Domain: Natural Science — Atmospheric Science
Target concept: Simulation of precipitation induced by silver iodide as a condensation nucleus, promoting the formation of dense water droplets that drip along the chamber walls.

Video generation prompt: After the stratified cloud mass was formed in the glass chamber, silver iodide powder was slowly sprinkled into the cloud from the top of the chamber using a small spoon, and the chamber was continuously photographed.

Evaluation guide:
(i) Target concept: Heterogeneous nucleation-driven droplet growth and gravitational drainage in a controlled cloud chamber, presented as a simplified tabletop analog of silver-iodide cloud seeding (this chamber is not cooled below freezing, so it models nucleation-driven liquid-droplet growth rather than the ice-crystal formation that silver iodide triggers in real supercooled clouds).
Minimum mechanism: Silver iodide must be introduced as a solid particulate (not dissolved, aerosolized, or gaseous); it must contact the saturated cloud layer; nucleation on the powder's surface must trigger localized droplet growth exceeding the critical size for drainage; drainage must occur along the gravity-aligned inner wall surface due to surface tension and adhesion.
(ii)Storyline: [Phase 1] Static shot reveals sealed glass chamber with two visibly distinct horizontal cloud layers (upper dense, lower translucent). [Phase 2] Small metallic spoon enters frame from top, holding visible gray-white powder. [Phase 3] Powder is released and falls vertically into the upper cloud layer; particles remain discrete until contact. [Phase 4] Immediate localized increase in cloud opacity at the impact zone; no delay, no diffusion-only response. [Phase 5] Within one continuous visual interval after contact, cohesive droplets emerge at the upper cloud–wall junction and flow downward without interruption, maintaining wall contact and vertical alignment. Perspective remains fixed side-view; no camera movement, zoom, or angle shift; all causal transitions occur within a single uncut take.

Manual:
Experimental Procedure
1. Fill sealed glass chamber with humid air and cool base to form stable stratified cloud mass (dense upper layer, clearer lower zone).
2. Hold small metal spoon containing silver iodide powder at chamber top opening.
3. Slowly sprinkle powder downward into upper cloud layer.
4. Maintain fixed side-view camera position and record continuously.
Observation of Experimental Phenomena
- Silver iodide powder enters cloud as discrete gray-white particles.
- Cloud layer immediately densifies locally where powder lands.
- Dense water droplets form at cloud–chamber wall interface and drip continuously downward along inner wall surface.
Summary of Experimental Principles
In real clouds, silver iodide's crystalline structure closely resembles ice, so it acts as an effective glaciogenic (ice-forming) nucleus: in supercooled (below-freezing) cloud droplets it triggers heterogeneous ice-crystal nucleation, and the resulting ice crystals grow at the expense of the surrounding liquid droplets (the Bergeron-Findeisen process) before eventually falling as precipitation. This chamber is not cooled below freezing, so it serves as a simplified visual analog: the introduced powder provides extra nucleation surfaces within the saturated cloud layer, promoting localized liquid-droplet growth that drains along the chamber wall under gravity, illustrating the seeding concept without reproducing ice-crystal formation.

Prompt Grounding rubric:
level_1: No glass chamber visible; no stratified cloud mass present; no silver iodide powder shown; no spoon present; no sprinkling action depicted; no dripping water droplets visible on chamber walls.
level_2: Glass chamber is present but empty or filled with uniform fog (no stratification); either silver iodide powder OR spoon is present, but not both; no sprinkling action shown; no water droplets on walls.
level_3: Glass chamber is present with a visibly stratified cloud mass (two or more distinct horizontal layers of differing density/transparency); silver iodide powder and the small spoon are both present and co-located at the chamber top; the sprinkling action is depicted (powder moving downward from the spoon toward the cloud); water droplets are visible on the chamber walls, though their exact position along the wall relative to the powder's entry point is not yet clearly established.
level_4: All elements from score 3 are present AND water droplets are visibly present, forming continuous vertical streams along the inner wall surface; the chamber remains static with a fixed viewpoint; no extraneous objects (e.g., hands, labels, text overlays) enter the frame.
level_5: All elements from score 4 are present AND: (a) powder is visually distinct as fine gray-white particulate (not mist, smoke, or liquid spray), (b) cloud stratification shows clear upper dense layer and lower clearer zone, (c) droplets initiate *only* at wall-cloud interface and propagate downward in unbroken streams, (d) spoon remains fully visible and stable throughout sprinkling, (e) no occlusion, cut, or viewpoint shift occurs at any point.

Scientific and Causal Correctness rubric:
level_1: No causal relationship between silver iodide and droplet formation; droplets appear spontaneously or from unrelated sources (e.g., condensation from cold surface, external water injection); cloud shows no response to powder; powder appears as vapor/smoke/liquid instead of solid particulate.
level_2: Silver iodide powder is shown contacting cloud, but no state change in cloud occurs; droplets appear only on outer wall or ceiling (not inner wall); droplets are spherical and stationary (not dripping); cloud remains uniformly diffuse with no localized densification near powder path.
level_3: Powder contacts cloud and cloud exhibits localized densification (increased opacity or texture) directly beneath sprinkling zone; droplets appear on *inner* chamber walls; droplets move downward continuously (not pulsing or reversing); however, droplet onset is delayed or inconsistent relative to powder entry, or droplets appear in non-adjacent regions without spatial continuity from cloud-wall interface.
level_4: All elements from score 3 are present AND: (a) droplet formation initiates *only* where cloud contacts chamber wall, and begins promptly after the powder enters the cloud layer (no droplets appearing before contact or after a long unexplained delay), (b) droplet streams originate right at the cloud-wall boundary line, (c) cloud densification is confined to the region immediately surrounding the falling powder path, (d) no evaporation, rebound, or splashing of droplets is shown.
level_5: All elements from score 4 are present AND: (a) powder particles remain visibly solid and discrete until full immersion in cloud (no premature dissolution or dispersion into gas), (b) densification propagates radially outward from powder impact point within cloud, (c) droplet streams maintain consistent vertical orientation and merge smoothly without branching or splitting, (d) no secondary phenomena are inconsistent with this liquid-only tabletop analog (e.g., no ice-crystal formation, since the chamber is not cooled below freezing; no upward motion of the seeded droplets; no unnatural suspension of large, precipitation-sized droplets).

Spatiotemporal Consistency rubric:
level_1: Chamber disappears/reappears; cloud mass teleports or reconfigures discontinuously; spoon or powder vanishes mid-action; droplets appear in different locations without motion path; abrupt lighting shift or exposure change breaks continuity.
level_2: Chamber geometry distorts (e.g., perspective warping, fisheye stretch); the cloud layer shifts vertically without a motion cue; the spoon rotates or changes size abruptly; droplets blink in and out without fading or moving; the lighting's apparent direction reverses from one frame to the next with no camera movement to explain it.
level_3: The spoon stays above the cloud, the cloud stays inside the chamber, and the droplets stay on the inner wall surface, all maintaining consistent spatial relationships; motion is continuous with no jumps, freezes, or stutters; the light source's position and brightness stay constant, so shadows on the chamber and spoon keep the same direction and depth throughout; no object interpenetration occurs (the spoon does not pass through the chamber lid, and droplets do not float off the wall).
level_4: All elements from score 3 are present AND: (a) chamber walls retain rigid planar appearance (no bending, bulging, or transparency fluctuation), (b) cloud layers retain fixed vertical alignment (no shearing or sliding relative to each other), (c) droplet streams show smooth parabolic or linear descent without jerking or frame-skipping motion, (d) no inter-frame flicker or aliasing artifacts affecting object edges.
level_5: All elements from score 4 are present AND: (a) the chamber, spoon, and cloud show no visible geometric distortion, warping, or stretching across the sequence, (b) there is no temporal discontinuity such as duplicated, missing, or reordered frames, (c) there is no lighting anomaly such as specular flare, bloom, or inconsistent cast shadows, (d) occlusion is consistent (e.g., if the spoon partially blocks the view of the cloud at the start, that same occlusion persists logically throughout).