For many countries in Europe, today is Midsummer Day. It’s marked with bonfires and other celebrations. It marks the middle of summer, which began back in May.

Astronomically, though, today marks the start of summer in the northern hemisphere. It’s the summer solstice — the longest day of the year. It marks a turning point for the Sun, which will begin to move southward after today.

Regardless of whether it was considered the start of summer or its middle, the solstice had great significance for cultures around the world. They held festivals and religious ceremonies to celebrate the light.

Many cultures used natural alignments to track the Sun’s motions along the horizon, allowing them to pinpoint the date. They also made their own alignments.

One of the most famous examples is Stonehenge in England. But there are plenty of examples in the Americas as well.

In the United States, many are still found in the southwest, in the remnants of ancient pueblo sites. Many of the solstice markers are spirals carved or painted on rock surfaces. The rising Sun passes through cracks or notches in the nearby rocks, creating daggers of light across the spirals.

Other markers were built into houses or ceremonial structures. Narrow windows, for example, might allow the sunlight to shine onto symbols on the opposite wall — symbols dedicated to the rising Sun on the summer solstice.

We’ll have more about the solstice tomorrow.

Script by Damond Benningfield