22 objects · Free category practice
Space size guessing game
Planets, moons and spacecraft are brought down to a single visual scale. Planet questions measure diameter, not orbital distance. Equatorial and mean diameters are labelled separately.
The world is waiting.
Preparing your size challenge…
Explore the space collection
Each five-round set is generated from this collection. Your category scores are separate from the mixed daily streak. Read the chosen dimension and measurement note after each reveal.
space
Mercury
4,880 kmdiameterRounded equatorial diameter published in NASA’s planet-size guide.
spaceVenus
12,104 kmdiameterEquatorial diameter from NASA’s planet-size guide.
spaceEarth
12,756 kmdiameterRounded equatorial diameter; the polar diameter is slightly smaller.
spaceMars
6,792 kmdiameterEquatorial diameter from NASA’s planet-size guide.