Vern’s most popular novel “Around the World in 80 Days” (1872) was written in troubled times as the Franco-Prussian war was raging at the time. Verne himself was conscripted. Also his father died during this period. The novel is hardly SF, but it does contain in the resolution of the story some discussion of time as related to the Earth’s rotation. Because the adventurers travel eastward, their days are shortened by 5 minutes for each degree of longitude crossed. Hence when the hero, Phileas Fogg, arrives back in Britain, thinking he has lost the bet to travel around the world in the specified time, he is actually a day earlier than he believes and thus wins the bet.
In “Mysterious Island” (1875) it is revealed that Captain Nemo did not die at the end of “20,000 Leagues” but took the Nautilus to the eponymous island, where he rescues some Americans who have crash-landed in a balloon. In this work, he discusses the possibility of using hydrogen as a fuel, produced by the electrolysis of water.
His only interplanetary adventure is the extremely unlikely tale “Hector Servadac” (1887), better known as “Off On A Comet”. In this a group of Frenchmen are on a piece of land which is torn off the Earth by a passing comet. It takes them quite some time to discover what has happened, by which time they have travelled out as far as Saturn. They discover that their comet is a short-period one and will once again have a grazing collision with Earth.
They avoid being crushed by ascending in a balloon at the last moment and the piece of land is miraculously re-attached. The comet is never seen again.
In “Clipper of the Clouds” (1886) and “Robur, The Conqueror” (1904), he discusses heavy-than-air flight, ironically not long before it was actually achieved.
Verne’s most far-seeing work is the short story “In the Year 2889” (1889). This is the most science-fictional of all his works but is believed to have been written by his son, Michel Verne. However, as it was composed under his father’s close supervision and is based on his ideas of scientific progress, we can accept this as one of the elder Verne’s canon. It is full of predictions: energy can be stored and released in any form, human lifespans have been increased, there are flying cars, regular communication has been established with the Martians, there are video conferences, and travel across oceans in pneumatic tubes at 1,500 kilometres an hour. Because it is believed that a civilisation may exist on the far side of the moon, some businessmen leave a conference with the aim of finding a way of turning it around!
In his posthumously-published novel, “The City in the Sahara”, Verne describes broadcast power, VTOL-aircraft powered by hydrogen, and guided missiles. Unusually for Verne, the book has a heroine.