Climb for a few minutes, if you will, into the mind of a person who lived in, say, Mesopotamia, oh, 2,000 years B.C.

You would know nothing of astronomy — only the lights in the night sky. You would know nothing of planets and tilted axes and rotating orbs. You would know hardly anything about science at all.

So, you would try to make sense of your world as best you could — by ascribing everything you could not understand and reason out to some beings greater than you, some great gods and goddesses that controlled your puny existence.

You believe that you are alive and the world around you is there because the great god Marduk tamed the monsters of chaos and darkness.

But you also believe that this is an ongoing battle. Every year the monsters begin to creep in and try to take over — and the period of sunshine begins to get smaller and smaller — until Marduk goes into battle and pushes the darkness back once again.

If you truly believe this — and there is no reason not to in your time — you also have to believe that it is possible that Marduk might lose this battle. And then you and all around you will be plunged into eternal darkness. This is a real and horrible thought. So, it behooves you to do anything you can to help Marduk. Maybe that means lighting fires to chase away the dark. Maybe that means making sacrifices and offerings to the one fighting on your behalf. Maybe it means gathering together to dance and make merry; maybe it means hours of silent, anxious vigil.

Whatever you did, you would rejoice when the battle was won and light began to move back into your world.

Repeated in various forms in various lands, these were the first observations and celebrations of the winter solstice.

As the centuries moved on, and peoples came to understand the cycles of the year and of light and darkness, there were still observances — but this time not so much in desperation as in celebration. The sun was being "reborn," and life would go on.

In Scandinavia, the winter festival was called the juul or yule, and included the custom of burning huge logs, while people sat around the fire, drinking mead and listening to minstrels singing about ancient legends.

One of the most widely known festivals was the Roman Saturnalia. During this many-day celebration, there was boisterous merry-making. Homes were decked with boughs of evergreens. Lamps were burned to ward off the spirits of darkness. Schools were closed; the army got time off; criminal executions were put on hold; families and friends visited each other, often bringing good-luck gifts; masters feasted with slaves, who were given the freedom for one day to say and do what they wanted.

In time, some early peoples became quite adept at tracking the movement of the heavens. Their lives were tied to the seasons, to the growth of food, the harvest and the storage of food to get them through the nongrowing winter months.

Eventually, a number of civilizations created temples, observatories, tombs and other monuments to help them track the solstices and equinoxes so that they were more in tune with the seasons.

Stonehenge, on England's Salisbury Plain, is one of the more famous examples of this. There, monolithic stones are aligned to mark both summer and winter solstice.

Newgrange, a huge circular stone structure in Ireland, is another example. Estimated to be about 5,000 years old, Newgrange was constructed so that a shaft of sunlight shines deep into its central chamber at dawn on the day of winter solstice. The light illuminates carvings of spirals, sun discs and other shapes.

Maeshowe, on the Orkney Islands off the coast of Scotland, has a similar function, built to perfectly capture the rays of the setting sun at the solstice.

Other such structures are found in other parts of the world, ranging from the medieval Great Zimbabwe in Africa to the Sun Dagger of Chaco Canyon and other rock art scattered throughout the North American Southwest.

New studies are finding that some medieval churches throughout Europe also include solar observatories. Usually, a small hole in the roof allowed in a beam of light that would trace a path along the stone floor, which was often marked by inlaid-tile motifs.

These would have come, of course, after Christianity adopted the time of the winter solstice as the time of the birth of Jesus — giving us Christmas.

Early Hebrew people celebrated Hanukkah, a festival of lights that also honored the Maccabees' victory over the Greeks at this time of year. In fact, it is still tied to the solar calendar. It begins on the 25th day of Kislev, three days before the new moon closest to the winter solstice.

Nearby, the Persians lighted fires to honor Mithras, god of light. The Egyptians did the same for Isis, the mother of their sun god, Horus.

The early Christian church did not celebrate the birth of Christ. Not until the 4th century, did it feel the need of such a celebration, and by then the actual date of birth was long forgotten. In A.D. 350, Pope Julius set the date of Christ's birth on Dec. 25 — which was the day of the winter solstice, according to the Julian calendar at the time.

There was little historical reason for the date; but there was tremendous symbolic significance. The "re-birth of the sun" following the darkest day of the year became the "birth of the Son," who was praised for bringing light into the world.

Over the next centuries, as more and more people joined the Christian faith, they brought many of their solstice customs and celebrations with them: yule logs, evergreens, presents, special lights became part of Christmas.

Not everyone was happy with that. In 17th-century England, after Oliver Cromwell and the Puritans came to rule, they deemed Christmas celebrations as too pagan. They prohibited the singing of carols and the hanging of evergreens. Christmas was to be a somber fast day.

But in other places, such as Germany and Holland, the festivities continued, with decorations, music and a jolly spirit of Christmas known as Kriss Kringle.

Today Christmas incorporates a blend of all these traditions, and still is celebrated, both literally and symbolically, as a bright spot at the darkest time of the year.

Science of the solstice

The reason we have solstices — and seasons, for that matter — is because the Earth is tipped on its axis at a 23 1/2 degree angle away from an upright spin. For half of its rotation around the sun, it tips its northern hemisphere toward the sun, and summer is the result in that hemisphere. For the other half of the year, because the axis continues to point in the same direction, the reverse is true.

The solstice occurs when the Earth reaches its greatest distance from the sun. Looking east at the sunrise, you would see it come up at its farthest point south.

The name "solstice" comes from two Latin words: sol for sun, and stice for standing still, as it appeared to the ancients that the sun came to a stop before reversing its course.

The winter solstice occurs between Dec. 21-23. This year, the actual solstice — the moment when the sun is directly over the Tropic of Capricorn — occurs on Dec. 22 at 6:08 UT (Universal Time, which has replaced Greenwich Mean Time in the scientific lexicon). This puts it as 11:08 p.m. on Dec. 21 MST.

Because the sun has its lowest arc in the sky, the solstice is the shortest day of the year. It is considered the first day of the astronomical season of winter.