Sound in an empty pocket was an impossibility. But the five-hundred-ton Harmonic Core sang with the voice of an awakening titan.
It wasn’t an airborne sound.
There was no dense air at Mile Twenty to carry squeezing waves across the open overhead frame. Instead, the tone traveled directly through the solid crystal-clear lattice of the sapphire monolith, down through the forged nickel-steel trunnions, and into the main framework of the Spire.
The entire twenty-mile tower hummed like the soundboard of a huge grand piano.
Giles Croft felt the shaking surging through the soles of his heavy leather work boots.
It set his teeth chattering in his jaw. Then it made his steel clockwork pencil buzz against the brass clip of his clipboard.
On the pulpit display, the laser vibrometer showed a pure, unvarying sine wave swaying at four hundred and thirty-two cycles per second.
“Shaking wave height: twelve hair-fractions,” Toby Karr reported. His fingers gripped the edge of the transit table to steady his hands.
