THE LABORATORY DOOR opened to admit a newcomer, Lou Graham, head of the electronics crew.
He said, “I’ve got it!”
The chattering noise level died out about three decibels at a time. Lou said, “When a steel magnet is etched in acid, the north pole shows selective etching!”
I shook my head. “Lou,” I said, “we don’t know whether Venus has a magnetic field, whether it is aligned to agree with the Earth’s—nor even whether the Venusians have discovered the magnetic compass.”
“Oh, that isn’t the reference point,” said Lou Graham. “I’m quite aware of the ambiguity. The magnetic field does have a vector, but the arrow that goes on the end is strictly from human agreement.”
“So how do you tell which is the north pole?”
“By making an electromagnet! Then using Ampere’s Right Hand Rule. You grasp
