The Cockrell Sundial at the Houston Museum of Natural Science

Guiding the Houston Museum of Natural Science (HMNS) as CEO and president, Joel A. Bartsch manages an expanding collection that has been in place for more than a century. One of the permanent features that Joel Bartsch oversees is the Cockrell Sundial.

Created from black granite in 1989 and unveiled at the Autumnal equinox, the sundial was a collaborative project of HMNS and Rice University staff members. A major feature of the outdoor sundial is the gnomon, which has an angle precisely designed for its location. As the sun shines on the gnomon, the shadow cast intersects with hour lines, which are marked with Roman numerals.

While the sundial cannot reflect daylight savings time, it does have a feature that makes its time more accurate. This is a brown line that points in a due north direction, with the noon line offset from that.

This reflects the fact that Houston is within a standard time zone based on the Earth’s rotation that reflects the longitude of New Orleans and Memphis, rather than the city’s actual location. In those other cities, the noon line is exactly due north. In Houston’s case, the noon line is offset at 95oW from true north to compensate for this geographical difference within a unified time zone.