Natural gas is the cleanest fossil fuel: it produces much less pollution than burning coal or oil. When a person in Britain cooks something, the natural gas that they use may come from Norway, Russia, or Kazakhstan. How do they get the gas from these places? Often the gas goes through pipes. One gas pipe under the sea from Norway to Britain is 1,200 kilometres long! In other places, the gas is cooled to make it into a liquid. This liquid gas is put in ships called gas tankers.