StarWatch: Moravian College Astronomy

APRIL 2022

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lunar phases

1337 APRIL 3, 2022: Happy Moon, Smile Down on Me: There is a curious lunar phenomenon that is best seen in late winter and early spring, and becomes most prominent nearest to the vernal equinox. I call it the “Smiley Moon.” I first heard the phrase about a dozen years ago from a remark made to me by a woman at church who had seen the moon smiling down on her several nights previously. I chortled internally at first, but then realized that my conversations with acquaintances are often laced with comments about odd things that they have witnessed in the sky when they know that I teach astronomy. I actually enjoy these types of dialogues because many times I get the opportunity to explain the observations which they have viewed, and sometimes buried within what was perceived, is the discovery of a real “diamond in the rough.” Such was the case with the smiley moon. • Later that same evening, my wife, Susan, and I were catching a program on the tube. Our living room window faces west and through the gauzed curtains, I could see a horned moon, well before first quarter that was presenting a wide grin above the treetops just like a Halloween pumpkin, but obviously without any teeth. I made two imaginary dots above it for the eyes, and voila; there it was, the smiling moon shining down on me. I remember getting up and going outside, just a little bewildered, thinking something like, “You’ve been watching the moon all of your life, Gary, photographing it and observing it through telescopes, and you never put that idea together?” • The explanation is really quite simple. In late winter and early spring, the plane of the Earth’s orbit called the ecliptic, which represents the sun’s yearly path against the stars and is very nearly the moon’s monthly orbital path across the sky, is tilted at a steep angle to the western horizon. As the moon rapidly pulls up and away from the sun after its new phase, the crescent or horned shape, which forms as the result of the sun’s light reflecting from the moon’s surface, is nearly parallel to the horizon, creating the smile. • Starting tonight, April 3, about an hour after sundown, look for a thin smiley moon near the horizon, but high enough that you will not have to seek a special location for its observation. During the next several days that follow, the moon will appear higher in the heavens with an even wider grin until it reaches first quarter on April 9. The effect, however, will become less pronounced near its setting time. You will also have to stay up later to catch the moon near the horizon where the effect is most pronounced. Binoculars will make the view more enjoyable and also allow you to observe the new moon in the old moon’s arms, the reflected light from a nearly full Earth reflecting back to us from the unlit portions of the moon. This can also be seen easily with the unaided eye if conditions are very transparent, and the crescent phase is thin. Consider having some fun with the smiley moon tonight! It’s a real hoot and also another astronomical sign that spring has arrived! Ad Astra!

1338

APRIL 10, 2022: God and the Universe

Over the course of several weeks, I have been writing about our strange universe and how over a century, physicists have been attempting to understand its creation and evolution. Do we live in a multiverse, simultaneously coexisting along with many other universes? Can we understand the conditions that existed before the Big Bang, the event that started our present universe on its expansion and eventual acceleration? Is our universe nothing more than a giant computer simulation similar to the concepts evoked in the Matrix films or is the cosmos merely a graduate student’s advanced science thesis, someone who lives in an ultra-intelligent civilization that is trying to understand the many pathways that sentient life can follow? Don’t laugh at these ideas because the question regarding us living in a matrix had a 50 percent endorsement from scientists in one survey. • Most tomes are sterile in their description of the universe and none of them except Michio Kaku’s book, The God Equation, has ever discussed with any compassion whether the universe is sentient, whether there was a primal designer, or whether God exists. • “I couldn’t imagine living in a world where God didn’t exist. I wouldn’t want to,” was Palmer Joss’s answer to Eleanor Ann Arroway’s query about humanity’s need to self-delude itself by inventing an infinite being for its own spiritual comfort (Contact, 1997). On this sentiment, I am definitely on Palmer’s side of the debate. I do believe in a sentient universe, in God. The conflict between science and religion is eloquently portrayed in the feature film, Contact, where Palmer, “...a man of the cloth without the cloth,” defines both religion and science as disciplines that are engaged in the “pursuit of truth.” • The main tenant of religion, faith, is believing in something for which there is no provable outcome or reasons for its existence. The foundations of science are based upon empirical observations and stipulate testable hypotheses to prove their validity. The matrix universe, our existence occurring because of some advanced alien science project, or string theory uniting the four forces of nature are all untestable at the present time, yet stand as viable hypotheses in the minds of many of our finest physicists. Why is it so difficult for these same individuals to believe in God or a benevolent governing force which permeates the universe? These are rhetorical questions for which I have no answers although in a survey of some 3567 physicists and biologists living in the US and the United Kingdom, only 10 percent of the respondents had no doubts about the existence of God. • One condition that we will all face is dying, the sobering realization that the universe will shortly continue without us being present in a corporal sense. A friend of mine, Nicholas Knisely who obtained his Master’s Degree in physics with the hope of continuing his research in quantum mechanics, but instead became an Episcopal priest, and is now Bishop of the Diocese of Rhode Island, has a very interesting position regarding what happens when we die. He feels that our souls transition from the corporeal world of space and time to become a part of the invisible world of other dimensions that exists all around us but which will forever be invisible to our senses. You do not have to believe in string theory to accept his ideas, but you do have to have faith that there is more to our universe than simply meets the eye. Ad Astra!

1339 APRIL 17, 2022: What Year Do We Really Follow?: When we think about the year, we normally consider that it is the period of time required for the Earth to complete one orbit around the sun (with respect to the fixed stars). And indeed, that is the definition of the sidereal year, the word “sidereal” coming from the Latin, sidus, meaning star. It has 365.256363004 (365.26) days if you really want to get technical, a longer interval of time than the less accurate Julian Calendar which was used to mark the year and inaugurated by Julius Caesar on January 1, 45 BC. It contained 365.2500… days, 365 or 366 days in a year depending upon a leap year day that occurred on years evenly divisible by four. • The problem with the Julian year was that it gained on the sun, meaning that seasonal holidays like Christmas would cycle forward through the years. This effect can be seen in Christian orthodox religions that still follow the Julian calendar. The Julian Christmas in 2022 will be celebrated, based upon the present Gregorian calendar, on January 7, 2023. By the year 2100, this date will move forward to January 8. The Julian calendar gains one day every 128 years. Easter, which was set by the sun’s crossing of the vernal equinox marking the first moment of spring, would get closer to the celebration of Christmas. Something had to be done to correct this error. • Enter the Gregorian calendar which was introduced to Catholic countries in 1582 by Pope Gregory XIII, dropping leap years that occurred on century years that were not evenly divisible by 400, making this calendar accurate to one day in 3236 years. A modern Gregorian year “approximates” 365.242189669781 days. However, both the Julian and Gregorian calendars are not following the true orbital cycle of the Earth, the sidereal year which contains 365.26 days. • The Julian and Gregorian calendars marked the tropical year, the period of time required for the sun to cross the vernal equinox twice. This crossing denotes the first moment of spring when the sun is positioned directly over Earth’s equator as it transitions from favoring the Southern Hemisphere to shining more directly over the Northern Hemisphere. The vernal equinox actually slides westward by a very small amount each year, completing one cycle around the heavens in 25,772 years. This is called the precession of the equinoxes. • So what would happen if the sidereal year, the true orbital period of the Earth, was used to define the year? The fixed holiday dates like Christmas and the Fourth of July would slide backwards against the seasons, meaning that we would eventually be celebrating Christmas in the heat of summer. Because we use the tropical year, a year that is fixed to the seasons, only the stars will change their appearances. Christmases of the future will see the holiday still occurring at the start of winter, but with the autumn stars serving as a backdrop of the nighttime sky. • There are other years like the anomalistic year, which is the interval from Earth’s closest position to the sun, perihelion to perihelion. That cycle equals 365.25964 days, while the eclipse year, the moon’s crossing of the plane of the Earth’s orbit from south to north, ascending node to the ascending node, equals 346.62007 days. The Gregorian calendar, our civil (governmental) calendar, now the most widely accepted timetable in the world, is set to the tropical year, not the sidereal or any other year, keeping our daily routine just a little saner over long stretches of time and in nearly perfect step with the sun. Ad Astra!

1340 APRIL 24, 2022: All of the “Naked Eye” Planets Big and Small: The evening and morning skies are putting on quite a show with all of the “naked eye” planets visible between them this week. Normally that would not make headlines, but the easy viewing of the most elusive of them, Mercury, is what makes this an opportunity worth pursuing. • Above the western horizon, Mercury should be easily spotted about 30 minutes after sundown, just a little more than a clenched fist with the thumb on top held at arm’s length. The Messenger God never gets any more than 18 to 28 degrees away from the sun as it circles Sol. That depends upon whether its angle of greatest elongation, greatest angular distance from the sun, occurs when the planet is closest to the sun or farthest from Sol. Whether we see it easily or with great difficulty also depends upon how the plane of its orbit is tilted to the horizon. If the path is inclined at a low angle, as it occurs in the fall, it might be possible for the entire apparition to go unnoticed, especially for European observers at higher latitudes. However in the springtime, Mercury’s orbit is inclined at its steepest angle to the horizon. As Mercury comes around from the back of the sun and becomes visible in the west, it pulls away from Sol to race upward into the evening sky. That angle for us (40 degrees north latitude) in late April is currently about 75 degrees. So even though this maximum eastern elongation is only 20.6 degrees from the sun on April 29, Mercury will still be 14 degrees above the western horizon 30 minutes after sundown. Then on May 1, a one percent ultra, ultra-thin crescent moon stands below Mercury and six degrees above the western horizon 30 minutes after sundown. Binoculars should produce a spectacular view if your western horizon is unobscured. The following evening, May 2, the 4.4 percent illuminated crescent is only four degrees above and to the left of Mercury. That will also produce a memorable sight through binoculars. Look for earthshine, light reflected by the moon back to us from a nearly full Earth. Earthshine is seen on the unlit portion of the moon and gives it a dusky appearance. • There also is good viewing in the east this week during the morning twilight. Here you will find all of the other planets able to be seen with the unaided eye. On April 24, in order from lowest to highest in the sky, will be Jupiter, Venus, Mars, Saturn, and even the waning crescent moon. Be at your observing location with an unobscured east to southeast horizon about 40 minutes before sunrise. Locally for the Lehigh Valley, that is about 5:30 a.m. By April 25th, the waning crescent moon will have moved between Mars and Saturn, then joining Mars and Venus/Jupiter on the 26th, and hugging the horizon under Jupiter on the 27th. Watch as Jupiter and Venus approach each other to within a half degree, the angular diameter of the moon, on April 30. All of these events will make for better viewing if you own binoculars, but use a telescope if you have one for April 30. In the same field of view, you will witness Jupiter, its four Galilean moons of Io, Europa, and Callisto on the Venus side of Jupiter, and Ganymede on Jove’s other side, as well as the Goddess of Beauty herself in its waning gibbous phase under the brightening dawn sky. Enjoy! Ad Astra!