June Solstice: Celebrating the longest day of the year

The June Solstice and the December Solstice are two breathtaking celestial occasions that occur each year. These solstices are critical to the Earth's orbit around the Sun, providing the longest and shortest days of the year. The June solstice, also known as the summer solstice in the Northern Hemisphere, is a captivating phenomenon that occurs when the Sun reaches its highest point in the sky directly above the Tropic of Cancer. This celestial occurrence signifies the northernmost latitude the Sun reaches throughout the year. Following this pivotal event, the Sun begins its gradual journey southward. For those curious about the specific time and date of the June solstice, in Dibrugarh, Assam, India, it is set to take place on Wednesday, 21 June 2023, at 20:27 IST. In Coordinated Universal Time (UTC), it will occur at 14:57 on the same day.

June Solstice: Longest Day of the year in the Northern Hemisphere

The term "solstice" finds its roots in the Latin words "sol" meaning "Sun" and "sistere" meaning "to stand still." This name is apt as the solstices mark the moments when the subsolar point, the spot directly beneath the Sun on the Earth's surface, halts its north-south movement. During the December solstice, the subsolar point reaches its southernmost position, pauses briefly, and then begins its northward journey until it crosses the equator on the day of the March equinox. At the June solstice, the subsolar point reaches its northernmost point before embarking on its southern journey once again.

The apparent movement of the Sun across the sky gradually shifts in the months leading up to the June solstice. The position of sunrise and sunset creeps northward until it reaches its northernmost point on the day of the solstice. From that point onward, the Sun's daily path begins its gradual shift southward.

The June solstice brings us the longest day of the year in the Northern Hemisphere. Due to the Earth's axial tilt, the Northern Hemisphere leans toward the Sun during this time, resulting in an abundance of sunlight throughout the day. This tilt is most pronounced during the solstice, providing an extended period of daylight. The further away a location is from the equator, the more prominent this effect becomes. Tropical regions may experience slightly longer days of just over 12 hours, while the temperate zones enjoy significantly extended daylight. In the Arctic Circle, a unique phenomenon known as the Midnight Sun or polar day occurs, where the Sun remains above the horizon for the entire day, creating a surreal experience for those fortunate enough to witness it.

June Solstice: Shortest Day of the year in the Southern Hemisphere 

On the contrary, the June solstice marks the shortest day of the year in the Southern Hemisphere. As the Southern Hemisphere tilts away from the Sun during this time, the length of daylight diminishes. Similar to the Northern Hemisphere, the farther a location is from the equator, the more noticeable this effect becomes. Regions within the Antarctic Circle experience polar night, where the Sun remains below the horizon for the entire day, casting an enchanting darkness upon the land.

June Solstice: Significance

The June solstice holds great significance for the seasons. In the Northern Hemisphere, it marks the official start of summer, ushering in warmth and longer days. Conversely, in the Southern Hemisphere, it signals the onset of winter, with shorter days and cooler temperatures prevailing. It is commonly believed that the longest day of the year corresponds to the earliest sunrise and the latest sunset. However, in most locations, the earliest sunrise actually occurs a few days before the solstice, while the latest sunset takes place a few days after. This intriguing phenomenon is a result of the intricate workings of Earth's rotation and its elliptical orbit around the Sun.

While many consider June 21 as the date of the June solstice, it's important to note that it can occur anywhere between June 20 and June 22, depending on the specific time zone. Solstices falling on June 22 are relatively rare, with the last occurrence taking place in 1975 and the next one not expected until 2203. The variability in the date of the solstice stems from the fact that our calendar, known as the Gregorian calendar, does not perfectly align with the Earth's tropical year—the time it takes for the Earth to complete one orbit around the Sun. The Gregorian calendar consists of 365 days in a common year and 366 days in a leap year, while the actual tropical year spans approximately 365.242199 days. 

This slight discrepancy causes the timing of the solstices and equinoxes to gradually drift away from the calendar, resulting in the solstice occurring about six hours later each year. To realign the calendar with the tropical year, a leap day is added (almost) every four years, shifting the equinox and solstice dates back to an earlier position. The precise timing of the equinoxes and solstices is influenced by various factors, including variations in the length of the tropical year and the Earth's orbital and daily rotational motion. These intricate dynamics, such as the "wobble" in the Earth's axis known as precession, contribute to the ever-evolving nature of these celestial events.