What happens if you float in space without a suit?
The Real Answer
You would lose consciousness in about 15 seconds and die within minutes. Exposure to the vacuum of space causes rapid decompression: the air in your lungs expands and tears the tissue, your blood boils at body temperature (not instantly — the water in your blood boils, but the liquid part stays), and your body swells as gases expand in your tissues. You don't freeze immediately because space is a vacuum and heat loss requires a medium — you'd actually cool down very slowly. The lack of oxygen is what kills you first.
Your body is a water balloon filled with air pressure and the sun. Take away the container and you become a biological science experiment that lasts exactly long enough for you to realize what's happening. You'll expand, boil, and asphyxiate simultaneously — which is three terrible ways to die happening at once, so at least you're efficient about it.
Why People Ask This
This question usually arrives after watching a sci-fi movie where someone gets 'blown out' of an airlock, or after realizing how close space actually is to where planes fly. There's also a persistent myth that you'd freeze instantly, which sounds dramatic enough that it becomes the story people repeat. The real answer — that you boil and expand and run out of oxygen in a weirdly slow, horrifying way — is somehow worse.