Florian Gessler is in his workshop. For someone alternately presented as Faust, Geppetto, and Frankenstein by the popular press his workshop was rather modest. Ribbon windows flood the room with filtered light. The view was good. Two SSUs sat on work stands. One is powered down and partially disassembled, and the other is going through a startup sequence with the core switched on. The chassis is fitted with a trio of industrial manipulators that are going through an elaborate series of movements. The arms unfold, extend, and telescope, each basic movement repeated in all possible sequences. The effect is a little like a ballet and card tricks at the same time. The sensor head rotates to regard me. The ring of orange light around the eye illuminates me in infrared for the SSU, and seems to contemplate me for a moment before the head rotates back to a rest position. The SSU (Standard Serial Unit) is not a true AI, but rather a mimic. It’s a networked learning device that draws upon a large matrix of scripted responses for basic tasks, and is a fundamental building block of the Titan City experience.

Gessler has noticed me, and gives me a small sharp nod and a quick dart of the eyes.

“One moment.”

He passes his hand over the input terminal and grasps the holo icon for ‘lock’. The arms of the SSU fold up tight against the cylindrical body. The orange light dims.

“Are you adjusting?”

“Yes. There’s just this odd sensation sometimes. It’s like an aircraft passing overhead, but it’s almost musical. Like the way a pipe organ feels when it’s loud.”

“It’s come to be called ‘The Hum’.” Gessler explained as he doffed his gloves and lab coat for his usual trim jacket in white. “It’s a combination of the active suspension elements in the buildings and the harmonics of the outer aerostat. You can’t really escape it. Some of the older buildings implemented an active damping system, but you got some strange second-order harmonics happening that had unpleasant effects. In the end, it was easier to just live with it. In a couple days you won’t notice it. Shall we go?”

I nodded and we exited the way I came, our feet echoing down a long corridor to the bright glass elevator with its stunning view. It sounded hollow, and it was never possible for me to completely forget that the buildings were little more than moored dirigibles, and that the impression of solidity and permanence was make believe.

Gessler contemplated me with a distant expression, his white suit stained gold in the afternoon light. He cocked his head and grinned.

“What do you know about Shukra-A?” he asked, eyes narrowing but the grin remaining.