During a lunar eclipse, which is when the Earth lines up exactly between the moon and the sun, the moon appears darker because the Earth obscures the sun with its shadow. Only light from Earth’s atmosphere reaches the moon, which can tint the moon reddish with light reflected from sunsets and sunrises on Earth.

While glasses were absolutely necessary for last year's solar eclipse, they are not needed to safely view this year's total lunar eclipse.

Earth’s shadow will block most of the light that illuminates the lunar surface, creating what is known as a blood moon.