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Answer: Earth is the third planet from the Sun and the fifth largest, about 7,926 miles (12,756 km) across at the equator, orbiting at an average 93 million miles, which defines one astronomical unit. It is the only planet in the solar system with liquid water on its surface.

Key facts

• Position and size: third from the Sun; the biggest of the four rocky (terrestrial) planets but only fifth largest overall.
• Distance: about 93 million miles (150 million km). Sunlight takes about eight minutes to arrive.
• Water and life: most of the surface is covered in liquid water, and Earth is the only place known to host life.
• Name: unlike the other planets, Earth's English name comes from Old English and Germanic words rather than Greek or Roman gods. The name is about 1,000 years old.

How NASA studies it

NASA treats Earth as one dynamic, connected system, using satellites and models to track things like water supplies, atmospheric conditions and airborne dust and smoke. NASA notes that understanding other planets starts with understanding our own, and that Earth data is made available to everyone.

Why it matters

Studying Earth gives the baseline for comparing other worlds and for planning missions to the Moon and Mars.

Claims

• id: C1 claim: Earth is the third planet from the Sun and the fifth largest. source: S1 evidence: "is the third planet from the Sun, and the fifth largest planet"
• id: C2 claim: Earth's equatorial diameter is 7,926 miles. source: S1 evidence: "With an equatorial diameter of 7,926 miles (12,756 kilometers)"
• id: C3 claim: Sunlight takes about eight minutes to reach Earth. source: S1 evidence: "It takes about eight minutes for light from the Sun to reach our planet."
• id: C4 claim: Earth is the only planet with liquid surface water. source: S1 evidence: "it is the only planet in our solar system with liquid water on the surface"
• id: C5 claim: NASA explores Earth as one connected system. source: S2 evidence: "NASA explores Earth as one dynamic, connected system."

Sources

• [S1] Facts About Earth. NASA. https://science.nasa.gov/earth/facts/ . License: US government work, public domain. Accessed 2026-11-04.
• [S2] Earth. NASA. https://science.nasa.gov/earth/ . License: US government work, public domain. Accessed 2026-11-04.

License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted).

@misc{iil_note_7ryd3x43,
  author = {{iinventedlight}},
  title = {{Earth basics: our home planet in numbers}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-04},
  url = {https://iinventedlight.com/library/notes/earth-basics/},
  note = {Permanent ID iil:note:7ryd3x43. License: CC-BY-4.0.},
}

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