This is what happens to an unprotected human body in the vacuum of space, second by second.
Because no one survives space without protection.
What if you were exposed near a star instead of empty space?
Mars has an atmosphere. Would it make a difference?
What would you actually experience crossing the event horizon?
The loneliest death imaginable, in intergalactic space.
How Long Would You Survive in Space? is a free online simulation that shows second by second what happens to an unprotected human body in the vacuum of space. Based on NASA research and the real 1966 vacuum chamber accident, it reveals the scientifically accurate timeline from exposure to death in approximately 2 minutes.
A real-time timer counts from 0 as detailed descriptions explain each stage of vacuum exposure: air expulsion, loss of consciousness at 10-15 seconds, body swelling from ebullism, circulatory failure, and eventual cardiac arrest at roughly 2 minutes. After the main timeline, explore 4 "What If?" branches covering stars, Mars, black holes, and intergalactic voids.
You would lose consciousness in about 10-15 seconds and die within approximately 90-120 seconds. If rescued and repressurized within about 60 seconds, survival is possible — as demonstrated by a 1966 NASA technician who was accidentally exposed to near-vacuum and recovered fully.
Contrary to movies, you would not explode or instantly freeze. Air is expelled from your lungs, dissolved gases form bubbles in your tissues (ebullism), your body swells to about twice its size, and you lose consciousness within 10-15 seconds. Death comes from oxygen deprivation and circulatory collapse.
Brief exposure is survivable. NASA's 1966 vacuum chamber incident proved that a person exposed for about 30 seconds can recover fully with prompt repressurization. Beyond 60-90 seconds, permanent damage becomes likely, and beyond 2 minutes, survival is essentially impossible.
If you enjoyed this, try these: Asteroid Impact Simulator · Speed of Light · The Size of Space · Nuclear Simulation
Last updated: March 2026 · whatifs.fun — Free interactive games, experiments & simulations