This week’s question was asked by friends.
QUESTION: What is meant by a Super Blue Blood Moon?
ANSWER: It will be a special sight in the early morning hours of Wednesday, Jan. 31. The last time this rarity occurred was 150 years ago in 1868, when Andrew Johnson was president, having inherited the office when Abraham Lincoln was assassinated. Three things will be going on at once.
First, a blue moon is a second full moon occurring in the same month. It has nothing to do with the color blue. A blue moon happens every 2.5 years.
Secondly, a super moon, like the one visible on New Year’s Day, 2018, and again on Jan. 31, is the term used when a full moon is closest to the Earth in its orbit, making it appear a tad bigger and brighter than normal.
Thirdly, there will be a lunar eclipse. The Earth lines up between the sun and the moon. The Moon moves into the shadow of the Earth. Put another way, the light from the Sun that normally hits the lunar surface is blocked, casting a shadow over the Moon.
Where does this “blood moon” idea come from? During a total lunar eclipse, the Earth blocks all direct sunlight from hitting the Moon’s surface. However, the Moon does not turn completely dark. Some sunlight still reaches the Moon’s surface, but it must pass through the Earth’s atmosphere.
The shorter wavelengths of light, the blue colors, are scattered in every direction. The bluish colors are filtered out, while the longer wavelengths of red and orange get through. It’s the same phenomena that gives us red sunrises and sunsets. The Moon takes on a reddish hue, almost copper penny color, as the longer wavelengths strike the Moon’s surface. The Moon has a “blood” hue to it.
What about the Super Moon concept? The orbit of the Moon around the Earth is not a perfect circle. It is an ellipse, or oval path. Once a month the Moon will be closest to the Earth, called perigee. Once a month the Moon will be farthest from the Earth (apogee). On Jan. 31 the moon will be about 223,000 miles away from Earth, compared to an average distance of 239,000 miles, and the greatest distance of 252,000 miles. Linus’ “great moon rising out of the pumpkin patch” in late January will appear about 14 percent bigger than normal.
The best views of the Super Blue Blood Moon will not be in the United States, but rather New Zealand, Australia, Indonesia and eastern Asia. For most of the United States, the total lunar eclipse will take place at a time very close to when the moon is setting on the western horizon.
What can we expect in Monroe County on the morning of Jan. 31? Look slightly above the west-northwest horizon. The eclipse will begin at about 4:50 a.m. Totality, when the Moon moves completely into the Earth’s shadow, starts at 6:51 a.m. and reaches maximum at 7:20 a.m. You will recognize that it is daylight by that time. The Moon slips below the western horizon at 7:23 a.m.
We here in the Tomah and Sparta area will see some of the eclipse, better than those on the east coast, and not a good as Americans on the west coast. That’s assuming we have good weather.
No precautions are necessary to view a lunar eclipse, no special glasses needed, as was necessary during the total solar eclipse in August 2017. Try to pick a location of highest altitude, say the top of a building, or up on Hwy. A, south of Tomah. It’s best to have clear unobstructed view of the western sky. Perhaps get away from city lights, use binoculars, dress warm, and take some coffee, tea or hot chocolate.
The term blue moon goes back to the 1500s, and in more modern times with the publication of Pierce Egan’s 2-volume Real Life in London books. In one book, a character says to another, “How’s Harry and Ben − haven’t seen you in a blue moon.” Since then, the phrase has a meaning of “rarely.”
Send questions and comments to: firstname.lastname@example.org.
Larry Scheckel is a retired Tomah High School physics teacher.