On the morning of December 21, there will be a total lunar eclipse.

This eclipse will be the second to occur this year. However, it will be the first total lunar eclipse to occur during a winter solstice since 1638, according to NASA.

Robert Antonucci, a professor of physics at UCSB, said the eclipse will begin at 11:40 p.m. and will end at 12:53 a.m.

According to Robert Geller, a professor of physics at UCSB, a lunar eclipse occurs when the Earth casts its shadow upon the moon as a result of being positioned between the Sun and the moon.

“[A] lunar eclipse occurs when a shadow in sunlight, cast by the Earth, falls onto the moon. With the moon in the shadow, it appears dark. All three objects must be lined up: the Sun, Earth and moon, in that order, all on a straight line,” Geller said. “Due to orbital dynamics, this special alignment only occurs a couple of times a year. Predicting lunar eclipses is done most accurately by modeling the orbital dynamics and looking for occurrences of this special alignment.”

However, contrary to popular belief, the moon will not just disappear from the night sky, but rather become very red in color, Antonucci said.

“If you look at a star through a dust cloud, the star will appear more red. The dust scatters the blue light coming from the star due to the blue light’s small [wavelength]. The red light is bigger and has longer wavelengths that allow it to oscillate past the particles. This same process occurs when sunlight passes through the Earth’s atmosphere,” Antonucci said. “The Earth’s atmosphere scatters the blue light and lets the red light hit the planet directly. This is why the Sun would appear more red to people on Earth than it would to astronauts. And this effect is also what causes our sky to be blue with all the scattered blue light in our atmosphere. When the Earth’s shadow passes in front of the Moon it blocks all direct light coming to the Moon. But there is still light shining through the Earth. This light that hits the Moon after having gone through the atmosphere is all red light and thus gives the Moon its red color during an eclipse.”

The eclipse may be masked by current weather conditions within California, but many are still hoping to observe it, seeing as a lunar eclipse during a solstice is significantly rare.