Stone Age people in Ireland appear to have built tombs based on a detailed knowledge of how the Sun moves across the sky during the year.

Tombs at the archaeological site of Loughcrew in County Meath align with the rising Sun at the spring and autumn equinoxes.
The inside of the chambers are spectacularly illuminated by a shaft of sunlight at dawn on these days, said Frank Prendergast of the Dublin Institute of Technology.

It suggests settlers in the area some 5 to 6,000 years ago knew the yearly cycle of the Sun and perhaps centred their lives around it.

Tombs found elsewhere in Ireland have been found to point towards the rising Sun at the summer and spring solstices.

At these times, the Sun reaches its most northerly and southerly points in the sky, which can be easily observed from any place on Earth.

The equinoxes - in late March and late September - are not so obvious and can only be pinpointed by tracking the passage of the Sun across the entire year.