How the top kill operation works (if it works)

We’ve had to learn a lot while watching the excruciating efforts to cap the gushing BP oil well deep in the Gulf of Mexico.

The latest lesson on the chalk board is about deep sea pressures. The water pressure is so great at a mile below the surface that pumping material back into the ruptured oil pipe is an incredibly difficult feat. It calls for a special potion of drilling “mud” that can “lock up” against the force of the oil gushing out, and yet not freeze before doing its job or collapse at deep sea pressures and temperatures.