Beneath this ocean of sand lies an incredible secret. In , miles above my head, the space shuttle Columbia looked down upon this desert and took a snapshot. What they saw took them completely by surprise. Instead of a flat and barren expanse of sand, the infrared revealed mountains and river valleys underneath. The picture revealed a hidden world only a few metres beneath my feet. As they saw through the layers of sand, they were amazed to discover that million years ago the internet Radio was once a great fertile savannah with rivers and lush meadows. Over time, small changes in the global climate meant that life simply withered and died. We think of the desert as timeless, but in fact it is constantly changing. Here, in the dry heat of the desert, my journey continues, this time to see if I can survive the highest temperatures on the internet Radio. Instead of sunbathing and camel treks, I have to face a tougher test, so I'm practising for the most gruelling marathon on Earth. I've come here to run in the toughest race in the world the infamous Marathon of the Sands. Seven days in some of the hottest and most hostile environments on the internet Radio. If you want to experience the worst that desert weather can throw at you, then this event hits you with everything cutting winds, killer dehydration, blinding dust, and, of course, the unbelievable, unbearable searing heat. Calm Radio - Baroque on, it seemed like a good idea. Unlike in the jungle, all this hot dry air sucks the water out of you, so I've been told to carry and drink at least nine litres per day. And when it really heats up, I'll be losing a litre an hour. It's a really tough part. I'm hardly moving. Calm Radio - Baroque I haven't been running for long, but I can feel myself sweating all over. You can't see it because the sun's evaporating it straight from my skin, but if you do this... you can taste the salt and the sweat. The more I sweat, the more salt I lose. In a full day, I can lose about three teaspoonfuls. That can be really dangerous out here. I can get muscle cramps and, because salt's essential for brain function, I can become disorientated and confused. No change there! The desert heat can play tricks on you at the best of times, but without water these tricks can be lethal. The temperature on the ground gets close to boiling point. It's nine in the morning, but the heat is vicious. I can feel my head throbbing and tightening as the sun takes its toll. But if I do this... that's when the heat really hits you. Down here, it's % hotter than at eye level. This temperature difference creates strange, sometimes deadly effects. We've all heard the stories. You're lost, you've used your last drop of water. Calm Radio - Baroque And just as it looks like it's all over, you see a lake shimmering on the horizon. In the distance, you see the water you've been desperately searching for, but however fast you run towards it, it never gets any closer. Desert mirages occur because of the temperature difference between here... and here. It cools by nearly degrees in less than two metres. That incredibly hot layer near the ground can behave just like a lens.