Seeing Invisible Light

Seeing Invisible Light - Infrared image of asteroid belt around a young star
JWST infrared image of never-before-seen asteroid belts around a star 25 light-years from Earth

In ancient times, people looked up into the night sky in wonder. Without modern light pollution, they could have seen the stars more clearly, but they had only their unaided eyes to see the majestic sky. The first revolutionary change occurred when Galileo made and used an optical telescope. However, he was limited by being able to see only the visible spectrum of light. Today, astronomy involves “seeing” invisible light.

Light is electromagnetic radiation, and our vision can detect only a very narrow range of the electromagnetic spectrum. But astronomers today have instruments that allow them to “see” light frequencies in wavelengths outside the human vision range. Yesterday we discussed two portions of the spectrum invisible to our eyes – radio waves and microwaves. Those frequencies can tell us many things about the universe God created. Today, we will examine more ways of seeing invisible light.

The higher the light frequency, the shorter its wavelength. Microwaves have wavelengths between one meter and one millimeter. The next higher frequency of light has wavelengths below one millimeter, so they are called submillimeter waves. One weakness of optical telescopes is that visible light can’t penetrate clouds of gas and dust in regions where stars are forming, but submillimeter waves can. However, water vapor in our atmosphere absorbs submillimeter waves, so astronomers build observatories for studying them in dry, high-altitude locations such as the mountains in Chile and Hawaii.

We find infrared light at even higher frequencies and, thus, shorter wavelengths. Although we can’t see infrared energy, we can feel it as heat. The James Webb Space Telescope (JWST) leads the revolution in infrared astronomy. Scientists have used infrared sensors to measure the temperature of stars, including our Sun, but the Webb Telescope takes that to a new level. It can detect emerging stars hidden by clouds of dust and gas. The JWST can also observe matter that is only a few degrees above absolute zero. In only its second year, JWST has sent back images that allow us to see space objects we have never seen before.

Just above the infrared frequencies, we find optical light. Optical telescopes have been showing us many features of the universe since Galileo, but they have limitations. Not all objects in space produce optical light. For example, we can only see the planets in our solar system because they reflect the Sun’s light. Also, our atmosphere scatters optical light giving us the blue sky in the daytime and atmospheric blurring of the stars at night. Optical telescopes are usually the only option for amateur sky watchers, but for the sharpest viewing, professional astronomers locate their optical telescopes on tall mountains or in space. The Hubble Space Telescope is the leader in optical astronomy.

Although visible light can tell us much about God’s creation, seeing invisible light has opened a new understanding of how the Creator has produced the elements essential for life. Three types of light have higher frequencies and shorter wavelengths than visible light. Those short wavelengths contain the energy to harm or destroy life, but God has provided the protection we need. We will look at that tomorrow.

— Roland Earnst © 2023

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