We're approaching another "cross-quarter day" in the earth's annual orbit around the sun. It is, in fact, the most famous of the cross-quarter days for modern cultures, due to the tradition of Halloween, which is the most famous and most actively-celebrated surviving remnant of the cross-quarter day festivals that took place to mark these important stations of the year in many ancient cultures.
We've examined the concept of cross-quarter days in previous posts such as this one. To shed some more light on the subject, and the upcoming day in particular, let's take a look at the paths of the sun through the sky as marked out by the unknown builders of the observatory at Mystery Hill, New Hampshire (in the United States).
The diagram above shows that the builders of this observatory placed stone markers at points aligning with the rising and setting of the sun on certain important days of the year, including the two solstices (the summer solstice being the point of northernmost rising and setting, and the winter solstice the point of southernmost rising and setting of the sun along the eastern and western horizons each year) and the equinox (a point between these northernmost and southernmost points, where the sun will rise and set on the two equinoxes as it passes through on its way north to the summer solstice and south the the winter solstice points each year).
As explained in the previous post discussing Mystery Hill (linked above), this site was first reported in 1826, but it was not until the 1960s that astute observers began to suspect that it contained astronomical alignments, and not until the beginning of the 1970s that they began to be demonstrated conclusively.
The diagram above is laid out such that north is upwards (and indicated by a north-seeking arrow, which the ancient builders also marked with a series of fang-shaped stones drawn in the top of the diagram, the central "tooth" being the largest and indicating north, the the auxiliary stones to either side thought to represent markers indicating the direction of Thuban, a star in Draco which was located near the celestial south pole millenia ago). East in the diagram is therefore to the right, and west to the left, and south is indicated by a stone wall drawn in the diagram which is constructed of a long thickened "wall" of stones oriented due north-south in the observatory itself.
Of course, the earth turns towards the east, meaning that the diagram above moves towards the right during the course of the earth's rotation, causing celestial objects (including the sun) to trace out pathways from right to left in the diagram -- from the east to the west. The sun will thus rise on the eastern horizon (beyond the diagram) on the right, and will do so at its northernmost point on the day of summer solstice. The rising point on that day each year is indicated by a large triangular standing stone indicated on the diagram.
During the day, as the earth turns, the sun will trace out an arc in the sky, always remaining between the observer and the southern horizon at this latitude (this fact can be understood from the next diagram below), and will then set on the western horizon at its northernmost point, marked by another impressive standing stone which is indicated on the diagram above as well.
The sun reached the summer solstice -- or, more properly, the earth reached the point in its orbit that creates the summer solstice conditions -- back in June of this year (on the 21st), discussed in this previous blog post. As earth continued on its annual track, the sun's rising point progressed southward, moving towards the fall equinox and onward towards the winter solstice.
The reason the sun's rising and setting points move along the horizon is discussed in greater detail in the Mathisen Corollary book. A brief diagram, shown below, should give some explanation. It shows the earth tilted on its axis, going around the sun on a plane that is viewed "edge-on" so that it looks like a flat horizontal line. An observer on the earth is drawn in the northern hemisphere, and as the earth rotates he will see the sun only as earth's turning brings him around to face it each day (so "day" is when facing to the right for the observer on the "left earth" at winter solstice and "day" is when facing to the left for the observer on the "right earth" at summer solstice). The angle of the sun as it arcs through the sky will be very different for the observer on the earth at right (summer solstice) than at left (winter solstice), and its rising and setting points will be as well.
Between the solstices and the equinoxes (which divide the year into four portions and were thus also known as the "quarter days"), ancient cultures also tracked intermediate stations known as the "cross-quarter days," which fall on the approximate calendar dates of August 8 (after Summer Solstice on the way towards the September Equinox, halfway between the two), November 8 (after September Equinox, halfway to the Winter Solstice), February 4 (after the Winter Solstice, on the way towards the Spring Equinox and halfway between those two stations), and May 6 (halfway between the Spring Equinox and the Summer Solstice).
These dates are taken from Martin Brennan's essential book, The Stars and the Stones (page 39), discussed in this previous post. Of course, just like the solstices and equinoxes, the actual calendar dates drift slightly from year to year, as the calendar gets slightly out of line with the orbiting earth and then is brought back again by the insertion of a day during the leap year).
In addition, the ceremonies and festivals associated with the cross-quarter days have generally been moved to the first of the month in Europe, so that they are now most closely associated with traditions centered around the first of August, the first of November, the first of February, and the first of May, or the day following (such as in the case of Ground Hog Day) or the night immediately before (such as Halloween).
The Celtic festivals and ceremonies associated with the cross-quarter days are Lughnasad (the early August cross-quarter day), Samhain (the early November cross-quarter day), Imbolc (the early February cross-quarter day), and Beltane (the early May cross-quarter day). These names all have various spellings and variations.
The Catholic church incorporated the cross-quarter days as Lammas (August 1), All Saint's or All Hallow's Day (November 1), and Candlemas (February 1).
The cross-quarter days were also associated with the start of the seasons of summer and winter, which is why the solstice dates were known as Midsummer and Midwinter. This website discussing the cross-quarter days aptly points out that if summer didn't start until Summer Solstice (June 21 or 22), then it would make no sense to call the summer solstice Midsummer.
That site also notes the parallels between the cross-quarter days of November and May, in that the night before each one was associated with the thinning of the barrier between the world of the living and the dead, such that both October 31st and April 30th were thought to be nights of witches and spirits. The two cross-quarters are connected in that the October-November cross-quarter marks the beginning of the darkest segment of the year (in the northern hemisphere), containing at its mid-point the winter solstice, and the April-May cross-quarter marks the beginning of the brightest segment of the year (in the northern hemisphere), containing at its mid-point the summer solstice.
Because these cross-quarter days were very important to the ancient Celts and Druids, the presence of observatories in the New World with clear markers for both the quarter days and the cross-quarter days is noteworthy. It is, of course, possible that these stone observatories are the creations of native peoples of North America, and that their marking of the cross-quarter days arose in isolation of the attention paid to the cross-quarter days in other cultures in other parts of the world.
However, this is not the only possibility, nor is it necessarily the most likely possibility, in light of other evidence of ancient trans-oceanic contact that is rarely mentioned by conventional histories (see for example the discussions here and here). It is very possible that sites such as Mystery Hill, New Hampshire were created by Celtic visitors or settlers in the New World thousands of years ago, or perhaps that the builders were influenced by relatively brief contact with ancient Celtic travelers. Since it is also possible that the Celtic culture was influenced by another ancient culture, it is also possible that another ancient culture other than a Celtic culture built or influenced the building of the sites in North America which preserve markers of the quarter days and cross-quarter days.
In any case, it is worth taking the time to understand the celestial mechanics that create the quarter days and the cross-quarter days, and how the stone observatories preserve these heavenly activities with markers on the ground. If you have access to a suitable piece of ground, you could designate a central observation point and then mark the sunrise and sunset points on the quarter and cross-quarter days for yourself. Since a significant cross-quarter day is about to arrive, this is an excellent time to start just such an observatory, if you are so inclined!