The winter solstice is a celestial milestone that marks the shortest day and longest night of the year. In 2024, the winter solstice occurs on Saturday, December 21 at 4:20 a.m. ET in the Northern Hemisphere.

This moment is more than just an astronomical event – ​​it’s a turning point in our annual journey around the Sun.

Why is the winter solstice the shortest day of the year?

The Earth’s axis is tilted at an angle of 23.4 degrees, and this tilt is responsible for the changing length of daylight throughout the year.

During the Northern Hemisphere summer, the North Pole is tilted toward the Sun, resulting in longer days. However, in winter, the North Pole is tilted, causing shorter daylight hours.

At the winter solstice, the sun appears at its lowest point in the sky, resulting in the fewest hours of daylight of the year.

For example, New York will have just 9 hours and 15 seconds of sunlight, while Los Angeles, which is further south, will enjoy slightly more at 9 hours and 53 minutes, depending on the time and date.

This phenomenon occurs because the tilt of the Earth determines how much sunlight different parts of the globe receive. On December 21st, it reaches its tilt from the Sun in the Northern Hemisphere, giving us the shortest day and longest night.

Interestingly, the shortest day of the year does not necessarily correspond to the earliest sunset.

For example, sunset on December 8 in New York City was at 4:28 PM ET, but on the solstice it will be four minutes later at 4:32 PM ET.

Is the winter solstice always on the same day?

Not quite. While the winter solstice usually falls on December 21st or 22nd, it can occasionally occur on December 20th or 23rd. These variations occur because of the elliptical orbit of the Earth around the Sun and the way we measure time according to the Gregorian calendar.

The rarest dates of the winter solstice are December 20 and 23. For example, the last solstice on December 23rd was in 1903, and the next one will not occur until 2303. A solstice on December 20th is also rare, with the next one expected in 2080.

Why is it called the winter solstice?

The word solstice comes from the Latin term solstitium, which means “the sun stands still”. This name reflects the apparent pause in the sun’s movement across the sky before it changes direction.

Around the winter solstice, the sun appears to rise and set in the same place on the horizon for several days before rising higher again, heralding longer days.

In the Northern Hemisphere, this is called the winter solstice because it coincides with the beginning of astronomical winter. However, for those in the southern hemisphere, December 21st is the summer solstice, which marks the longest day of the year.

A seasonal opportunity for stargazing

The winter solstice is a great time to admire the night sky thanks to its long and dark night.

“As we orbit the solar system, we can admire different parts of the night sky at different times of the year,” Baskill said.

“In the summer months we have a great view of the center of our galaxy, and in the winter months we have a great view of the other half of the sky – including the constellation Orion and the amazing star-forming gas clouds that fill it.” that part of heaven.”