When flames burn on Earth, heated gases rise from the fire, drawing oxygen in and pushing combustion products out. In microgravity, hot gases don't rise. ... Space flames can also burn at a lower temperature and with less oxygen than fires on Earth.

What happens if you light a lighter in space?

But what happens when you light a candle, say, on the International Space Station (ISS)? "In microgravity, flames burn differently—they form little spheres," says Williams. ... Unlike flames on Earth, which expand greedily when they need more fuel, flame balls let the oxygen come to them.

How does fire burn in space without oxygen?

Without gravity, hot air expands but doesn't move upward. The flame persists because of the diffusion of oxygen, with random oxygen molecules drifting into the fire. Absent the upward flow of hot air, fires in microgravity are dome-shaped or spherical—and sluggish, thanks to meager oxygen flow.