Scale Comparison

Earth vs the Moon, to scale

The Moon feels large in the sky because it is close, not because it rivals Earth. Set on one honest diameter scale, the pair reads as a planet with a substantial companion rather than two near-twins.

Shared physical scale
7,099km
Moon3,470 km
Earth12,742 km

Scale insight

Earth's diameter is about 3.7 times the Moon's.

That ratio matters because the Earth-Moon system is unusual among the major planets. The Moon is far too small to be mistaken for a peer of Earth, yet it is still large enough to shape tides, stabilize Earth’s axial tilt over long timescales, and dominate the appearance of our night sky.

The visual intuition many people carry is skewed by distance. The Moon seems imposing because it is nearby and familiar. A true scale comparison resets that instinct. Earth remains the far larger body, and the Moon reads as a substantial but clearly secondary world.

Objects

Open each object in context

Moons

Moon

3,470 kmdiameter

The Moon is Earth's natural satellite and our clearest visual anchor on planetary scale. It is still drifting away from Earth by about 3.8 centimeters each year, a slow tidal migration that has been reshaping the Earth-Moon system for billions of years.

Object class
Rocky moon
Mass
~0.012 Earth masses
Host
Earth
Estimated age
~4.5 billion years
Composition
Silicate rock
Visual creditGregory H. Revera / CC BY-SA 3.0Source: Wikimedia Commons
Planets

Earth

12,742 kmdiameter

Earth is the rocky planet on which we live and the most familiar anchor for planetary scale. It remains the only world known to host life, with long-lived surface oceans that have shaped both its geology and its atmosphere.

Object class
Terrestrial planet
Composition
Silicate rock and iron core
Temperature
~288 K mean surface
Estimated age
~4.54 billion years
Host
Sun
Visual creditNASA / Apollo 17 crew / Public domainSource: Wikimedia Commons

Between the smallest and the largest, perspective is everything.

About

Scale of Space is a scroll-based journey through the universe, placing objects on a single logarithmic scale so you can compare size across an unbroken range.

Guides turn parts of that scale into curated essays, while focused views let you explore the same range through specific groups of objects.

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