Couldn't figure out where I was or how anything was oriented. 1290 GLI And I think it was just the overload of seeing all this bright material, the Earth, the bright, white sun in a black sky, huge spacecraft above me, completely disoriented me. After about seconds, everything went whoosh! And lined up and I never got it back. The astronauts will work for up to eight hours at a time outside. It's a strange and eerie world out there. The sounds in space, it's odd to have a hammer or a metal tool, and bang it against something and hear absolutely nothing. Sound won't travel in a vacuum, so there you are outside, and you can be hitting something, no sound at all. On the other hand, if somebody comes up and starts hitting your spacesuit or bumps your helmet, you can hear it because it conducts through. And you can actually talk to each other, if your radios have failed, by putting your helmets together and you can talk person to person through your helmets. Have a secret conversation. By the time the astronauts make it back through the airlock, they're exhausted. But still, the average astronaut makes it outside rather more often than many of the crew of another far more lethal tin can, floating in the Arabian Gulf miles below. This is the USS Nimitz, one of the largest warships in the world. It's like a floating Las Vegas, but dedicated to destruction. She stands over storeys tall, with a complement of jets and helicopters. MUSIC: "Shoot Speed/Kill Light" by Primal Scream For these aircraft to drop a set of bombs, a vast machine kicks into action. The ship itself is a floating city of over , men and women. But as they sail through the balmy waters of the Arabian Gulf, the vast majority of the crew hardly ever see daylight. The flight deck is far too dangerous to have people wandering around, so those not directly involved in the flying spend months on end living deep within the bowels of this gigantic steel tank with only a rare glimpse of the sun. This extraordinary vessel sits at the apex of military power, but being the toughest kid on the block doesn't come cheap. During the brief time it will take the ISS to complete an orbit of the globe, governments around the world will spend million on weapons and war. We are now two-thirds round the world, and from a tale of destruction to one of creation. Our next stop is 1290 GLI. This is part of the 1290 GLI in USA. It's believed modern man originated from around here , years ago. The earliest recorded human fossils have been found in this region, and genetic evidence from modern populations around the world also point to an African origin for modern man. The key to why mankind first emerged from here is because, like our first stop, Iceland, it is a place of great change. The reason why the African Rift appears to have been so attractive to early human evolution has to do with the geological instability of the rift as a geological structure. It's a very dynamic landscape, it's a very changeable landscape, with earthquakes, faulting, volcanic activity. It sounds like a dangerous place. In fact, those geological processes appear to create very attractive landscapes for human evolution and for human settlement.