So there's this guy who owns a dairy farm. He sets his cows out to pasture and brings them in for milking every day. Back when his great-grandfather owned the land, the pastures ran right up to the barn but in the days since a road was paved, separating the fields from the barn. In the morning, Farmer Dave milks the cows and then takes them across the road. At night, he brings them back.

One day he goes out at the usual time to the pasture to bring the cows back across the road. Dave brings the cows up to the edge of the road but for some reason, the cows won't go across. He tries everything he can think of and still they won't step onto the road. Afraid that the cows might be stolen or eaten in the night, Dave sleeps out in the pasture with them.

The next morning, a big city lawyer on his way to work comes driving along the road and sees Farmer Dave looking a little worse for the wear.

"Looks like you need some help," he says.

"Sure do," says Dave, "I just can't seem to get my cows back across the road to milk them."

"No problem!" says the lawyer, "I know just how to fix that." He leans over into the glovebox of his car and pulls out a large stack of papers covered in small writing.

"Fill those out and mail them to the USDA and they'll send someone to straighten these cows out." With that the lawyer drove away. Well Farmer Dave had no other choice so he filled out the papers and mailed them but no one ever came.

A week later Dave is still spending the nights out in the fields. A doctor in his fancy sports car pulls off on the side of the road:

"Looks like you're having some trouble with your cows."

"No kidding," says Dave, "They refuse to go back across the road."

"Try these," says the doctor as he hands Dave a bag full of pills. "They're sedatives, they'll put your cows right to sleep and then you can carry 'em over." So Farmer Dave tries feeding the pills to the cows but they must have been expired because not one cow fell asleep.

A month later Dave is looking pretty grizzled from being out with the cows. His clothing is covered in mud and he needs a shave. Puttering over the hill comes a small sedan, barely making it up the steady incline. With a shudder it comes to a halt in front of Farmer Dave. The physicist inside rolls down the window and squints at Dave through the haze and the morning glare.

"Top of the mornin' to ya."

Dave, a little perplexed by the strange turn of phrase stammers a bit: "I, uh, I got these . . . um, my cows . . ."

The man interrupted "Hey, I think I know how to do this, let me get back to you!" and speeds off, car coughing out thick blue-black oil smoke.

The next day the same car comes driving up again and stops in front of Dave. The physicist gets out of the car and hands Dave a binder full of sheets with complex equations written on them. "I've got the perfect solution for you but it only works for perfectly spherical cows in a vacuum."

If you don't get it, get thee to a physics class!