To find your favorite coffee shop in an unknown city, getting
directions via satellite works like a charm. But that technology
won’t get you from Earth to Jupiter. So theorists have proposed
a new type of positioning system based on …  Pulsing Stars Could
Fill in for GPS Satellites   sciencenewsSo theorists have
proposed a new type of positioning system based on blinking
stars instead of satellites. By receiving radio blips from
pulsars, stars that emit radiation like clockwork, a spacecraft
above the atmosphere could figure out its place in space.
Though the navigation system proposed by Tartaglia and
colleagues is just a proof of concept, a GPS-like system under
construction in Europe called Galileo could implement the ideas
within a decade, he says.  The principle behind the pulsar
positioning is not too different from ordinary GPS. The GPS
receiver in a car or phone receives radio signals from
satellites orbiting the Earth. The satellites are synchronized
with atomic clocks to emit signals simultaneous