So.

How do you weigh a fart?

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Dr. Michael Levitt, who has decades

of research experience in flatology,

indicates that the typical daily volume

output is between half a liter and 2 liters

of gas once cooled to room temperature.

If you pretend that the fart obeys the ideal gas

law from high school chemistry class, which it probably

does to a decent approximation, you

could work out the mass of the fart

once you know the average molecular mass

of a fart particle.

To get that, we need to know what gases are in a fart

and what ratio they're found in.

This turns out to vary a lot by person and by diet.

I ballparked some average numbers from a paper

in a medical journal that measured the gas

mix in 10 subjects who had been fed

a normal diet plus a bunch of baked beans each day.

I got a density of around 1 gram per liter.

Now, I'm going to assume that our intrepid astronaut has

recently downed a burrito or two,

and would produce 1 full liter, i.e.

1 gram worth of fart mass over a 24 hour period.

For a per fart analysis, assuming a typical 10

to 20 individual farts over the same period,

you would get somewhere between 0.05

and 0.1 grams of mass per fart.

That number may be off by a factor of two or so,

but I doubt it's off by a factor of 10.

And that's how you weigh a fart.

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