Size It Up

ALL ANSWERS · SPACE · DAILY No. 10 · SEPTEMBER 13, 2026

Size It Up Space answer: September 13

The five Space silhouettes for September 13, with the true sizes. If you have not played yet, this page is a spoiler — play these five first, then come back to argue with the numbers.

Day 10 ran from Dione (1,123 km) to Uranus (50,720 km). The widest gap was round 4, Io against Dione, at 3.2×; the closest call was round 5, Callisto against Mercury, only 1.0× apart — the kind of round that separates a 90 from a 60.

  1. ROUND 1

    Ganymede (Jupiter’s moon · mean diameter) vs Europa (Jupiter’s moon · mean diameter)

    Europa · reference · 3,122 km
    Ganymede · true diameter · 5,262 km

    1.7× wider than Europa

    Ganymede, a moon of Jupiter, has a mean diameter of about 5,262.4 km. This is the body’s size, not an orbital distance.

  2. ROUND 2

    Neptune (mean diameter) vs Uranus (mean diameter)

    Uranus · reference · 50,720 km
    Neptune · true diameter · 49,240 km

    1.0× shorter than Uranus

    Neptune has a mean diameter of about 49,244 km. This is the body’s size, not an orbital distance.

  3. ROUND 3

    Rhea (Saturn’s moon · mean diameter) vs Triton (Neptune’s moon · mean diameter)

    Triton · reference · 2,705 km
    Rhea · true diameter · 1,527 km

    1.8× shorter than Triton

    Rhea, a moon of Saturn, has a mean diameter of about 1,527 km. This is the body’s size, not an orbital distance.

  4. ROUND 4

    Io (Jupiter’s moon · mean diameter) vs Dione (Saturn’s moon · mean diameter)

    Dione · reference · 1,123 km
    Io · true diameter · 3,643 km

    3.2× wider than Dione

    Io, a moon of Jupiter, has a mean diameter of about 3,643 km. This is the body’s size, not an orbital distance.

  5. ROUND 5

    Callisto (Jupiter’s moon · mean diameter) vs Mercury (mean diameter)

    Mercury · reference · 4,879 km
    Callisto · true diameter · 4,821 km

    1.0× shorter than Mercury

    Callisto, a moon of Jupiter, has a mean diameter of about 4,820.6 km. This is the body’s size, not an orbital distance.

Beat these tomorrow

Every round is worth up to 100 points: within 6% of the true size scores 100, half or double scores 45, five times off scores zero. The daily puzzle is the same five for everyone and refreshes at midnight in your time zone; if you want more than five, Size It Up Unlimited draws fresh pairs from the whole library for as long as you like.

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MixedAnimals, planets and everyday things. AnimalsLength, height or wingspan — every round names the axis. GeographyEast–west or north–south span, never area. Pop CultureCheck the version. Compare the measured dimension. VehiclesLength end to end, or height for the ones that stand upright. DinosaursCompare estimated body length, from snout to tail tip. SpaceCompare body diameter. Rings and orbital distances are excluded. Everyday ObjectsLength, height or width — every round names the axis. InsectsBody length or wingspan — read the named measurement. LandmarksRead the named height, length or main span — including its endpoints. Food & DrinkRead the selected size and axis — length, diameter or container height.
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