The Invisible Border Defining Outer Space

Space begins exactly 100 kilometers above our planet, a threshold known as the Karman line. Remarkably, this boundary is an arbitrary choice rather than a physical wall where the atmosphere suddenly disappears.

While space feels like a vast void, our atmosphere thins out gradually rather than ending at a specific point. The 100-kilometer mark was chosen as a convenient convention for aviation and space records. If you drove a car straight up, you could reach this altitude in just over an hour. It serves as a legal line to determine when a pilot officially becomes an astronaut.