The Sun God Ra bakes down on Karjini, Western Australia. Photo: Howe
Ahoy campers, and welcome to June! We're spinning through the seasons and approaching the summer equinox, June 21st. That means the sun is tracking higher in the sky, sending its rays down through our atmosphere at a more vertical angle. So the sunlight passes through less air and the filtering affect of earth's atmosphere is less. Add in longer daylight hours, and it's cooking time for the next couple months - Total sunburn alert. You too, could be a lobster with a little inatttention.
Perhaps a little Dr. Science background is in order: Light is a form of electromagnetic radiation, self-propagating waves that oscillate at a particular frequency. For geekaholics, the electrical and magnetic components of each wave oscillate in phase, perpendicular to each other and the direction that the radiation travels. Since oscillating electrical fields generate a magnetic field, and vice versa, these oscillating components, together, keep the wave self-propagating.
However - energy exhibits both wave-like and particle-like behaviors, (this is called the wave-particle duality). In the particle model of electromagnetic radiation, a wave consists of energy packets (particles) called photons. The wave's frequency is proportional to the particle's energy, so more energetic packets operate at a faster vibration and shorter wavelength. Classed by frequency (length) of waves, the electromagnetic spectrum runs the gamut from the very-long-wave radio emissions, through infrared, the visible spectrum, and on to very short wavelength "high photon energy" frequencies like ultraviolet light, X-rays and gamma rays.
High photon energy particles and waves can be nasty. At wavelengths of around 500 nanometers and shorter, about the tipping point between blue-violet light and ultraviolet, photon particles become high-energy enough to knock electrons around in whichever atoms they strike. This creates a change in charge in the atom, shifts electrons around, and creates what is called a free radical - any atom or molecule that has unpaired electrons in its outer orbital shell.
The electrons in an atom are where chemical bonding takes place. Atoms with paired outer-shell elctrons tend to be stable, inert and non-reactive. Atoms with unpaired electrons in their outer orbital shells are highly reactive, attempting to achieve stability again by bonding/sharing electrons with another atom, or stealing them outright, which forms another free radical, and a chain reaction.
Free radical chain reactions, created by high photon energy ultraviolet light, create the phenomena we know as sunburn. This also affects the retinas of our eyes as snow-blindness. It's basically the same process that cracks your car's dashboard, or fades your fiberglass kayak. While well built-up tans look great, the process actually damages collagen and reticulin, reducing skin elasticity and creating stiffer, less elastic supporting fibers in the skin. It's the devil's highway to lizard legs.
Your eyes are at even more risk. Oxygen is an element that's particularly susceptible to free radical chain reactions, and your eye's retinas are the most oxygenated tissue in your body - a big reason to invest in decent sunglasses and wear them whenever you're outside, even on overcast days.
Meteorologists know that summer's high sun angles make for stronger than normal UV levels. (You can get daily UV forecasts on the web at Weather Underground.) For example, on a cloudy winter day here at 6,800 feet in Utah, the UV level might be forecast at 3, the level where health authorities recommend you begin wearing sunscreen. Southern hemisphere locations like Argentina or New Zealand, underneath the infamous ozone hole, can see daily UV highs of 16. Add another 50% for high altitude climbers in the Himalayas, due to the thin atmosphere and reflective snowpack. Now, here in Slickrock Country on the cusp of June, UV levels are hovering around 10, plenty for a serious nuking if you're out for a day without hat, glasses and boucoup sunscreen.
Here's a handy tip: You can easily generate tables of sun (or moon) rise and set times by visiting the U.S. Naval Observatory's Sun and Moon Rise/Set Tables web page. Choose your intended location from a town list, or by entering coordinates, and voila! Very handy for planning dawn starts, or knowing how long you've got until it's headlamp time. So hike safe out there. Slather on the SPF 50, and wear those shades religiously. It's gonna be a long, hot summer.-- Steve Howe
P.S. I'm off on assignment for a week in Southern Utah. I'll try to post, but no promises. This place is WiFi wasteland.