Knowledge Atlas

Universe · Depth 3 · Introductory · 1 min read

Satellites

Anything that orbits a planet, natural like the Moon or artificial like Sputnik: how they stay up, how fast they travel, and what we learn from them.

Evidence Level 2 · AuthoritativeOpen on the map
On this page
  1. What is a satellite?
  2. Why satellites don’t fall down
  3. How fast do they go?
  4. What we learn from satellites
  5. Real-life examples
  6. Evidence & sources

What is a satellite?

A satellite is anything that orbits a larger body. The Moon is Earth’s natural satellite: it continually falls around Earth rather than onto it.[2] Artificial satellites do exactly the same thing. The first, Sputnik, was launched by the Soviet Union on 4 October 1957.[1]

Why satellites don’t fall down

They do fall: constantly. But a satellite also moves sideways so fast that, as it falls, Earth’s surface curves away beneath it. Newton pictured this with a cannon on a mountaintop. Fire the cannonball fast enough and it falls completely around Earth.[1] Read more in Orbits.

How fast do they go?

A satellite in a circular orbit close to Earth travels at about 8 kilometres per second, about 17,500 miles per hour, and completes an orbit in about 90 minutes.[1] (That works out to around 16 orbits a day.)

What we learn from satellites

Satellites give us a view no ground station can. Climate scientists, for example, use satellite observations to measure changes such as the shrinking spring snow cover in the Northern Hemisphere, and Earth-orbiting satellites have helped them see the big picture of our changing climate.[3]

Real-life examples

  • Watching snow from space

    Satellite observations show that spring snow cover in the Northern Hemisphere has decreased over the past five decades.[3]

  • Seeing the big picture

    Earth-orbiting satellites have helped scientists see the big picture of how the climate is changing.[3]

  • Sixteen sunrises a day

    A satellite in low orbit circles Earth about every 90 minutes, so it sees roughly 16 sunrises and sunsets every day.[1]

Connected across the map

Learn more

Short descriptions are our own summaries. The resources belong to, and are run by, their publishers.

Evidence & sources

Level 2 · Authoritative

Supported by highly reputable institutions such as government agencies, universities or standards bodies.

Why this level? The physics of satellites is well established; this page also describes how satellites are used. Facts come from NASA and a peer-reviewed astronomy textbook.

This is a Knowledge Atlas editorial classification of the sources we could find, not a certificate of truth. How we evaluate knowledge

Sources

Based on 3 sources from 2 institutions: OpenStax, NASA.

Show all 3 sourcesHide the list
  1. ScholarlyOpenStax (Rice University)· Academic publisherAstronomy 2e, 3.5 Motions of Satellites and SpacecraftOpened and checked against this page on 28 Sept 2026 · License: CC BY-NC-SA 4.0
  2. ScholarlyOpenStax (Rice University)· Academic publisherAstronomy 2e, 3.3 Newton’s Universal Law of GravitationOpened and checked against this page on 28 Sept 2026 · License: CC BY-NC-SA 4.0
  3. AuthoritativeNational Aeronautics and Space Administration· Government agencyEvidence (Climate Change)Opened and checked against this page on 28 Sept 2026