Dr. Judith S. Young, Department of Astronomy
University of Massachusetts, Amherst, MA 01003
October 11, 2000


Stone circles are found world-wide, many of which have astronomical alignments and serve as calendars -- they are the original observatories. To help the general public, K-12 students, and University students taking Astronomy to experience and understand the cycles exhibited by the Sun and Moon and the cause of the seasons, I began creating a stone circle, which I call a Sunwheel, on the U.Mass. campus in 1992. A preliminary Sunwheel has been in place since May 1997, consisting of a dozen 2-3' high boulders in a circle 100' across. Stones mark North, South, East, and West, as well as the summer and winter solstice sunrise and sunset directions. This preliminary Sunwheel is an active arena for enhancing the K-12 science curriculum and for public outreach; over 800 students and teachers, and 2500 members of the general public visited the Sunwheel from 1997-1999, during which time I gave 73 presentations at the site.

Through a grant from the National Science Foundation, funds are now available for the addition of 8'-10' tall standing stones at the U.Mass. Sunwheel. The design requirements and construction specifications for the U.Mass. Sunwheel have been carefully determined with the features of safety and stone stability at the approved site as prime considerations. Consultants who have contributed in course of determining the design are Dr. Don DeGroot, Professor of Civil and Environmental Engineering at U.Mass., and Mr. Allen Williams, owner and experienced stone artist of the Chester Granite Company in East Otis, Massachusetts. This document describes the relevant features of the Sunwheel site, the observationally determined locations for the 8'-10' tall standing stones, the stones themselves, and the specifics of the construction which will contribute to the safety and stability of the standing stones. Finally, the construction plan is presented, with detailed budgetary information regarding the estimated cost of constructing the enlarged Sunwheel.

I. Introduction

For thousands of years, human beings have been intrigued by the cycles in nature. Astronomically, these cycles include the daily rising and setting of the Sun, Moon, planets and stars, the monthly cycle of phases of the Moon, and the yearly cycle of the seasons. The long-term repeatability of these cycles provided an indication to human beings throughout time of the presence of order in the Universe. Ancient cultures learned how to use the Sun as a calendar, and in particular, to mark the seasons through observations of the location of sunrise and sunset along the horizon (cf. Hawkins 1965; Williamson 1984). Indeed, circles of standing stones with solar alignments, and occasionally lunar alignments, are found throughout the world (Zink 1979). These stone circles were constructed with a detailed understanding and knowledge of astronomy by peoples of a wide variety of cultures on Earth, dating as far back as 4,800 B.C. (Zink 1979).

The U.Mass. Sunwheel is a stone circle which is both an observatory and a calendar. The stones in the Sunwheel mark N, S, E, and W for orientation, and also mark the summer and winter solstice sunrise and sunset directions along the horizon. As an observatory, the Sunwheel provides a fixed arena from which daytime or nighttime observations of the sky can be made. As a calendar, the location along the horizon of sunrise or sunset on a particular day give the observer an indication of the approximate day of year. The Sunwheel is valuable because it takes a complex scientific phenomenon and puts it into an everyday context which people of all ages can experience and understand for themselves. Visitors learn how the Sun's position in the sky changes with the seasons. Through the implementation of daytime presentations for K-12 students, as well as sunrise and sunset gatherings on the solstices and equinoxes for the general public, I have taught everyday astronomy to over 1500 individuals in the past 2 years. Increasing public understanding of the daily and annual motions of the Sun in the sky will not only contribute to increasing science literacy among school children and the general public, but it can help promote curiosity about nature and help people to feel connected to the larger Universe.

After conceiving the idea in 1992 to build a Sunwheel on the U.Mass. campus as an arena for teaching astronomy, I selected the desired site and began observations of the sunrise and sunset directions on the solstices and equinoxes. Formal permission to use the proposed site for the U.Mass. Sunwheel was unanimously granted on Oct. 17, 1995 by the Faculty Senate Committee for Physical Planning here at the University. In May of 1997, a preliminary Sunwheel was constructed south of the Alumni Stadium with funds provided by a Healey Endowment Grant from the University of Massachusetts. This preliminary stone circle is 50' in radius, and comprised of stones which are ~2' feet tall. These stones serve as place holders for the planned 8'-10' tall monoliths, preserving the proper directions in which to look for the sunrise and sunset on the solstices and equinoxes, and making the Sunwheel a useful teaching tool and a public gathering spot to learn astronomy. In June of 1999, I added a semi-permanent exhibit to the site, with simple and informative signs describing the significance of each direction and solstice marker. Through these explanations, visitors are able to learn about the annual change in the Sun's location along the horizon, about the variations in the elevation of the Sun in the sky at noon throughout the year, and about where on Earth an observer will find the Sun directly overhead at noon on each solstice and equinox. With this explanatory information added to the standing stones themselves, the Sunwheel becomes an outdoor educational exhibit which can be enjoyed by anyone at any time of day throughout the year.

In September of 1999, I received a grant from the National Science Foundation to add the large stones to the Sunwheel. I had already located the tall standing stones in the spring of 1999, at the Chester Granite Company, in East Otis, Massachusetts, owned and operated by Allen and Kathleen Williams. There I found natural standing stones for the Sunwheel at an affordable price. These stones are in the 7'6" to 10' tall range, each very beautiful, weighing in the 3 ton range.

In the fall of 1999, Prof. Don DeGroot in the U.Mass. Department of Civil and Environmental Engineering began a program to auger 6 boreholes in the ground at the Sunwheel site in order to inspect the subsurface soil and install groundwater monitoring wells. The results of his study were used to make specific recommendations regarding the installation of the 8'-10' tall standing stones at the Sunwheel, with respect to the design suggestions made by Allen Williams. At the present time, the money for the stones and construction is in hand, the design is specified, the standing stones have been selected -- we are simply waiting for the ground to dry and harden so the stones can be delivered and construction can begin. Since the NSF money runs out on July 31, 2001, construcion B of the enlarged stone circle is planned to take place before July 2001, and probably during the autumn of 2000 or winter of 2001.

This document describes the Sunwheel site, the astronomical observations made to determine the stone placement, and the characteristics of the 8'-10' tall standing stones to be added to the Sunwheel. Next, the specifics of the design for placing the standing stones at the Sunwheel will be described, along with the detailed construction plan regarding the step-by-step procedure for installing the standing stones at the Sunwheel.

II. The Sunwheel Site

In order for a Sunwheel to be most useful, it is necessary for the site to be in an accessible open area, far from buildings and trees, where there is an especially clear view of the eastern and western horizons. Here at the University of Massachusetts, I selected the site and began observations of the solstice and equinox sunrise and sunset directions in September of 1992. The Campus Physical Planning Committee of the Faculty Senate voted unanimously on Oct. 17, 1995 to approve the placement of the U.Mass. Sunwheel in an open field near the south end of campus.

To determine the proper placement for the standing stones in the Sunwheel, it is necessary to observe the precise locations of the rising and setting Sun on the horizon as seen from the center of the Sunwheel at the times of the winter solstice, autumnal or vernal equinox, and summer solstice. Actual observations are necessary because each site has a unique horizon, and the standing stones will be situated to mark the actual direction toward which the Sun rises and sets along the horizon. The solstice and equinox sunrise and sunset observations were made in 1996. Also in 1996, a site survey was conducted at the Sunwheel with the help of my colleague Dr. Steve Schneider of the Dept. of Astronomy, to determine true N, S, E, and W relative to the spot selected to be the center, as well as the azimuths of the solstice sunrise and sunset directions. At the same time, we measured the elevation of the horizon in each of the cardinal and solstice directions; the local horizon has a mean elevation of only ~5°, varying from 2° in the West to 7° in the East. In addition, the elevation of the spots located 60' from the center of the Sunwheel in each of the cardinal and solstice directions was determined; across the site, variations in ground level are within +-1' of the elevation of the center.



Figure 1 schematically illustrates the basic components of the U.Mass. Sunwheel, and the observed angles to the solstice sunrise and sunset directions as seen from the center. The small dots represent the stones in the preliminary Sunwheel, and the large dots represent the 8'-10' tall stones. The angles to the solstice sunrise and sunset stones relative to the E-W direction, as viewed from the center of the Sunwheel, have an average value of 32° 54', with variations which depend on the local horizon. Because of the dependence of the observed azimuth of sunrise and sunset on the observer's latitude and local horizon, Figure 1 applies only to the U.Mass. Sunwheel.




Figure 2 illustrates the elevation angle of the horizon as seen from the center of the Sunwheel in each of the solstice and cardinal directions, and the ground level variations at a distance of 60' from the center of the Sunwheel. These data are essential for determining the heights needed for the tall standing stones in the enlarged Sunwheel. Photographs of the appearance of the preliminary Sunwheel are shown in Figures 3 and 4.





III. The Standing Stones

The plan for the enlarged Sunwheel includes the addition of 14 standing stones at a radius of 60' from the center, one for each of the solstice sunrise and sunset directions, one each for North and South, 2 standing stones in each of the East and West directions, and one for each of the northern and southern extremes of moonrise and moonset. These stone locations are shown as the large dots in Figures 1 and 2.

The plan for the tall standing stones is that they mark N, S, E, and W, as well as the locations of sunrise and sunset along the horizon on the solstices, and moonrise and moonset for the extremes reached every 18.6 years. The heights needed for the standing stones to just reach to the horizon at a distance of 60' from the center depends on the angle of elevation at the horizon, the elevation of the ground, and the height of the observer. Table 1 shows the heights needed for the Sunwheel standing stones in each direction, based on the elevation of the horizon and the variations in ground level for an eye level 4' above ground. In most cases, stones in the 8'-10' tall range are ideal as calendar points in the Sunwheel. For a Sunwheel with a radius of 60', the outer circumference of the circle of standing stones is 377'. Thus, an angle of 1° as seen from the center is equal to 1.05' around the circumference. Since the Sun's angular diameter is 0.5°, this corresponds to a linear dimension of 6" at the outer radius of the Sunwheel. Therefore, to preserve the directions marking the sunrise and sunset on the solstices, it is desirable to locate the top or center of each of the large standing stones to an accuracy of ~4".

The stones which have been selected for the Sunwheel are natural monoliths, and will be purchased from the Chester Granite Company in East Otis, Massachusetts. The main stones are in the 7'6"-10' tall range, with the bottoms sawed flat. Photographs of the 10 stones are shown in Figures 5, 6, 7, 8, 9, 10, 11, and 12. Table 2 lists the approximate dimensions of the base of each stone -- 7 of the stones have bases which are 20"-30" by 50"-70", 2 are smaller, and 1 is larger. The size of the base of each standing stone is important for determining the size of the slab which will be needed as part of the foundation of each stone. This in turn determines the size of the hole needed for the foundation of each stone. These dimensions are given in Table 2.

In the current plan, there are 4 additional stones which will be included in the Sunwheel, and these will mark the northern and southern extremes in the dierction to the rising and setting of the Moon, equivalent to the summer and winter solstice sunrise and sunset directions for the Sun. Because the Moon's orbit is tilted by 5° to the ecliptic, the Moon will reach the northern and southern rising and setting extremes every 18.6 years. These extremes are referred to as a major lunar standstill, similar to the way in which a solstice is a standstill in the rising and setting direction for the Sun. In azimuth, the angular offset of the lunar standstill directions from the solstice directions is 8°, assuming no changes in the elevation of the horizon. Stones in the 5'-6' range have been selected to mark the lunar standstill directions, as shown in Figures 13, 14, 15, and 16. The Moon stone dimensions, orientations, azimuths, and hole locations are given in Tables 2, 3, 4, 5, and 6.

Prior to construction of the Sunwheel, the hole for the foundation of each stone will be dug. The precise location of each foundation hole will depend on the shape of the stone, and will be shifted in azimuth for the stones whose peaks are not centered over the base. Three of the stones have significant curvature or offsets between the peak of the stone in relation to the base. Table 3 indicates the position of the peak relative to the base, which needs to be included when computing the location of the foundation hole.

The final detail regarding the standing stones has to do with which face will be seen from the center of the Sunwheel. The precise orientation of each stone then determines the orientation of the foundation hole for each stone. Table 4 presents the information regarding the selected orientations of the Sunwheel standing stones.

IV. Construction Design

The design which will be used in the installation of the 8'-10' tall standing stones at the Sunwheel was initially suggested by Allen Williams of the Chester Granite Company, based on his experience in dealing with supporting tall standing stones. With this suggested design in hand, the Sunwheel site was studied by Prof. Don DeGroot and members of the U.Mass. Dept. of Civil and Environmental Engineering, with the goal of determining the specifications regarding the weight bearing capacity of the soil, monitoring the water level, and providing recommendations regarding the construction of the enlarged Sunwheel. Specifically, the issue of the stability of the stones was addressed, and again, the design suggested by Allen Williams was endorsed. What follows is a description of the basic design to be used in the installation of the Sunwheel standing stones. The plan which will be used to implement this design follows.

(a) Foundations of Standing Stones

The standing stones purchased from the Chester Granite Company are all sawed flat on the bottom, so that each may sit on top of a granite slab foundation. These granite slabs will each be 12" thick, and will cover an area no smaller than 4'x4'. The actual size of each slab, which depends on the actual size of the base of each standing stone, ranges from 4'x4.5' to 4'x6' (see Table 2). The top of each granite slab will be placed approximately at ground level.

The foundation holes will be excavated to a depth of 3.5', and the lower 2.5' will be filled with 3/4" crushed stone. To ensure that the crushed stone does not mix with the soil over time, each foundation hole will first be lined with Geotextile on the sides and bottom. The 3/4" crushed stone will be placed in the hole to a depth of 18" and then compacted. Another layer of Geotextile will be placed in the hole, with another 12" of crushed stone, atop of which the the granite slab will be placed. Finally, crushed stone will be used to fill in the excavated area around each granite slab. Figure 17 (below) illustrates the basic components of the construction design.

(b) Installation of Standing Stones

The standing stones will each be supported on a granite slab which rests on a bed of crushed stone. In addition, each standing stone will be anchored to it's granite slab base with a stainless steel rod 1" in diameter and 20" long. It is a true engineering challenge to align the standing stones to within a few inches and also to anchor them properly, which involves drilling into the granite slabs at the Sunwheel site when the standing stones are installed. Prior to being brought to the site, the bottom of each standing stone will have a 10" deep hole drilled into it with a 1.375" bit. Then, the perimeter of the stone at its base will be marked with the location of this hole (i.e. the endpoints of 2 perpendicular lines, which intersect at the hole, will be marked).

To install the standing stones, each one will be picked up in a sling to avoid damage, and then lowered over the granite slab base stone. When the standing stone in the sling is lowered into the correct orientation, the outline of the standing stone and the marks locating the drilled hole will be transferred to the surface of the granite slab. With the standing stone still in the sling, it will be moved aside so that a hole can be drilled 10" into the granite slab, again with a 1.375" bit. Then, a 20" long stainless steel rod, 1" in diameter, will be placed in the granite slab, and the standing stone will be lowered onto this pin. A compound will be used along with the stainless steel dowel to complete the fastening system. Finally, epoxy will be placed between the stone and slab at 4-5 locations to bond the standing stone to its foundation.

V. Construction Plan

There is a very specific order to the steps which must be carried out to complete the construction of the Sunwheel. Some of these steps are related to the engineering, some to the construction, and still others to the rules in place at the University. The individuals listed below are Judy Young (JY), Gene Stewart (GS), Allen Wlliams (AW), Physical Plant (PP), Denise Sallee (DS), Vera Rubin (VR), and Robert Rubin (RR). The steps in the process of construction are:

(1) select the standing stones (JY + GS)

(2) order stainless steel rods (JY) (3) get contracts for site work approved and signed (JY + PP + DS) (4) mark the foundation holes on the ground (5) apply for "dig safe" from University (JY)

(6) arrange for filmmaker to make video (JY)

(7) publicize likely date of construction (JY) (8) call in the volunteers (JY) (9) mark off Sunwheel with yellow tape so equipment will go around it (JY)

(10) order Geotextile 1 week prior to foundation digging (JY)

(11) order crushed stone to be delivered 1-2 days before the foundation work will begin (JY)

(12) call Allen Williams as soon as site preparation is planned (JY)

(13) arrange for date of site work with Karl's Excavating

(14) SITE WORK (JY + Karls' + AW)

(15) SET STANDING STONES (JY + AW + Karls') (16) site clean-up (JY + ?) (17) have a dedication ceremony and party!

* * * * * * *

Acknowledgements: I am most grateful for the site at U.Mass. which has been provided for the Sunwheel. Without this land, the Sunwheel would not exist. I also gratefully acknowledge the start-up funds received from the Healey Endowment at U.Mass., the funds received from NASA and the NSF, and the donations of many generous individuals, especially Ann Hastings, Nick Scoville and Dave Sanders. Your support has made it possible to turn a dream into a reality. There are many individuals who have provided support for the Sunwheel Project through a willingness to contribute their time and energy. Special thanks are due to Daniel Steele for making a model of the Sunwheel; to Laura Young for getting up for the summer solstice sunrise in 1996 to help mark the sunrise direction, and for helping me with the sunrise and sunset gatherings at the Sunwheel on the solstices and equinoxes from 1997-2001; to Gene Stewart for helping select the large standing stones and for helping raise money during the U.Mass. Craft Fair each December; to Steve Schneider, Astronomy Professor at U.Mass., who helped conduct the site survey; to Mary Musgrave, Associate Dean of the College of Natural Sciences and Mathematics here at U.Mass., for enlisting the help of the civil and environmental engineers on campus to evaluate the Sunwheel site; to Don DeGroot, Professor of Civil and Environmental Engineering at U.Mass., for studying the soil quality and the design suggested for the foundations of the stones at the Sunwheel; to Allen and Kathleen Williams, owners of the Chester Granite Company, for their love of the stones, and their patience with me in planning the Sunwheel; to Selene Weber for her imagination as to what we could create; to Dean Cardaisis in Landscape Architecture for advice regarding the Sunwheel site; to Jack Rogala, head of Grounds Services, for helping provide access to the Sunwheel site and finding me a bridge to use; to Steve Konieczny at Karl's Excavating, who patiently helped me figure out the cost of constructing the Sunwheel each time a new design was suggested; to Jim Wright, Program Director for Education and Human Services at the National Science Foundation, for agreeing with me that the Sunwheel is a good idea and worthy of funding by the NSF; and to Fred Byron, Vice Chancellor for Research at U.Mass., for waiving the overhead on my NSF grant, thereby giving the project additional funds. You have each contributed an essential part to the success of the Sunwheel, and for that I am grateful. Now if it would just stop raining so the ground could dry out ...

  A project conceived by Dr. Judith S. Young
 Professor of Astronomy, University of Massachusetts, Amherst
 e-mail: Judith Young

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Last Update: 7/03/2003