Understanding Our Local Cosmic Community

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“All The Colors of the Night” HDR Capture of the Full Moon by Golden Spiral Photography

The idea of “time” will be laid out plain in my upcoming book, “The Truth About Everything“, but I think a good grasp on basic astronomy always makes things easier to understand; if even just to understand by proportion and magnitude alone, exactly how “time by design” works. I will continue this series as much as I think people need the background information (I know it helps me often just to look back on all this) and because this is basic astronomy and does not require much of a rewrite, I am not going to; I think it is best to have others that have said it best, say it here as well but in their own language.

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“Luna” – Golden Spiral Photography

Apogee and Perigee of the Moon

Apogee and perigee refer to the distance from the Earth to the moon. Apogee is the furthest point from the earth. Perigee is the closest point to the earth and it is in this stage that the moon appears larger. Looking at the moon in the sky without anything to compare it to, you wouldn’t notice any size difference. But the difference in size can in fact be quite significant. If you were to photograph a full moon at apogee and perigee (using the same lens), here’s the difference:

full moon at apogee and perigee
Astronomers have formulas for computing the exact distance at any point in time, but the average distance from Earth is 237,700 miles (382,500 km).

Effects of Apogee and Perigee

The apogee and perigee of the moon have an effect on the tides here on Earth. When the moon is at apogee, the furthest distance from the Earth, it has less gravitational pull which, along with other factors that influence the tides, can contribute to lower tides or lower variation in the high/low tide level. When the moon is at perigee, closer to the Earth, there is much more gravitational pull which contributes to the opposite effect: higher tides or greater variation in the high and low tide.

(Excerpt taken from: http://www.moonconnection.com/apogee_perigee.phtml)

The gods Máni (left) and Sól(right), the personified Moon and Sun in Norse mythology, as depicted in an illustration by Lorenz Frølich(1895)

The Moon’s regular phases make it a very convenient timepiece, and the periods of its waxing and waning form the basis of many of the oldest calendars. Tally sticks, notched bones dating as far back as 20–30,000 years ago, are believed by some to mark the phases of the Moon. The ~30-day month is an approximation of the lunar cycle. The English noun month and its cognates in other Germanic languages stem from Proto-Germanic *mǣnṓth-, which is connected to the above mentioned Proto-Germanic *mǣnōn, indicating the usage of a lunar calendar among theGermanic peoples (Germanic calendar) prior to the adoption of a solar calendar. The same Indo-European root as moon led, via Latin, to measureand menstrual, words which echo the Moon’s importance to many ancient cultures in measuring time (see Latinmensis and Ancient Greekμήνας(mēnas), meaning “month”).

crescent Moon and a star are a common symbol of Islam, appearing in numerous flags including those of Turkey and Pakistan.

The Moon has been the subject of many works of art and literature and the inspiration for countless others. It is a motif in the visual arts, the performing arts, poetry, prose and music. A 5,000-year-old rock carving at Knowth, Ireland, may represent the Moon, which would be the earliest depiction discovered. The contrast between the brighter highlands and darker maria create the patterns seen by different cultures as the Man in the Moon, the rabbit and the buffalo, among others. In many prehistoric and ancient cultures, the Moon was personified as a deity or other supernatural phenomenon, and astrological views of the Moon continue to be propagated today. The Moon has a long association with insanity and irrationality; the words lunacy and loony are derived from the Latin name for the Moon, Luna. Philosophers such as Aristotle and Pliny the Elderargued that the full Moon induced insanity in susceptible individuals, believing that the brain, which is mostly water, must be affected by the Moon and its power over the tides, but the Moon’s gravity is too slight to affect any single person. Even today, people insist that admissions to psychiatric hospitals, traffic accidents, homicides or suicides increase during a full Moon, although there is no scientific evidence to support such claims.

(Above excerpts from wikipedia – click on any of the hyperlinks to follow).

“Moon” by Johannes Hevelius

Now that I have provided a few basics of the moon let us continue to general orbits, alignments and conjunctions of our local celestial wonders.

Orbits, Alignments & Conjunctions

Looking down on the north pole of the Earth, we can say that the planets revolve around the Sun in a counter-clockwise direction – west to east. The orbital velocities of the planets range from about 48 km/s for Mercury to 5 km/s for Pluto.

The mean orbital velocity of Venus is 35.02 km/s. The orbits of all the planets lie very close to the plane of Ecliptic. Pluto’s orbit, at 17°09′, has the greatest angle of inclination to the Ecliptic. Although all planetary orbits are elliptical, most of them are almost circular.

The eccentricities range from 0.007 for Venus, which is the most circular, to 0.249 for Pluto, which is the most eccentric, and all are less than 0.1 except for Mercury and Pluto. Mercury has the shortest period of revolution (about 88 days), and Pluto has the longest (about 248 years). Planetary alignments can be characterized by two different methods of calculation.

The first way is typically what people first imagine when they hear the phrase planetary alignment, being the view-point of the solar system from above the Sun’s “north pole.” From this angle; the planets form a straight line from the Sun’s elliptical equator outward. The second type of alignment is one in which the planets follow a straight line traced out on the elliptical plane.

Since the planets have all orbital planes that remain symmetrically within a few degrees of the Earth’s orbital plane, they will appear to follow a straight line on the sky during certain time-periods of movement. This “straight line” is referred to as the ecliptic, which is represented as a great circle on the sky with the Earth at the center of this circle.

The apparent yearly path of the Sun through the stars is called the ecliptic. This circular path is tilted 23.5 degrees with respect to the celestial equator because the Earth’s rotation axis is tilted by 23.5 degrees with respect to its orbital plane. Be sure to keep distinct in your mind the difference between the slow drift of the Sun along the ecliptic during the year and the fast motion of the rising and setting Sun during a day.

ecliptic on the celestial sphere

The ecliptic and celestial equator intersect at two points: the vernal (spring) equinox and autumnal (fall) equinox. The Sun crosses the celestial equator moving northward at the vernal equinox around March 21 and crosses the celestial equator moving southward at the autumnal equinox around September 22. When the Sun is on the celestial equator at the equinoxes, everybody on the Earth experiences 12 hours of daylight and 12 hours of night for those two days (hence, the name “equinox” for “equal night”).

The day of the vernal equinox marks the beginning of the three-month season of spring on our calendar and the day of the autumn equinox marks the beginning of the season of autumn (fall) on our calendar. On those two days of the year, the Sun will rise in the exact east direction, follow an arc right along the celestial equator and set in the exact west direction.

Solar diurnal path during the seasons



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When the Sun is above the celestial equator during the seasons of spring and summer, you will have more than 12 hours of daylight. The Sun will rise in the northeast, follow a long, high arc north of the celestial equator, and set in the northwest. Where exactly it rises or sets and how long the Sun is above the horizon depends on the day of the year and the latitude of the observer.

When the Sun is below the celestial equator during the seasons of autumn and winter, you will have less than 12 hours of daylight. The Sun will rise in the southeast, follow a short, low arc south of the celestial equator, and set in the southwest.

The exact path it follows depends on the date and the observer’s latitude. Make sure you understand this. No matter where you are on the Earth, you will see 1/2 of the celestial equator’s arc. Since the sky appears to rotate around you in 24 hours, anything on the celestial equator takes 12 hours to go from exact east to exact west.

Every celestial object’s diurnal (daily) motion is parallel to the celestial equator. So for northern observers, anything south of the celestial equator takes less than 12 hours between rise and set, because most of its rotation arc around you is hidden below the horizon.

Anything north of the celestial equator takes more than 12 hours between rising and setting because most of its rotation arc is above the horizon. For observers in the southern hemisphere, the situation is reversed. However, remember, that everybody anywhere on the Earth sees 1/2 of the celestial equator so at the equinox, when the Sun is on the equator, you see 1/2 of its rotation arc around you, and therefore you have 12 hours of daylight and 12 hours of nightime everyplace on the Earth. The geographic poles and equator are special cases.

At the geographic poles the celestial equator is right along the horizon and the full circle of the celestial equator is visible. Since a celestial object’s diurnal path is parallel to the celestial equator, stars do not rise or set at the geographic poles. On the equinoxes the Sun moves along the horizon.

At the North Pole the Sun “rises” on March 21st and “sets” on September 22. The situation is reversed for the South Pole. On the equator observers see one half of every object’s full 24-hour path around them, so the Sun and every other star is above the horizon for exactly 12 hours for every day of the year.

tilt of Earth's rotation axis

Since the ecliptic is tilted 23.5 degrees with respect to the celestial equator, the Sun’s maximum angular distance from the celestial equator is 23.5 degrees. This happens at the solstices. For observers in the northern hemisphere, the farthest northern point above the celestial equator is the summer solstice, and the farthest southern point is the winter solstice.

The word “solstice” means “sun standing still” because the Sun stops moving northward or southward at those points on the ecliptic. The Sun reaches winter solstice around December 21 and you see the least part of its diurnal path all year—this is the day of the least amount of daylight and marks the beginning of the season of winter for the northern hemisphere. On that day the Sun rises at its furthest south position in the southeast, follows its lowest arc south of the celestial equator, and sets at its furthest south position in the southwest. The Sun reaches the summer solstice around June 21 and you see the greatest part of its diurnal path above the horizon all year—this is the day of the most amount of daylight and marks the beginning of the season of summer for the northern hemisphere. On that day the Sun rises at its furthest north position in the northeast, follows its highest arc north of the celestial equator, and sets at its furthest north position in the northwest.

Sunset positions throughout the year
The seasons are opposite for the southern hemisphere (eg., it is summer in the southern hemisphere when it is winter in the northern hemisphere). The Sun does not get high up above the horizon on the winter solstice. The Sun’s rays hit the ground at a shallow angle at mid-day so the shadows are long. On the summer solstice the mid-day shadows are much shorter because the Sun is much higher above the horizon.

Configurations

To locate the positions of a planet in its orbit relative to the Earth and the Sun, special positions, called configurations, have been defined. When a planet, as seen from the Earth, is in the same direction as the Sun, we have a conjunction. When an inner or inferior planet – that is Mercury or Venus – is on the near side of the Sun or passes between the Sun and the Earth, we have an inferior conjunction.

Since the dark side of the planet points in our direction it is invisible. When the planet is on the far side of the Sun – on the opposite side of the Sun from the Earth – we have a superior conjunction and it is again invisible to Earth-bound observers.

As the planet moves away from conjunction, its angular separation from the Sun increases. This angular separation, which is just the angle between the line joining the Earth to the Sun and the line from the Earth to the planet, is called the elongation of the planet.

When the line from the Earth to the planet is tangent to the planet’s orbit, the elongation has its maximum value and the planet is said to be at greatest elongation. At this special position Venus can be observed very well.

Configurations of the planets For a superior planet, like Mars or Jupiter the following configurations occur:

 

  1. Opposition, when the planet seen from the Earth is on the opposite side of the Earth from the Sun – in space the exterior planet and the Earth are on the same side of the Sun. That is the time you can observe the planet best, because it rises at sunset and sets at sunrise
  2. Western quadrature, when the planet is west of the Sun and forms a 90° angle with the Earth-Sun direction.
  3. Conjunction, when the planet is on the opposite side of the Sun from the Earth – the Earth, Sun, and planet are in a line and the planet is hidden by the Sun
  4. Eastern quadrature, when the planet is east of the Sun and forms a 90° angle with the Earth-Sun direction.

(This portion of the article comes from http://www.astronomynotes.com/nakedeye/s5.htm)

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Kepler’s laws

In 1600, using the observations of Mars’ orbit made by Danisch astronomer Tycho Brahe (1543 – 1601), the German astronomer Johannes Kepler (1571-1630) published his three laws of planetary motion:

  1. The planets orbit the Sun in ellipses, with the Sun at one focus.

  2. The line joining the Sun and a planet sweeps out equal areas in equal times.

  3. The period of revolution of a planet, and the semi-major axis of its orbit (half the longest dimension of the ellipse), are related to each other such that the square of the period is proportional to the cube of the semi-major axis of the orbitKepler’s laws were one of the tools which opened the door to the age of modern astronomy; the other was the invention of the telescope by Galileo Galilei nine years later and its use for astronomical research and observation.

    (This last part was taken from http://www.imcce.fr/vt2004/en/fiches/EIS-C1_pf.html a wonderful resource)

    Coming Soon: Does our sun have a binary twin? 😉 -Aquarian Philosophy

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