34 Shade Planning for America’s Schools Chapter 5 THE EARTH-SUN RELATIONSHIP For any shade planning team, the primary objective is to ensure that shade falls in the right place, at the right time of day, throughout the year. A shade planning team should include members with at least a working knowledge of the Earth’s relation to the sun. This chapter is designed to: • Graphically illustrate the effects of daily and seasonal changes in solar angles on the length and direction of shadows. • Provide a basic introduction, or reintroduction, to the Earth’s relationship to the sun and solar geometry. • Provide a list of resources that can assist the planning team in ensuring that shade falls in the right place, at the right time of day, throughout the year. Latitudeis a north-south measurement of any position on the Earth. Measured in degrees, latitude is 0° at the equator and 90° at the North and South Poles. The line that connects all locations of the same latitude is called a parallel. Shade planning teams will need to know the latitude to determine where a tree or structure will cast its shadow throughout the day. Longitudeis a west-east measurement of any position on the Earth. The line that connects all locations of the same longitude is called a meridian. Longitude, like latitude, is measured in degrees, with 0° occurring at the Greenwich Meridian or Prime Meridian. Measurements of longitude range from Prime Meridian at 0° to 180° going either west or east. The 180th meridian east is the International Date Line. Shade planning teams will need to know their longitude to determine solar noon. Solar Noonis the time of day when the sun is aligned with true north and true south and is specific to each longitude. In the northern hemisphere, a shadow cast by a vertical pole at solar noon will point toward true north. Solar noon is also the midpoint between sunrise and sunset. Key Terms and Concepts
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