast array of electromagnetic waves surrounding us.
What Exactly is the Electromagnetic Spectrum?
The electromagnetic spectrum encompasses waves (or, according to wave-particle duality, packets of energy known as ‘photons’) generated by the movement of charged particles within an electric field. This motion produces electromagnetic waves, which represent oscillations in both electric and magnetic fields.
Electromagnetic waves travel through a vacuum at light speed; however, their frequency and wavelength define their unique properties. For instance, radio waves, which have low frequency and long wavelengths, possess less energy compared to higher frequency and shorter wavelength X-rays.
The portion of the electromagnetic spectrum that we can perceive ranges from 400 to 700 nanometers.
A Rainbow: More Than Meets the Eye
A rainbow occurs when sunlight disperses into its various wavelengths of electromagnetic radiation. Raindrops in the atmosphere function like tiny prisms, bending the light.
This bending of light causes violet light to refract the most, while red light refracts the least. Interestingly, our eyes are only capable of detecting certain wavelengths; infrared radiation is present just above the red light, and ultraviolet light is found just below violet light — both remain invisible to us.
In an intriguing experiment in 1800, Sir William Herschel measured the temperatures of different colors of visible light dispersed by a prism. He discovered that while red light had the highest temperature within the visible spectrum, the area just beyond red (invisible to him) was the hottest of all — this was the inception of our understanding of infrared radiation.
Life Beyond the Visible
Evolution has not equipped us to perceive the full spectrum of electromagnetic radiation. Although we can feel infrared radiation as warmth and utilize other electromagnetic waves for practical applications like X-ray imaging, our limited vision has allowed humanity to survive and thrive. After all, our capacity to detect visible light is sufficient for recognizing potential threats, like a sabre-toothed tiger.
Imagine if our eyes could perceive other segments of the electromagnetic spectrum; our understanding of the universe would be transformed. Take the Crab Nebula, for example: while the visible light captured by the Hubble telescope provides a stunning image, it represents merely a fraction of the visual information available if we could see in radio, infrared, or X-ray wavelengths.
Certain creatures, such as bees and butterflies, can detect ultraviolet radiation. Some flowers have patterns visible only in UV light that guide insects to their nectar, akin to runway lights for airplanes.
Additionally, snakes possess specialized 'pit organs' on their heads that enable them to sense infrared radiation, a crucial advantage when hunting warm-blooded prey.
Next time you find yourself enchanted by a rainbow, take a moment to appreciate the array of colors. Yet, remember that you are witnessing only a minuscule portion of the magnificent electromagnetic spectrum.
The first video titled "God, Angels, and Electromagnetic Radiation: Life Among the Invisible" explores the unseen aspects of our universe during the 2022 Gold Mass at Notre Dame.
The second video, "Limits of Human Vision," discusses the wavelength boundaries of human perception, showcasing how much remains outside our visual capabilities.