The Fédération Aéronautique Internationale has demarcated the Karman Line – which lies at an altitude of 100 kilometers (330,000 feet; 62 miles) above the Earth’s sea level – as the boundary where space begins. But, NASA spokesperson Dan Huot explains from a physical science’s perspective that “there is no hard-definable point where space begins; the atmosphere just gradually decreases the higher you get.” So, where does space actually start? Watch Seeker explains in the video.