Right outsideSky
Your own shadow by full moonlight
When: All year
On a clear night at full moon, moonlight is bright enough to cast a sharp shadow of you on the ground. Moonlight is sunlight reflected off the Moon, hundreds of thousands of times fainter than direct sun.
Why this time of year
This is a full-moon card: it belongs only to clear nights of the full moon, in any month of the year.
How to notice it
- Pick a spot that is already dark, away from porch lights and streetlights, with a clear view of the Moon.
- Without looking straight at the Moon, look at a pale or bare patch of ground such as a path or driveway for your shadow, on the side of you away from the Moon.
- Wave your arms and watch the shadow move.
- Look at the colors around you. In moonlight they look muted because the eye's dim-light cells do not see color.
Try this with kids: Can you make your shadow wave at you by moonlight? Can you tell what color your coat is?
Good to know: The eye's dim-light cells, called rods, see brightness but not color.
Safety
- Walk carefully at night: a flashlight is fine for getting there (a red light keeps night vision best), and watch for uneven ground, roots, and roads.
- Kids should go with a grown-up and stay on familiar ground.
Sources
- science.nasa.govNASA: 'Moonlight is actually reflected sunlight'; 'a full moon directs enough sunlight towards our planet to cast sharp shadows on the ground.'
- montana.eduJoseph A. Shaw, Montana State University, Optics & Photonics News Nov 2005: moonlight 'about 463,000 times weaker than sunlight, is not bright enough to stimulate our color vision'; rods see dim light without color.
- nps.govNational Park Service: 'Give your eyes 30 minutes to adjust to the darkness'; a red-light headlamp or red-film flashlight keeps night vision.
Checked against these sources on October 2, 2026.