Quickfire Science: Project Loon
This week Google launched 30 huge plastic balloons in New Zealand to test the technology for 'project Loon'; a planned balloon network which could bring internet access and mobile phone signals to remote locations and countries where the networks on the ground are not fully developed. Here's the Quickfire Science...
The balloons are made of layers of polythene 15 meters wide and 12 meters high - and are filled with helium so they can float into position.
Each balloon will ascend to an altitude of 20 km, to a layer of the atmosphere known as the stratosphere. At that height, you'd need a pair of binoculars to see them in the sky.
At this altitude, weather balloons usually end up bursting, since the helium inside them expands as they rise. However, the multiple layers of plastic in Google's balloons are designed to stop them from popping.
Anyone who wants to use the network will need to attach an antenna to their home - this will send a signal to the nearest balloon. The data will then be relayed from balloon to balloon before being sent back to a ground station on earth.
Each balloon can provide internet access over distances of up to 40km, and because they are so high up, buildings and hills won't create signal black spots.
The system will aim to deliver data at a similar speed to 3G networks already used by mobile phones - but might eventually be even faster.
The balloons carry solar panels, which will provide all of the power needed to keep the on-board radio antennas and electronics running.
The balloons will not be tethered and will float around naturally in the stratosphere. However the team will be able to direct the balloons to move up and down, which they hope will allow them to switch between layers of wind which move in different directions and at different speeds.
By using the wind to blow the balloons around in this way, they hope to be able to build automated computer systems which will keep the balloons in formation.
Over time, currents like the jet stream will cause the balloons to drift over large distances - but the team hope that the balloons will eventually form a global network, and those serving South Africa may, for example, eventually serve South America and come around the globe again.