* No Clear Boundary: The Earth's atmosphere gradually thins as you ascend, with no abrupt line dividing it from space.
* Different Definitions: Different organizations use different criteria:
* 100 kilometers (62 miles): This is the Kármán line, widely used by aeronautical and astronautical organizations. It's where air becomes too thin to sustain aerodynamic flight.
* 80 kilometers (50 miles): The US Air Force defines this as the start of space for astronaut status.
* 120 kilometers (75 miles): Some definitions use this altitude as the start of space for space objects like satellites.
In Feet:
* Kármán Line: 328,084 feet
* US Air Force Definition: 262,467 feet
* Other Definitions: 393,701 feet
Ultimately, it depends on the context and the definition you're using.
