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What did Explorer 1's instruments discover around Earth?

Radiation belts of charged particles held in place by Earth's magnetic field.

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  1. Radiation belts held by Earth's magnetic field ✔
  2. A thin ring of ice around Earth
  3. A layer of ozone at the edge of space

Why: James Van Allen's instrument on Explorer 1 counted fewer cosmic rays than expected, because strong radiation was swamping it. That revealed belts of charged particles trapped by Earth's magnetic field, now called the Van Allen belts.

Huh, didn't know that: Another U.S. satellite confirmed the radiation belts two months after Explorer 1 launched.

The dad joke
Why did the Van Allen belts never fall down? Earth's magnetic personality held them up.
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References

Answer: Radiation belts held by Earth's magnetic field. James Van Allen's instrument on Explorer 1 counted fewer cosmic rays than expected, because strong radiation was swamping it. That revealed belts of charged particles trapped by Earth's magnetic field, now called the Van Allen belts.

  1. NASA JPL, Explorer 1 www.jpl.nasa.gov/missions/explorer-1
    discovery of radiation belts around Earth held in place by the planet's magnetic field
    Checked 2026-10-10.

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