In a zero G spacecraft, it would be just a small sphere of flame that lasts a couple of seconds and goes out..
round
Very good question. The candle will burn, there have been experiments in space to this effect, the flame reacts to gravity and burns up on earth. In low to no gravity places, the flame makes a more spherical shape; much more efficient incidentally.
Particle diffusion states that the distribution of heat is smooth and relative to it's state. The highest level of combustion is in the bottom, the largest (widest) part of the candle flame. The process moves upward, lessening in activity till there is none, forming the tip you see. For it to be any other shape there would have to be outside elements that influence the process and distribution.
The spacecraft shape
The shape of a candle affects how fast it burns because if you have a round candle it would be shorter than a cylinder. The smaller the shape the faster it burns.
textbooks
A cylinder
Cylinder innit
When a candle melts it gradually loses its shape, and turns into a puddle.
A candle is shaped like a cylinder a cylinder looks like the image down below.
You would find the area of the inside and outside shape (pretending that the inside shape was not in the outside shape). then, you would take the area of the outside shape and subtract the area of the inside shape.
An inscribed shape is inside a circumscribing shape.