"Spherical cow" has become a metaphor for highly simplified scientific models of complex real life phenomena. The joke goes:
Milk production at a dairy farm was low, so the farmer wrote to the local university, asking for help from academia. A multidisciplinary team of professors was assembled, headed by a theoretical physicist, and two weeks of intensive on-site investigation took place. The scholars then returned to the university, notebooks crammed with data, where the task of writing the report was left to the team leader. Shortly thereafter the physicist returned to the farm, saying to the farmer "I have the solution, but it only works in the case of spherical cows in a vacuum."
So, naturally, I had to make one.
Step 1: Materials
Step 2: Face
Draw a cow face on one side of the ball. I sketched it in with pencil first.
Note: The valve is at the bottom.
Step 3: Tail
Draw a tail on the opposite side.
Step 4: Body
Cover the rest of the ball with irregularly shaped blotches. You can also add udders if you feel like it.
Step 5: Done
That's it! Give one to your favorite physics geek.