Noon Shadows on the JR

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.

diagram of noon shadow at equinox

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:

Comments

Great graphic!

Hi Jenn,

Love the Earth, JR and sun graphic!

Leslie

thanks, leslie!

it took me a while to figure out all the angles and math involved, so i decided to make up a graphic to help everyone else figure it out!