Tomorrow (September 23, 2011) is the September equinox (also referred to as autumnal in the northern hemisphere)—the moment in time when the sun crosses the equator and heads southward along its path. At this moment, which officially occurs at 9:04 am Coordinated Universal Time (UTC), the Earth’s axis is perpendicular to the line connecting the centers of the earth and sun. On this day, it is possible to calculate one’s latitude by determining the angle of the shadow cast by the midday sun.

Tomorrow, I will gather up some willing scientists and follow the procedures listed in the online activity Noon Shadows on the Equinox. If you have time during the day on Friday, I hope you’ll join me in this easy activity! If you do, make sure to post your results on the Equinox Shadow Data page.

Resources:

• Noon Shadows on the Equinox: http://ux1.eiu.edu/~tmccollum/equinox/noon_shadows.html
• timeanddate.com—September Equinox: http://www.timeanddate.com/calendar/september-equinox.html