Space and science in Esperanto: planets, stars, sciences

In Esperanto the Sun is suno, the Moon luno, a star stelo and a planet planedo. Planet names are international and end in -o (Marso, Jupitero, Plutono), school subjects end in -io or -iko (astronomio, biologio, fiziko), and the people who work in them are -isto words or shorter roots (fizikisto, astronomo). Everyday sky words are on the nature page. Pronunciation guides show the stressed syllable in capitals; it is always the second-to-last (see the alphabet).

#Planets of the Solar System

Counted from the Sun, the planets are Merkuro, Venuso, Tero, Marso, Jupitero, Saturno, Urano and Neptuno.

The order comes from ReVo, which defines Marso as la kvara planedo "the fourth planet" of the solar system. Most planet names double as names of gods: ReVo lists Marso as the Roman god of war and Urano as the Greek god of the sky. The weekdays lundo, mardo, merkredo are separate words, not built from planet names, and take a small letter; see days and months.

#Capital letters: suno or Suno?

Planet names are normal proper names: capital letter, no la (Marso, sur Marso). Suno, luno and tero are ordinary words. PMEG notes that people often write la Suno with a capital when they mean our Sun as a name, and such names keep la, like la Granda Ursino. Capitals are not compulsory, so both spellings occur.

#The Solar System and beyond

#Astronomy and space travel

Verbs: orbiti "to orbit", rondiri "to circle" (ReVo: the Moon rondiras ĉirkaŭ the Earth), turniĝi "to turn, rotate" (the Earth turns around its axis, akso), ekflugi "to take off" (ReVo: a kosmodromo is the place for the ekflugo of spaceships), observi "to observe".

#How are space words built?

More in suffixes and word building.

#School sciences and scientists

Two patterns explain the list. When the person has no root of its own, add -ist- to the science: fiziko → fizikisto. PMEG points out that fiziko cannot also mean the physicist, because it is the name of the science. Many names in -io have a parallel root without the i: biologio → biologo. The -iisto forms are possible, but the double i is clumsy, so people prefer the short root, and PMEG says not to coin astronomisto. PMEG calls the -olog- of biologo an ex-suffix: an international ending, not a regular Esperanto suffix. Subjects and classroom words are on the school page.

#Laboratory and experiment

#Space and science in sentences

#Common questions

#How do you say "planet" in Esperanto?

Planedo. Pluto, Plutono, is a nanplanedo "dwarf planet"; ReVo says it was counted as the ninth planet until 2006.

#Are planet names capitalised in Esperanto?

Yes. They are proper names, so Marso and Jupitero take a capital and no la. A capital on la Suno, and likewise la Luno and la Tero, is optional; PMEG says la Suno is often written that way.

#How do you say "space" in Esperanto?

Kosmo for outer space, with kosma "of space" and kosmoŝipo "spaceship". ReVo labels spaco for outer space evitinde "to be avoided".

#What is the difference between astronaŭto and kosmonaŭto?

None in Esperanto: ReVo defines astronaŭto as kosmonaŭto, a person who travels into space.

#How do you say "scientist" or "physicist" in Esperanto?

Sciencisto or scienculo for a scientist and fizikisto for a physicist; a biologist is a biologo and an astronomer an astronomo.

#Sources

• ReVo: suno, sunsistemo, luno, plenluno, novluno, tero, eksterterano, planedo, nanplanedo, kometo, asteroido, galaksio, Lakta Vojo, universo, nana
• ReVo: Merkuro, Venuso, Marso, marsano, Jupitero, Saturno, Urano, Neptuno, Plutono
• ReVo: stelo, stelaro, falstelo, konstelacio, Oriono, Granda Ursino, meteoro, eklipso, luneklipso, suneklipso, orbito, akso
• ReVo: raketo, satelito, teleskopo, observi, observejo, stelobservejo, observatorio, kosmo, spaco, kosmonaŭto, astronaŭto, kosmoŝipo, kosmodromo
• ReVo: astronomo, astronomio, fiziko, fizikisto, ĥemio, kemio, ĥemiisto, biologio, biologo, matematiko, matematikisto, geografio, geografo, geologio, geologo, meteorologio, informatiko, scienco, sciencisto, scienculo
• ReVo: laboratorio, eksperimento, hipotezo, teorio, mezuri, pruvi, mikroskopo, atomo, molekulo, energio, gravito
• PMEG: majuskloj ĉe propraj nomoj, la ĉe propraj nomoj, la kaj konata afero (la suno)
• PMEG: IST, I (geografio → geografo), OLOG, IĜ (La tero turniĝas ĉirkaŭ sia akso)