Size It Up

ALL ANSWERS · SPACE · DAILY No. 18 · SEPTEMBER 21, 2026

Size It Up Space answer: September 21

The five Space silhouettes for September 21, 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 18 ran from Ariel (1,158 km) to Jupiter (139,800 km). The widest gap was round 1, Triton against Venus, at 4.5×; the closest call was round 3, Ariel against Umbriel, only 1.0× apart — the kind of round that separates a 90 from a 60.

  1. ROUND 1

    Triton (Neptune’s moon · mean diameter) vs Venus (mean diameter)

    Venus · reference · 12,100 km
    Triton · true diameter · 2,705 km

    4.5× shorter than Venus

    Triton, a moon of Neptune, has a mean diameter of about 2,705.2 km. This is the body’s size, not an orbital distance.

  2. ROUND 2

    Neptune (mean diameter) vs Jupiter (mean diameter)

    Jupiter · reference · 139,800 km
    Neptune · true diameter · 49,240 km

    2.8× shorter than Jupiter

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

  3. ROUND 3

    Ariel (Uranus’s moon · mean diameter) vs Umbriel (Uranus’s moon · mean diameter)

    Umbriel · reference · 1,169 km
    Ariel · true diameter · 1,158 km

    1.0× shorter than Umbriel

    Ariel, a moon of Uranus, has a mean diameter of about 1,157.8 km. This is the body’s size, not an orbital distance.

  4. ROUND 4

    Titan (Saturn’s moon · mean diameter) vs Callisto (Jupiter’s moon · mean diameter)

    Callisto · reference · 4,821 km
    Titan · true diameter · 5,150 km

    1.1× wider than Callisto

    Titan, a moon of Saturn, has a mean diameter of about 5,149.5 km. This is the body’s size, not an orbital distance.

  5. ROUND 5

    Europa (Jupiter’s moon · mean diameter) vs Oberon (Uranus’s moon · mean diameter)

    Oberon · reference · 1,523 km
    Europa · true diameter · 3,122 km

    2.0× wider than Oberon

    Europa, a moon of Jupiter, has a mean diameter of about 3,121.6 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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