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Desert sands

The harsh daylight and intense night-time darkness of the desert can play tricks on your eyes

Leigh Spielberg

Posted: Friday, February 1, 2019

Every time I look directly at that very faint cluster of stars, the one to the left of Orion’s Belt, it seems to disappear,” said my wife, pointing at a spot high in the desert sky. “Why can’t I see it when I look straight at it?”

Good question. I had noticed it as well, and had mulled it over while waiting for our host to prepare the traditional cardamom-flavored coffee that is ubiquitous in Oman. My answer involved the spatial distribution of rods and cones in the retina, and their relative sensitivities in scotopic conditions.

It then occurred to me why a fellow traveller in our Bedouin camp had been wearing a red headlamp to read after sunset; red light leaves rods’ dark adaptation undisturbed, allowing him to look right back up at the stars without having to wait for his rods to start ‘working’ again.

It got me thinking about the reasons why we like to travel. Everyone has their own preferences: exoticism, luxury and warmth are high on most peoples’ list. I enjoy all the above, but my favorite reason to travel is to see. Who knows, maybe it’s just the ophthalmologist in me talking right now, but I like the views to jostle me out of my standard mental routine. Views and contrasts. A desert day’s bright white light and its night’s pitch black seem to delineate the two ends of the full spectrum of what our retinas were intended to perceive.

The night sky above the Omani dunes is spectacular. The clear, cloudless skies, dry air and the absence of light pollution allow the stars to shine as they did for our earliest ancestors. There are so many stars that the familiar constellations are difficult to distinguish. They seem to get lost in a riot of stellar illumination. The only celestial bodies I could identify with confidence were the brightest planets.

I love the desert. Love it. Mostly because of the intensity of the light and the purity of the colors. The bright blue sky, the pale beige sand and the seemingly random, occasional spots of green are a pleasure to behold. The same dry air and clear skies that make stargazing so intense allow for dazzling photographs of a quality that I just can’t seem to reproduce when I visit the jungle, with its thick humidity and hazy light. My photos look crisp and colorful. The bright light allows for super-fast shutter speeds, eliminating the possibility of motion blur.

Desert vistas are marvellous in all directions. But there are also elements of surprise hiding in plain sight. A strolling camel is surprisingly difficult to see. It blends into the sand and dunes with a naturally camouflage so common in nature, like a lion in the grasses of the African savannah. It blends in until the last moment and all of a sudden, there it is, stepping on to the road, its beige, lumbering silhouette finally contrast with the black pavement of the street ahead.

“Watch out!!” screamed my wife. I slammed on the brakes and was nearly rear-ended by a truck. It was a near miss. Judging from the camel’s height as compared to our 4×4 desert cruiser, I tried not to think about what would happen if we were to hit one as it crossed the road. But thereafter, we both broadened our visual horizon to spot camels before they crossed our path.

Travelling in Oman is a visual delight. The sun is stunningly bright, and the light sand and white buildings make sunglasses essential. But in the desert, many things are not as they appear. Distances are difficult to judge. Objects often seem closer than they really are. Beige goats are nigh-on impossible to see as they scamper up and down the rocky outcroppings of the arid mountain highlands. I thought our guide was joking when he first pointed them out to us. I didn’t see anything until I “learned” how to look for them, by scanning the diagonal ridges in the direction that they slope rather than horizontally, which is what our plains-evolved gaze is designed to do.

What looks like a small sandbank nearby is in fact a huge dune in the distance. Mirages on the surface of the highway mesmerise and distract. Caused by unusual diffraction of light due to temperature differences between the road and our eyes, they can confuse drivers and caravans alike.

The people of Oman seem to have taken this all into account, and everything manmade is a study in contrasts. The pale camels are often decorated with bright red harnesses that match the seats on their humps, where we sat during our desert treks.

Whoops, gotta go! Our camels are ready to take us to see the sunrise from the top of the region’s tallest dune. Voilà!

Dr Leigh Spielberg is a vitreoretinal and cataract surgeon at Ghent University, Belgium


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