What Every Altitude Does to Your Body

What thin air does to your body, step by step from the beach to the edge of space, and the gear that keeps you alive at each height. Sleeping above about 2,500 m can bring altitude sickness; at about 5,500 m each breath holds half the oxygen it does at sea level; on Everest about a third. At a jet's cruising height a rapid decompression leaves 15-30 seconds of useful consciousness, and around 19 km (the Armstrong line) water boils at body temperature. Then three record stratosphere jumps, the edge of space, and the way back down. General science education, not medical advice. 00:00 Intro 00:27 Sea Level 01:17 2,500 m: Altitude Sickness 02:21 4,000-5,500 m: Half the Oxygen 03:56 The Death Zone: Everest Without Oxygen 05:14 10.7 km: Jet Cruise and Decompression 06:42 19 km: The Armstrong Line 07:43 The Stratosphere Jumps 09:05 The Edge of Space 09:52 Coming Back Down Sources: CDC Yellow Book 2026, High-Altitude Travel and Altitude Illness (AMS risk at at least 2,450 m sleeping altitude, 25% of Colorado visitors, hangover-like headache 2-12 h after arrival, fitness does not protect, 500 m/day above 3,000 m, HAPE/HACE, descent) FAA Advisory Circular AC 61-107B CHG 1 (21% oxygen; half the oxygen molecules at 18,000 ft; oxygen at night above 5,000 ft; brain oxygen saturation 87% at 12,000 ft; decompression effects; times of useful consciousness; euphoria) 14 CFR 25.841 (cabin altitude max 8,000 ft) and 25.1447 (masks presented before 15,000 ft); FAA AC 121-24E (own mask first) NASA Glenn Research Center Earth Atmosphere Model (pressure and temperature by altitude) MedlinePlus, Blood gases (normal PaO2 75-100 mm Hg, SaO2 94-100%) Champigneulle et al. 2024, J Physiol 602:5449 - Expedition 5300, La Rinconada Pizzo/West, American Alpine Journal 1984 (253 mm Hg on the Everest summit); Peacock 1998, BMJ 317:1063 (bottled oxygen above 6,500 m) Grocott et al. 2009, N Engl J Med 360:140-149 (arterial blood gases at 8,400 m on Everest) Guinness World Records (Messner and Habeler, 8 May 1978); Szymczak et al. 2021, Front Physiol 12:696335 (the Death Zone above 8,000 m) NASA Armstrong Flight Research Center, 50 Years of Spacesuits (Armstrong line, blood stays under pressure); NASA Goddard Imagine the Universe, Human Body in a Vacuum Smithsonian National Air and Space Museum, Air & Space Quarterly 2023 (Kittinger, 1960); National Museum of the USAF (Excelsior III) FAI World Air Sports Federation records (Baumgartner 2012; Eustace 2014) FAI, Statement about the Karman Line (100 km); FAA Commercial Human Space Flight Recognition (50 statute miles) NASA EVA operations handbook / National Academies (spacesuit at 4.3 psi, 100% oxygen) Animation: Body Redline. #humanbody #altitude #science