“What are tracers, Mr. Taylor?” Teena asked.
Eddie shot her a quick scowl. He doubted that his father wanted to be bothered with questions at the moment. Then Eddie noticed one of the students holding the wandlike probe—or diode—of a Geiger counter down close to the leaves of one plant. It seemed a strange thing to be doing. Who would prospect for uranium in plants.
“That’s a good question, Teena,” Mr. Taylor said. “Glad to see you’re interested.” He turned and spoke to the student with the Geiger counter. “Jim, you want to explain to this young lady, and my son here, what tracers are?”
Eddie smiled to himself. His father was the kind of a professor who believed his students should have the chance to use their knowledge whenever possible.
“Maybe we should all listen to this,” Eddie’s father said to the others.
They gathered around as the dark-haired student switched off the Geiger counter, swallowed a bit uncomfortably, and turned to face the outdoor classroom which Teena’s question had formed on the spot.
“Well, er—” Jim began, addressing Teena, “a tracer is a radioactive isotope which we—well, send out on a journey, then follow it with a Geiger counter.”
“I’m afraid that’s not too clear, Jim,” Mr. Taylor said. “Teena’s not an atomic scientist. Can you simplify it for her?”
“Oh, I know what a radioactive isotope is, Mr. Taylor,” Teena said proudly.
“You do?” Eddie’s father said in surprise.