The next tunnel ended in a great hemispherical chamber lidded by a bulging transparent dome. A man-thick pillar rose through the rock floor to a seal in the center of the dome. Above the seal, gleaming against night and stars, a multi-jointed metal arm reached out blindly into space. The arm ended in what might have been a tremendous iron puppy dish.

Forward was in a horseshoe-shaped control console near the pillar. I hardly noticed him. I’d seen this arm-and-bucket thing before, coming in from space, but I hadn’t grasped its size.

Forward caught me gaping. “The Grabber,” he said.

He approached us in a bouncing walk, comical but effective. “Pleased to meet you, Carlos Wu. Beowulf Shaeffer.” His handshake was not crippling, because he was being careful. He had a wide, engaging smile. “The Grabber is our main exhibit here. After the Grabber there’s nothing to see.”

I asked, “What does it do?”

Carlos laughed. “It’s beautiful! Why does it have to do anything?”

Forward acknowledged the compliment. “I’ve been thinking of entering it in a junk-sculpture show. What it does is manipulate large, dense masses. The cradle at the end of the arm is a complex of electromagnets. I can actually vibrate masses in there to produce polarized gravity waves.”

Six massive arcs of girder divided the dome into pie sections. Now I noticed that they and the seal at their center gleamed like mirrors. They were reinforced by stasis fields. More bracing for the Grabber? I tried to imagine forces that would require such strength.

“What do you vibrate in there? A megaton of lead?”

“Lead sheathed in soft iron was our test mass. But that was three years ago. I haven’t worked with the Grabber lately, but we had some satisfactory runs with a sphere of neutronium enclosed in a stasis field. Ten billion metric tons.”

I said, “What’s the point?”

From Carlos I got a dirty look. Forward seemed to think it was a wholly reasonable question. “Communication, for one thing. There must be intelligent species all through the galaxy, most of them too far away for our ships. Gravity waves are probably the best way to reach them.”

“Gravity waves travel at lightspeed, don’t they? Wouldn’t hyperwave be better?”

“We can’t count on their having it. Who but the Outsiders would think to do their experimenting this far from a sun? If we want to reach beings who haven’t dealt with the Outsiders, we’ll have to use gravity waves…once we know how.”

Angel offered us chairs and refreshments. By the time we were settled, I was already out of it; Forward and Carlos were talking plasma physics, metaphysics, and what are our old friends doing? I gathered that they had large numbers of mutual acquaintances. And Carlos was probing for the whereabouts of cosmologists specializing in gravity physics.