The force of gravity is what keeps everything on Earth in its proper position, including humans. We would plummet into space without it. Space doesn’t have gravity or oxygen, as we all know. Have you ever wondered whether some events unfold in space in a manner similar to that which occurs on Earth? Let’s take something as easy as starting a fire as an example. Earthly fire is readily ignited, and its flame always faces upward. But consider what would happen if a matchstick were ignited in an environment with no gravitational pull. Will the flame burn brighter or go out? Let’s investigate.
It goes without saying that it is impossible to start a fire in space since there is no oxygen or oxidizer to maintain the combustion process. The environment inside spacecraft and the International Space Station is somewhat different from Earth: an open flame behaves extremely differently because of the millions of times reduced gravity, even though the air composition is the same.
NASA Johnson Space Centre produced a picture that shows how fire burns inside a spaceship vs on Earth. On Earth, the flame may be seen growing higher than a matchstick, but in zero gravity, it seems like a blue bulb. In zero gravity, there is no force forcing flames upward, hence they do not ascend. Instead, the flame forms circular patterns that resemble drops; this happens because hot air cannot ascend in the absence of gravity.
Let’s look at how combustion works in our world. Imagine yourself cooking marshmallows on a hillside over a big campfire that is wonderfully burning away. You pause to think about the fire itself. How does the whole thing work? As the fuel, which is wood, warms up during combustion, the air around it becomes less dense. The fact that the hot air rises and leaves the vicinity of the fire is very advantageous since gravity pulls heavier objects downward. As the heated air is released, fresh air is drawn into the aperture, generating a fresh supply of air that is high in oxygen.
In microgravity, there is no updraft and a whole different mechanism for oxygen to reach the flame. This kind of experiment was originally conducted in 1997 on the Columbia space shuttle. Flames that were flying within the space shuttle might burn for a long time in a sealed compartment as part of the Structure of Flame Balls at Low Lewis-number (SOFBALL) experiment. The shape of the flame instantly astonished scientists. Unlike how a fire’s flame is extended on Earth, it is spherical in microgravity, like a fireball. The flame develops at the fuel-air boundary because of the slower process of diffusion feeding the spherical flame. To put it another way, the entire surface of the flame acts as the “bottom,” reacting with fresh air in a rough sphere that is close enough to the fuel source to ignite.