The Karman line is a convention

The Kármán line is commonly set at 100 km as a conventional boundary between aeronautics and astronautics. There is no physical wall between atmosphere and space, and different organizations or purposes can use other boundaries. A 2009 research study proposed about 118 km for a boundary associated with the transition from atmospheric winds to motion dominated by charged particles; this does not replace the widely used conventional threshold. The illustration is AI-generated.