Christmas Candle Conundrum

[Bonzo 2000]

With Christmas candles burning all around, I want to post 2 questions:

1.  If you lit a candle in a totally wightless but air filled environment (eg a space casule), what shape would the flame be?

2. I remember a science based tv programme from the seventies starring the excellent and animated Prof Magnus Pyke. In one show he was demonstrating various odd effects of centrifugal force.  He had a lit candle sitting on the edge of a rotating record turntable, with the candle inside a tall glass tube to protect the flame from the draught created by the movement.  As the turntable increased speed, the candle flame began to lean inwards towards the centre of motion. I cant recall the prof's arm waving explanation, but its puzzled me since. Any theories?

[Hippy]

Question 1 postulated:

As there will be burning, and the flame gases will displace some cooler and more dense air gases, the flame will form as near a sphere as it can, provided that there is no other air movement. There is no gravity, so the cooler and more dense air will have no direction towards which to gravitate. After a few moments of burning, however, a convection current will be established in a particular and random direction. Once this has started the energy from the flame will fuel this and the flame will lean in that direction.

 

Question 2 explained:

Inside the cylinder, centrifugal force will tend to make things go towards the circumference of the circular path taken on the turntable. The flame is hot and therefore the gases are a lot less dense than the surrounding air. The denser air, being heavier, goes to the outside forcing the lighter and less dense flame inwards.

.

[Bonzo 2000]

Well Done on both counts, Hippy.  Are you in fact Magnus Pyke under a pseudonym?

[Hippy]

No. (Waving arms around to demonstrate fact!)

[magicdice]

tape a helium balloon to the roof of your car; see how it acts when you turn corners

 

also tape a helium balloon to the floor of your car, and see how that one acts when you corner.

that also demonstrates the candle in the tube scenario, and it doesn't have to do with the heat. possibly resistance of some sort? i can't recall, i'll get back to you after a couple of christmas margaritas

[robojoos]

you can also do the same thing by sticking a cork in a pop bottle filled with water. the water is denser than the cork so the cork will go the opposite of what seems normal