Humanity has a strange tendency to think of physics in terms of how it operates on Earth, despite the fact that our little ball of mud amounts to little more than a speck of roach poop in the grand scheme of things. If you really want to see how physics works, you need to go zero gravity, man.
Zero-G environments are totally a part of our physical universe, and an overwhelmingly dominating part at that. This means ye olde laws of physics are totally at work in there, too. They just like to operate like a goddamn maniac.
Fire Turns into Floating Spheres of Glowing Energy
Before reading further, take a moment to go light something in your house on fire. That flame looks like that due to gravity, specifically the fact that hot air rises. The flame is fueled by oxygen, letting the excrement of carbon dioxide and water vapor heat up and lower in density. Eventually, they float away, only to be replaced with fresh, cool oxygen to be murder-burned. However, take that shit to zero gravity, and things will get weird. Fireball weird.
Yep, that there is a space flame. In zero gravity, puny Earth things like buoyancy and convection don't exist. So when you light a match, the carbon dioxide goes nowhere. It just gathers around the flame like hobos around a barrel fire. Meanwhile, the flame keeps happily engorging itself with oxygen until the hobo CO2 all around it snuffs it out.
Left: Normal flame. Right: Awesome ball of space fire.
That flame shape you're used to can only happen because the fire forces hot air to rise upward. Since none of that really happens in zero gravity, the flame just expands in all directions in a desperate search for random oxygen particles. Essentially, this means fires in zero gravity are lower in temperature, consume less oxygen, are dimmer in terms of brightness ... and totally float around like fireballs if you, say, ignite a floating drop of gasoline.
How astronauts resist the temptation to start mage duels the second their spacecraft leaves the atmosphere, we'll never know.