Tens of thousands of satellites could be added to Earth orbit in the next few years to provide broadband Internet, if companies and governments build and launch all the networks, or ‘megaconstellations’, they have publicly announced. The sheer number of these could mean that hundreds are visible all night long, affecting the sky like never before in human history. “These constellations are changing dramatically the way space has been used,” says Piero Benvenuti, an astronomer at the University of Padua in Italy and a former general secretary of the International Astronomical Union (IAU).

Nature