Kepler's Somnium ("The Dream") is a work of fiction that is sometimes regarded as the first example of science fiction (e.g. by Carl Sagan). In it, Kepler describes a journey to the Moon and various scientific observations, along with a number of autobiographical notes or similarities. The scientific observations cover things like what the solar system would look like from the Moon and could put it in the category of "hard science fiction". But it has been suggested that Kepler wrote these ideas in a work of fiction because they might have been considered heretical. Although the Copernicean model would have been less heretical when it was published after his death, more heretical concepts in the book include the possibility of "aliens" on other worlds.

What was the reaction to Somnium when it was published? Was it considered a curiosity and nothing more - "a badly written piece of fiction" perhaps? Or was the physics in it taken more seriously by natural philosophers and other learned people?

  • 2
    $\begingroup$ Love the heresy tag. $\endgroup$
    – HDE 226868
    Commented Nov 11, 2014 at 23:10
  • $\begingroup$ Sprague de Camp and others consider True Story by Lucian (2nd century AD) to be the first example of science fiction. "In witnessing one interplanetary battle between the People of the Moon and the People of the Sun as the fight for the right to colonize the Morning Star, Lucian describes giant space spiders who were "appointed to spin a web in the air between the Moon and the Morning Star, which was done in an instant, and made a plain campaign upon which the foot forces were planted..." publicdomainreview.org/2013/06/26/lucians-trips-to-the-moon $\endgroup$
    – Conifold
    Commented Nov 13, 2014 at 1:21
  • $\begingroup$ @Conifold Interesting. There are many claimants of course. Much depends on how you define sci-fi. Eg Shelley's Frankenstein is another that many claim as the first example of sci-fi Literature with a Big L. $\endgroup$
    – winwaed
    Commented Nov 13, 2014 at 1:27
  • $\begingroup$ Except that Lucian is a lot earlier than Mary Shelley. $\endgroup$
    – fdb
    Commented Jan 28, 2015 at 22:45
  • $\begingroup$ @fdb Didn't say he wasn't. Mary Shelley is claimed as "proper" Literature - something Somnium isn't usually classed as, for instance.There are many claimants and it depends on a lot of things - what you defined as (or consider important) amongst things like "Literature", science, fantasy, legend, etc. $\endgroup$
    – winwaed
    Commented Jan 29, 2015 at 2:08

1 Answer 1


I think that the authoritative Introduction by Edward Rosen to his translation with commentary of :

can give us the necessary informations.

It seems quite clear that the booklet was not intended to be a sci-fi novel at all.

The origin is in the draft of Kepler's dissertation of 1593 on the motions of the moon [page xvii]

Kepler refers to it as his Lunar Astronomy [page xviii] and around 1609 he

constructed the framework of the Dream [...] in order to introduce a supernatural agency for the purpose of transporting a professional astronomical observer to the moon [page xix].

In 1629 Kepler mentioned his "Astronomy of the Moon or of the Celestial Phenomena as seen from the Moon" as a possible choice for a

mathematical textbook suitable for use in the classroom [page xx-xxi].

The posthumous book was published in 1631 by Kepler's son [page xxi].

According to reference into Rosen's introduction, the first reactions to the book judged it bizarre or satyrical [page xxiii].

Browsing Kepler's notes, we can see [page 68] clear discussion of celestial phenomena, with reference to Aristotle as well as Kepler's own Epitome of Copernican Astronomy.

Kepler published during his life several books explicitly copernicans; thus, I do not think that the "narrative form" was due to the necessity of concealing his ideas [see Addendum].

In addition, the idea of extra-terrestrial life does not seem to be a key fature of the book.

The "narrative form" of the book must be understood in the Renaissance and Humanists context, with reference to Erasmus, Thomas More and Campanella and their Utopia's as well as Plutarch's treatise "On the Face Which Appears in the Orb of the Moon" (Περὶ τοῦ ἐμφαινομένου προσώπου τῷ κύκλῳ τῆς σελήνης - De facie in orbe lunae), included into the collection of 78 essays and transcribed speeches named Moralia (Ancient Greek : Ethika).

Kepler's notes refer also to True History (Ancient Greek: Ἀληθῆ διηγήματα) the a parody of travel tales by the Greek-speaking Syrian author Lucian of Samosata and to Ignatius His Conclave (Latin: Conclave ignati) published anonymously in 1611 (and thus, presumibly, Kepler was unaware of the name of the author) by the metaphysical poet John Donne.

We must be aware that this "strange" book was drafted in a time when there was not yet a clearcut division between science, philosophy, humanities ...

Note : for a book-lenght analysis of :

Johannes Kepler’s Somnium, [as] a work heavily indebted to the Neoplatonist cosmological allegory as a literary form

see :


Some chronology can help :

  • Copernicus, De revolutionisbis : published 1543; in March 1616, the Roman Catholic Church's Congregation of the Index issued a decree suspending De revolutionibus until it could be "corrected"

  • Kepler, Epitome astronomiae Copernicanae : published in three parts from 1618–1621

  • Kelper died : 1630

  • Descartes, Le Monde : written between 1629 and 1633

  • Galileo, Dialogo : published 1632

  • Galileo found "vehemently suspect of heresy" and condemned : 1633

  • Descartes' decision to not to release Le Monde upon news of the conviction of Galileo : 1633

  • Kepler's Somnium : published 1634

My conclusion is that the chronology does not support the hypotheses that Kepler's decision not to publish the Somnium was due to the condemnation of Copericanism.

  • 1
    $\begingroup$ Mauro, As I said "less heretical" but other aspects of the book could be considered heretical. Eg. Bruno had been burned at the stake for speculating other worlds with 'aliens' (amongst other things) $\endgroup$
    – winwaed
    Commented Nov 18, 2014 at 19:20

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