by Ceacy Henderson
One of the intangible benefits of farming is that winter is a time of year when the pace of activity has to slow down. I use this time to study things that interest me. Recently, I acquired a fabulous DVD of the NOVA program, Secrets of the Sun. I have watched it over and over. It is a glimpse into the composition and properties of the ultimate energy source that makes life even possible on planet earth. The program allows us to see the high-resolution images that are streaming back from a satellite, the Solar Dynamic Observatory, launched by NASA in Feb. 2010. Spectacular is an understatement.
As beautiful and fascinating as these images are, what is more astonishing is what scientists have learned about how the energy of the sun reaches earth. As a result of nuclear fusion, photons, miniscule packages of heat and light, are created in the sun’s dense core. It takes millions of years for these photons to reach the surface of the sun. But once the photons are released from the sun, it takes just a little over 8 minutes for them to reach the earth. They travel 93 million miles at 186,000 miles per second and arrive right here for me to see in the form of sunlight. Of course, I am not seeing the photons themselves. Rather the light from the photons makes it possible for me to admire the snow and watch the colorful birds at the feeder outside my window.
Photons travel at varying wavelengths, and different species of animals have evolved ways to detect those differing wavelengths, mostly through their visual organs. The shortwave, high intensity photons are at one end of the light spectrum. Gamma rays and x-rays are the shortest but are not visible to us. And we can’t see in the ultraviolet range either, but many birds and insects can. Human eyes evolved to see in the middle wavelengths that we call visible light. The world looks very different for species that can see ultraviolet light however. For example, some hawk species, like the kestrel and the red tailed hawk, can see in the ultraviolet range and can spot mice hundreds of feet below them in grass because mice leave territorial urine scent marks. The urine marks happen to be visible in ultraviolet light, alerting the hawks to the trails frequented by the resident mouse. We could be looking right at these trails and be unable to find them.
At the other end of the spectrum are the low intensity, long wavelengths like infrared, which snakes can use to hunt at night in the dark. The snakes are not actually seeing red light, but rather have a highly sensitive organ in their head that allows them to detect minute thermal signals. Interestingly, there are insects that also have this ability; one of those is the bed bug!
So what happens to all these photons when they get here? I love this part. They are either absorbed or reflected back out to space. So, when I am sitting in my garden feeling the warmth of the sun on my skin, I am absorbing photons that were made millions of years ago and have traveled 93,000,000 miles!!! Every day little bits of the sun become part of me. Not just by absorbing sunlight, but also because all the plant food that I eat has also absorbed photons, and the milk from my goats is the metabolic product of all the plants that they have eaten. All the plants in the world use photons as an energy source to photosynthesize.
You don’t have to be a physicist to appreciate how fabulous our sun is. On earth, the energy radiating from that immense star is made manifest in every plant and animal, in the wind, and the waves, in rainbows, the great cycles of our weather, and the eerily beautiful light shows of the aurora borealis. And isn’t it fantastic to realize that there is part of the sun made manifest in each and every one of us too. It is astounding to think that, in so many ways, we are made of starlight.