What is the winter solstice? Celebrations, science, live broadcast

In 2022, winter The solstice occurs in the Northern Hemisphere December 21. Although it’s not as dramatic as 2020 Conjunction of Jupiter and SaturnThe longest night of the year is an important turning point. Astronomical winter It begins, and the days gradually get longer again.

Curious why this happens? WIRED spoke with Tanso Dylana former postdoctoral fellow for the Transiting Exoplanet Survey (TESS) at MIT, is working to better understand the winter solstice and our planet’s relationship with the Sun.

To visualize what happens in space during the winter solstice, start by thinking of a giant glass ball surrounding Earth, and let’s ignore the planet’s rotation (which complicates everything). “If you look at the three-dimensional sphere that surrounds us, known as the celestial sphere, the Sun and all other objects in the solar system move through a plane in this celestial sphere, known as the ecliptic plane,” Dylan says.

“While doing this, the sun changes its tilt,” he says. deviation and Right ascension They are the two main axes of the celestial sphere. “In this frame of reference, the Sun is at its southernmost position when it is the winter solstice from our perspective in the Northern Hemisphere.”

The winter solstice occurs in the Northern Hemisphere when North Pole It is tilted to the furthest point from the sun. The Arctic Circle is shrouded in darkness and experiences its longest night of the year. In the Southern Hemisphere, the summer solstice occurs simultaneously with the South Pole tilted toward the sun and the Antarctic Circle Midnight sun.

NASA’s Spaceflight Fundamentals online tutorial includes a section on Celestial sphere with illustrations For anyone who enjoys exploring the idea further.

The low position of the sun during the winter solstice will cause you Midday shadow To be exceptionally long. Although important to humans, the solstice has little meaning in relation to the larger universe.

Solstices are defined in relation to the Earth-Sun system, not necessarily the entire solar system. “We attach a lot of meaning to them because the Sun is so sacred to us, and its position in the celestial sphere, as a function of time over the course of the year, is very important,” says Dylan. “It determines the climate. Throughout the year, it tells us when crops will mature. This is very important, especially for historical civilizations.