Detailed info
The inner globe spins once every 4.2 minutes about a horizontal axis, so riders are pressed against its inside surface. Felt gravity is 1 g on the spin equator and falls off as cos(latitude): about 0.44 g at the 64° park edge and near zero at the poles. That is why the towers crowd the equator and the poles are parks. Bolt Tower's Z-shape is a lopsided mass, so the spin axis cones around by about 7° once every six turns. The outer shell turns the other way about the bulb's vertical axis, and the ZeniTrams roll between the two like the balls of a bearing.
The stadiums are drums, each turning on its own drive shaft for its own gravity: none at the shaft, 1 g at the wall. Motors in a base station on the park floor turn the shaft, and the drum turns with it, clear of the ground. A colosseum (1.4 miles from its shaft to its wall) turns once every 95 seconds; an arena (0.5 miles) once every 57. A colosseum stands straight up at a pole, on the city’s own axis, where the city adds no pull of its own. An arena stands near a pole, where the city’s own spin still pulls 0.3 g, almost along the ground, so it leans 45° on its shaft toward its pole: weight at its wall swings only between 0.86 and 1.14 g (0.7 to 1.3 standing upright), and its field gets a steady 0.27 g. The court is dished, 17 feet deep at its rim, so that pull and the court’s own turning together press straight into the floor; gravity boots do the rest, for the players here and the robots in the colosseums. Its open end faces across the park, over the colosseum, to the quad it belongs to.Getting in. A coiled ramp climbs the shaft’s housing, which does not turn, to the hub at the middle of the drum’s floor, where the drum barely moves: you step aboard as onto a slow turntable, weightless. From the hub a spiral walkway winds outward under the rows, and you grow heavier with every step, so the walk to your row is how you get used to it.The seats. The spin presses everyone outward, so for a fan the inner face of the next row out is the floor. Every row is a step higher than the one inside it, so each sees over the row in front, and the seats recline so every fan looks straight ahead at the field, like a planetarium seat. A skybox stands on the wall itself, the floor of anything the spin presses outward, with its glass for a ceiling: the field is overhead and ahead, toward the shaft. The arenas are Steady Ball stadiums, their bleachers out to the court in the center, and the court turns against the drum, so players keep moving round the shock zones; the colosseums hold the robot battles, their bleachers drawn back toward the wall, leaving the middle to the giant robots.Steady Ball field is in the center, on the hub, in its holographic enclosure, with the steady ball on a line hung from thin cross cords strung across the top of the drum, anchored at both ends so it springs back after a hit; the cords come down for robot battles. Being on the shaft, the field is near weightless at a colosseum, so players wear gravity boots, which is why a player with an o-ball keeps one foot on the ground. The inner rows are light too, so their seats have restraints. With Spin on, the drums turn.
Spin for 1 g 1 rev / 4.2 min (0.24 rpm)
Equator speed ≈875 mph
Bolt Tower ≈7° off-pole
Spin arrows circle each part that turns and turn with it, pointing the way it goes. Their colors are the axis colors of 3D software, on this scene's own axes: red for X and green for Y, which is up. The grid turns about a diagonal between X and Y, not about Z, so blue marks the third spin and not an axis. Each time is how long that part takes to turn once.
Red: the inner globe About its horizontal axis, X. The upright ring. Green: the outer shell About the bulb's vertical axis, Y. The level ring. Blue: the ZeniTram grid About the diagonal between those two. The tilted ring.
Physics shows the spin axis with its wobble cone, and gravity. Each arrow shows which way is down and how strong (on the floor 2.5 miles long for 1 g, to stand clear of the towers; on the cut face, where things are smaller, a mile for 1 g), ending where it is measured; the rings join places of equal gravity. Gravity points straight away from the spin axis, so on the floor it leans from straight down by the latitude, toward the equator: at 30° the ground feels like a 30° slope rising toward the park, and at the park edge gravity is 0.44 g and mostly along the ground. These arrows show the city’s own gravity; a stadium makes its own by spinning. The floor's arrows show in the cutaway and from the core. The cut face shows the rest: the neck spins with the shell, so its gravity points away from the bulb's vertical axis, weak by the elevator core and stronger toward the outer wall; the control drum gives 1 g on its floor; and the hangar, the screw base, and the observatory never spin, so they are weightless.