Manhattanhenge is a phenomenon that occurs twice a year in New York City when the setting Sun aligns with the east-west streets of Manhattan, creating a stunning visual effect. The term "Manhattanhenge" was coined by astrophysicist Neil deGrasse Tyson.
The occurrence of Manhattanhenge can be explained by the geometry of the city's street grid combined with the tilt of the Earth's axis and its orbit around the Sun. Here are the key scientific explanations:
Earth's axial tilt: The Earth is tilted on its axis by about 23.5 degrees relative to its orbit around the Sun. This tilt causes the Sun's position in the sky to vary throughout the year. During summer solstice, around June 20-21, the Sun reaches its highest point in the sky (at its maximum altitude) during the day. Conversely, during winter solstice, around December 21-22, the Sun is at its lowest point in the sky (at its minimum altitude). These are the times when Manhattanhenge occurs.
Alignment with the street grid: Manhattan's street grid is primarily aligned with the cardinal directions of north, south, east, and west. The east-west streets of Manhattan create an opportunity for the setting Sun to align perfectly with the city's streets during the solstices. When the Sun is aligned with the streets, it appears to be framed between the buildings, creating a stunning effect where sunlight extends along the entire width of the street.
Horizon view: To observe Manhattanhenge, the view must be unobstructed toward the west-northwest (for the full Sun alignment) or the west-southwest (for the half Sun alignment) along the major cross streets, such as 14th, 34th, 42nd, and 57th streets.
It's important to note that while Manhattanhenge is a captivating phenomenon, it is a product of the Earth's axial tilt and the city's layout rather than a purely scientific term or concept. Similar alignments with the Sun can be observed in other cities with east-west street grids as well.