She said after a moment, "Harla says he has heard of it as a theory. But he is not quite prepared to believe that it does indeed exist as anything but an abstract physical concept."
"Tell Harla that Doctor Carter's awkward position is a direct result of our ability to reduce the tunnel effect to operate on gross matter."
"He realizes that. But now he wants to know why you didn't fire one of the lower animals as a test."
"Tell him that using animals for laboratory experiments is only possible in a police state where the anti-vivisection league can be exiled to Siberia. Mink coats and all. And let his Venusian mind make what it can of that. Now, Teresa—"
"Yes?"
"Tell Harla, very carefully, that pressing the left-hand button will flash the tunnel car back here as soon as he closes the airlock. But tell him that pushing the right-hand button will create another bias voltage—whereupon another mass of matter will cross the junction. In effect, it will rip a hole out of this laboratory near the terminal, over there, and try to make it occupy the same space as the tunnel car on Venus. None of us can predict what might happen when two masses attempt to occupy the same space. But the chances are that some of the holocaust will backfire across the gap and be as violent at this end, too."
"Harla says that he will touch nothing until he has been assured that it is safe."
"Good. Now, Tom," he said, addressing me, "how can we tell right from left?"
"Didn't you label 'em?"
"They're colored red on the right and green on the left."