Why is the Sun's Light Exactly at this Spot on My Wall

June 12, 2024


DaleH_epod_image0 (03C)

Photographer: Dale Hugo 
Summary Author: Dale Hugo

First of all, it’s the date of the spring equinox and the Sun is setting due west, therefore my west-facing octagonal window projects the sunlight straight across the entryway to the wall beyond. We have a raised ranch type house, so the front door is behind me and below.

But the real reason dates back to 1787 and the Northwest Ordinance given by George Washington to the U.S. Congress. President Washington was a former surveyor, and the first thing described in the ordinance is how to lay out the pattern of boundaries for settling the land in the territory to the north and west (what would later become the states of Ohio, Indiana, Michigan, Wisconsin Illinois, and Minnesota). The ordinance specifies straight north/south and east/west boundaries to sections of land that are 1 mile on a side. The sections were originally sold for $1 (one U.S. dollar) per square mile! 

Here in the state of Illinois, the patchwork of farms, townships and roads are all on this layout. Naturally a subdivision such as mine has streets that are parallel to the original roads and the street in front of my house is exactly north/south. Thus, sunlight lines up east-west to correspond to the equinoxes, and that’s why it projects this sunbeam to that same place exactly on the date of the spring and fall equinox. Photos taken on March 19, 2024.

Arlington Heights, Illinois Coordinates: 42.0884, -87.9806

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