It marks the longest day of the year in the Southern Hemisphere.
CHINA: The Winter solstice marks the end of the harvest season and is celebrated with family gatherings and a big meal, including rice balls called tang yuan.
A little about winter solstice: The event takes place every year on December 21. In the Northern Hemisphere, it occurs when the sun is directly over the Tropic of Capricorn, which is located at 23.5° south of the equator and runs through Australia, Chile, southern Brazil, and northern South Africa. This is the shortest day of the year, too - but with the moon this full, we've got plenty of reason to stay out howling.
The number of daylight hours peaks at summer solstice - in the United Kingdom, summer solstice sees 16 hours, 38 minutes and 19 seconds of daylight to be enjoyed.
Although some people think that the whole day is the solstice, there is actually a specific time in the day when the solstice occurs. But scientifically speaking, it's the shortest day of the year in the Northern Hemisphere. In fact, the last solstice to take place on December 23 was in 1903, and it won't happen again until 2303.
However, when you're looking out into a clear sky on Friday night, the moon will appear full to you - and could be so bright that people with pretty good eyesight could read by it. The annual Ursids meteor shower should hit its peak a day or two after the solstice event.
Experts reckon the best time to see the shooting stars will be in the early hours of Saturday morning, when it's darkest.