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What the equinox 'henge' effect tells us about U.S. cities
NPR • • science
Key Points:
- The fall equinox marks shorter days and seasonal change, and in some U.S. cities like Chicago, sunrises and sunsets align strikingly with east-west streets, creating phenomena such as "Chicagohenge."
- This alignment is due to city grids oriented along cardinal directions, a design rooted in ancient practices where cities were planned with celestial and cosmological considerations in mind.
- Modern city grids, especially in the Midwest and Great Plains, follow orthogonal layouts that unintentionally produce these solar alignments during equinoxes, offering a contemporary echo of ancient astronomical observances.
- Cities like Washington, D.C., Phoenix, and Denver also offer opportunities to witness "henge" moments, though some cities with grids aligned to local geography rather than compass points experience these phenomena on different dates.
- While the equinox sun alignment is popular for photography and social media, experts advise safety precautions such as avoiding standing in streets and being cautious of sun glare while driving during these times.
