The Moon huddles quite close to Antares this evening. The star represents the heart of the scorpion. They’re low in the southwest at nightfall.

The Moon and Antares both played important roles in the astronomy and skylore of many cultures. And in at least one case, they may have overlapped.

Close encounters between them – especially at full Moon – may be recorded in grooves carved on the island of Gotland. It’s in the Baltic Sea, off the southeastern coast of Sweden. There’s evidence that it was inhabited thousands of years ago.

Archaeologists have charted about 3600 grooves. Some are carved into the bedrock, but most are found on boulders. The grooves are up to a few feet long, a few inches wide, and one or two inches deep. They’re found in groups.

The grooves in a group follow slightly different alignments. A study a couple of decades ago suggested those alignments were astronomical – they pointed toward the rising and setting points of the full Moon at certain times of the year.

In particular, the study found possible alignments in the largest set of grooves – 32 in all. Calculations revealed that they lined up with the Moon when it passed Antares at 19-year intervals – an important cycle in the Moon’s path along the horizon. The series could have started at the spring equinox almost 5200 years ago, and continued for centuries – a possible record of lunar encounters with the scorpion.

Script by Damond Benningfield