I am sitting in chat right now and having a smoke.
The heater of the cigg was resting on the bottom of the ashtray when all of a sudden, it ballanced itself on the egde.
The end with the heater was much longer than the end that was sticking out over the edge of the ashtray, and this got me wondering…
Did this ballance happen because the heater is hot? Does the hot ‘embers’ make that end of the cigg a little lighter? (Line of thinking:Heat Rises.)
Damn it.
:smack:
Mods, can this be moved to GQ please?
Actually, heat is energy. Adding energy to an object will add mass. The amount of mass added would be the amount of energy divided by c[sup]2[/sup], so it probably would not be to small to measure. I think the filter is heaver than the tobacco. When the tobacco burns, it loses more mass in smoke than it gains in heat. So it is the burning that makes the lit end lighter, not the heat.
Heating things up causes them to expand. As a result, a hot air balloon floats because the envelope containing the air (the balloon) has less air in it then the air outside the balloon at a lower temperature. This might be what you’re thinking about.
For a solid object it might expand to a greater or lesser degree and theoretically the surrounding air will have more surface area to get ‘under’ the object and lift it up so the object might seem lighter on your scale. However, heat the same object in a vacuum while it sits on a scale and the weight will remain largely the same (or get heavier as DrMatrix explained). The only caveat to that is if heating the object causes particles to be able to get away from it (ala boiling water losing mass to steam) in which case you might get lighter. For, say, a hunk of metal I don’t think you’ll notice much difference if it’s merely heated to a moderate temperature that doesn’t allow it to melt.
Heat doesn’t rise.
True, Mangetout. I believe what Kwyjibo was trying to say is that warmer air rises… wait… that still doesn’t work.
Oh well. 
Hey, it was early in the morning and the part of my brain that handles physics wasn’t quite up yet.
Yeah, but low-density hot objects can create a rising plume of warm air… which then creates an upward-pointing drag force on the object it flows across.
A classic physics trick: make a cylinder of tissue paper, stand it on end on a (non-flammable!) tabletop, then ignite the top edge. As the flame burns down the cylinder, at some point the cylinder suddenly flys upwards. It’s dragged aloft by the rising plume of hot air created by the flame.
But regarding the cigarette, maybe the end rose upwards because that end lost some mass as it burned, which shifted the balance point. Remember that tabacco is mostly made of carbon, hydrogen, and oxygen, and it all turns into gas as the material burns. If a big chunk of ash should drop off the end of the cig, then it’s obvious why the balance shifted. But when the tabacco slowly turns into invisible gas, the reason for the shifting mass isn’t so obvious.
That’s probably all it was. It was early when I witnessed this and my brian tried to kick in and I figured it might have somehting to do with the heat.
It was just one of those things where you think, “Why did that happen???” and think there is some really fancy physics reason.