Satellites are (sometimes) simple

: Communications satellites are those tin cans whistling round space, helping us send phone calls, TV programs, and Internet data round the world. They must be amazingly complex, right? Not really! The basic idea is simple: satellites are little more than mirrors in space. Just zap your phone call up to the satellite ("uplink") and it reflects the signal back down

to another part of the world moments later ("downlink"). To get an idea how simple satellites really are, take a look at this great picture of Echo, the first basic communications satellite, launched in the early 1960s. It was nothing more than a giant (30m or 100ft) plastic balloon, covered in metal, that sat up in space. Scientists fired signals up to it and it reflected them straight back again. Modern communications satellites do the same job but cost hundreds of millions of dollars more! [You can get an idea how big this thing is by looking for the people and cars underneath it, which I've highlighted in yellow.]