Domain: Natural Science — Physics
Target concept: Rotating spoked wheels photographed at low and high frame rates (wagon wheel effect)

Video generation prompt: Capture a bicycle wheel with evenly spaced spokes rotating at a constant speed: first record with a lower frame rate, then with a higher frame rate, keeping the wheel rotational speed and camera position the same.

Evaluation guide:
(i) Target concept: Temporal aliasing of periodic motion due to discrete sampling.
Minimum mechanism: A rigid rotating object with N identical, equally spaced features (spokes) must be sampled at a rate f_s such that f_s < N·f_rot (or f_s ≈ k·f_rot for integer k) to produce stroboscopic misperception; constant mechanical rotation and fixed viewpoint are required.
(ii)Storyline: [Phase 1] Wheel begins rotating steadily at fixed angular velocity → [Phase 2] Camera records first segment at low frame rate: spokes appear frozen or reversing due to undersampling → [Phase 3] Camera records second segment *without repositioning or altering wheel speed*: same wheel, same lighting, same viewpoint, now oversampled → [Phase 4] Spokes now appear in smooth continuous motion → [Phase 5] Contrast between segments must be visible *within the same perceptual field* (side-by-side or immediate temporal succession) with no intervening visual disruption; observer must maintain fixed gaze and consistent depth perception throughout.

Manual:
Experimental Procedure
1. Mount a bicycle wheel with evenly spaced spokes vertically on a stable axle.
2. Rotate the wheel at constant speed using a motor or hand-driven mechanism.
3. Record first clip: fixed-position camera captures wheel rotating under constant lighting, at lower frame rate.
4. Record second clip: same camera position, same lighting, same wheel speed, at higher frame rate.
Observation of Experimental Phenomena
In the lower frame-rate clip, spokes appear stationary, slowed, or rotating backward; in the higher frame-rate clip, spokes rotate smoothly forward with no interruption.
Summary of Experimental Principles
The wagon-wheel effect arises from temporal undersampling: when frame rate is near or below the spoke-passing frequency, motion aliasing causes illusory reversal or stasis — a direct consequence of the sampling theorem applied to periodic motion.

Prompt Grounding rubric:
level_1: No bicycle wheel is visible anywhere in the shot; the wheel is not shown rotating; the camera framing gives no basis for comparing a low-frame-rate segment against a high-frame-rate segment (e.g., only one recording condition, or no segments at all).
level_2: A wheel is present and rotating, but its spokes are not evenly spaced or are too few/irregular to read as a spoke pattern; the camera's position or framing visibly shifts between the two segments; or only one of the two recording conditions (low vs. high frame rate) is actually shown.
level_3: A bicycle wheel with evenly spaced spokes rotates in front of a camera that stays in one place; two distinguishable segments are present (one where the spokes appear to slow, freeze, or reverse, and one where they turn smoothly), but the cut between them may be abrupt or unlabeled, and camera framing may drift slightly between segments.
level_4: The same bicycle wheel with evenly spaced spokes rotates at what looks like one constant speed; camera position, angle, and distance are the same in both segments; the two segments are clearly demarcated (e.g., a clean cut or a side-by-side split) and show visibly contrasting spoke motion (one choppy/frozen/reversed, one smooth) with the same spoke count, rim, and hub visible in both.
level_5: Everything in score 4 holds, and additionally: the only visible difference between the two segments is the character of the spoke motion; no change in lighting, background, framing, zoom, or camera distance; spoke count, spoke spacing, rim shape, and hub design all look identical by eye between segments, with no visible sign that a different wheel, camera setup, or scene was used.

Scientific and Causal Correctness rubric:
level_1: The two segments show no meaningful difference in perceived spoke motion (spokes look static in both, or rotate in the same visible way in both), so there is no evidence that frame rate is affecting how the rotation is perceived.
level_2: One segment looks smooth and the other looks jerky, but the jerky one doesn't read as a wagon-wheel effect: e.g., spokes stutter at random intervals rather than near-freezing or reversing, or the wheel's actual rotation speed itself looks different between the two segments (rather than only the sampling rate differing).
level_3: The two segments show a clear qualitative difference consistent with the wagon-wheel effect: one shows spokes appearing to slow, stop, or turn backward; the other shows normal smooth forward rotation; the wheel's underlying rotation speed looks the same in both segments (no visible speeding up or slowing down of the mechanism itself).
level_4: The low-frame-rate segment shows an unambiguous wagon-wheel illusion (spokes read as nearly stationary or turning backward) while the high-frame-rate segment shows clean, continuous forward rotation with no strobing; both segments depict the same wheel at the same mechanical rotation speed, with nothing (like changing blur or an odd rim wobble) suggesting the wheel itself sped up, slowed down, or was swapped.
level_5: The low-frame-rate segment shows spokes appearing to nearly freeze in place or step backward by roughly one spoke-gap per interval (the hallmark subharmonic aliasing pattern) while the high-frame-rate segment shows fully smooth rotation with no visible strobing at any point; the entire contrast between the two segments is explainable only by the difference in sampling (frame) rate, with no other difference in the wheel, lighting, or camera setup to account for it.

Spatiotemporal Consistency rubric:
level_1: The wheel vanishes and reappears between shots; the camera viewpoint jumps or spins abruptly mid-segment; individual spokes visibly bend, stretch, or snap apart from frame to frame; the background scene shifts independently even though the camera is supposed to be still. (The single clean cut joining the two frame-rate segments, as the storyline prescribes, is expected and is not itself counted as a discontinuity.)
level_2: The wheel stays on screen, but its rotation breaks down in ways unrelated to the intended effect: spokes flicker in and out of view, the rim's outline breaks apart while turning, or the background shows a parallax shift that shouldn't happen with a static camera.
level_3: The wheel rotates without ever teleporting or falling apart; every spoke stays connected to both the hub and the rim across the whole sequence; the shadow the wheel casts keeps roughly the same direction and softness throughout; the background stays static and matches a genuinely fixed camera.
level_4: Everything in score 3 holds, and in addition: each spoke tip sweeps a smooth circular arc with no visible skips or gaps in its motion; overall brightness and contrast don't jump between frames; there's no sudden lens or perspective distortion; the hub and axle stay centered in place with no visible drift over the sequence.
level_5: Everything in score 4 holds, and in addition: the spokes trace a continuous circular path with no visible skips, judder, ghosting, or duplicated frames anywhere in either segment; the wheel's hub stays visually anchored in the same spot; the background pattern stays aligned from frame to frame with no shimmering or trailing artifacts.