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- Life on Earth is powered by the Sun. We are bathed in its radiant energy on a daily bases. Each square meter exposed to sunlight is receiving 1,360 watts of energy.
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- Only 40% of this energy is in the form of visible light. 60% of the Sun’s energy is invisible infrared light that our skin can perceive as heat but our eyes can not record because the wavelengths are too long for the cells in our retinas. Infrared wavelengths are at about ½ the thickness of human hair.
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- Infrared part of the spectrum was discovered when the image of a prism was studied by William Herschel. He put a thermometer on each color to see what color was the hottest, red, green, blue? To his surprise the hottest spot was a dark spat outside the spectrum next to the red.
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- The infrared rays do not stimulate nerves in the retina in the eyes but they are of optimum size ( wavelength) to jostle whole atoms and molecules in the skin. Infrared is not heat but in this way it can produce heat.
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- Amazingly, it works both ways jostling atoms can emit infrared light. You can feel the result on you skin from an infrared heat lamp.
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- The wavelength of infrared light vibrates the molecules in glass. Glass windows become a barrier not transparent to infrared but smaller wavelengths of visible light easily pass right through. This effect works in both directions trapping heat inside a “greenhouse”.
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- Air molecules are the right size to scatter blue light . Thus the sky is blue. But, if you wear yellow-tinted glasses that block the blue light, but , pass the red light distant mountains can appear sharp and clear. The haze caused by the blue light scattering is significantly reduced. This is how “ amber” blue-blocking sunglasses work.
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- The Earth, along with the rest of the Solar System, is 27,200 lightyears orbiting from the center of the Milky Way. Interstellar dust blocks visible light from giving astronomers a clear view of the center of our Galaxy. Infrared telescopes can “see” through the light pollution giving astronomers a way to map out the center of our Galaxy.
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- Another window for astronomers opens up in the infrared because the Universe is expanding. Space is being added. The light from distant galaxies passing through expanding space gets “ Redshifted”, the wavelengths wide into the infrared range. Therefore infrared telescopes can see deeper back in time through more expanding space.
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- Astronomers can now “ see” more distant galaxies with there new infrared detectors. The wider wavelengths offer another advantage. Modern telescopes can use “ adaptive optics” to remove the image distortions created by the Earth’s atmosphere. This computer generated compensation created by flexible mirrors works with the wider wavelengths, not so as well with shorter wavelengths. Technology improvements may soon improve this so visible light images can be made clearer as well.
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- The wavelength of blue light is 400 nanometers.
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- The wavelength of red light is 700 nanometers.
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- Greater than 700 nanometers out to 10,000 nanometers is the spectrum wavelengths of infrared. Beyond that is microwave wavelengths.
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