Why do flames point up?

Question

It's bothered me for a while now, but the way I see it, it must have something to do with gravity since gravity determines which way is up...which brings up another question: what happens when you light flame in a space shuttle where there is no gravity.

Answer 1

Warm air always rises over colder air (Open the door of a hot oven and feel which way the heat goes).  Fire is hotter than the air around it.  So Fire (flame) rises.  Nothing to do with gravity at all.

And you can't light a fire in space, as you need oxygen for things to burn.  There is no oxygen in space.  Sorry to disappoint...

Answer 2

it points out in zero gravity, away from the flame source due to expanding gases. That's assuming no flowing fuel, like a torch.

Answer 3

Because heat rises and flames need to be fed with oxygen

Answer 4

flame is simply hot gases. hot air rises because cold air is more dense and falls under the influence of gravity. flame in space?!? interesting you mention that.

as there is no or nearly no gravity the flame would spread in all directions... maybe.... but you need to replenish the oxygen supply. this on earth is done by convection currents (hot air rising, coll air falling due to gravity!) no gravity = no convection current = no flame....

is diffusion of oxygen enough to keep the fire going.... i dont know but id love to go to space to find out!

this is ofcourse assuming you are doing it inside a ship where there is available oxygen!

Answer 5

A flame is plasma... which in density is less than air.  When something is less dense than air, it 'floats' up due to the pressure gradient of our atmosphere...

You can also imagine it in more detail via Archimedes Buoyancy physics.

Interestingly,.. if you have a flame in a centrifuge, the flame would point towards the centre of rotation!!!!

Gravity DOES play a role... because it's gravity that pulls the bulk of the air closer to earth, to crreate a higher pressure low down, and lower pressure higher up.

If there was no gravity, then heat won't rise... it would just expand in all directions.. as in any 'fires' or explosions in space.  In spaceships, the fuel is combined with oxygen and due to the design of the rocket (funnell shaped), the explosion and fire is directed in the opposite direction to which ever way the spaceship wants to travel.