For those who have gathered over the centuries at Stonehenge - the imposing prehistoric monument that has dominated Salisbury Plain in southwest England for some 4,500 years - it was probably clear how the Sun could have influenced its design.

The central axis of the stone circle was, and still is, aligned with sunrise in midsummer and sunset in midwinter, and the stones dramatically frame sunrise and sunset when the days are longest and shortest.

The idea that Stonehenge was somehow linked to the moon gained ground in the 1960s. However, the concept had not been explored systematically, says Clive Ruggles, emeritus professor of archaeoastronomy in the faculty of archaeology and ancient history at the University of Leicester.

This summer, archaeologists are using a little-known lunar phenomenon that occurs every 18.6 years to investigate it as part of their work to understand why Stonehenge was built.

Like the sun, the moon rises in the east and sets in the west. However, the rising and setting of the moon moves from north to south and vice versa in the space of a month. The northern and southern extremes also change over a period of about 18.5 years. Lunar stasis is when the northernmost and southernmost moonrise and moonset are farthest apart.

"Moonrise changes every day and, if you track it for a month, you find that there is a northern boundary and a southern boundary beyond which the moon never rises (or sets)," explains Fabio Silva, senior lecturer in archaeological modelling at Bournemouth University, by email.

"If we were to observe these boundaries over 19 years, we would find that they change like an accordion: they expand to a maximum limit (the major lunar standstill) and then begin to contract to a minimum limit (the minor lunar standstill)."

This major lunar standstill is scheduled for January 2025, but between now and mid-2025, the Moon may appear, to a casual observer, unusually low and high in the night sky during the lunar month.
With images in association with Ivan Tang/LoveTravelTheWorld.