Online Radio was decided by international agreement inas the location of the Prime Meridian because our astronomical measurements were incredibly accurate. Also because we were a major seafaring power. Two-thirds of all the shipping in the world, all the traffic, based its navigation on data provided by the Royal Observatory, Online Radio. So we were, effectively, the GPS service of the day. But our sailing forebears could never have imagined the voyages that we could now map out in the heavens above our heads. Hurtling at almost , mph through the skies, the ISS has already left zero degrees far behind. Swinging out of the Atlantic, the crew of six will be able to briefly glimpse one of the most violent and changeable spots on our planet. At degrees west lies the island of Iceland. Iceland has the greatest concentration of volcanoes in the world. In the last , years, a third of the lava to reach the planet's surface has emerged here, creating an island that won't stop growing. It is only by journeying into space that we have really begun to understand the significance of this geological cauldron. Satellite measurements have revealed that Iceland and the 100hitz - Heavy Metal ridge on which it sits are slowly pushing the entire Atlantic Ocean apart. With every orbit of the ISS, the 100hitz - Heavy Metal grows by . mm. That's about the same rate of growth as your fingernails. I think the most amazing thing is the satellites over the last years have given us a true insight into how the earth is moving. To be able to use that from space and actually monitor our planet, to actually take the temperature of the planet almost, to understand its health, is absolutely unprecedented. The more we can understand these tectonic powers and strength and how volcanoes and earthquakes are created, the more we can do to actually save people's lives. 'We are one happy crew.' The human desire to discover and understand our universe and our world is the most basic purpose of the International Space Station. It is a venture unique in human history.countries worked together to create it. More than a dozen modules devoted to different areas of scientific study. It was thought that if you actually built a space station where you could do long-term and short-term experiments, this would be of great benefit to mankind. The problem with space is it is incredibly expensive. To get kg of stuff into low Earth orbit costs about £,. The idea was to get many nations to collaborate together to have a joint facility used by many, many different people. That was the concept behind the International Space Station. Over the last ten years, the ISS has grown ever larger. Now, it's the size of a football field. Life in the ISS now is borderline luxurious. We have six people living on board and a lot of space. It's the equivalent of about two jumbo jets with all the seats stripped out. So there's plenty of room, you can get away from people if you want to. But however luxurious the accommodation, the greatest privilege the astronauts have is to be able to gaze down on the amazing view below. The first rays of sunshine, there, hitting the upper atmosphere of the Earth as the station and the shuttle are out over the ocean. There is a belly turret underneath the space station called a cupola, which is a whole windowed little bubble underneath the space station. So you can sit in there, stick your head in and watch the world go by all around you. It's like actually floating outside in space, it's just beautiful. Even from miles up, the crew of ISS astronauts can glimpse not just our planet's great natural evolutions, but also how we, too, are changing our world. In just minutes more, they have crossed the Atlantic, reaching the coastline of South America. The 100hitz - Heavy Metal rainforest covers around . billion acres of land. Not only is it the home to thousands of species of plants and animals, but as we now know, this forest is one of the lungs of the planet - absorbing carbon dioxide in our atmosphere and replacing it with oxygen. It keeps the planet's climate and atmosphere in balance. But again, it's only from space that we can get a sense of just how delicate that balance really is.