When the moon passes through the Earths shadow, it causes the moon to look very unusual for a short period of time. This event is called a lunar eclipse, and it occurs roughly twice a year. There is one viewable to folks outside of North America on June 15, so sit back and learn more about how lunar eclipses work in this video! This video is also available in stereoscopic 3D, viewable by many kinds of 3D devices, including common red/blue paper glasses that you might have lying around! To view this video in 3D, click here: Credit goes to TheWusa from de.wikipedia.org for the illustrations that this videos light scattering animations are based on.  This video is public domain and can be downloaded at: Like our videos? Subscribe to NASAs Goddard Shorts HD podcast: Or find NASA Goddard Space Flight Center on facebook: Or find us on Twitter: