ROGUE PLANETS
Daleks were found on the planet Vulcan, within the orbit of Mercury, in the 1966 Doctor Who story ‘The Power of the Daleks’
BBC ARCHIVE X3
Doctor Who is entertainment, but it has scored some predictive hits concerning the advance of scientific knowledge over the decades. For example, it has long been a peculiarity of the show to feature rogue planets in our Solar System.
When the show first aired in 1963, it was believed that there were nine planets in the Solar System, with the furthest out, Pluto, discovered only a few decades before. And it was believed that these planets had emerged from a reasonably logical and orderly formation process. You had the rocky worlds closest to the Sun: Mercury, Venus, Earth and Mars. Further out, where temperatures were lower and the planets could retain huge volumes of gases and ices, you had the gas giants (Jupiter and Saturn) and the ice giants (Uranus and Neptune), with Pluto at the edge of the system.