Wednesday, December 1, 2010

Winter Solstice AND Lunar Eclipse

We’re heading to what the ancients might call a magical time. On December 21, during the longest night of the year, our round white Moon will rise and then darken into red for several hours.

This is the rare combination of a total lunar eclipse, when the Moon passes through the Earth’s shadow, and the Winter Solstice, the time at which the Sun is at its southernmost point in the sky.

“The Moon often looks blood-red during a lunar eclipse,” says Marc Taylor, Coordinator of the Andrus Planetarium at the Hudson River Museum. “It’s colored by the clarity of the atmosphere, and every earthly sunrise and sunset taking place at that moment.”

The geometry is like this, he explains.

MOON EARTH <---- [93 million miles] ---> SUN

The eclipse will become noticeable at 1:33 AM on December 21st. The darkest part will take 72 minutes. Unlike a solar eclipse, a lunar eclipse is totally safe to watch. “Through binoculars, the Moon will look brighter and you'll see more detail, but a lunar eclipse is really about the overall experience of seeing a darkened Moon hanging in the sky. It's best viewed with the unaided eye,” says Taylor.

In order for an eclipse to happen, there MUST be a full moon.

We know that the tides are caused by the gravitational pull of the moon. So does that mean that we will notice a higher tide on the Hudson River on December 21?

“Yes,” says Vicky Garufi, Beczak’s Director of Education, “although it may not be very noticeable here in Yonkers. Both the Moon and Sun cause tides on Earth’s waters. When the Earth, the Sun and the Moon are in alignment, the combined gravitational pull creates very high and very low tides. This is called a spring tide—the name has nothing to do with the season.” (Read more here.)

“There won't be another eclipse coinciding with a solstice (winter OR summer) until 2094. And that one will only briefly be visible from the East Coast,” says Marc Taylor. So stay up late or get yourself out of bed to look at the sky on December 21—you won’t have another chance for 84 years.

—Lenore Person

All around the world, the long dark night of the Winter Solstice causes people to gather around candles or bonfires to feast and “sing back the sun.” Beczak Environmental Education Center takes part in this tradition with its Winter Solstice Celebration on December 19.