"Micromégas" (1752) is a short story by the French philosopher and satirist Voltaire. It is a significant development in the history of literature because, along with Voltaire's story "Plato's Dream", it is a seminal work in the genre of science fiction.
The technique of using an outsider to comment on aspects of western culture was popular at this period. Voltaire used it again in Zadig. Montesquieu, too, applied it in Persian Letters, as did José Cadalso in Cartas marruecas and Tomás Antônio Gonzaga in Cartas Chilenas.
The story is organized into seven brief chapters. The first describes Micromégas (small/large), an inhabitant of one of the planets that orbits Sirius. His home world is 21.6 million times greater in circumference than the Earth. Micromégas stands 20,000 feet tall. When he is almost 450 years old, approaching the end of his infancy, Micromégas writes a scientific book examining the insects on his planet, which at 100 feet are too small to be detected by ordinary microscopes. This book is considered heresy, and after a 200-year trial, he is banished from the court for a term of 800 years. Micromégas takes this as an incentive to travel around the Universe in a quest to develop his intellect and his spirit.
His first stop is Saturn, where he befriends the secretary of the Academy of Saturn, a man less than a third of his size (standing only 6,000 feet tall). They discuss the differences between their planets. The Saturnian has 72 senses; the Sirian has 1,000. The Saturnian lives for 15,000 Earth years; the Sirian lives for 10.5 million years. At the end of their conversation, they decide to take a philosophical journey together.
Eventually, they arrive on Earth and circumnavigate it in 36 hours, with the Saturnian only getting his lower legs wet in the deepest ocean and the Sirian barely wetting his ankles. They decide that the planet must be devoid of life, since it is too small for them to see with the naked eye. In the Baltic Sea, the Saturnian happened to spot a tiny speck swimming about, and he picks it up to discover that it is a whale. As they examine it, a boatful of philosophers returning from an Arctic voyage happens to run aground nearby.
The travellers examine the boat and, upon discovering the lifeforms inside it, they conclude that the tiny beings are too small to be of any intelligence or spirit. Yet they gradually realize the beings are speaking to each other, and they devise a hearing tube with the clippings of their fingernails in order to hear the tiny voices. After listening for a while, they learn the human language and begin a conversation, wherein they are shocked to discover the breadth of the human intellect.
The final chapter sees the humans testing the philosophies of Aristotle, Descartes, Malebranche, Leibniz and Locke against the travellers' wisdom. When the travellers hear the theory of Aquinas that the world was made uniquely for mankind, they fall into an enormous fit of laughter. Taking pity on the humans, the Sirian decides to write them a book that will explain the point of everything to them. When the volume is presented to the Academy of Science in Paris, the secretary opens the book only to find blank pages.
See also 
- Gutenberg Project Romans — Volume 3: Micromegas (in French)
- Gutenberg Project Romans — Volume 3: Micromegas (in English)
- An English translation of Micromegas
- Online text of Plato's Dream
- Analysis, Plot overview (in French)
- Micromégas, audio version (in French)