杏吧原创

How long would it take an average cow to fill the Grand Canyon with milk?

Answers to this question varied hugely, ranging from the pedants who argue over the definition of an average cow to defeatists who claim the stench would be too great. The order-of-magnitude experts won the day, with a surprising number of them calculating an answer similar to the first one below 鈥� Ed

鈥� Obviously the first job would be to divert the Colorado river, which would otherwise interfere with the process. Secondly, the canyon would need to be dammed to retain the milk. Thirdly, because this is a desert environment, huge refrigeration capacity will be required to prevent the milk turning to cheese. And finally, to prevent loss of liquid by evaporation, the canyon will need to be hermetically sealed.

So, preparation complete, let鈥檚 wheel in Daisy, the average cow. In the UK average milk yield per day per cow is in the range 15 to 20 litres. So let鈥檚 settle on 17.5 litres. The canyon is 446 kilometres long by an average of 16 kilometres wide and 1.6 kilometres deep, which gives a volume of about 10 million billion (10¹⁶) litres. So by simple division Daisy would take about 1.8 million million (1.8 脳 10¹²) years to fill the canyon. This assumes the canyon has a rectangular cross section; for a triangular cross section, the time would be halved.

Now, suppose you don鈥檛 want to wait 300 times the age of the planet for your canyon full of milk. Instead, you could divert the world鈥檚 entire milk production to the canyon. This adds another requirement 鈥� a milk pumping infrastructure of epic proportions 鈥� unless you choose to use dried milk, which would be cheaper to transport, and then rehydrate it with water from the river. The UN Food and Agriculture Organization estimates that global milk production in 2004 was 504 million tonnes, which is equivalent to 489 billion litres, giving an estimated fill time of only about 20,000 years 鈥� still a pretty long job.

Jon White, Rampton, Cambridgeshire, UK

鈥� It all depends upon the size of the tanker truck the cow chooses to drive, the time it would take to drive from the milk distribution point, the inflow and outflow of the tanker truck, the ability to change the absorption and evaporation rates of the milk, and the ability of said cow to effectively block the exit route of the Colorado river.

Other considerations, of course, would be does the cow work an 8-hour day, does she ever get a day off, or does she work 24/7?

鈥淒oes the cow work an 8-hour day, does she ever get a day off, or does she work 24/7?鈥�

In a tangential vein, what subsidies would the US government be giving to the dairy farmers? This could be the making of another watershed in reality TV.

Bob Friedhoffer, New York City, US