part2

PART 2: DRIVING UNDER THE INFLUENCE OF SUNLIGHT

Deep in the heart of the sun hydrogen atoms smashed together, fusing into helium atoms and releasing tremendous amounts of energy. The immense mass of the star, more than 300,000 times the mass of the Earth, was pressed inwards under the influence of its own tremendous gravitational forces. The pressure contained the reaction, keeping it from exploding catastrophically. The center of the sun raged at the unimaginable temperature of ten million degrees Kelvin. Heat convected through its body and radiated from its surface. Electric fields induced magnetic fields; magnetic fields induced electric fields; and electromagnetic waves set forth for a journey through the solar system and beyond. Moving at a speed no other thing in the universe could attain, the light waves spread out past the orbits of the inner planets. Roughly eight minutes later some of the rays entered the Earth's atmosphere, bending, scattering, bouncing giddily through the gasses and dust that surrounded the little planet. The wavelength popularly known as "sky blue" found its self scattered far and wide, even more so than its shorter or longer wavelength companions. Light reflecting off of distant objects traveled farther, scattering blue light more. The farthest objects looked blue gray and dimmer than the closer ones.

The effects of blue scatter in the atmosphere. The most distant mountains look dim and blue.

The sun shone on. Fusing hydrogen. Creating helium. Sending light and heat to the surface of the Earth where plants busily stored its energy to make their own sugars. Grazing animals feasted on the plants, storing some energy in their bodies and using the rest to move around. The plants that weren't eaten died and added their nutrients to the soil for other plants. Some were buried by sediments and through intense pressure and millions of years converted into coal and oil. Carnivores preyed on the plant eaters, taking the stored energy to use for their own purposes. Humans ate from all three groups, using the energy to think, move, and build things. The things they built ran on the energy of burning coal and oil from plants that had lived millions of years before. Life flourished in the glow of the sun. Four and a half billion years of continual sunlight had gradually transformed this world from a barren glob of rock and magma into a home for billions of grateful life forms.
Father groaned and tried to adjust the driver's side sun visor to block the light that glinted in his eyes. He squinted at the road ahead of him. The pavement was hot, and right above it hovered a thin layer of hot air. Light sped up as it entered the less dense hot air and bent upward so much that to Father it looked like the sky was reflected on the surface of the road. Even though the pavement was dry, it appeared to have a shiny wet patch that always stayed just a ahead of the van. The road also reflected light up at him, as did the hood of the vehicle.

A road mirage. The red arrow represents a ray of light from the sun.

"Look in the glove compartment," he told Mother seated beside him. "See if you can find my sunglasses."
The dark glasses were located and handed over to Father who put them on with a happy sigh. "Much better." The deceptively simple shades consisted of several layers around the glass lenses. Like the hero of some epic fantasy story, light trying to enter had to pass through a series of traps and trials.

On its front surface a thin layer of reflective molecules prohibited half the light from entering at all. Undaunted, that light bounced off to go elsewhere. The light that made it through the first layer then passed easily through a coating intended only to protect the lenses from scratching. Immediately after this, however, it came to the dreaded polarizing layer. Here, light waves vibrating in any direction other than vertical were blocked. The light that reflected off of the flat road and the hood of the van had been vibrating horizontally. The polarizing layer stopped it, much to Father's great relief. Beyond the polarizing film was the thick brown tinted lens which absorbed much of the highly scattered blue light and had a coating to block the harmful ultraviolet wavelengths. Finally, light that managed to overcome all these obstacles was permitted to enter Father's eyes. It did so, however, only after passing through one final coating on the backside of the glasses. This last layer prevented light that bounced off the skin around Father's eyes from making a distracting reflection on the inner side of the lenses.

The coatings on a sunglasses lens. The yellow arrow represents a ray of light.

The family drove on. Past the inlet where tides sloshed back and forth daily under the influence of the moon's gravity. Through broad valleys carved by the relentless grind of huge glaciers fourteen thousand years earlier. Up the steep winding dirt road into a mountain range crumpled and uplifted in a continental collision fifty million years ago. Father and Mother took turns driving and reminisced about a previous camping trip. Little Sister read books about dogsled racing. Big Sister half listened to the ramblings of Brother about the finer points of programming computers, and stared idly out the window at the world illuminated by the reflected waves of visible colors. Puppy slept. She had spent a busy morning worrying about whether or not she would be included in excursion, and she was very tired.
Finally, they arrived at their destination, a muddy parking lot at the start of their chosen hiking trail. Yawning and stretching, they stepped out into the sunlight.

[References used on this page: (Tyson, 2004), (Holladay, 2001), (HAO, 2003)] See bibliography PREVIOUS PAGE MAIN PAGE NEXT PAGE