Astronomical achievement

The "ravaged colossus" of Stonehenge, with its monumental circle of standing stones, attracts thousands of visitors a year to the tiny town of Amesbury in England.

Now New Zealand is about to get its own Pacific version - Stonehenge Aotearoa - scheduled to open next month.

Dismiss any notion of cringemaking kitsch replicas of Ye Olde Stonehenge. This is a full-scale adaptation of the original monument, specifically designed for its location in the Wairarapa, and representing the first stage in the construction of a "working astronomical observatory".

According to Richard Hall, president of the Phoenix Astronomical Society, who has spent three years co-ordinating hundreds of volunteers for the project, it has been accepted that the primary purpose of Stonehenge and other stone circles or henges built all over Europe and in the Pacific, was as a calendar. "Most of the henges are aligned with the axis oriented towards sunrise at the summer solstice in one direction and sunset at the winter solstice in the other. It's easy to see why these markers of seasonal changes would be so important for human survival. Even nomadic peoples would have needed to know when it was time to move," says Hall.

To what extent the alignment was for astronomical as opposed to ceremonial significance has been a rich source of contention among archaeologists, astronomers and historians for the past 200 years.

The Stonehenge that survives - remnants of the Sarsen circle's 30 lintel-topped monoliths which encompass five enormous trilithons - is actually Stonehenge III, the third and final stage which was built over hundreds of years between 3000 and 2001BC. Although Stonehenge III covers a much smaller area than the original henge, the size of the stones, weighing between 25 and 50 tonnes and dragged into position from a quarry more than 30km away, make it easily the most impressive.

But it is likely that the earlier versions, with their longer sightlines, have more claim to astronomical accuracy. Stonehenge III is an astronomically symbolic monument for ritual purposes.

The first Stonehenge was a 100m earthwork ring with an opening aligned with the moon's most northern point. Later an inner ring of 56 chalk-filled holes - the Aubrey Holes, named after their 17th century discoverer, John Aubrey - was added, along with two mounds and two "station stones", which together mark the corners of a rectangle centred on the inner circle. The sides of the rectangle are aligned to mark the extreme rising and setting times of the sun and moon, suggesting that the site may have been especially selected for this reason, since it is only at that latitude that these extremes are joined by a right angle.

Whatever the historic truth, Hall is much more concerned with using Stonehenge Aotearoa to expose people, especially young people, to the scientific truth, beauty and heritage of our own southern skies and to underline the connection between all cultures, ancient and modern.

In addition to the 24 pillars that form the henge and mark astronomically significant cycles, a 5m-high obelisk indicates the position of the south celestial pole and casts a shadow which will be used to mark a 10m-long analemma - the rather wonderful "figure of eight" pattern that the sun's daily position traces over a year. The pillars are each identified by their relationship to stars important to Maori astronomy. The henge also incorporates the navigational points of the Polynesian star compass that guided Pacific explorers to Aotearoa.

Hall has long been an exponent of Maori and Pacific astronomy, strongly supporting the move to celebrate Matariki, the Maori New Year celebration of winter solstice. He has also co-authored a book on Maori astronomy. His recently released How to Gaze at Southern Stars, is an idiosyncratic mix of astronomy, starlore and anthropology for beginners, bound to inspire the reader to cast an eye heavenwards.

Volunteers put in something like $350,000 worth of voluntary labour to build this extraordinary monument. Hall has also convinced the Royal Society of New Zealand to contribute $55,000 because of the monument's potential to raise the public profile of science.

Hall counters scepticism about whether the monument will attract more interest in the cult fringes of pseudoscience than in real science with a disarming inclusiveness. He welcomes everyone.

Sure, there'll be druids dancing and solstice weddings and astrologers checking out the ascendancy of the sun in Libra - but the same people will come face to face with facts like precession. That's the 26,000 year "wobble" in the earth's axis, which means that star signs, based on the apparent path of the sun through the zodiacal constellations, have shifted by about a day per century - far from their original dates.

And then there's the economic potential. The Phoenix Astronomical Society's website gets up to 40,000 international hits a day, and tour operators line up to bring busloads to a site that links to cultural, educational and spiritual interests. So it is not surprising that the Wairarapa councils and local iwi have been more than co-operative.

The benefits are likely to be just as tangible in terms of the development of skills and talent. Already, the first astronomy graduates inspired by the project have emerged and several have undertaken post-graduate studies.

In spite of huge international investment in astronomy and astrophysics, there is a perception that this is a narrow and esoteric field. Yet a recent British survey showed that astronomy graduates were the most commercially sought after of the physical scientists, mainly because they have a high degree of proficiency in a range of sciences and technologies.

Even more compelling is that the cosmos offers unlimited opportunity to study the behaviour of matter in extreme conditions which cannot be modelled in laboratories, increasingly relevant as new technologies push the boundaries. And the cost. For small countries like New Zealand the price of fundamental research is astronomical. Last year a $7 million telescope, the largest in New Zealand, was opened at the University of Canterbury's observatory at Mt John, Lake Tekapo. It was almost entirely paid for by Nagoya University, proof that our southerly latitude, clear skies and skilled academic and technical workforce can attract international investment.