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FEBRUARY 2, 2020: Not So Mysterious a Moon
Last Friday evening, friends of mine, Peter Detterline, David Fisherowski, and I returned from
, a wonderful Italian restaurant in Douglassville, PA. It’s one of those places where I have never had a disappointing meal. Over dinner our discussions revolved around a grant that Peter and I were applying for that would help to advance astronomy and research opportunities for the College. Were we all in agreement? Were we all on the same page? How could we get the biggest bang for our buck? At the end of dinner there was consensus on how we were going to proceed. Returning from our meal, the darkened fields surrounding Pete’s home were lit in an eerie blue wispy light, with clouds of mist hovering near to the ground, a surreal “Halloweenish” type of appearance. Pete glanced up at the undefined globe of light that was shining through the clouds and remarked, “There goes Betelgeuse.” It brought a spontaneous burst of laughter against a backdrop of what had been a mostly serious but enjoyable conversation that evening. Pete was right; the diffuse moonlight was about the correct brightness for Betelgeuse going supernova. I used to hate the moon, the bane of my existence for making any type of astronomical observation, until one day it dawned on me that the moon itself could be a fun object to watch with just the unaided eye or through a telescope. Pete has sketched it, and he and Dave have taken a wonderful set of images of its surface. I have been more of a telescopic gawker when it comes to viewing its surface, although wide-field photography has played a part in my lunar observations. Telescopically, I’m always amazed at the sharp, crisp detail of crater walls casting jagged shadows across the barren expanses of a smooth crater floor. It brings out the explorer in me. What would I feel like walking on its surface? The detail is particularly vivid when the air is steady with the telescope focused on the moon’s terminator, the region where night is changing into day, and shadow details are most pronounced. It is something I want my learners to witness. The moon brightens and dims in a regular pattern of shapes or phases as the nearside, which is always pointing in our direction, proceeds through its day and night cycles. To make this happen, sunlight reflects from different parts of its surface in a regular, prescribed fashion during its orbital cycle. Let me repeat that again. The moon moves through its phases because it is revolving—orbiting the Earth, and as we watch these series of events transpire, we are actually witnessing the day and night cycle occurring on the moon, something that takes only 24 hours on Earth, but averages 29.53 days for Luna to complete. It is so simple a concept that college students actually have difficulty grasping its straightforwardness. Third graders, however, don’t, as I witnessed from years of teaching in the ASD Planetarium, “my home away from home” for 38 years before coming to Moravian College. Next week, more about simple concepts regarding the moon which seem hard to grasp.
FEBRUARY 9, 2020: Don’t “Give Yourself to the Dark Side”
“It is the only way you can save your friends. Yes, your thoughts betray you. Your feelings for them are strong, especially for [your] sister. So, you have a twin sister. Your feelings have now betrayed her too. Obi-Wan was wise to hide her from me. Now his failure is complete. If you will not turn to the Dark Side, then perhaps she will”
(Star Wars: Episode VI – Return of the Jedi
, Lucasfilm, 1983).
No, no, no, Luke, don’t do it. Fight! The Force is strong within you. Feel its power. You know that the moon has no dark side, but many others are weak and need you as an example to lead them.
There are certain terms that astronomers use to describe the hemisphere of the moon that we see and the part of the moon which cannot be seen. The moon keeps its same face pointed towards the Earth, a function of tidal forces that caused Luna to rotate (spin) at a slower rate until the moon completed one rotation in the same amount of time necessary to complete one revolution. That happened 4.5 billion years ago as soon as the moon formed near to the Earth. Tidal synchronization occurs on Mercury, two orbits for every three rotations, the four largest natural Galilean satellites of Jupiter, and scores of other smaller natural satellites orbiting their planets throughout the solar system. All parts of the moon go through a day and night cycle. When the moon is new, in the same direction as the sun, the hemisphere that we never see is in full daylight. When the moon is full and opposite to the sun, and visible all night, the hemisphere that we do not see is in full darkness. As we observe the moon proceeding through its phases during the course of a 29.5-day period, we are simply observing the moon’s day and night cycles. The hemisphere (side) of the moon which we continually observe and is closest to us has been termed the nearside, yet in the many astronomy books about the moon that I own that term cannot be found in any of its indices. However, nearside is recorded in the
Facts on File, Dictionary of Astronomy
and in the online
Oxford English Dictionary
, but not in
. That’s not my gripe, however; it is the term given to the hemisphere that we cannot see which most people call the dark side. Thankfully, that term cannot be found in any of my books on the moon nor in the dictionaries cited above. My guess is the term originated from sayings like “darkest Africa,” where human knowledge was lacking about an area that was mysterious. Darkest Africa was also popularized by the explorer, H. M. Stanley, of Stanley and Livingstone fame. Today astronomically, the term dark side of the moon is obsolete, associated with a hemisphere of the moon that never receives sunlight. Nothing could be farther from the truth. So don’t give into the dark side, but embrace the light of the FARSIDE. That is where the truth lies Darth Vader. Luke knew that all along.
FEBRUARY 16, 2020:
FEBRUARY 23, 2020: