Earth & Space Science · free reference
Part 4: Earth in Space
Day and night, Seasons, The Moon and its phases, Eclipses and The Sun. Every fact lists its source, and you can share a link to any topic.
In short: Earth spins once about every 24 hours. The side facing the Sun has day, and the side facing away has night.[1][2]
Facts
- The Sun only seems to move across the sky. Really, Earth is spinning.[2]
- When your side of Earth faces the Sun, you have daytime.[2]
- As Earth turns your side away from the Sun, you have night.[2]
More facts
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- Earth spins around once about every 23.9 hours.[3]
- A solar day on Earth, one full cycle of day and night, is about 24 hours.[1]
- Measured against the faraway stars, one spin takes about 23 hours and 56 minutes.[1]
- Days are very different on other planets: Jupiter spins once in about 10 hours, while a day lasts 1,408 hours on Mercury and 5,832 hours on Venus.[1]
Key words in three languages
(4)
| English | Spanish | Portuguese |
|---|---|---|
| Day[4] | Día[5] | Dia[6] |
| Night[4] | Noche[5] | Noite[6] |
| Rotation[4] | Rotación[5] | Rotação[6] |
| Earth's Axis[4] | El eje de rotación de la Tierra[5] | Eixo da Terra[6] |
Each word cites a page that uses it.
More practice
(6)
- Science game: Sun, moon and stars patternsThe Experiments You Run · free, no account neededFree
- Science game: Shadows, day and nightThe Experiments You Run · free, no account neededFree
- Grade 1 science practice questionsQuestions from every science topic in the grade, with answers · freeFree
- Grade 5 science practice questionsQuestions from every science topic in the grade, with answers · freeFree
- Lesson: Sun, moon and stars patternsGrade 1 · full lesson with practice and a checkMembers
- Lesson: Shadows, day and nightGrade 5 · full lesson with practice and a checkMembers
Members-only items are marked. The science game and the worksheets by grade are free.
Sources (6)
- NASA Space Place · How Long Is One Day on Other Planets? · spaceplace.nasa.gov/days/en (page updated Feb 9, 2021; checked Oct 26, 2026)
- NASA Goddard Space Flight Center, StarChild · StarChild Question of the Month for March 2001: Why is there day and night? · starchild.gsfc.nasa.gov/docs/StarChild/questions/question31.html (page updated Mar 2001; checked Oct 26, 2026)
- NASA Science · Facts About Earth · science.nasa.gov/earth/facts (page updated Dec 5, 2025; checked Oct 26, 2026)
- IAU Office of Astronomy for Education (OAE) · Astronomy Translation Network glossary: English term list · astro4edu.org/resources/glossary/search (checked Oct 26, 2026)
- IAU Office of Astronomy for Education (OAE) · Glosario: lista de términos en español · astro4edu.org/es/resources/glossary/search (checked Oct 26, 2026)
- IAU Office of Astronomy for Education (OAE) · Glossário: lista de termos em português do Brasil · astro4edu.org/pt-br/resources/glossary/search (checked Oct 26, 2026)
See something we should correct about “Day and night”? Tell us.
In short: Seasons come from Earth's tilt, not from its distance to the Sun. When the north has summer, the south has winter.[1]
Facts
- Seasons happen because Earth is tilted.[1]
- Seasons are not caused by Earth getting closer to or farther from the Sun.[1]
- Earth does not spin straight up and down. It leans to one side a little.[1]
More facts
(3)
Key words in three languages
(5)
| English | Spanish | Portuguese |
|---|---|---|
| Earth's Axis[3] | El eje de rotación de la Tierra[4] | Eixo da Terra[5] |
| Orbit[3] | Órbita[4] | Órbita[5] |
| Seasons[3] | Estaciones[4] | Estações do ano[5] |
| Equinox[3] | Equinoccio[4] | Equinócio[5] |
| Solstice[3] | Solsticio[4] | Solstício[5] |
Each word cites a page that uses it.
More practice
(9)
- Science game: Daylight through the seasonsThe Experiments You Run · free, no account neededFree
- Science game: Moon phases, eclipses and seasonsThe Experiments You Run · free, no account neededFree
- Science game: Shadows, day and nightThe Experiments You Run · free, no account neededFree
- Grade 1 science practice questionsQuestions from every science topic in the grade, with answers · freeFree
- Grade 6 science practice questionsQuestions from every science topic in the grade, with answers · freeFree
- Grade 5 science practice questionsQuestions from every science topic in the grade, with answers · freeFree
- Lesson: Daylight through the seasonsGrade 1 · full lesson with practice and a checkMembers
- Lesson: Moon phases, eclipses and seasonsGrade 6 · full lesson with practice and a checkMembers
- Lesson: Shadows, day and nightGrade 5 · full lesson with practice and a checkMembers
Members-only items are marked. The science game and the worksheets by grade are free.
Sources (5)
- NASA Space Place · What Causes the Seasons? · spaceplace.nasa.gov/seasons/en (page updated Jul 29, 2025; checked Oct 26, 2026)
- NASA Science · Facts About Earth · science.nasa.gov/earth/facts (page updated Dec 5, 2025; checked Oct 26, 2026)
- IAU Office of Astronomy for Education (OAE) · Astronomy Translation Network glossary: English term list · astro4edu.org/resources/glossary/search (checked Oct 26, 2026)
- IAU Office of Astronomy for Education (OAE) · Glosario: lista de términos en español · astro4edu.org/es/resources/glossary/search (checked Oct 26, 2026)
- IAU Office of Astronomy for Education (OAE) · Glossário: lista de termos em português do Brasil · astro4edu.org/pt-br/resources/glossary/search (checked Oct 26, 2026)
See something we should correct about “Seasons”? Tell us.
In short: The Moon goes through eight phases about every 29.5 days, from new Moon to full Moon and back. It is rocky, cratered and always shows us the same side.[1][2]
Facts
- The Moon has eight phases. They go: new Moon, then waxing crescent, then first quarter, then waxing gibbous, then full Moon, then waning gibbous, then third quarter, then waning crescent.[1]
- The full set of phases repeats about every 29.5 days, roughly once a month.[1]
- Some nights the whole face of the Moon shines. Other nights we see only a thin curve of light.[1]
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- The Moon is about 238,855 miles (384,400 kilometers) from Earth on average.[2]
- The Moon is less than one-third as wide as Earth. Its radius is about 1,080 miles (1,740 kilometers).[2]
- Scientists think the Moon probably formed after an object about the size of Mars crashed into Earth billions of years ago.[2]
- The Moon's rocky surface is covered with craters made when asteroids, meteorites and comets hit it.[2]
- The dark patches are called maria, Latin for "seas." They are huge crater basins that filled with lava, not water.[2]
- The Moon has only an extremely thin layer of gas, and there is no air to breathe.[2]
- We always see the same side of the Moon from Earth.[2]
- Of all the planets in our solar system, only Earth has exactly one moon.[3]
Key words in three languages
(12)
| English | Spanish | Portuguese |
|---|---|---|
| crater[4] | cráter[5] | cratera[6] |
| exosphere[7] | exosfera[8] | exosfera[9] |
| Moon[10] | Luna[11] | Lua[12] |
| Lunar Phase[10] | Fase lunar[11] | Fase lunar[12] |
| New Moon[10] | Luna nueva[11] | Lua Nova[12] |
| Full Moon[10] | Luna llena[11] | Lua Cheia[12] |
| waxing crescent[1] | luna creciente[11] | lua crescente[12] |
| first quarter[1] | cuarto creciente[13][11] | quarto crescente[14] |
| waxing gibbous[1] | luna gibosa creciente[11] | crescente gibosa[12] |
| waning gibbous[1] | luna menguante gibosa[11] | gibosa minguante[12] |
| third quarter (last quarter)[1] | cuarto menguante[13] | quarto minguante[14] |
| waning crescent[1] | luna menguante[11] | lua minguante[12] |
Each word cites a page that uses it.
More practice
(6)
- Science game: Sun, moon and stars patternsThe Experiments You Run · free, no account neededFree
- Science game: Moon phases, eclipses and seasonsThe Experiments You Run · free, no account neededFree
- Grade 1 science practice questionsQuestions from every science topic in the grade, with answers · freeFree
- Grade 6 science practice questionsQuestions from every science topic in the grade, with answers · freeFree
- Lesson: Sun, moon and stars patternsGrade 1 · full lesson with practice and a checkMembers
- Lesson: Moon phases, eclipses and seasonsGrade 6 · full lesson with practice and a checkMembers
Members-only items are marked. The science game and the worksheets by grade are free.
Sources (14)
- NASA Science · Moon Phases · science.nasa.gov/moon/moon-phases (page updated Aug 3, 2026; checked Oct 26, 2026)
- NASA Science · Moon Facts · science.nasa.gov/moon/facts (page updated Feb 12, 2026; checked Oct 26, 2026)
- NASA Science · Facts About Earth · science.nasa.gov/earth/facts (page updated Dec 5, 2025; checked Oct 26, 2026)
- U.S. Geological Survey, Volcano Hazards Program · About Volcanoes · usgs.gov/programs/VHP/about-volcanoes (checked Oct 26, 2026)
- Universidad Complutense de Madrid, Geodivulgar · El volcán · ucm.es/geodivulgar/el-volcan (checked Oct 26, 2026)
- Toda Matéria (Brazilian education reference) · Vulcão: o que é, como se forma e quais suas partes · todamateria.com.br/vulcao (checked Oct 26, 2026)
- NOAA JetStream (National Weather Service) · Layers of the Atmosphere · noaa.gov/jetstream/atmosphere/layers-of-atmosphere (page updated Feb 17, 2026; checked Oct 26, 2026)
- RAE-ASALE, Diccionario de la lengua española · exosfera · dle.rae.es/exosfera (checked Oct 26, 2026)
- Toda Matéria (Brazilian education reference) · Camadas da atmosfera terrestre e suas características · todamateria.com.br/camadas-da-atmosfera (checked Oct 26, 2026)
- IAU Office of Astronomy for Education (OAE) · Astronomy Translation Network glossary: English term list · astro4edu.org/resources/glossary/search (checked Oct 26, 2026)
- IAU Office of Astronomy for Education (OAE) · Glosario: lista de términos en español · astro4edu.org/es/resources/glossary/search (checked Oct 26, 2026)
- IAU Office of Astronomy for Education (OAE) · Glossário: lista de termos em português do Brasil · astro4edu.org/pt-br/resources/glossary/search (checked Oct 26, 2026)
- RAE-ASALE, Diccionario de la lengua española · cuarto (cuarto creciente, cuarto menguante) · dle.rae.es/cuarto (checked Oct 30, 2026)
- Universidade Federal do Rio Grande do Sul (UFRGS), Instituto de Física · Fases da Lua · astro.if.ufrgs.br/lua/lua.htm (checked Oct 30, 2026)
See something we should correct about “The Moon and its phases”? Tell us.
In short: A solar eclipse happens when the Moon blocks the Sun; a lunar eclipse happens when Earth's shadow falls on the Moon. Never look at the Sun without proper eclipse glasses.[1][2]
Facts
- A solar eclipse happens when the Moon moves between the Sun and Earth.[1]
- In a total solar eclipse, the Moon covers the whole face of the Sun.[1]
- In an annular eclipse, the Moon looks a little smaller than the Sun, so it does not cover all of it.[1]
More facts
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- In a partial solar eclipse, the Moon covers just part of the Sun, which then looks like a crescent.[1]
- A lunar eclipse happens at full Moon, when Earth lines up between the Sun and Moon and Earth's shadow falls on the Moon.[1]
- To look at a solar eclipse, always use eclipse glasses or another safe way of viewing the Sun.[1]
- Never look straight at the Sun during an eclipse without proper eye protection.[2]
- Ordinary sunglasses are not safe for looking at the Sun, even very dark ones.[2]
- Eclipse glasses should meet the international safety standard ISO 12312-2.[2]
Key words in three languages
(10)
| English | Spanish | Portuguese |
|---|---|---|
| Eclipse[3] | Eclipse[4] | Eclipse[5] |
| Solar Eclipse[3] | Eclipse solar[4] | Eclipse Solar[5] |
| Lunar Eclipse[3] | Eclipse lunar[4] | Eclipse lunar[5] |
| Total Solar Eclipse[3] | Eclipse solar total[4] | Eclipse solar total[5] |
| Annular Solar Eclipse[3] | Eclipse solar anular[4] | Eclipse solar anular[5] |
| Partial Solar Eclipse[3] | Eclipse solar parcial[4] | Eclipse solar parcial[5] |
| Shadow[3] | Sombra[4] | Sombra[5] |
| Umbra[3] | Umbra[4] | Umbra[5] |
| Penumbra[3] | Penumbra[4] | Penumbra[5] |
| Corona[3] | Corona[4] | Coroa[5] |
Each word cites a page that uses it.
More practice
(3)
- Science game: Moon phases, eclipses and seasonsThe Experiments You Run · free, no account neededFree
- Grade 6 science practice questionsQuestions from every science topic in the grade, with answers · freeFree
- Lesson: Moon phases, eclipses and seasonsGrade 6 · full lesson with practice and a checkMembers
Members-only items are marked. The science game and the worksheets by grade are free.
Sources (5)
- NASA Science · Types of Solar Eclipses · science.nasa.gov/eclipses/types (page updated Feb 13, 2026; checked Oct 26, 2026)
- NASA Science · Eclipse Viewing Safety · science.nasa.gov/eclipses/safety (page updated Mar 20, 2026; checked Oct 26, 2026)
- IAU Office of Astronomy for Education (OAE) · Astronomy Translation Network glossary: English term list · astro4edu.org/resources/glossary/search (checked Oct 26, 2026)
- IAU Office of Astronomy for Education (OAE) · Glosario: lista de términos en español · astro4edu.org/es/resources/glossary/search (checked Oct 26, 2026)
- IAU Office of Astronomy for Education (OAE) · Glossário: lista de termos em português do Brasil · astro4edu.org/pt-br/resources/glossary/search (checked Oct 26, 2026)
See something we should correct about “Eclipses”? Tell us.
In short: The Sun is our star: a huge, hot ball of hydrogen and helium about 93 million miles away. Its core is far hotter than its surface.[1]
Facts
- The Sun is a star: a hot, glowing ball made mostly of hydrogen and helium. It is about 4.5 billion years old.[1]
- From side to side, the Sun measures about 1.4 million kilometers, or about 865,000 miles.[1]
- Compared with other stars, the Sun is medium-sized.[1]
More facts
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- The Sun's visible surface, the photosphere, is about 10,000 °F (5,500 °C), which is "cool" for the Sun.[1]
- The core is the hottest part, at more than 27 million °F (15 million °C).[1]
- Earth is about 150 million kilometers, or about 93 million miles, from the Sun.[1]
- Inside, the Sun has a core, a radiative zone and a convection zone.[1]
- Earth's distance from the Sun is used as a measuring stick called one astronomical unit (AU).[2]
Key words in three languages
(8)
| English | Spanish | Portuguese |
|---|---|---|
| Sun[3] | Sol[4] | Sol[5] |
| Star[3] | Estrella[4] | Estrela[5] |
| Photosphere[3] | Fotosfera[4] | Fotosfera[5] |
| Corona[3] | Corona[4] | Coroa[5] |
| Sunspot[3] | Mancha solar[4] | Mancha solar[5] |
| Nuclear Fusion[3] | Fusión nuclear[4] | Fusão nuclear[5] |
| Solar Wind[3] | Viento solar[4] | Vento solar[5] |
| Astronomical Unit[3] | Unidad Astronómica[4] | Unidade astronômica[5] |
Each word cites a page that uses it.
More practice
(6)
- Science game: Sun, moon and stars patternsThe Experiments You Run · free, no account neededFree
- Science game: Sunlight warms the EarthThe Experiments You Run · free, no account neededFree
- Grade 1 science practice questionsQuestions from every science topic in the grade, with answers · freeFree
- Kindergarten science practice questionsQuestions from every science topic in the grade, with answers · freeFree
- Lesson: Sun, moon and stars patternsGrade 1 · full lesson with practice and a checkMembers
- Lesson: Sunlight warms the EarthKindergarten · full lesson with practice and a checkMembers
Members-only items are marked. The science game and the worksheets by grade are free.
Sources (5)
- NASA Science · Sun: Facts · science.nasa.gov/sun/facts (page updated Sep 17, 2026; checked Oct 26, 2026)
- NASA Science · Facts About Earth · science.nasa.gov/earth/facts (page updated Dec 5, 2025; checked Oct 26, 2026)
- IAU Office of Astronomy for Education (OAE) · Astronomy Translation Network glossary: English term list · astro4edu.org/resources/glossary/search (checked Oct 26, 2026)
- IAU Office of Astronomy for Education (OAE) · Glosario: lista de términos en español · astro4edu.org/es/resources/glossary/search (checked Oct 26, 2026)
- IAU Office of Astronomy for Education (OAE) · Glossário: lista de termos em português do Brasil · astro4edu.org/pt-br/resources/glossary/search (checked Oct 26, 2026)
See something we should correct about “The Sun”? Tell us.