Earth Sciences Forum

AstrumAspicio · Joined: 30 Jul 2007 Posts: 14

Pt-2:

Now that we have a few definitions under the belt, let us continue.

The Celestial sphere:

When we look up at the stars in the night sky they appear to be stationary relative to each other. As the Earth moves from one side of the Sun to the other, the displacement of those stars due to parallax is less than one second of arc even for the nearest star (Proxima Centauri). One way of looking at this is a fixed sphere of stars surrounding the Earth/Sun system. This is often referred to as the Celestial Sphere. This is why some of the ancient civilizations considered the stars to be holes in a tapestry.

Since we are talking distances and parallax, let’s briefly take a moment and describe such. The more familiar term for the layman when referring to stellar distances is called a light year. This is the distance light will travel in one calendar year. For example the closest star to our Sun, Proxima Centauri, is approximately 4.22 light years from our solar system. The light we see from there today was actually generated by that sun 4.22 years ago. Astronomers use another term for stellar distance that may be not so familiar: the Parsec. A Parsec (parallax-arcsecond) is the distance needed for one astronomical unit (AU) to subtend one second of arc. An AU is the average distance from the Earth to the Sun or approximately 93 million miles, and an arcsecond is 1/60 of an arcminute, which is 1/60 of a degree. It turns out a Parsec is about 3.26 light years. Thus for an observer sitting 3.26 light years from the sun, the distance from the sun to Earth’s orbit subtends one arcsecond.

Conversely, an observer on the Earth will see an object positioned one Parsec away appears to shift by up to two arcseconds over the course of a year. If one sighting is made when the line from the Sun to the Earth is 90 degrees from the line of observation, 6 months later the Earth will be on the opposite side of it’s orbit. Since the radius of the Earth’s orbit is one AU, the diameter is 2 AU’s. This change in apparent position from different viewing locations is called parallax.

Proxima Centauri (at 4.22 Light Years or roughly 1.3 Parsecs), shows parallax of about one-and-a-half seconds of arc over the course of a year – too small to be discerned without special high-precision equipment. Most stars are much further away than Proxima Centauri, so for most practical purposes the stars are fixed – at least for periods less than a decade.

Even though it appears the stars remain in “fixed” locations in the night sky, over a period of decades and centuries the stars do move relative to each other and relative to the Earth. The star catalogue based on the epoch B1950 and the one based on the epoch J2000 would reveal minor differences due to these motions.

Another interesting item of note is that the constellations we see are made up of the brightest stars. Even in the same constellation these stars are at vastly different distances from the Earth. Some may be very bright stars that are very distant, and these may appear dimmer than closer stars that are not actually generating nearly as much light. The brightness of a star is called its magnitude. There are two ways astronomers measure magnitude: Apparent Magnitude and Absolute Magnitude.

The Apparent Magnitude is how bright a star appears to us here on the Earth. The Absolute Magnitude is how bright a star would appear if it were exactly ten parsecs away from the Earth. (Close to 33 light years).

Two notes:

1) Apparent magnitude is usually denoted with a small “m” and absolute magnitude uses a capital “M”.

2) The magnitude scale is backwards of what you might think: the larger the number the fainter the object. The brightest star is Sirius with magnitude of –1.5m, while somewhat dimmer Vega is defined as 0m, and planet Venus may become as bright as –4.4m. The typical human eye can just barely see a star with a magnitude of +6m, but Earth-based telescopes may see stars as dim as +18m, and the Hubble can see stars as feint as +30m.

The Ecliptic Plane:

Since the Earth is tilted (23.5 degrees) in reference to the path it sweeps out in its orbit about the Sun, this path projected onto the celestial sphere does not fall on the celestial equator. This imaginary plane is called the ecliptic. Note: This angle between the ecliptic and the equatorial plane is called The Obliquity of the Ecliptic.

This imaginary plane crosses the celestial equator in two places (called the equinoxes). The Vernal Equinox falls in the spring as the Sun appears to cross the ecliptic going north and the Autumnal Equinox falls in autumn when the Sun again crosses the ecliptic, this time going south. Note: Vernal comes from the Latin vernalis, meaning spring. Also the term equinox relates to the word equal since both day and night are close to the same, 12 hours during the equinox.

The points where this plane is the farthest above (north) and below (south) the celestial equator is called the solstices. In the northern hemisphere of the earth, the most northern point of the ecliptic is called the Summer Solstice and the southern most is called the Winter Solstice. In the Southern hemisphere of the Earth the reverse is true.

The zodiac lies along the plane of the ecliptic. Since the Earth is orbiting the Sun, the Sun appears to follow the plane of the ecliptic, making one complete circle in one calendar year. The name “zodiac” comes from the Greek meaning animal circle. In fact all of the 12 constellations of the zodiac are named after animals. Note: The path of the Moon and the other planets fall pretty much on this plane as well. Since it takes 365 days for the Earth to orbit the Sun and there are 360 degrees in a circle, the Sun moves pretty close to 1 degree per day.

Celestial Coordinates:

If, on the first day of spring (the Vernal Equinox), a line is drawn from the Sun through the Earth and out to infinity, that line is said to extend to a point referred to as The First Point of Aries. (So named because at one time this line pointed to the first star in the constellation of Aries)

The celestial sphere is tied to the Earth for its coordinate system. Project the Earth’s equator out to infinity and you have the equator of the celestial sphere. Likewise the north and south poles of the Earth points to the north and south poles of the celestial sphere respectively. This makes it very easy to map the sky referenced to the Earth. This coordinate system is called the Equatorial Coordinate System. It ties in closely with our own geographic coordinate system here on the surface of the Earth.

Note, however, the geographic coordinate system is fixed upon the surface of the Earth (Lat-Long) -- so it rotates with the rotation of the Earth. The celestial coordinate system is fixed to the celestial sphere and appears to rotate due to the Earth’s rotation. The equivalent of “latitude” in the celestial sphere (the angle of an object above or below the celestial equator) is called declination, with zero being on the equator. (This is pretty easy to relate to, since the celestial’s equator and poles appear to be fixed like our own earth.) The celestial sphere’s analog to “longitude”, called right ascension, and is not a “fixed” reference to the Earth. It is fixed to the stars instead, thusly rotating every 24 hours. Instead of using degrees, right ascension is measured in hours minutes and seconds. The Vernal Equinox is used as the zero reference for the right ascension. Since there are 360 degrees in a circle, the Earth rotates about 15 degrees every hour, so every hour of right ascension is equivalent to 15 degrees.

A declination of zero is on the equator and a right ascension of zero is at the Vernal Equinox. So on the first day of spring, when the Earth’s equator lines up with the line to the First Point of Aries, the Vernal Equinox will have the coordinates of 0 degrees and 0 hours. This has come to define the center point for an Equatorial Sky Chart

AstrumAspicio · Joined: 30 Jul 2007 Posts: 14

Pt-3:

On to the Earth-Sun system:

It takes one year for the Earth to rotate around the Sun one time and 24 hours to rotate on its axis. Think about this relationship. Not only is the Earth revolving on its axis, it is in motion about the Sun. (I know this is really basic grade school stuff, however, it will help in visualizing the concepts I am about to explain) Therefore the Earth moves 1/365th of its orbit about the Sun every day.

Ok, here is where that visualization will come in handy. Since a “day” is described by one complete rotation of the Earth on its axis, this equates from noon to noon (when a point on the Earth is directly pointed at the Sun). The term for this is called the Mean Solar Day. But here is the rub; the Earth has moved through 1/365th of its orbit during this period of time we called a day. Because the Earth has moved over a tiny bit from where is was the day before, it must rotate a tiny bit more to have the same spot facing the Sun at noon. This tiny bit is slightly less than one degree (the Earth’s orbit completes 360 degrees in 365 days). Thus the Earth actually rotates almost 361 degrees, not just 360, to complete a mean solar day.

Now let us think of this celestial sphere we have been chatting about. Remember the stars appear fixed in one location (at least on a daily basis). This means that one complete revolution of the Earth referenced to a star does not take that little bit of extra time to be over the same spot on the Earth. This “day” is referred to as a Sidereal Day. It takes approximately four extra minutes for the Earth to have the Sun over the same location on the Earth than a star.

This is the difference between a Sidereal Day (23 hours, 56 minutes) and a Mean Solar Day (24 hours).

Also the Earth is tilted on its axis from the plane of the ecliptic by 23.5 degrees. That tilt causes the North Pole to be currently pointed towards Polaris. As the Earth moves around the sun its pole stays pointed at Polaris. This is the cause of the seasons we experience. Note. This tilt varies back and forth from 21.6 degrees to 24.5 degrees approximately every 41,000 years.

There is also a precession of our pole and it sweeps a complete circle in the sky (think of the Earth as a top wobbling as it rotates) about every 26,000 years. This gives us different pole stars as the north pole of the Earth sweeps out a circle on the celestial sphere.

There are also a number of other motions that must be taken into consideration over the years, such as the precession of the aphelion. Our Earth’s orbit around the Sun is not a perfect circle. It is an ellipse with the closest point of the orbit called perihelion and the furthest point called aphelion. Currently perihelion occurs in early January, and aphelion falls in early July. However, this is not always the case. The aphelion and perihelion change over the centuries and sweeps thru the calendar year with a periodicity of around 22,000 years. By the way, the amount a circle is “squished” to create an ellipse is called its eccentricity. If the eccentricity is equal to zero the orbit will be a perfect circle (also known as a degenerate ellipse). An eccentricity between zero and one, not inclusive, describes the elliptical path of an orbit – a highly eccentric orbit has eccentricity close to one. In the case of eccentricity equal exactly to one, the path is a parabola, and eccentricity greater than one describes a hyperbola. Although natural forces tend to circularize most orbits over time, achieving an eccentricity of exactly zero is extremely unlikely in nature.

The eccentricity of Earth’s orbit is very small. However, even this changes over time. Its eccentricity varies periodically about every 100,000 years. There are also other motions affecting the orbit, caused by the Moon, Jupiter and the Sun: these are called Nutations. One of the major nutations has a period of 18.6 years.

This cursory look at the Time-Earth-Sun finally leads is into a discussion of the Earth-Moon system where I was driving to in the first place.

Whew! Time to get some coffee. Very Happy

(hope I am not being too wordy so early on)

AstrumAspicio · Joined: 30 Jul 2007 Posts: 14

Pt-4:

Ok, let us take a look at the Moon:

Currently, the evidence points to a catastrophic collision of another body with the Earth not long after the formation of the Earth. This collision is what is believed to have formed the Moon. Originally the Moon was much closer to the Earth and its period did not match its rotation. Over the years the Moon has become tidally locked with the Earth resulting in the Moon keeping one face to the Earth (Its rotation on its axis matches the period of its orbit). This tidal locking will eventually cause the Earth and Moon to keep one face to each other since the Earth is affected by tides as well. (However, under current stellar evolutionary theory, the Sun will go nova before this happens) A more in-depth discussion of this is continued in the following paragraphs.

Some of the following questions;

1) How was it formed?

2) What is it made of?

3) How far away is it?

We are now gaining the knowledge to be able to answer (at least in part).

1) How was the Moon formed?

There were at least five major ideas that were proposed as to the formation of the Moon.

Fission – The Moon split off from the Earth.
Capture – The Moon was captured by the gravity of the Earth.
Condensation – The Moon coalesced out of the same “stuff” the Earth did.
Colliding Planetesimals – Formed from colliding Planetesimals during the early formation of the solar system.
Collision – A body collided with the Earth causing a piece of the Earth’s crust to form the Moon from a resultant ring produced by that collision.

The evidence points to the collision theory. First, the Moon does not have an iron core. This pretty much rules out that it coalesced from the same cloud of debris that the Earth did. Second, throughout the solar system, the oxygen isotopes have been found to be different. If the Moon were captured, it too would not match the Earth’s oxygen isotope ratio (which it does). Fourth, by looking at the angular momentum and energy required, the theory that the Moon spun off the Earth after the Earth formed does not hold up.

This leaves us with the Collision theory as the best model we have for the formation of the Moon. The resultant collision caused a ring of debris from the Earths crust to form outside the Roche limit. If it had not, tidal forces would have not allowed for the Moon we see today.

A more in depth discussion of tidal locking since the Moon is tidal locked to the Earth. The reason the Moon keeps one face to the Earth (Its rotation on its axis matches the period of its orbit) is it is tidally locked to the Earth. Here is a more in depth explanation. The total angular momentum of the earth moon system, which is spin angular momentum plus the orbital angular momentum, is constant. (The Sun plays apart also) Friction of the oceans caused by the tides is causing the Earth to slow down a tiny bit each year. This is approximately two milliseconds per century causing the moon to recede by about 3.7 centimeters per year. As the Earth slows down, the Moon must recede to keep the total angular momentum a constant. In other words as the spin angular momentum of the earth decreases, the lunar orbital angular momentum must increase. Here is an interesting side note. The velocity of the moon will slow down as the orbit increases.

Another example of tidal locking is the orbit period and rotation of the planet Mercury. What is interesting about this one is that instead of a 1:1 synchronization where Mercury would keep one face to the Sun at all times, it is actually in a 2/3:1 synchronization. This is due to the High eccentricity of its orbit.

There also can be more than one body “locked” to each other. Let’s take a look at the moon Io. Io is very nearly the same size as the Earth’s moon. It is approximately 1.04 times the size of the moon. There is a resonance between Io, Ganymede, and Europa. Io completes four revolutions for every one of Ganymede and two of Europa. This is due to a Laplace Resonance phenomenon. A Laplace Resonance is when more than two bodies are forced into a minimum energy configuration.

There are also examples of tidal locking in the asteroid belt.

First, the asteroid belt has an estimated total combined mass of less than 1 tenth of the Earth's moon. Second, Jupiter has a profound effect on the asteroid belt.

Since Jupiter has a semimajor axis of 5.2 AU (I AU is the distance from the Sun to the Earth) it ends up with an orbital period of 11.86 years. Since the asteroids are not all at the same distance from the sun, there orbital periods will differ in a direct relationship to their distance from the sun. This will result in some of them having an orbital period of one half of Jupiter. This puts those particular asteroids in a 2:1 orbital resonance with Jupiter. The result of this resonance is gaps called Kirkwood's gaps.

The rub is why did not this asteroid belt form a small planet? The reason is the gravitational force of Jupiter. It perturbs the asteroids giving them random velocities relative to each other.

Another effect of both Jupiter and the Sun on the asteroid belt is a group of asteroids that both precede and follow Jupiter in its orbit by 60 degrees. These asteroids are known as the Trojans.

2) What is the Moon made of?

From here:

http://lunar.arc.nasa.gov/science/geochem.htm

Primary elements: The lunar crust is composed of a variety of primary elements, including uranium, thorium, potassium, oxygen, silicon, magnesium, iron, titanium, calcium, aluminum and hydrogen. When bombarded by cosmic rays, each element bounces back into space its own radiation, in the form of gamma rays. Some elements, such as uranium, thorium and potassium, are radioactive and emit gamma rays on their own. However, regardless of what causes them, gamma rays for each element are all different from one another -- each produces a unique spectral "signature," detectable by an instrument called a spectrometer. A complete global mapping of the Moon for the abundance of these elements has never been performed.

Hydrogen and helium: Because its surface is not protected by an atmosphere, the Moon is constantly exposed to the solar wind, which carries both hydrogen and helium -- each potentially very valuable resources. One natural variant of helium, [3]helium, is the ideal material to fuel fusion reactions. When scientists develop a more thorough understanding of fusion, and can practically implement such reactions, the Moon will be a priceless resource, since it is by far the best source of [3]helium anywhere in the Solar System.”

This pretty much answers the question; are there valuable materials up there?

3) What is the distance to the Moon?

The mean distance to the Moon is approximately 238,800 miles. From past experience, we can design spacecraft to get there in about three days. This is far shorter than the months the early voyages took to the new world.

Final thoughts on the Moon:

So here we have this tremendous resource at our fingertips. Unfortunately (not unlike the early explorers), the initial cost is staggering. However, in the long run it would end up being an invaluable resource for both material and scientific study. One of the big advantages is that the Moon keeps one side facing the Earth. This minimizes communication problems between the two bodies. Also since the backside of the Moon is shielded from the Earth, it would be an ideal spot to place a radio telescope array.

Since we are now talking about orbiting bodies, let us digress just a wee bit further and briefly talk about orbits:

There are different sizes and shapes of orbits. We use the term Semi-Major Axis to measure the size of an orbit. It is the distance from the geometric center of the ellipse to either the apogee or perigee (The highest (apo) and the lowest (peri)). Apoapsis is a general term for the greatest radial distance of an Ellipse as measured from a Focus. Apoapsis for an orbit around the Earth is called apogee, and apoapsis for an orbit around the Sun is called aphelion.

Periapsis is a general term for the smallest radial distance of an Ellipse as measured from a Focus. Periapsis for an orbit around the Earth is called perigee, and periapsis for an orbit around the Sun is called perihelion.

The terms Gee and Helios comes from the Greek words “Ge” (earth) and “Helios” (Sun) respectively.

First lets talk a bit about “where it is”. An orbit is a nothing more than an object falling around another object. Both Kepler and Newton came up with a set of laws that describe this phenomenon.

Kepler’s three laws of planetary motion:

1) The orbit of a planet is an ellipse with the sun at one of the foci
2) The line drawn between a planet and the sun sweep out equal areas in equal times.
3) The square of the periods of the planets is proportional to the cubes of their mean distance from the sun.

So what is that telling us? In a nutshell, all orbits are ellipses, the close to the body you are orbiting the faster you go (e.g. if you have a highly elliptical orbit the satellite or planets velocity will increase as it approaches the object being orbited and decrease as it get further away)

These laws not only apply to planets and satellites, but to any orbiting body.

Note: Super geek alert:

-For an orbiting body this is not entirely correct. It turns out that both bodies end up orbiting a common center of mass of the two-body system. However, for satellites, the mass of the Earth is so much greater than the mass of the satellite, the effective center of mass is the center of the Earth.-

Newton’s three laws (and law of gravitation):

1) The first law states that every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force. (Commonly known as inertia).

2) The second law states that force is equal to the change in momentum (MV) per change in time. (For a constant mass, force equals mass times acceleration F=ma).

3) The third law states that for every action there is an equal and opposite reaction. In other words, if an object exerts a force on another object, a resulting equal force is exerted back on the original object.

Newton’s law of gravitation states that any two bodies attract one another with a force proportional to the product of their masses and inversely proportional to the square of the distance between them.

Note: Super geek alert #2:

-Actual observed positions did not quite match the predictions under classical Newtonian physics. Albert Einstein later solved this discrepancy with his “General Theory of Relativity”. -

There are four classical “tests” that cemented General Relativity:

1) In November of 1919, using a solar eclipse, experimental verification of his theory was performed by measuring the apparent change in a stars position due to the bending of the light buy the sun’s gravity.

2) The changing orientation of the major axis or Mercury not exactly matching classical mechanics.

3) Gravitational Redshift.

4) Gravitational Time Dilation.

So what is all this trying to tell us? Planets, satellites, etc orbit their parents in predictable trajectories allowing us to “know” where they will be at any given time. A set of coordinates showing the location of these objects over a period of time is called its ephemeris.

AstrumAspicio · Joined: 30 Jul 2007 Posts: 14

Pt-5: (WHEW LAST PART) Hope I was not too bold in posting so much all at once)

FINALLY let go back to the beginning of my screed (LOL) and talk about time keeping and leap seconds!

Historically, time has been measured by the rotation of the Earth on its axis and the time it takes to rotate once about the Sun (a year). However, both of these are not uniform enough for precise calculations.

One of the units of time is called the second. It used to be defined as 1/86,400 of a Mean Solar Day. This was good enough for early calculations, but don’t forget that the Earth is slowing down due to tidal forces so that ends up changing over time. After a number of intermediate steps the second was finally redefined as:

-The duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom. (Atomic time); also known as Coordinated Universal Time (UTC).-

Since the Earth is slowing down approximately 1.4 milliseconds per day per century, this deceleration causes the Earth’s rotational time to vary from atomic time. The current true (instantaneous) rotation rate of the Earth is called UT1 (which is a non-uniform rotation). Over a period of a year the difference between it and UTC can approach a full second. However, since the Earth’s rotation is non-uniform, it is monitored continuously. If the difference between UT1 and UTC approaches 0.9 seconds, a leap second is added or subtracted from UTC to keep it uniform with the Earth’s rotation. So far all of the leap seconds have been positive. This correlates with the Earth slowing due to tidal braking.

Note: Since the GPS time does not have leap seconds added or subtracted, it is diverging with UTC with every second added to UTC. Currently it is different by 14 seconds. This can cause some consternation when flying a satellite or spacecraft that uses GPS. If your ephemeris is calculated in GPS time and you receive a “vector” in UTC time, it will be off by 14 seconds. You just cannot add 14 or subtract 14 seconds and press on. The rub is that not only has the satellite moved 14 seconds in-track, the Earth has rotated underneath by 14 seconds (cross-track) as well. This is especially noticeable for the high inclination orbits. Vectors have to be recalculated when translating between GPS and UTC.

Remember, the deceleration of the Earth is not uniform. There may be a number of factors that cause this non-linearity such as snow and ice loads, earthquakes and others we haven’t even thought of. This could account for the variations between leap seconds requirements that we have experienced in the past. However, the Earth will continue to slow down and the deceleration will still vary.

One final item: There is an ongoing debate whether to do away with leap seconds all together and just go with UTC. The problem with this is, over an extended period of time, the hours will no longer be tied to the solar day and noon may well end up in the evening. Another suggestion is to redefine the period of one second to more closely match the current rotation of the Earth. This too has its problems as the second will required “redefining” periodically as the Earth continues to slow down.

NileQueen · Posted: Tue Jul 31, 2007 10:56 am Post subject:

Baywax · Joined: 23 Jul 2007 Posts: 113 Location: Pacific West Coast

AstrumAspicio,
your amazing perseverence in enlightening us about planetary evolution, orbit and physics is astounding! This is the kind of background that I am missing when I come in, guns blazing, asking about Velikovsky 's and Clarke's suppositions concerning Venus, Jupiter and Mars. I can only hope you'll address some of these questions and utilize your stellar understanding of planetary mechanics to further disclose what may be the truth about these ideas.

I fully understand the peril of emotional, personal and other motivational influences that can obscure the truth. I welcome any concrete evidence that supports or detracts from past speculations such as the idea that Venus was extracted from Jupiter (somehow) setting the stage for some of the features we see in the solar system today. But believe me I'm not an astronomer.

During 12 years in Physical Anthropology I've often relied on reports, stories and myths to guide me to physical truths about the past. And I haven't been disappointed very often. That's why I've lent some credence to certain aspects of Velokovski's and other's use of similar research methodologies.

Thank you!
_________________
Anyone who conducts an argument by appealing to authority is not using his intelligence; he is just using his memory. Leonardo Da Vinci

Time flies like an arrow, fruit flies like a banana.
W.C. Fields

Baywax · Joined: 23 Jul 2007 Posts: 113 Location: Pacific West Coast

This was thought to be the birth place of Venus by Velikovsky. Out of the "Great Red Spot"

_________________
Anyone who conducts an argument by appealing to authority is not using his intelligence; he is just using his memory. Leonardo Da Vinci

Time flies like an arrow, fruit flies like a banana.
W.C. Fields

Baywax · Joined: 23 Jul 2007 Posts: 113 Location: Pacific West Coast

Messenger and Venus Express compile data on clouds etc.... during a duel orbit of Venus, July 19/07

http://www.esa.int/SPECIALS/Venus_Express/SEMVN4HYX3F_0.html

AstrumAspicio · Joined: 30 Jul 2007 Posts: 14

1st - my apologies for such a huge data dump on your site. I tend to get carried away.

2nd - I am putting a post together (much smaller) showing why Venus did not originate from Jupiter in the past few thousand years.

-M-

Baywax · Joined: 23 Jul 2007 Posts: 113 Location: Pacific West Coast

Baywax · Joined: 23 Jul 2007 Posts: 113 Location: Pacific West Coast

Another tid bit from pre-history (no actual date) about Venus.

An oral-traditional story from Tanzania (tends to support the idea that Venus "visited earth" and carried on its way afterwards)

Baywax · Joined: 23 Jul 2007 Posts: 113 Location: Pacific West Coast

In defence (of using folklore and ancient records) I have to point out that the only records of the Super Nova that created the Crab Nebula are derived from the 1000 year old observations and suppositions of ancient cultures. Here are some of the accounts..... and they don't sound all that different from the accounts I've given of the "long day", the "long night" or what was even called "Venus visiting Earth".

Baywax · Joined: 23 Jul 2007 Posts: 113 Location: Pacific West Coast

Please bear with me as I expose another myth that points to Venus as being expunged from Jupiter around 3600 years ago.

This is to hold this thread over until someone can show us the astrophyics that will completely rule this sort of claim out (which was originally made by Velokovski (sp).)

Going with Greek mythology, Zeus gave birth to [Venus] when he had a very terrible headache, so terrible he split his head open, and out popped [Venus].

Venus is associated with Lucifer and Satan in folklore and mythology...."Lucifer, how you have fallen, cast out of the Heavens"... can be read as a celestrial event, something grand happening in the stary nights, something so big that people took notice and felt afraid...

....Especially when they didn't have Dolby Surround Sound or THX or HD or BlueRay discs in boxes blasting the **** out of they're homes every night! They weren't used to big, flashy occurances as this one might have been.
Wink

_________________
Anyone who conducts an argument by appealing to authority is not using his intelligence; he is just using his memory. Leonardo Da Vinci

Time flies like an arrow, fruit flies like a banana.
W.C. Fields