Meaning & use
Kármán line
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Meanings
nounsingular
The height above the earth, about 100 kilometers, that is widely treated as the point where the atmosphere ends and space begins.
Grammar: Usually used with 'the' and treated as a single fixed point: the Kármán line, at the Kármán line.
Patterns
- the Kármán line
- at the Kármán line
- above the Kármán line
- cross the Kármán line
The rocket passed the Kármán line three minutes after launch.
Anything above the Kármán line is normally counted as being in outer space.
Pilots who fly past the Kármán line are often called astronauts.
nounsingulartechnical
The rule or standard that uses this height when deciding whether a flight counts as spaceflight.
Grammar: Refers to the convention itself rather than the height; often followed by 'is used' or 'sets'.
Patterns
- the Kármán line sets something
- under the Kármán line
- the Kármán line is used to decide something
Many countries follow the Kármán line when they award astronaut wings.
Under international practice, the Kármán line decides whether a test flight is a space mission.
Because the Kármán line is only a convention, some scientists argue for a lower boundary.
Common combinations
- cross the Kármán line
- The capsule crossed the Kármán line and sent back pictures of the curve of the earth.
- above the Kármán line
- Satellites above the Kármán line need no wings because there is almost no air.
- at an altitude of about 100 kilometers
- The balloon burst at an altitude of about 100 kilometers, close to the Kármán line.
- the edge of space
- Tourist flights now aim for the edge of space, just past the Kármán line.
- suborbital flight
- A suborbital flight may reach the Kármán line without going into orbit.
- space tourism
- Space tourism companies promise passengers a view from above the Kármán line.
Synonyms and how they differ
- edge of space
- A looser everyday phrase for roughly the same height; it is vaguer and not tied to the exact 100 km figure.
- boundary of outer space
- A descriptive phrase used in legal and scientific writing; it sounds more formal than the Kármán line.
- space border
- An informal, journalistic way of saying the same thing; it is not a technical term and has no fixed height.
Word family
- von Kármán proper noun
- The surname of the engineer Theodore von Kármán, after whom the line is named.
- Kármán vortex street noun
- A technical term in fluid dynamics, also named after von Kármán, describing a repeating pattern of swirling vortices.
Commonly confused: Kármán line or ozone layer? Kármán line or orbit?
Kármán line vs ozone layer
The ozone layer is a real band of gas in the upper atmosphere, about 15–35 km up, far below the Kármán line; it is a physical layer, not a convention.
Kármán line vs orbit
Orbit means moving around the earth at high speed; a craft can cross the Kármán line without ever reaching orbit.
Practice
A news report says a test pilot flew just past the Kármán line. What does this mean?
Choose one answer.
The Kármán line is the accepted boundary of space at about 100 km, so passing it means reaching that height. Option 1 is wrong because reaching orbit requires far more speed and height, and option 2 confuses the Kármán line with the much lower ozone layer.
Make it your own
Write a sentence using “Kármán line”, then check it and compare it with the examples above.