The Caravan of Light will start out in the Thar Desert in India. There are four important survival considerations when traveling through the desert:

• Water
• Shade
• Color
• Ground

Water: A Gallon A Day

When the thermometer hits 100 degrees F (37.8 C), people without water die within a couple of days. At these kinds of temperatures, the desert traveler needs at least a gallon of water a day. If you conserve energy and stay in the shade, every gallon of water is equal to another day of life. If you decide to move, doing so at night is a good choice. A healthy person could make about 20 miles (32 km) on a gallon of water (4L) in the cooler night air. If you travel in the daytime heat, two to three times as much water is needed.

The reason you need so much water is because your body works best in a narrow temperature range. That temperature is around 98.6 degrees F (37 C). This is the temperature at which your body functions best. As your temperature rises, as can happen in the desert, things begin to go haywire. If your temperature reaches 103 degrees F (39.4 C) you will only survive for a short time. To control how hot you get, your body uses a property of water. When water evaporates it takes heat with it. The sweat that forms on your skin is what keeps you from overheating. If you take a canteen of water and a desert water bag (a type of canteen made out of tightly woven canvas which allows the bag to sweat) and placed both water containers in the sun, the water in the solid canteen could reach 110 degrees F (43.3 C) while the desert bag would be 70 degrees F (21.1 C). Evaporation keeps the desert bag 40 degrees (22.2 C) cooler than the canteen, just as the sweat from your body keeps you cool. Of course the desert bag eventually dries up unless you replenish the water.

Shade

In the desert there aren't many trees or bushes. This means less shade. Less shade means you absorb more of the sun's rays, which makes you sweat more to stay cool. That's not good when you are trying to conserve water. So you need a way to make shade. Desert people carry tents, but even two poles with fabric strung between can help. Get something between you and the sun.

Color

In the desert, wear white clothing. White reflects heat. Even the Turags, a desert people famous for their blue-black clothing, wear white outer garments occasionally. Next, cover your entire body. The reason desert people completely clothe themselves, even in the heat of the day, is because it slows the rate that sweat leaves the body. In other words, ration sweat, not how much you drink.

Ground

Finally, we come to how the ground figures in all this. Desert sand can get so hot that it burns people's feet when they are wearing shoes. But, if you get only one foot above hot desert sand, the air can be 30 degrees F. cooler. By staying above the ground you keep from heating up as fast. This is the reason that some desert nomads carry awkward looking cots aboard their camels. When they camp, they can sit in the cooler air away from the ground.

Caravan Riddles

• Why would the Turags wear dark clothing if they lived in the desert?