So a biologist, engineer and physicist are called to help make a dairy farm more efficient...
The biologist tells the farmer that he should feed the cows certain hormones to make it lactate more. The farmer asked how much it'll cost and the biologist says it'll cost many thousands of dollars.
The engineer proposes to make a better milking machine to get more milk per cow. The farmer asks how much it'll cost and the engineer says it'll cost many thousands of dollars.
The farmer then asks the physicist how much his idea will cost. The physicist say "It'll cost nothing and can be implemented immediately!" The farmer was astonished and ask how this is possible. The physicist responds, "Now assume a spherical cow.....Uniformly emitting milk in all directions..."