The Summer Solstice occurs in the northern hemisphere when the sun travels along its northernmost path in the sky, giving us the longest amount of daylight on that day. Francis K. Beirne looks at how the solstice has been celebrated in different ways by different races down through the centuries.
At the summer solstice, the sun travels the longest path through the sky, and that day therefore has the most daylight. When the summer solstice happens in the northern hemisphere, the North Pole is tilted about 23.4° (23°27´) towards the sun. Because the sun’s rays are shifted northward from the Equator by the same amount, the vertical noon rays are directly overhead at the Tropic of Cancer (23°27´ N).
Six months later, the South Pole is inclined about 23.4° toward the sun. On this day of the summer solstice in the southern hemisphere, the sun’s vertical overhead rays progress to their southernmost position, the Tropic of Capricorn (23°27´ S).
In the northern hemisphere, the June solstice occurs when the sun travels along its northernmost path in the sky. This marks the astronomical start of summer in the northern half of the globe. In the southern hemisphere, it’s the opposite: the June solstice marks the astronomical start of winter, when the sun is at its lowest point in the sky. This year, the summer solstice occurs on Tuesday 21st June.
The solstice marks the official beginning of summer in the northern hemisphere, occurring when Earth arrives at the point in its orbit where the North Pole is at its maximum tilt (about 23.5 degrees) toward the sun, resulting in the longest day and shortest night of the calendar year. (By longest “day,” we mean the longest period of sunlight hours.) On the day of the June solstice, the northern hemisphere receives sunlight at the most direct angle of the year.
The word ‘solstice’ comes from Latin solstitium – from sol (Sun) and stitium (still or stopped). Due to the Earth’s tilted axis, the sun doesn’t rise and set at the same locations on the horizon each morning and evening; its rise and set positions move northward or southward in the sky as Earth travels around the sun through the year. Also, the sun’s track in the sky becomes higher or lower throughout the year.
The June solstice is significant because the sun reaches its northernmost point in the sky at this time, at which point the sun’s path does not change for a brief period of time.
After the solstice, the sun appears to reverse course and head back in the opposite direction. The motion referred to here is the apparent path of the sun when one views its position in the sky at the same time each day, for example, at local noon. Over the year, its path forms a sort of flattened figure eight, called an analemma.
