Solar System model

• 1. Jupiter at South Station

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  Solar System models have been built for centuries. Few illustrated the challenge as directly as the installation the Boston Museum of Science spread across its city. The museum placed bronze planet models in major public buildings, each mounted on a labeled stand. Jupiter's model occupied the cavernous waiting area of South Station. That basketball-sized sphere was 1.3 miles from the Sun, which stood at the museum itself.

  The distance between the Earth and the Sun is almost 12,000 times the diameter of Earth. At true scale, planets shrink to specks and the spaces between them grow enormous. The objects in the Boston installation did not move. They sat still while commuters passed. That stillness was the lesson: the solar system is mostly empty, and even a city can barely contain it.

  The Rymdpromenaden, meaning "Spacewalk," was established in Gothenburg, Sweden in 1978. It is among the oldest permanent outdoor scale installations still standing. Others now exist in dozens of cities and towns. Their Suns range from a few centimeters wide to objects measurable in tens of meters. Each navigates the same impossible arithmetic by choosing a different trade-off.

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• 2. Machines That Moved

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  Traditional orreries offered a different kind of accuracy than outdoor scale models do. Many used clockwork mechanisms to display the relative speeds of planets. A viewer could watch Jupiter drift while Mercury completed multiple laps. These machines were correctly scaled in time, not in distance. A correctly-timed orrery and a correctly-spaced one were always two separate problems.

  Scotland's Kirkhill model, built in 1776, has long since decayed. While orreries and tabletop models often showed relative sizes, they were rarely built to true scale. The enormous ratio of interplanetary distances to planetary diameters made that impossible in any indoor display. The scale that mattered most, the emptiness between planets, was the one consistently left out.

  Planetенmodell Hagen in Hagen, Germany, established in 1959, was among the first permanent outdoor installations to attempt true scale. At one to one billion, its Sun measures 1.4 meters across and Earth is 1.3 centimeters wide. The trail from Sun to Pluto covers 5.9 kilometers. That distance would appear again and again in outdoor models built in the decades that followed.

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• 3. Walking to Neptune

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  The Sagan Planet Walk in Ithaca, New York, established in 1997, compresses the solar system to a scale of one to five billion. At that ratio, the Sun is 30 centimeters across. Walking from the Sun to Pluto covers 1.2 kilometers. The full journey fits inside a city neighborhood.

  The Voyage National Program applied a one-to-ten-billion scale across American public spaces. First installed on the National Mall in Washington, D.C. in 2001, copies spread to Space Center Houston and Kansas City, Missouri in 2008. Corpus Christi, Texas received an installation in 2009. Dover, New Hampshire joined in 2023. At that scale, Earth measures one centimeter in diameter.

  The Thousand-Yard Model, available as a teaching template, replaces abstract numbers with everyday objects. Earth is a peppercorn. Jupiter is a walnut. Neptune is a coffee bean. The scale of the planets matches the scale between them, so size and spacing are simultaneously correct. The Lafayette Walk in Detroit, Michigan, used the same scale to demonstrate what it called "(un)imaginable distances." Its description noted that the distances involved were "nowhere near Graham's Number." That installation was later dismantled.

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• 4. Country-Wide Models

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  Sweden's Solar System, begun in 1998, stretches 300 kilometers from Stockholm outward. Its Sun is a 71-meter globe in the capital. Earth, at 65 centimeters in diameter, sits 7,600 meters from the Sun. Visiting the outer planets requires a car and hours of travel.

  Solar System Drive in Coonabarabran, Australia, established in 1997, offers 205 kilometers of drivable route at a scale of one to 38 million. The Space for MUCO project in Belgium, established in 2004, covers 147 kilometers at a scale of one to 40 million. That project identifies its planet sculptures as non-scale. The distances between planet positions still follow the stated scale.

  The North American Solar System Model in Saskatchewan, Canada, began construction in 2025. At its scale of roughly one to 44 million, the Sun measures 31.53 meters across. Inner terrestrial planets are reachable on foot. The gas giants require a car. When complete, the model will span 133.1 kilometers from the Sun to Pluto.

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• 5. Beyond Pluto

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  The Otford Solar System Model in Otford, England, places Pluto 900 meters from the Sun. But the same scale extends further. At one to 4,595,700,000, Proxima Centauri falls proportionally in Los Angeles, California. Barnard's Star lands in Port Stanley, in the Falkland Islands. Sirius is placed in Sydney, Australia. Ross 154 sits in Christchurch, New Zealand.

  The Akaa Solar System Scale Model in Akaa, Finland, established in 2017, places its Proxima Centauri marker in Yulara, Australia. Melbourne's Solar System model, established in 2008, expresses the same star's proportional distance as a route from Melbourne, around the poles, and back. That circumnavigation is how the model conveys a distance with no earthly equivalent.

  In the Akaa model, the Sun is 0.46 meters across. Pluto sits 1.958 kilometers away. The nearest stellar neighbor is represented not by a local marker but by one positioned on another continent.

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• 6. Tiny Suns, Real Distances

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  MIT's Infinite Solar System, installed along the "Infinite Corridor" in Cambridge, Massachusetts in 2018, uses a scale of one to 30 billion. At that ratio, the Sun measures 4.6 centimeters across. Earth is 0.43 millimeters wide. Pluto sits 200 meters from the Sun. The entire solar system fits within a single academic building.

  The Solar System Lawn Model at Griffith Observatory in Los Angeles, California, takes compression further still. At a scale of one to 105 billion, it is engraved in the front sidewalk. The Sun is 1.32 centimeters wide. Pluto sits 56 meters away. Both the MIT and Griffith models show that precision in a scale model does not depend on physical size.

  The Vienna Solar System, under construction since 2018, combines physical planet markers with an augmented reality overlay. At a scale of one to 163,764,706, its Sun measures 8.5 meters across and Earth is 7.78 centimeters wide. No other permanent installation in the record pairs physical planet models with an augmented reality component.

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