Microgravity complicates everything. Much of our sense of “how things work” is influenced by gravity. Don Pettit uses a soldering iron to boil water, and we see how it both is and isn’t different from a pot and stove on Earth.

This is pretty cool. Don Pettit guides us through boiling water in microgravity. We’ve seen that well-understood phenomena can behave very differently with the gravity turned down. A candle flame doesn’t take on its familiar stretched oval and doesn’t burn as hot, because hot air doesn’t rise up and stretch the flame, and cool air doesn’t rush in and feed the flame.


Pettit first shows us a soldering iron heating up water that’s stretched over a hoop like a bubble wand. Convection causes the fluid to move, whisking hot fluid and the bubbles created inside it away from the iron, and exposing cooler water to the hot iron.

Then Pettit shows us a drop of water on the soldering iron, and explains how the convection does the same thing. Bubbles form, move away from the iron and out towards the side of the drop, occasionally popping on the surface. It looks surprisingly like the way water back on Earth would boil.