Gravity is a hang gliding core partner.
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Gravity may be called a power source of conventional hang gliding.
Gravity holds the air to our planet Earth; then we may hang glide; but just having that is insufficient; that gravity and air subsist, hang gliding is made possible. For instance, be inside a bubble of air in mid space far from significant sources of gravity (or be inside an air chamber that is in a trajectory that nets the equivalent of zero gravity) and hang gliding from simple "falling" does not occur; some artificial acceleration to the glider mass would need to be given to get a reaction with the air in that bubble, say push for launching, but the push energy would be used up in resistance to the air impacts, so movement would be damped.
Try to hang glide in a vacuum, though still in a gravity field: no hang gliding, just drop. So air or the like is another core partner to hang gliding. So, air could be another topic for focus. Other core matters: pilot, wing, wing shape, being, time, decision, arrangement, act, ...
At some point in considering known core hang gliding partners, a particular scene with its particular combination of the serving partners will provide a certain satisfaction in hang gliding for a particular pilot; such resultants will vary by the pilot. Moon City hang gliding pilots will have their resultants to experience. Space gliders falling to the Sun with resistance from the solar wind will have their resultant gliding experience.
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There could be substitutes for gravity for exotic hang gliding. Consider artificial gravity. Consider having a magnetic field and a glider of magnetic-responsive material, but be an air or fluid bubble. This does not exhaust attractive fields. And there may be scenes where exotic hang gliding occurs not in air, but in some other gas or liquid. This present topic aims to remain with the gravity focus for hang gliding.