Cosmic Quest
Inspect the planets in a compact 3D solar system, then ask four questions about how the sky really works. Distances, sizes and speeds are compressed so every world stays visible — the lessons below show the true scales separately.
Explanatory modes
Each lesson has one control and a clear scale label. Schematic means the geometry is arranged to explain, not measured from today’s sky.
Choose a question to open its lesson. The solar system above follows along.
Why does Mars sometimes seem to move backwards?
Earth moves faster on the inside track. When it overtakes Mars, the line of sight from Earth to Mars swings backwards against the distant stars for several weeks — apparent retrograde motion. Mars itself never reverses.
Schematic: circular, flat orbits with the true periods (365.25 and 687 days) and mean distances (1 and 1.52 AU).
What are Rahu and Ketu, if they are not planets?
The Moon’s orbit is tilted about 5° to the ecliptic, the plane of Earth’s orbit. The two planes cross along a line; its ends are the ascending node (Rahu) and the descending node (Ketu). Eclipses can only happen when a new or full Moon falls near a node.
Schematic: tilt drawn three times larger than the real 5.1° so it is visible. The node line turns once in about 18.6 years.
How big are the planets compared with one another?
Jupiter is about 11 times wider than Earth. The 3D scene above enlarges small worlds so they stay visible; here the discs keep their true proportions.
True relative diameters (equatorial). Spacing between discs is arbitrary.
How far apart are the planets, really?
Neptune is 30 times farther from the Sun than Earth. Sunlight takes about 8 minutes to reach Earth and over 4 hours to reach Neptune.
Linear scale of mean distance in astronomical units (1 AU ≈ 149.6 million km). Body sizes are not shown.
Illustrative · schematic · astronomy