Chimney Rock National Monument

• Six months later a smaller crowd congregates around the Heel stone to witness the midwinter Sun setting within the stone circle.
• But a hypothesis has been around for 60 years that part of Stonehenge also aligns with moonrise and moonset at what is called a major lunar standstill.
• There is now an abundance of archaeological evidence that indicates the solar alignment was part of the architectural design of Stonehenge.

Lunar standstill

• It is these longer sides that are thought to align with the major lunar standstill.
• These southern and northern limits of moonrise (or set) change on a cycle of 18.6 years between a minimum and a maximum range – the so-called minor and major lunar standstills, respectively.
• The major lunar standstill is a period of about one and a half to two years when the northernmost and southernmost moonrises (or sets) are furthest apart.

• The strongest evidence we have for people marking the major lunar standstill comes from the US southwest.
• Of six cutting dates, four correspond to major lunar standstill years between the years AD1018 and AD1093, indicating that the site was renewed, maintained or expanded on consecutive major standstills.
• Returning to southern England, archaeologists think there is a connection between the major lunar standstill and the earliest construction phase of Stonehenge (3000-2500 BC), before the sarsen stones were brought in.
• The major lunar standstill hypothesis, however, raises more questions than it answers.

A search for answers

• It’s unclear whether the Moon would have been strong enough to cast shadows and how they would have interacted with the other stones.
• This collaboration will result in events showcasing and debating the lunar alignments at both Stonehenge and at Chimney Rock.

Erica Ellingson receives funding from the US Department of Agriculture. This institution is an equal opportunity provider. Amanda Chadburn and Fabio Silva do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.