SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/aero-space-boundary-benchmark

What altitude is widely used as the start of space?

100 kilometers, about 62 miles.

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  1. 100 kilometers ✔
  2. 10 kilometers
  3. 1,000 kilometers

Why: Earth's atmosphere thins gradually, so there is no sharp physical edge. A widely accepted benchmark places the start of space at 100 kilometers.

Huh, didn't know that: Some United States organizations use 50 miles for awarding astronaut recognition.

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Why did the rocket cross the Karman line? To get to the other space.
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References

Answer: 100 kilometers. Earth's atmosphere thins gradually, so there is no sharp physical edge. A widely accepted benchmark places the start of space at 100 kilometers.

  1. Aerospace Dimensions Module 5, Space Environment akwg.cap.gov/media/cms/Module_5__Space_Environment_C640727DEF762_83c5b.pdf
    62 miles, or 100 kilometers, is the most widely accepted altitude where space begins.
    Checked 2026-10-10.

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