motion
a change of position that does not entail a change of location
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 + Grok
Purpose and description
Enable an AI agent to recognise and assess changes of position within a retained location, and decide whether such motion may start, continue, change or stop.
A kinematic change of a body's orientation or of the relative positions of its parts that leaves a reference location untranslated: for a rigid body, a displacement that keeps at least one point fixed and does not keep all body-fixed lines parallel to their initial orientations (Euler: every motion about a fixed point is a rotation about an axis through that point).
It can be Recognise positional change while checking that the declared location remains retained.; Compare observed progression with an expected local trajectory or configuration sequence.; Detect reversals, recurrence, pauses and departures from the permitted range.; Assess whether a proposed continuation would cross a location boundary or encounter an obstruction.; Select an available and authorised intervention, such as starting, slowing, reversing or stopping the motion.; Reclassify or segment an episode when it changes from local motion into relocation..
Distinguishing features
At least one positional quantity changes over an interval; occupying a position alone does not establish motion.
The location criterion remains satisfied throughout the assessed interval; returning to the starting location does not by itself qualify a trip as motion under this entry.
The moving subject is explicit: a part can change location even when the whole containing it remains in one location.
Rotation or articulation qualifies only when the recorded position representation captures that change and the location criterion remains satisfied.
An apparent change caused solely by moving the observer or changing coordinates is distinguished from a change relative to the declared reference frame.
Scope
+ The moving entity or part and the position that changes
+ The reference frame and criterion under which location remains unchanged
+ Changes of orientation, articulation or local position that satisfy the retained-location criterion
+ The motion's progression, rate, range and recurrence
+ Constraints and available interventions on the motion
- Relocation or travel in which the entity changes location
- Routes and journeys between locations
- The enduring identity and composition of the moving entity
- Deformation whose recognition requires modelling changes of shape rather than position
- The intention or task that motivates a motion
- Forces and energy transfers as independently modelled phenomena
Characteristics
- Moving subject
- Reference to the entity or identified part whose position changes Prevents the position of a part from being confused with the location of its whole.
- Reference frame
- Declared spatial frame and its relation to the subject's retained location Makes positional change interpretable and allows observer-induced changes to be identified.
- Location retention criterion
- Named place, bounded region, fixed anchor or another explicitly defined criterion, with applicable tolerance Determines whether a positional change belongs to motion or crosses into relocation.
- Position representation
- Local coordinates, orientation, joint configuration or an explicitly defined combination Identifies what changes without assuming that position means only a single spatial point.
- Positional excursion
- Minimum, maximum and range in metres, radians or declared configuration units Shows the extent of motion and whether it approaches a positional or location boundary.
- Motion rate
- Metres per second, radians per second or declared configuration units per second Supports assessment of progression, timing and intervention needs.
- Temporal pattern
- Single excursion, oscillating, continuously rotating, irregular or unresolved Distinguishes completion from recurrence and helps interpret reversals or pauses.
- Observed motion state
- Changing, stationary, intermittently changing or indeterminate over a stated interval Separates observable movement from assumptions about whether an intended motion has finished.
- Remaining permitted excursion
- Distance or angle to an applicable limit, with direction and uncertainty Supports decisions to continue, slow, reverse or stop before a constraint is breached.
Analytical facets
- substance
- activity
- origin
- conceptual
- agency
- inert
- mobility
- not-applicable
- scale
- not-applicable
- affordances
- observable
Also called
+199
Where this came from
oewn:2024 · CC BY 4.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 5 bundles · 9 layers · 16 findings · 24 questions.
Position within location Establishes what changes position and the sense in which its location stays unchanged.
The registry distinction cannot be applied without separate, explicit accounts of position and location.
Moving subject and frame
Identifies the subject of motion and the frame used to describe its positional change.
Subject-relative position
Record the moving whole or part, the positional quantities tracked and the frame in which they change.
- Which entity or part changes position, and is that position represented by local coordinates, orientation or articulation? definition
- What observation or report establishes change in the declared frame rather than merely a change of viewpoint? provenance
Retained location boundary
Makes the criterion separating local positional change from relocation assessable.
Location retention throughout
Record the applicable location criterion and whether it holds over the assessed interval, including any gaps in evidence.
- What location must remain unchanged, and what spatial extent or tolerance defines remaining there? boundary
- Does the evidence support retention throughout the interval, or could the subject have left and returned between observations? measurement
Positional evolution Describes the actual course and extent of positional change within the retained location.
Recognising motion and judging its progression requires more than a start position and an end position.
Local path and excursion
Captures the sequence of positions or configurations traversed and its spatial extent.
Traversed position sequence
Record observed positional progression, its range and any unobserved portions of the path.
- Which local positions, orientations or joint configurations were traversed, and in what order? measurement
- What is the largest excursion from the reference position, and which parts of that excursion are inferred rather than observed? measurement
Rate and recurrence
Describes how quickly positional change proceeds and whether its pattern repeats.
Motion timing pattern
Record rate, reversals and recurrence using quantities appropriate to the position representation.
- How quickly does the tracked position change, and where does the motion accelerate, slow or reverse? measurement
- Does the motion repeat, and what observed period and variation support that judgement? measurement
Motion state and evidence Supports judgements about whether motion is occurring and where an episode begins or ends.
Small excursions, intermittent motion and repeating cycles can make apparent stillness or completion misleading.
Detectable positional change
Relates claims of movement or stillness to observation timing and precision.
Change versus observation limit
Record the evidence and resolution supporting a motion-state judgement, including uncertainty from sparse sampling.
- What positional difference exceeds the observation uncertainty and counts as detectable change? measurement
- Could the sampling interval hide a full cycle or an excursion between apparently identical positions? boundary
Episode segmentation
Distinguishes pauses, reversals and completed motion episodes.
Start, pause and end
Record the criteria used to delimit an episode without treating every momentary stop as completion.
- What evidence identifies the onset and end of this motion episode? definition
- When position stops changing, what distinguishes a pause or turning point from a completed episode? boundary
Permitted motion and intervention Connects the remaining motion range and available controls to decisions about continuation or intervention.
An agent must judge what may happen next within both the retained location and the motion's applicable constraints.
Excursion and clearance limits
Identifies limits and obstructions along the anticipated positional progression.
Continuation envelope
Record the permitted range and clearance of the moving subject, including moving extremities where relevant.
- Which next positions would exceed an articulation limit, encounter an obstruction or violate the retained-location criterion? boundary
- How much distance or angular travel remains before the nearest applicable limit along the anticipated motion? measurement
Control and response
Identifies feasible interventions and how their effects on motion can be checked.
Intervention feasibility
Record available and authorised controls, their expected positional effects and evidence of the actual response.
- Which available and authorised actions can start, slow, reverse or stop this motion under its current constraints? action
- What positional observations would confirm that an intervention worked before the motion reaches an applicable limit? action
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Kinds and varieties
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Fixed-axis rotation (pure spin: every material point circles a stationary axis)
- Fixed-point rotation (spherical motion about one immobile point; a single equivalent axis by Euler's theorem)
- In-place or pivot rotation (turn about an instantaneous centre at or under the body, as when opposed wheels give zero turning radius)
- Oscillation and vibration (periodic displacement about an equilibrium with no net change of the system's location)
- Anatomical joint motion (flexion, extension, abduction, adduction, pronation, medial/lateral rotation about a joint axis while the person or segment-base stays put)
- Attitude motion (roll, pitch and yaw treated apart from path: the location of the mass centre may be held fixed in the analysis)
- Precession and nutation (motion of the rotation axis itself while a point or mean location remains)
- Articulated relative motion of parts (gestures, hinged mechanisms and doors whose frame or hinge line does not translate)
- Which of these kinds and varieties hold for the sense of motion this model covers, and on what evidence? provenance
Identifiers and schemes
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Wikidata - Q107617 - rotation: circular movement about a centre or axis; the closest item to this location-preserving sense
- Wikidata - Q79782 - motion (physics): parent covering both change of position and change of orientation; too broad if used alone
- Wikidata - Q1129632 - translational motion: the complementary neighbour (orientation preserved, location changes)
- ISO 80000-3:2019 - item 3-6 (symbols ϑ, φ) - rotational displacement / angular displacement, unit radian
- ISO 80000-3:2019 - item 3-16 (symbol N) - rotation as number of revolutions, quantity of dimension one: N = θ / (2π rad)
- Which of these identifiers and schemes hold for the sense of motion this model covers, and on what evidence? provenance
Standards and regulation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- ISO 80000-3:2019 Quantities and units - Part 3: Space and time (ISO): names, symbols and SI units for angular measure, rotational displacement and rotation
- ISO 80000-3:2019/Amd 1:2025 (ISO): amendment to the same quantities-and-units part
- JIS Z 8000-3 (Japanese Industrial Standards): national adoption of ISO 80000-3, including 回転変位 (rotational/angular displacement)
- SI unit radian for plane angle and rotational displacement, as used in ISO 80000-3 and the International System of Quantities (not a separate law of motion)
- Which of these standards and regulation hold for the sense of motion this model covers, and on what evidence? provenance
Real-world use
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- A motor rotor, flywheel, ceiling fan or spinning top turning on a shaft or point that does not translate
- A door, hatch or robot joint swinging about a hinge whose line stays put
- A standing person turning the head, flexing a limb, or gesturing: body-segment motion without locomotion
- A differential-drive robot rotating in place when the wheels are driven equally in opposite directions (instantaneous centre at the axle midpoint)
- Vehicle or aircraft attitude (roll, pitch, yaw) logged separately from the flight-path or ground-track location
- Earth's daily spin about its axis, analysed apart from its orbital change of location
- Oscillatory and rotational rheometry and other tests that twist or rock a specimen about a fixed geometry
- Which of these real-world use hold for the sense of motion this model covers, and on what evidence? provenance
Typical measurements
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- angular (rotational) displacement θ - 0 to 2π per full turn; may be signed and may exceed one turn for continuous spin - rad
- number of revolutions N = θ/(2π rad) - a fraction of a turn for a pose change; unbounded for a running rotor - 1 (dimensionless)
- angular velocity ω - near 0 for quasi-static reorientation; tens to hundreds of rad/s for common industrial rotors - rad/s
- angular acceleration α - 0 in steady spin; large and brief during start, stop or impact (order of magnitude set by the machine, not a universal band) - rad/s²
- oscillation amplitude of a material point about equilibrium - micrometres to millimetres in ordinary machinery vibration; larger in structural sway - m
- attitude angles (roll, pitch, yaw) relative to a reference frame - typically within ±π of a chosen zero; aircraft pitch often a few tenths of a radian in cruise - rad
- Which of these typical measurements hold for the sense of motion this model covers, and on what evidence? provenance
Failure modes and hazards
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Intended fixed-axis rotation becomes free-body motion if the hinge, bearing or shaft fails, so the body translates as well as turns
- Rotor unbalance and resonance: residual mass offset converts spin into vibration that fatigues bearings and mounts
- Finite rotations do not commute: applying roll then pitch is not the same pose as pitch then roll, a recurring source of control and robotics error
- Confusing this motion with curvilinear translation (a gondola that stays upright on a wheel) underestimates or overestimates orientation change
- Anatomical over-rotation: hyperextension or forced rotation beyond the joint's physiological range
- Unexpected gyroscopic coupling (precession) when a spinning rotor's axis is itself turned
- Which of these failure modes and hazards hold for the sense of motion this model covers, and on what evidence? provenance
Regional variation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- English school astronomy contrasts rotation (spin in place) with revolution (orbit, a change of location); everyday English often uses rotate for both
- French: mouvement is the broad term; déplacement is more readily read as change of place, rotation as the in-place sense
- German: Bewegung is broad; Ortsveränderung and Fortbewegung mark change of location / locomotion, Drehung or Rotation the in-place turn
- SI practice records ω in rad/s; much engineering still reports rotational speed in r/min (rpm) even in jurisdictions that have adopted ISO 80000-3
- Anatomical movement names (flexion, abduction, pronation) are internationally Latin-based; clinical names of the planes (transverse vs horizontal) still vary by school
- Which of these regional variation hold for the sense of motion this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- translation / locomotion / change of location - Test whether a distinguished point (centre of mass or body-frame origin) is displaced and whether all body-fixed lines remain parallel; if yes to both, it is translation, not this sense.
- general rigid-body motion (Chasles screw) - Test the pitch of the equivalent screw: a pure rotation has zero translation along the axis; a general displacement has a non-zero parallel translation.
- curvilinear translation (circular path without turning) - Test orientation: if body-fixed lines keep their direction while the body rides a curve (Ferris-wheel gondola staying upright), the body is translating, not rotating.
- revolution / orbital motion - Test whether the centre of mass itself travels around another body; Earth's orbit changes location, Earth's spin does not.
- deformation / strain - Test distances between material points: they are preserved in rigid rotation and change under strain.
- rest - Test whether orientation and the relative positions of parts are constant in the chosen frame.
- parliamentary or legal motion (homonym) - Test the referent: a proposal in a deliberative body is not a physical change of a material body.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of motion this model covers, and on what evidence? provenance
Sources
- Rotation - Wikipedia (Wikimedia Foundation) - Defines rotational motion as movement that leaves at least one point unchanged; contrasts it with translation and with curvilinear translation that preserves orientation; states Chasles' decomposition into rotation plus translation.
- motion (Q79782) - Wikidata (Wikimedia Foundation) - Broader parent item: a body is in motion if it changes position or orientation relative to its surroundings; lists linear motion and rotation as parts.
- Kinematics of rigid bodies - Rotations - University of California, Berkeley - Euler's theorem on motion about a fixed point; general rigid-body motion as translation plus rotation; Chasles screw (rotation plus translation along the same axis).
- Rigid-body pose, translation and rotation (course notes) - Georgia Institute of Technology - Operational test: a rotation keeps at least one point fixed and does not keep all lines parallel; a translation keeps no point fixed and keeps all lines parallel.
- ISO 80000-3:2019 Quantities and units - Part 3: Space and time - International Organization for Standardization - Defines rotational/angular displacement (item 3-6) as path length along a circle divided by distance from the axis, unit radian; defines rotation N as number of revolutions (item 3-16).
- Angular displacement - Wikipedia (Wikimedia Foundation) - Identifies angular displacement with ISO 80000-3 / ISQ; one revolution equals 2π rad; signed sense of rotation; 3-D form as axis plus magnitude (Euler).
- 5.1: Kinematics - Physics LibreTexts (Spiral Physics, DAlessandris) - Any rigid-body motion as superposition of translation of the centre of mass and rotation about an axis through that centre; the rotational part is the location-preserving piece.
- Types of movements in the human body - Kenhub - Clinical inventory of in-place body-segment motions about fixed joint axes (flexion, extension, abduction, rotation, pronation, elevation, etc.).
- Degrees of freedom (mechanics) - Wikipedia (Wikimedia Foundation) - A free rigid body has three rotational degrees of freedom distinct from three translational ones; vehicle attitude named roll, pitch and yaw.
What the second pass must settle
- Does the registry define location through a named place, a spatial region, an anchor or another criterion, and who determines its granularity?
- Does position explicitly include orientation and articulated configuration, or must those cases link to neighbouring registered things?
- How should the registry classify a moving part that changes location while its containing whole retains its location?
- Where should the boundary fall between positional motion and deformation when different parts move relative to one another?
- Does the registry already provide a world model covering this concept, and which neighbouring entries govern relocation and mixed episodes?