What is the winter solstice?
The winter solstice is the shortest day of the year in the northern hemisphere and the longest day in the southern hemisphere. The plastic globes you see with Earth upright at each pole are misleading. In reality, Earth tilts at an angle of about 23.5 degrees. As Earth orbits the sun, sunlight falls on different parts at different angles.
This is the reason we have four seasons. If Earth did not tilt, we would not have any seasons and life would be completely different. There would be 12 hours of light and 12 hours of darkness every day. It would be very boring.
When is the winter solstice?
The winter solstice is marked every December 21st, but this year it actually occurs on Friday, December 22nd at 3.27am. This is the moment when the sun appears directly over the Tropic of Capricorn, which is located at 23 degrees south of the Equator.
The word solstice comes from the Latin sōlstitium, which translates as sun still. To ancient people it looked like the sun stood still on that day.
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The grand stretch in the evenings in Ireland begins on December 21st. Each day will get gradually brighter until the summer solstice on June 21st.
Why is it important?
The winter and summer solstices are important events going back to ancient times. Observations of the sun’s movements across the heavens were vital to the cultivation of crops for ancient civilisations. The concept of rebirth inspired the festive practice of role-reversal best seen in the Roman festivities of Saturnali, when the role of slave and master would reverse, and, earlier, in Mesopotamian civilisations.
The winter solstice was a hugely important event in Celtic culture, as evidenced by two of the most famous landmarks on these islands, Stonehenge and Newgrange. Both monuments are aligned with the passage of the sun.
In Celtic culture the winter solstice marked the death and rebirth of the sun.
Why is Newgrange so important during the winter solstice?
Newgrange is one of the most astonishing prehistoric monuments in the world. At an estimated 5,200 years old, it is older than the pyramids at Giza and was built by our ancestors in the Stone Age.
Newgrange was built by a farming community that prospered on the rich lands of the Boyne Valley. Knowth and Dowth are similar mounds that together with Newgrange have been designated a World Heritage Site by Unesco.
Its burial chamber is aligned so that on the morning of the winter solstice a beam of light penetrates the roof-box and travels up the 19 metre passage and into the chamber. As the sun rises higher, the beam widens so that the whole chamber is dramatically illuminated.
Hundreds of people, some from overseas, come to Newgrange every year to witness this phenomenon, but it was only rediscovered by archaeologist Michael J O’Kelly in 1967. Acting on local lore, Prof O’Reilly stood in the chamber on the winter solstice and watched it “lighting up everything as it came until the whole chamber – side recesses, floor and roof 6 metres above the floor – were all clearly illuminated”.
It was one of the most significant archaeological discoveries in Irish history and made Newgrange world-famous.
[ Winter solstice: Sun lights up Newgrange burial chamberOpens in new window ]
Can I see the light enter the chamber?
Unfortunately not this year. There is an annual lottery for entry to the chamber. Of the 30,000 who typically apply, about 60 are allowed into the chamber. It is a 1-in-500 chance – better odds than the National Lottery, but still a long shot. And even if you do win, there is no guarantee you will see the phenomenon as the sun has to shine, which is also a lottery at midwinter.
Why is the winter solstice so close to Christmas?
It is not a coincidence that the two events are only days apart. The gospels are silent as to when Jesus was actually born. The only mention of any season is the reference to “shepherds watch their flocks by night”, which was most likely springtime in Judea, but it is mere speculation. Jesus could have been born on any day of the calendar year. Contrast with his death, which we know occurred during Passover, which is always in the spring.
The choice of December 25th as Christmas (the birth of Christ) dates back to about AD 350. Quite why that date was chosen is still a matter of speculation, but it is almost certainly to do with the winter solstice.
Jesus’s birth and the birth of the sun would have been dates that were widely understood by ancient people. Christians grafted on to pagan feasts. After all, they turned the Celtic festival of Samhain into All Saints and All Souls Day.