Sagan Planet Walk

The Sciencenter's Sagan Planet Walk is a walkable scale model of the solar system, located in Ithaca, New York. The model scales the entire solar system—both planet size and distances between them—down to one five billionth of its actual size. Consisting of 11 obelisks situated along a 1.18 km (0.73 mi) path through the streets of downtown Ithaca, the Planet Walk leads from the sun at Center Ithaca to Pluto at the Ithaca Sciencenter.

The exhibition was originally created in 1997 in memory of Ithaca resident and Cornell Professor Carl Sagan. In 2012, the model was expanded 7,630 kilometers (4,740 mi) to include a representation of the sun's closest neighboring star--Alpha Centauri—at the ‘Imiloa Astronomy Center at the University of Hawaii, making it the world's largest exhibition. In 2014, the inner planets and sun were removed as part of extensive construction being done to the Ithaca Commons, but have since been replaced. In 2015, a grant was approved to further expand the exhibition by installing an exoplanet Kepler-37d station on the Moon 384,500 kilometers (238,900 mi) away.

The scaled size of the sun is given by a 27.8 cm (10.9 in) diameter circular frame repeated at the top of each 6 ft (1.8 m) tall obelisk. Centered within each sun-sized frame, the proportional size of each planet is represented by a small sphere affixed in a glass window. All of the original planet locations were chosen not only for accuracy to scale but also to highlight local landmarks and public spaces within Ithaca. However, since the original installation of the Planet Walk the public library has moved to a new location, leaving Saturn no longer attached to a local landmark.

The obelisk for the Sun is located in the center of the Ithaca Commons, a pedestrian shopping area in the heart of downtown Ithaca. The round window representing the size of the sun at this station is roughly the size of a basketball, and in this obelisk only, contains no glass. All the subsequent obelisks in the solar system model have sun-sized glass windows containing their respective planets for the sake of comparison.

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