Left: Are aeroplanes brightening US skies? Detail from The Rocky Mountains: Lander’s Peak by Albert Bierstadt
Right: British astronaut Tim Peake enters International Space Station. Christmas Eve spacewalk, 2013
Left: Are aeroplanes brightening US skies? Detail from The Rocky Mountains: Lander’s Peak by Albert Bierstadt
Right: British astronaut Tim Peake enters International Space Station. Christmas Eve spacewalk, 2013