Chicagohenge: A Solar Phenomenon in Urban Planning

Chicagohenge Explained

Each year in Chicago, the sun creates a captivating effect known as ‘Chicagohenge’. During this event, the sun rises and sets straight down city streets such as Kinzie and Madison. This alignment happens one or two days each year, notably observed on September 22, 2017. The term ‘Chicagohenge’ draws inspiration from England’s Stonehenge, known for its solar alignment.

The Equinox Impact

The fall equinox marks shorter days and seasonal changes. It offers cities like Chicago a chance to witness sunrises and sunsets aligning with east-west running streets. Geoff Boeing, chair of the Department of Urban Planning and Spatial Analysis at the University of Southern California, notes how humans feel a unique connection with these celestial alignments. These alignments frame the universe in a literal sense.

Street Design and Solar Alignments

Michelle Nichols, senior director of public programs at the Adler Planetarium in Chicago, emphasizes that Chicago’s street design, which follows cardinal compass points, enables the ‘Chicagohenge’ effect. She explains that the tall buildings accentuate the experience, framing the sun as it rises or sets.

To witness the phenomenon, a wide street running east and west is essential. Elevation, like standing on a bridge or high platform, enhances the viewing experience.

The Historical Perspective

Many cities are designed in ways that connect to the skies. Boeing highlights that ancient cities often followed cosmic urban plans. Tenochtitlan, the precursor to Mexico City, exemplifies careful planning with astronomical knowledge.

Modern cities create their own points of connection between urban structures and celestial features. Even unintentional alignments during the equinox bring similar effects. Nichols suggests these occurrences remind us of the presence of the sky.

Understanding ‘Henge’ Alignments

Pixels align the streets, like Chicago and Denver, closely with compass points, suitable for equinox viewing. Boeing’s analysis shows how 19th-century urban planning spread across regions in the U.S., offering orthogonal grids that enhanced infrastructure development.

Other cities use grids aligned with geographical features. For instance, ‘Manhattanhenge’ deviates from equinox dates due to unique city layouts.

Safety Considerations

With the popularity of capturing these solar moments, Nichols calls for mindfulness. Dramatic sunlit scenes should be photographed from sidewalks, not streets. Safety is crucial, especially for drivers experiencing sun glare on east-west streets.

Traffic backups may occur due to reduced visibility from the intense sunlight during these alignments. Awareness and caution can help manage these effects.