Thanks for a fun question.
There's always a little bit of gravity about, even in the depths of
space, so scientists generally refer to "microgravity" rather than the
more colloquial term "zero gravity". To be on the safe side, though,
I conducted a Google search of [ flame ("zero gravity" OR
microgravity) ] and came right to some interesting sites that not only
describe what such a flame would look like...they show you what it
Check out the "Candle Flames in Microgravity (CFM) Home Page" run by NASA:
They describe the flame, show some cool pictures of the flame tending
towards a spherical shape, and have links to all sorts of interesting
information and discussion. This link in particular:
discusses the differences between the forces acting on a flame on
earth, and one in space.
The results of my Google search can be seen here:
and there are links to all sorts of other sites that provide both
general and highly technical information on the topic of your
I hope this information fully meets your needs. But if anything here
is unclear -- or if you would like additional information -- just let
me know by posting a Request for Clarification, and I'll be happy to
assist you further.