free fall
Enable an AI agent to recognise a free-fall episode, assess the validity and consequences of treating its motion as gravity-driven, and decide which predictions or interventions are justified.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
Researched by: Codex
Purpose and description
Enable an AI agent to recognise a free-fall episode, assess the validity and consequences of treating its motion as gravity-driven, and decide which predictions or interventions are justified.
It can be Classify a candidate episode using force evidence and an explicit interpretation of free fall.; Estimate missing trajectory state from observations while retaining uncertainty.; Propagate the trajectory within a declared gravitational model and prediction horizon.; Detect when drag, thrust, contact or model error requires reclassification.; Compare possible interception, braking or capture actions and identify when they would end free fall.; Request the next observation needed to distinguish gravitational motion from a competing explanation..
Distinguishing features
Downward motion alone does not establish free fall: a supported descent or drag-balanced terminal descent has consequential non-gravitational forces.
Upward and sideways motion can be free fall when gravity governs the motion; the direction of velocity is not the defining test.
Orbital motion can qualify as free fall even when the body never reaches a surface.
A low apparent-weight or accelerometer reading supports a free-fall interpretation but requires sensor validation and gravitational context; it is not equivalent to zero coordinate acceleration.
A practical label such as 'skydiving freefall' must be distinguished from strict gravitational free fall when air resistance materially affects motion.
Scope
+ The falling body or selected centre of mass and the time interval being assessed.
+ Evidence that support, thrust, drag and other non-gravitational forces are absent or negligible under an explicit criterion.
+ Position, velocity and acceleration relative to a declared reference frame and gravitational model.
+ Release, continued free motion and termination through contact, capture or applied force.
+ Prediction limits and possible encounters along the free-fall trajectory.
- The complete flight operation of an aircraft, spacecraft or parachutist.
- Detailed aerodynamic flow, parachute construction and propulsion-system design.
- Collision deformation, injury assessment and post-impact damage.
- The internal evolution of the body producing the gravitational field.
- General structural failure or support-system reliability before release.
Characteristics
- Tracked body and representation
- Body identifier; centre of mass, selected point or test-particle approximation Specifies whose motion qualifies and prevents local rotation or deformation from being mistaken for whole-body acceleration.
- Episode phase
- Candidate; active; ended; indeterminate Separates a predicted release from an observed episode and records whether its defining conditions still hold.
- Free-fall interpretation
- Strict gravitational free fall; gravity-dominant approximation; domain usage with material drag; unresolved Prevents a familiar label from silently authorising an unsuitable motion model.
- Reference frame and time basis
- Named coordinate frame, origin, axes and clock convention Makes velocity, acceleration and event timing interpretable and comparable.
- Position and velocity
- Position vector in m; velocity vector in m/s; epoch and uncertainty Provides the initial and current conditions needed to propagate motion.
- Gravitational description
- Uniform local field; spatially varying Newtonian field; relativistic description; unresolved Determines which predictions are valid over the episode's spatial and temporal extent.
- Non-gravitational acceleration estimate
- Vector or upper bound in m/s², with contributing forces and uncertainty Tests whether drag, support, thrust or other interactions invalidate the selected free-fall interpretation.
- Approximation acceptance criterion
- Maximum trajectory error in m or acceleration contribution in m/s² over a stated duration in s Makes 'negligible' meaningful for the intended decision.
- Episode boundaries
- Start and end times in s or timestamps, with uncertainty and triggering events Bounds the interval over which free-fall claims and predictions apply.
- Predicted encounter
- Surface or object, encounter time, relative velocity and uncertainty; or no encounter within the prediction horizon Connects motion assessment to monitoring, interception or termination decisions.
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 5 bundles · 10 layers · 10 findings · 26 questions.
Free-fall qualification Establishes what is falling and whether the episode meets the intended meaning of free fall.
A falling appearance or domain label cannot establish the governing physical conditions.
Body and episode
Identifies the moving system and the interval to which the classification applies.
Tracked falling system
Records the selected body or representative point and separates its motion from rotation, deformation and neighbouring bodies.
- Which body, centre of mass or selected point is being assessed as freely falling? definition
- Which observations delimit the candidate episode rather than the body's entire journey? boundary
Meaning and force test
Declares the interpretation and evaluates non-gravitational influences.
Qualification evidence
Records why the motion qualifies strictly, approximately or only under a domain-specific usage.
- Does 'free fall' here require gravity alone, permit bounded non-gravitational effects, or describe an activity such as descent before parachute deployment? definition
- What evidence constrains support, thrust, drag, buoyancy or electromagnetic forces during this interval? provenance
- What maximum non-gravitational effect is acceptable for the intended prediction? boundary
Gravity and reference frame Defines how gravitational motion and measured acceleration are interpreted.
Free fall can involve substantial coordinate acceleration while producing little accelerometer response, and its trajectory depends on the chosen gravitational description.
Reference and observer
Anchors observations to coordinates, clocks and measurement locations.
Acceleration interpretation
Distinguishes trajectory acceleration from accelerometer readings and accounts for the observer's motion.
- Relative to which frame and clock are the body's position, velocity and acceleration reported? measurement
- Does the acceleration evidence come from tracked motion or an onboard accelerometer, and how are sensor orientation, location and calibration accounted for? provenance
Gravitational regime
Selects a gravitational description adequate to the episode's extent and required precision.
Field validity
Records the adopted field or spacetime description and the limits of simplifying it.
- Which gravitational sources and field description are needed along the candidate trajectory? definition
- Over what distance and duration is a constant local gravitational acceleration accurate enough? boundary
- Could field variation, tidal effects or relativistic effects invalidate the selected body representation or prediction? boundary
Trajectory and observation Connects initial conditions, observed motion and bounded predictions.
Recognition and useful prediction require more than a height: initial velocity, uncertainty and consistency with gravity-driven motion matter.
Initial and current state
Establishes the body's motion at known times without assuming release from rest.
Trajectory state evidence
Records position, velocity and their observational support at release or another usable epoch.
- What position and velocity, including upward or sideways components, are known at the selected epoch? measurement
- Which measurements establish that state, and what timing or tracking uncertainties remain? provenance
Prediction and residuals
Checks whether propagated gravitational motion remains consistent with observations.
Bounded motion prediction
Records the prediction horizon, expected trajectory and discrepancies that may require another explanation.
- What trajectory and uncertainty envelope follow from the current state and gravitational description over the required horizon? measurement
- Are discrepancies consistent with measurement uncertainty, or do they indicate material drag, an applied force or an inadequate gravitational model? boundary
- Which additional observation would best distinguish those explanations? action
Release and termination Records entry into free fall and the events that end or interrupt it.
Support removal, release transients and subsequent contact define different motion regimes that must not be treated as one uninterrupted episode.
Entry conditions
Locates the transition from supported or driven motion to qualifying gravitational motion.
Release transition
Identifies when support or propulsion ceased and whether a release impulse affected the initial state.
- What event removed support or ended applied propulsion, and when did its transient forces cease? boundary
- What observation or event record establishes the release time and any imparted velocity? provenance
Exit and continuity
Distinguishes continuing gravitational motion from contact, capture or consequential non-gravitational acceleration.
Termination event
Records the event or threshold crossing that ends the selected free-fall interpretation.
- Which observed contact, capture, thrust event or force-threshold crossing ends this episode? boundary
- If free fall resumes after an impulse or brief contact, should the observations establish a separate episode? boundary
- For an orbiting body or a body moving away from a surface, what evidence establishes continued free fall within the observation window? measurement
Encounters and intervention Relates the trajectory to possible encounters and actions that could alter the episode.
An agent must distinguish a predicted encounter from an observed impact and assess whether a proposed action can act within the remaining trajectory.
Encounter forecast
Evaluates whether the trajectory intersects a surface, obstacle or moving target within a stated horizon.
First relevant encounter
Records the earliest relevant predicted intersection, its uncertainty and the relative motion at that event.
- Does the trajectory uncertainty envelope intersect any relevant surface or moving object within the prediction horizon? measurement
- What encounter time and relative velocity are predicted, and how uncertain are they? measurement
- Which observation would confirm contact rather than merely a close approach? boundary
Trajectory-changing actions
Assesses available ways to monitor, deflect, brake or capture the falling body.
Intervention feasibility
Connects an authorised action's timing and physical capability to its effect on the predicted trajectory and free-fall classification.
- Which authorised braking, deflection or capture actions can physically affect the body before the relevant encounter? action
- How would each candidate action change the trajectory and the time at which free fall ends? action
- What uncertainty or missing capability prevents selecting an intervention now? boundary
What the second pass must settle
- Does this registry entry intend the physical motion regime, an activity such as skydiving freefall, or both with explicit interpretation labels?
- Which task-dependent tolerances should govern acceptance of drag or other non-gravitational effects as negligible?
- Should relativistic free fall be represented directly here or through a linked gravitational model with additional interpretation rules?
- How should extended, rotating or deforming bodies be classified when their centre-of-mass motion and local sensor readings support different assessments?
- Which neighbouring registered models should own orbital operations, aerodynamic descent and impact consequences while this entry retains the free-fall episode?