To the Greeks she was Gaia (guy-ya), to the Romans Terra Mater - Mother Earth. Before her there was nothing but chaos. From that chaos she created herself (the first mother), and Uranus (the first father), also known as Father Sky. From the sky Uranus showered Gaia with his seed, and she nurtured it, and men and gods were born.
So say the ancient myths, and metaphorically the myths are right. Earth did create itself, as all planets do, out of the leftover dust and debris of a newly formed star. It took about three billion years, but over that immense period of time, a mixture of quantum and electrostatic attraction, gravity, and chance encounters slowly but surely conglomerated the dust into pebbles, into rocks, into boulders, into one really big boulder, and ultimately into planet Earth. Out of the chaos of a protoplanetary disk, our planet Earth did indeed create herself, just as the myths say.
From space, organic molecules, the stuff of life, carried on the backs of asteroids, comets and meteorites, rained down on the young, fertile Earth, like the seed of Uranus. Earth nurtured these seeds for an unimaginable length of time, with the profound patience of a mother, until they grew and evolved and eventually became men, and from the men, gods, once again just as the myths say.
So Earth, in a very real sense, is indeed the mother of the Human species. Earth gave birth to us, and no matter how far we may stray out into the Cosmos some day, visiting other suns, other planets, other forms of life, it will always be Earth we return to. Earth will always be our mother, and no matter where we might be in the vast expanse of the Universe, when we talk about home, we will be talking about planet Earth.
Of course, leaving Earth to roam the Cosmos is not something we will be doing anytime soon. With present technology, it would take us more than 50,000 years just to reach the next closest star system, and most likely we would have to travel many times farther than that to find a planet that would be friendly to Human life. The sobering reality of the Human condition is that for a very, very long time to come, Earth is the only home available to us, and yet it's already overcrowded and polluted, and heading down the dangerous road of global warming. This is no small thing, because if Earth becomes uninhabitable, we have nowhere else to go.
We are all passengers aboard Spaceship Earth, which is flying through space at a speed of 67,000 mph as we race around the Sun. Of course the Sun itself is flying through space at 450,000 mph, and taking us with it. And if you consider the Milky Way galaxy that contains our Sun is also flying through space at well over a million mph, our Spaceship Earth is actually moving along at quite a clip, and taking us on quite a journey.
It is a large spaceship, 7,900 miles in diameter, although the actual living quarters comprise only a tiny fraction of its overall size. The ground we stand on is merely a thin crust that extends only a few miles below our feet. And this crust is not even one solid piece, but broken up into several separate pieces known as tectonic plates. Plates that are not fixed in place, but floating on a deep ocean of extremely hot molten rock, known as magma. For underneath its thin, fragile crust, our Earth is mostly liquid. It is a maelstrom of liquid and semi liquid rock, becoming hotter and hotter the deeper it goes. The first 1,800 miles down is called the mantle. Then it becomes Earth's outer core, where the magma is the same temperature as the surface of the Sun. And then it gets hotter still. But nearing the center of our planet the pressure is so great, that even with the extreme heat, Earth's inner core is compressed into a solid ball of iron almost as big as the Moon.
The giant, spinning iron core as large as the Moon and as hot as the Sun is the engine that powers Spaceship Earth. It creates enormous plumes of molten rock that boil up to the surface, roll off the bottom of the crust as they cool, and fall back down towards the core again. This is a continuous cyclic phenomenon that occurs all over the planet. If the superheated molten rock finds a weak spot in the crust, it bursts out, and a volcano forms. Sometimes the energy of the magma disturbs the fragile crust, causing it to tremble and move, and where the tectonic plates meet, earthquakes and tsunamis are born.
The engine room of spaceship Earth is a very violent, scary place, and it is a sobering thought that we are separated from these extreme conditions by such a thin, fragile membrane of a crust. Should the forces within our planet ever escape through the crust in any significant way, all life on the planet would be doomed. And it's already happening, on the floor of the ocean, where magma is pouring through huge cracks in the crust. Fortunately for us, the weight of the ocean, miles deep, keeps the magma at bay.
The spinning engine core of Spaceship Earth also serves another purpose, absolutely critical to the survival of the life forms like us trying to survive on top of the planet's crust. Somewhat like the spinning armature of an electric motor working in reverse, Earth's spinning iron core creates an enormous electromagnetic energy field that extends far out into space, and very effectively deflects the lethal radiation emanating from the Sun. Without this magnetic field, life on Earth would not be possible. In the NASA diagram below, you can see how some of the solar radiation is able to sneak in at the poles, where the magnetic field is the weakest. The solar radiation appears in the sky as shimmering waves of color known in the north as the Northern Lights, or Aurora Borealis, and in the southern hemisphere they are the Aurora Australis.
Last, but far from least, Spaceship Earth provides its passengers with a breathable atmosphere. Although it is 78% nitrogen, it also contains just enough oxygen, 21%, for Earth's oxygen dependent lifeforms like us to thrive. Earth's atmosphere also filters out most of the harmful solar radiation that makes it past the magnetic shield created by its spinning iron core. If there were no atmosphere, there would be no life. This atmosphere is tenuous however, and delicately balanced.
The reason we experience seasons is because Earth is tilted sideways, 23.5 degrees. If Earth were straight up and down, like the planet Mercury, we would have no seasons. Weather would become minimal, and predictable. Every day would be the same. But because different parts of Earth are pointed towards the Sun at different times of the year, we experience dynamic unpredictable weather, and four distinct seasons.
In modern times, when we live in self contained shelters with artificial heat and light, the seasons have lost much of their significance, but in ancient times, the seasons literally controlled our lives, and the four days each year that marked the turning points of the seasons were observed with great ceremony and reverence all over the world.
For early Humans living in the Northern Hemisphere, the Autumnal Equinox was a very important day. For the previous three months, they had been watching the long days of summer gradually diminish, until at the moment of the Equinox, the days and nights were of equal length (equinox is Latin for equal nights). This was a crucial turning point in their lives. From this day on their world would slowly darken and grow colder as the days continued to shorten. It was a time to harvest and hunt, to prepare for the hard months ahead.
In Chichin Itza, Mexico, the ancient Mayans built an enormous temple pyramid to commemorate the occasion. It was constructed with tiered corners precisely aligned so that on the day of the Equinox the light of the setting sun projected a series of triangles running down the steps on the face of the pyramid and culminating in a ten foot tall snake head at the bottom. The snake was the great god Kukulkan, the plumed serpent. To this day, thousands of pilgrims from all over the world travel to the site to witness this extraordinary event on the day of the equinox.
For the next three months, our ancient ancestors huddled together, shivering, as temperatures plunged, and the darkness deepened, and fear gripped their hearts. Knowing nothing of orbital mechanics, they imagined larger than life gods were taking the Sun away, and they did everything they could to appease these gods, and convince them to bring the Sun back. And sure enough, on the day of the Winter Solstice, the Sun stopped (solstice is Latin for the standing still of the sun), and began to come back north again. It was truly a magical moment, and naturally, cause for unprecedented celebration. Time for more rituals and sacrifices. Time for unbridled revelry. Revelry that evolved through the ages and ultimately climaxed with the Romans - the original party animals - and their observance of the festival of Saturnalia, the ultimate party.
Saturnalia was centered about the god of time, the Greek god Cronos, known to the Romans as Saturn. The festival began with the loosening of symbolic woolen bonds around the feet of the statue of Saturn in the great temple of Saturn. Then the week long party began. To honour Saturn, who was also the god of agriculture, trees were decorated, and homes were festooned with greenery, especially holly boughs.
Presents were exchanged. It was a time when all were considered equal, slaves and senators alike. Roles were often reversed, with parents and masters doing the bidding of children and slaves. Clothing was optional during Saturnalia, and small peaked caps normally only worn by freed slaves, were worn by everyone. Groups of carollers, clad only in the small caps, were a common sight, and the air was filled with people shouting the festive greeting Io, Saturnalia! (pronounced Yo, Saturnalia!)
The atmosphere surrounding Saturnalia is described in a letter by Roman statesman Seneca the Younger, circa 50 AD:
"It is now the month of December, when the greatest part of the city is in a bustle. Loose reins are given to public dissipation; everywhere you may hear the sound of great preparations, as if there were some real difference between the days devoted to Saturn and those for transacting business....Were you here, I would willingly confer with you as to the plan of our conduct; whether we should eve in our usual way, or, to avoid singularity, both take a better supper and throw off the toga."
Early Christians were horrified by the debauchery of it all, but eventually decided if you can't beat them, join them, and made Saturnalia into a celebration of the birth of Christ. Although the name of the honored diety may have changed, most of the ancient rituals such as gift giving and the decoration of trees survive to this day. The festive greeting, Io Saturnalia, was changed to the familiar Merry Christmas.
Gradually over the next three months, the chill began to leave the air, and the days slowly began to lengthen again, until on the day of the Vernal (spring) Equinox the days and nights were equal once again. In the jungles of Mexico Kukulkan once again slithers down the steps of the temple, and all the peoples of the northern hemisphere celebrated the first day of Spring. To astrologers, it was the first point in Aries, and the start of the astrological calendar.
For the next three months Earth bristled with new life. Temperatures warmed and Earth turned green as both wild and cultivated crops burst from the soil. It was a time of hope and rebirth that culminated with the Summer Solstice, the longest day of the year, as the Sun once again appeared to stand still in the sky and prepare to start moving away south again. It was a time of abundance. It was also a time of magic, when spirits came out of hiding. Huge bonfires were lit to keep evil spirits at bay, while certain plants became endowed with miraculous healing properties - on that night only - and were quickly harvested.
It was a propitious time for lovers, and a time for unions, and marriage. It was a time of gaiety, and celebration. As the Sun stood still, the world stood still with it, and Humans marked the moment with ceremony and purpose. The ancient Stonehenge has been a traditional setting for these celebrations for thousands of years. The famous 16 foot high heelstone in the entrance of the henge marking the precise spot the sun rises on the morning of the Summer solstice. The evening of the solstice is known as Midsummer's Eve.
On June 6, 1990, as the NASA spacecraft Voyager I passed the orbit of Pluto,, over four billion miles from Earth, it looked back, and took a photo of our home planet. Caught in a beam of refracted sunlight, the mighty Earth that has hosted the sound and fury of the Human species for their entire existence is nothing more than a tiny pale blue dot, lost in the lonely darkness of space.
On October 13, 1994, the famous astronomer Carl Sagan presented this photo to the world in an historic speech at Cornell University. This is an excerpt from that speech:
We succeeded in taking that picture [from deep space], and, if you look at it, you see a dot. That's here. That's home. That's us. On it, everyone you ever heard of, every human being who ever lived, lived out their lives. The aggregate of all our joys and sufferings, thousands of confident religions, ideologies and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilizations, every king and peasant, every young couple in love, every hopeful child, every mother and father, every inventor and explorer, every teacher of morals, every corrupt politician, every superstar, every supreme leader, every saint and sinner in the history of our species, lived there on a mote of dust, suspended in a sunbeam.
The Earth is a very small stage in a vast cosmic arena. Think of the rivers of blood spilled by all those generals and emperors so that in glory and in triumph they could become the momentary masters of a fraction of a dot. Think of the endless cruelties visited by the inhabitants of one corner of the dot on scarcely distinguishable inhabitants of some other corner of the dot. How frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds. Our posturings, our imagined self-importance, the delusion that we have some privileged position in the universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity -- in all this vastness -- there is no hint that help will come from elsewhere to save us from ourselves. It is up to us. It's been said that astronomy is a humbling, and I might add, a character-building experience. To my mind, there is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly and compassionately with one another and to preserve and cherish that pale blue dot, the only home we've ever known.
As isolated from the Cosmos as Earth might seem to those of us trapped here on its surface, our planet is continuously interacting with the Universe around it, and extraterrestrial visitors land here every day. Visitors who are most likely responsible for bringing water to the planet, and quite probably even the germs of life itself. Visitors known as meteors...