farmdoc's blog post number 546

Reductio ad absurdum. It’s an argument in formal logic wherein a proposition leads to an absurd consequence. It popped into my mind as I was reading this article. In a bid to reduce carbon emissions, a Japanese airline’s started asking its passengers to go to the toilet before boarding. All Nippon Airways (ANA) claims empty bladders means lighter passengers, thus lighter aircraft and thus lower fuel use. The airline began a 30-day trial on 1 October. It says that based on an average human bladder capacity of 15oz, 150 passengers emptying their bladders before boarding would result in a lighter load of 63.7kg. And a lighter load means better fuel consumption and lower carbon emissions. Seems fine to me. But where will it reasonably stop? Fare rebates for passengers not using plane toilets? Refusal to carry passengers weighing more than a certain number of kilograms? Whatever. But the logically absurd consequence is that maximum fuel efficiency would occur when no passengers are carried at all. Which reminds me of this classic Yes Minister scene about the hospital with no medical staff. Talk about reductio ad absurdum.

PS It’s also been calculated that one litre of jet fuel’s used to make the electricity needed to flush a plane’s toilet once. Ho hum.