h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I have been thinking about this for a while and as it recently came up in conversation I find it is time to find an answer…
If a hot air is lighter than cold air (please no air weights the same its just less dense arguments this is a serious question) and we produce methane (farts) and If I remember right that is lighter as well how much methane and would we have to produce before the average person began to float? I am 88kg if you want some numbers.

Just bookmarking I'm afraid, cuz I'd like to know how many farts I'd have to store before I started floating too.

Queegle

Well, you need to find out how much a liter of methane weighs. Probably a few grams. And then divide 88.000 g with those few grams. And that should give you how many liters you need. Probably over a thousand. That's a whole lot of beans.

Looking at it again, it might be about 80 thousand liters. That's a whole lot.

You know, I might be completely wrong. Maybe it is the weight difference between atmospheric air and methane you should be looking at.

Just looked it up. It is the difference in weight you should look at. Atmospheric air weighs about 1.25 grams per liter, but I couldn't find it for methane.

If I were let loose in a library, I could probably work this out. The molar mass of methane is well known, as is the space filled by a mole of gas. Compare this to the 1.25 g per litre quoted, divide the 88kg by the shortfall, and you have the amount of gas.
Using the approximation that the air is made entirely of gaseous nitrogen (N2) with a molar mass of 28, and methane (CH4) with a molar mass of 16, that means that farts are 4/7 the mass of air.
So -3/7 * 1.25 = -0.54 g per litre of fart.
88000 / 0.54 = a bit over 164 THOUSAND LITRES of fart to float the person in question.
If you see a problem with my calculations, let me know. Otherwise, start sewing that fart balloon, it's gotta be big!

I looked on the internet, and all I could find was molar masses. No liters anywhere.

To an extent, it doesn't matter, as the amount (in moles) of gas in a certain area (in litres) is a constant at the same temperature and pressure. If you put that into the equation, all that matters is the ratio between molar masses of air and methane.

In a more practical way, have a look at the size of balloons filled with hot air to lift a basket with a few persons.

If you try to collect that order of volume of farts inside your body, you explode long before reaching it.

Very interesting!

So you'd have to construct something leading from your botty into a hot air balloon, wait a good few years (depending on your beans consumption) and eventually, one day, you may float away!

Queegle

except for the problem that farts are mainly air, with a small amount of methane, so the balloon woud be even bigger, and much more unsafe due to the air/methane mix it contained.

nobody light a match

Remember the Hindenburg!

Methane is much heavier than air... It's all the carbon, you see...

But, you could collect the methane, then feed it into a burner to power a hot air balloon...

If that is the case how much fart would it take to heat the air inside a hot air balloon. and then fly around the globe?

sorry marjin, but the hindenberg went because it's skin was treated with the same stuff that now fills the solid fuel boosters of the space shuttle.

a small spark, and off it went. that ignited the hydrogen, but it was the rocket fuel soaked skin tht was the problem.

Strange ideas about security they must have had:

Collect an enourmous amount of highly inflammable gas and pack it in even more inflammable sheet and then whish you a safe voyage!

what about fart powered flight ??????

I imagine you could make a car where you use the methane for the combustion engine, rather than petrol. I think in theory anything that explodes can be used.

"I think in theory anything that explodes can be used." is definately true for diesels. you can even run one on custard powder or on chip pan oil (after it has been filtered).

in fact you can see a methane powered deisel in dad's army. mr jones's butchers van worked this way.

petrol engines are much more fussy.