Fictional representations of the planet Venus have existed since the 19th century. Its impenetrable cloud cover gave science fiction writers free rein to speculate on conditions at its surface; all the more so when early observations showed that not only was it very similar in size to Earth, it possessed a substantial atmosphere. Closer to the Sun than Earth, the planet was frequently depicted as warmer, but still habitable by humans. The genre reached its peak between the 1930s and 1950s, at a time when science had revealed some aspects of Venus, but not yet the harsh reality of its surface conditions.