A shared habit of watching the sky

Almost every ancient society paid close attention to the Sun, because the rhythm of daylight and seasons governed farming, travel and ceremony. Many of them also made it central to religion.

The similarities do not necessarily mean the societies were in contact. Observing the same sky in different places can lead to related ideas without any shared origin.

Sun gods and rulers

In Egypt, the sun god Ra was one of the most important deities, and in the fourteenth century BCE the pharaoh Akhenaten promoted the worship of the sun disk, the Aten. In Greece, Helios personified the Sun, and in Rome the cult of Sol Invictus was made an official cult by the emperor Aurelian in 274 CE.

In the Andes, the Inca honored Inti and held the festival of Inti Raymi at the June solstice. In Japan, the goddess Amaterasu occupies a central place in myth, and the imperial family has traditionally claimed descent from her.

Monuments aligned to the Sun

At Newgrange in Ireland, a passage tomb built around 3200 BCE, a roof box lets the rising Sun at the winter solstice send a beam of light into the inner chamber for a few minutes. Stonehenge in England has a main axis aligned with the midsummer sunrise and midwinter sunset.

At Chichén Itzá in Mexico, the stairway of the pyramid known as El Castillo shows a pattern of light and shadow around the spring and autumn equinoxes. At Abu Simbel in Egypt, sunlight reaches the inner sanctuary of the temple on two days a year, around February 22 and October 22.

Calendars and agriculture

Solar observations underpinned calendars. The Egyptian civil calendar of 365 days, the Roman Julian calendar introduced in 45 BCE and the later Gregorian reform all try to match the length of the solar year.

Marking solstices and equinoxes helped communities decide when to plant, when to harvest and when to gather for ceremonies, which is why these dates carry so much symbolic weight.

Reading claims about ancient alignments

Some alignments are well documented and widely accepted. Others are weaker, because with enough lines on a map almost any monument can seem to point at something. Researchers therefore ask whether an alignment is precise, whether it recurs across many sites and whether the builders’ own records or customs support it.

Being careful about these questions does not reduce the wonder of the evidence. It helps separate what ancient builders demonstrably did from what later writers have imagined.