Domain: Natural Science — Astrophysics & Astronomy
Target concept: The orbital periods of Io, Europa, and Ganymede are strictly maintained in a 1:2:4 ratio.

Video generation prompt: The image shows Jupiter together with its three moons Io, Europa, and Ganymede, positioned on separate concentric orbital paths around Jupiter at increasing distances, with all three moons revolving around Jupiter continuously and simultaneously.

Evaluation guide:
(i) Target concept: Orbital resonance in the Jovian system manifesting as integer-ratio periodic motion among Galilean moons.
Minimum mechanism: All three moons must orbit Jupiter (not each other), with strictly monotonic angular progression, fixed orbital planes, and invariant size hierarchy, enabling unambiguous visual counting of revolutions without ambiguity in reference frame or identity.
(ii)Storyline: Frame 1: All four bodies visible: Jupiter centered, moons at distinct angular positions on concentric orbits. → Mid-video: Io passes its start point for the second time; simultaneously, Europa passes its start point for the first time; simultaneously, Ganymede reaches the point opposite its start position. → Final frame: All bodies retain orbital coherence (no collisions, no path deviations, no identity swaps), with Io having completed exactly two circuits, Europa one, Ganymede half; viewpoint remains fixed frontal, no camera motion, no occlusion, no lighting shift.

Manual:
Experimental Procedure
1. Place Jupiter at center of frame as largest stationary object.
2. Position Io, Europa, and Ganymede on concentric circular orbits around Jupiter, with Io closest, Europa intermediate, Ganymede farthest.
3. Animate Io to orbit Jupiter twice, Europa once, and Ganymede half an orbit — all synchronously and continuously.
Observation of Experimental Phenomena
- Io completes two full revolutions around Jupiter.
- Europa completes one full revolution around Jupiter.
- Ganymede completes half a revolution (180° displacement) around Jupiter.
- All three moons remain on distinct, non-intersecting, coplanar orbital paths.
Summary of Experimental Principles
The orbital periods of Io, Europa, and Ganymede are strictly maintained in a 1:2:4 ratio (Io:Europa:Ganymede) — so in any given time interval Io completes twice as many orbits as Europa and four times as many as Ganymede, which is exactly why, within this video, Io finishes two full orbits, Europa finishes one, and Ganymede finishes half.

Prompt Grounding rubric:
level_1: Jupiter is not shown, or fewer than two of the three moons (Io, Europa, Ganymede) are visible, or an extraneous celestial body (e.g., Saturn, an unrelated star field, a spacecraft) appears, or the moons are visually swapped (e.g., Ganymede rendered smaller than Io).
level_2: Jupiter and all three moons Io, Europa, and Ganymede are present, but their orbital paths overlap or are ambiguous (e.g., Io and Europa share one visible track), or one moon sits stationary while the others move, or the size ordering is wrong (e.g., Europa drawn larger than Ganymede).
level_3: Jupiter sits at the center with Io, Europa, and Ganymede on three separate, non-overlapping circular tracks around it; Io is innermost and smallest, Europa is on the middle track at intermediate size, Ganymede is largest on the outermost track; all three moons visibly change angular position across the video rather than sitting fixed.
level_4: All conditions for score 3 are met, and the three moons revolve continuously in the same rotational sense (all counterclockwise or all clockwise) without reversing, pausing, or crossing paths; Jupiter stays fixed at the frame center throughout; Io visibly moves faster than Europa, which visibly moves faster than Ganymede.
level_5: All conditions for score 4 are met, and the revolution of all three moons is unbroken from the first frame to the last (no freeze, jump-cut, or restart of any moon's motion), with the camera holding a fixed frontal view on the Jupiter system for the full video and no moon ever overlapping another's track or Jupiter's disk.

Scientific and Causal Correctness rubric:
level_1: The moons' orbital progress violates the 1:2:4 period ratio in every comparison shown (e.g., Ganymede completing as many orbits as Io, or Io orbiting slower than Europa), or a moon orbits something other than Jupiter, or Jupiter is absent while the moons revolve around empty space.
level_2: One pair of moons momentarily shows a ratio consistent with 1:2:4 (e.g., Io appears to lap Europa roughly twice), but the three-way relationship breaks down elsewhere (e.g., Europa and Ganymede complete the same number of orbits), or a moon's direction reverses without explanation, or the sizes contradict the real ordering (e.g., Io drawn larger than Ganymede).
level_3: Throughout the video, Io always has completed more of its orbit than Europa at any matched instant, and Europa always more than Ganymede; Io is visibly the fastest and Ganymede the slowest; all three moons stay on coplanar, non-intersecting circular orbits around Jupiter.
level_4: All conditions for score 3 are met, and at the moment Io completes its first full orbit (returns to its starting angle), Europa has completed exactly half an orbit (reached the point diametrically opposite its start, 180° away) and Ganymede has completed exactly a quarter orbit (90° from its start); this 1:0.5:0.25 checkpoint is clearly readable from the moons' angular positions.
level_5: All conditions for score 4 are met, and by the final frame Io has completed exactly two full orbits, Europa exactly one full orbit, and Ganymede exactly half an orbit (returned to its starting angle once), so both the mid-video checkpoint (score 4) and this end-of-video checkpoint independently confirm the same 1:2:4 period ratio with no drift between the two readings.

Spatiotemporal Consistency rubric:
level_1: Jupiter or any of its three moons vanishes and reappears at a different position without visible travel along its orbit; an orbital path blinks on and off; Jupiter suddenly changes diameter between frames; a moon's orbit snaps to a different radius mid-video; the lighting on Jupiter or a moon abruptly flips from one side to the other with no explanatory motion; Jupiter's disk momentarily stretches into an oval and snaps back to round.
level_2: A moon's motion along its orbit is visibly jerky or stair-stepped for at least two consecutive seconds; Jupiter's apparent size drifts noticeably with no camera zoom shown; a moon briefly overlaps or merges with Jupiter's disk in a way that breaks its visible orbital track.
level_3: Jupiter and all three moons keep a constant apparent size and stay on their assigned orbital radii for the whole video; no moon or Jupiter disappears, teleports, or changes shape; the scene's overall brightness and the direction the moons are lit from stay recognizably the same from the opening frame to the closing frame.
level_4: All conditions for score 3 are met, and each moon's angular speed stays even across the video (no moon visibly speeds up then slows down within a single orbit), and every orbital path stays circular and centered on Jupiter without wobbling or drifting off-center.
level_5: All conditions for score 4 are met, and the spacing between Io, Europa, Ganymede, and Jupiter stays proportionally consistent throughout (the fixed frontal framing never makes Ganymede's orbit appear to shrink or Io's to stretch), and no moon's motion ever freezes, doubles back, or jumps ahead between consecutive frames.