What Separates Space From Earth

The Kármán line serves as the delineation between Earth’s atmosphere and outer space positioned approximately 62 miles (100 kilometres) above mean sea level. Nevertheless, precisely pinpointing the boundary where space commences presents a challenge due to the gradual thinning of Earth’s atmosphere with increasing altitude. The atmosphere doesn’t abruptly cease but instead diminishes in density as altitude rises, resulting in a lack of a distinct upper limit.

Internationally, the treatment of outer space under the law is consistent in its accessibility to all for research purposes. The exact demarcation of where space begins remains ambiguous. Varying entities propose different thresholds: NASA and the US military regard space as commencing around 80 kilometres above Earth’s surface, while the Federation Aéronautique Internationale (FAI) and other nations advocate for the Kármán line, set slightly above 100 kilometres.

The FAI adopts the Kármán line as the boundary separating aeronautics from astronautics. According to their classification, activities within 100 kilometres of Earth’s surface fall under aeronautics, encompassing all air sports, while ventures exceeding this altitude belong to astronautics.

Ascending to altitudes approaching the Kármán line, air density diminishes significantly, posing challenges such as respiratory difficulties. Specialised cabin air becomes imperative for survival in these conditions. Beyond the Kármán line, the air becomes exceedingly thin, rendering conventional aircraft inoperable due to the lack of sufficient air for lift generation. Gravity’s influence diminishes at these altitudes, impeding conventional flight mechanisms.

The Kármán line’s namesake, Theodore von Kármán, a Hungarian-American physicist, undertook efforts to define the boundary between Earth and outer space in 1957. His expertise extended to fields such as hypersonic airflow, supersonic speed and aerodynamics.

The Kármán line represents a conceptual threshold, symbolising the transition from Earth’s atmosphere to outer space. Despite its prominence, the line’s exact location remains subject to interpretation, reflecting differing perspectives within the scientific and regulatory communities.