Each month I will describe sights of interest in the night skies of South Carolina. These sights will be broken down into three sections; what you can see with the naked eye, with binoculars, and with a small telescope. The best time to view the night sky is at and around the times when the Moon is not visible, what is known as a New Moon; which will occur this month on September 13. For September, your best viewing nights will be from September 6 to the 17. The Star chart below is set for Florence, SC on September 15 at 9 pm.
There will be a total eclipse of the Moon on the night of September 27. For an amateur astronomer this is a pleasant celestial event; the lineup is shown below.
For the non-astronomers the media tends to embellish celestial events. I predict that the media will have a field day with this eclipse. First of all this month’s eclipse occurs when the Moon is at perihelion; closest to the Earth. At its closest approach, the Moon is only 5% closer than the average Earth – Moon distance. Your eyes may or may not perceive that the Moon appears closer and therefore larger at perihelion. However the media will not mention average Moon distance or percentages, but they will instead call it a “Super Moon”! Therefore this will be a “Super Eclipse”! This hype is deceptive, but at least it is based on orbital mathematics.
I predict that the second media hype will be directed at the subject of a “Blood Moon”. What is a Blood Moon? It’s the new media term for a total lunar eclipse. Most total lunar eclipses have a reddish brown color. One might logically think that if the Earth totally blocks the light of the Sun from reaching the Moon, then the Moon should look black during a total lunar eclipse. If the Earth had no atmosphere, then this would be true. However, the Earth’s atmosphere acts like a lens and bends the Sun’s light around the Earth. We know from red sunsets that only the longwave red and orange can penetrate farthest through our atmosphere, therefore the small amount of light that reaches the Moon during a total lunar eclipse would have a reddish color; no blood, just physics, see below.
The next media hype is to add myth/prophecy to this month’s lunar eclipse. Lunar eclipses are somewhat rare, but four in a row about six months apart are really rare and are known as tetrads. This is being reported as a sign of some upcoming doom. Many celestial events have been used to portend some prophetic event. Some examples are: lining up of planets, comets, eclipses and meteor storms.
First, concerning rarity, this is the second tetrad in this century, and there will be six more before the end of this century; so this appears to be a doomed century. The media may also remind you that this Blood Moon tetrad coincides with some spring and fall religious holidays. Therefore, a tetrad that also overlaps these religious celebrations is so rare that it must be pointing to a doomsday event. Back to math and orbital calculations: In the last 2000 years we have had eight tetrads that have totally coincided with religious holidays, and the Earth is still here. My comments are not to minimize any beliefs; but are instead to make you aware that this tetrad is only a mathematical orbital coincidence.
At ScienceSouth we have an apparatus known as a wave pendulum; see two examples below.As all the balls are set in motion at the same time, they each swing in their own unique period, based only on the lengths each pendulum. However, after several swings, the periods of some of the balls begin to match up with other balls resulting in many different synchronized swings. This synchronization effect is analogous to the effects that result in eclipses of the Sun and Moon, and tetrads.
So go out and enjoy a fun celestial show and leave all the hype to the non-scientific branch of the news media.
It’s a ball!!!
I will make a final prediction for this month’s column. I predict that what I am about to tell you next about this month’s lunar eclipse will not be mentioned by any other non-science or science columnist!
First some background: If the Moon is a sphere, why don’t we see it as a three dimensional ball in the sky, instead of a flat disk? Most people say because it is too far away to see the curvature, but this is not so.
The first Moon landing finally cleared up this question. When the astronauts walked on the Moon, they noticed that the surface is covered with a fine powder. This fine dust tends to diffuse/scatter the bright Sun’s reflected light, called Lambertian reflection. A surface which gives equal reflectance at all observing angles is Lambertian reflectance, and this is what prevents us from seeing the Moon as a ball. Now, during a total lunar eclipse, the Moon is only dimly lit by a small amount of reddish sunlight refracting/bending around the Earth’s atmosphere. Under this low light, the bright diffuse reflected light is gone and a spherical Moon can sometimes become apparent. Observing a three dimensional Moon during a lunar eclipse is best achieved when the Moon is high in the sky from 10 pm onward, and this month’s eclipse will be in totality from 10:11 pm until 11:23 pm. There are many other variables in play but the timing of this eclipse sets up a great chance of seeing this effect.
So check it out this month, and for the first time in your life you may see the Moon as a sphere.
Naked Eye Sights: Lunar eclipse
Binocular Sights (7 to 10 power): Lunar eclipse
Telescope Sights (60-100mm): Use the hour of lunar darkness to check out your favorite targets.