Geogenesis: The Coming Into Being of Earth
First Presbyterian Church
January 12, 2014
To become aware of the sacramental nature of the cosmos;
to be open to the sacramental possibilities of each moment;
to see the face of Christ in every person;
these things are not novel,
but their rediscovery is the beginning of our health.
Our Great Story continues with the formation of our solar system 4.567 billion years ago. Two books are helping me tell this story. The first is Lloyd Geering’s,From the Big Bang to God: Our Awe-Inspiring Journey of Evolution. The second is Robert Hazen, The Story of Earth: The First 4.5 Billion Years, From Stardust to Living Planet. Robert Hazen is also featured in the Great Courses series, The Origin and Evolution of Earth: From the Big Bang to the Future of Human Existence.
The story of the evolution of the Universe and Earth is a pattern of long, long periods of nothing seeming to happen, 100s of millions of years, billions of years even, followed by an event that lasts a few seconds or a day that changes everything. The formation of the moon is such an event.
This leads to a philosophical puzzle. It really is against all odds that we exist. Had any of these random events been slightly different, such as the formation of the moon, the beginnings of life, and the evolution of life wouldn’t have happened, or at least happened the way it did.
But that is true with any history, isn’t it? You look back at your own life and think of the small events that could have gone many directions, but here you are. You wouldn’t be here as you are if it weren’t for some decision or event or series of decisions or events. We might think that it is planned and designed and orchestrated. Theologians even come up with a theological word, providence, to explain it. It must have been planned. Perhaps.
It is also the case that we look back to our individual lives or back to the origins of life on Earth from the vantage point of what we have become. There is no other vantage point. Had my mother not met my father or had she married the person who had courted her before him, someone else would be in this pulpit today. That person might be telling you this morning about the divine hand of providence that led him or her to Elizabethton.
Instead of a spirituality of providence I am beginning to develop a spirituality of randomness. From this perspective, I am aware that it is better to be lucky than skilled. Because of that I cannot ultimately credit myself for my life. I didn’t do anything to earn or get this life. It is pretty good. My life could have gone and still can go quite differently. If there is a skill to develop it would be adaptability. Nothing is permanent. Everything is change and random change at that.
We can be unhappy with change. We can wish things were like they were or even try to resist change, but that is a losing cause. It easily results in leaving one sad, afraid, and bitter. The spirituality of randomness invites me to be open to what is. To take notes. Those notes include telling of the changes I see and my experience of these changes. This is my life. This is what happened. I lived it. I am living it still. The spirituality of randomness invites me to see that others are in the same situation. We are all free-floating electrons looking for a positive charge. A little compassion is in order.
About 4.6 billion years ago a cloud of gas and dust in the suburbs of the Milky Way hovered and hung out. Who knows for how many billions of years it had been doing that. This particular cloud was on a plane, a hot spinning disc. Some random event, some hurtling ball of energy and vibration excited the hydrogen in this dust cloud and it began to shape itself. Gravity spoke up and said, “I have something to do.” It gathered this gas and dust into a ball, dense, massive, and hot. Hot, massive and pressurized enough to ignite fusion reactions. Our sun was born.
Solar wind resulted sending out the remaining material in the gas cloud. Gravity kept it from going out into space and instead put it into orbit around the sun. The sun contains almost all the mass of the solar system. 99.9% of the solar system’s mass is concentrated in the sun. All the rest, the 0.1% of the mass of gas dust and debris began to collide and form asteroids and comets and ultimately planets orbiting the sun.
In our system we have four rock planets and four gas planets. Mercury is a hot little rock closest to the sun. Venus is next. It is hot as well. Surface temperatures are about 900 degrees. It might have had small oceans of water but now the water appears to have boiled away. Carbon dioxide sealed in the sun’s energy and its atmosphere today is the result of runaway greenhouse gases. This might be an object lesson for Earthlings.
The third rock from the sun is Earth of course. Mars is the fourth planet and the last of the rockies. It is a tenth of the size of Earth but most Earth-like. Like Earth, Mars has an atmosphere and a lot of water. Its gravity is weak compared to Earth so it had a hard time holding the atmosphere. Underground there may be warm and wet reservoirs that harbor some life.
The asteroid belt is next followed by the huge gas planets.
Jupiter is the largest. Jupiter had hopes of being a star. As it is with those who would want to be a star, many are called but few are chosen. Jupiter wasn’t large enough or hot enough even as it has its own system of moons orbiting it like a mini-solar system. Astronomers note that two of three stars we see in the sky are binaries, that is two stars close together. Had the angular momentum of our system been different, Jupiter might have been bigger and hotter and he could have been that second star.
It wasn’t to be and that is good for us. Life might have evolved from a planet going around a binary star, and it could exist somewhere else but it would be tricky with the competing gravitational pulls. As it is, our sun is a nice size. Not too big to burn out too fast, not too small not to provide enough energy for life. Our sun is about half way through its life cycle. A long enough life for life.
Beyond Jupiter is Saturn with its frozen ice rings and then Uranus and Neptune. They all have their own moons. Saturn has two dozen moons, one of them, Titan, appears to have an atmosphere with organic compounds. It is a good place to explore for some signs of life.
Back to Earth.
This solar dust cloud might have existed for billions of years and in a relatively short period our sun ignites swallowing up 99.9% of the dust cloud’s mass and sends out rocks and gas through a violent solar wind. Thanks to gravity this stuff orbits the sun and crashes and collects into planets. One of these planets is Earth.
Earth is formed from this crashing debris. Earth is unique in that it has a big moon. How did we get the moon? There have been a number of theories. One is that the moon was formed by Earth’s leftovers. Another is that the moon was captured by Earth’s gravity. Another theory proposed by Charles Darwin’s son, George Darwin, is that the moon was once part of Earth and broke away.
The current theory within the last thirty years has the complicated scientific name, The Big Thwack. About 50 million years after the formation of the solar system, Earth is black. It has red streaks of volcanic magma. It is not a hospitable place. There is another smaller but nevertheless large competitor for Earth’s orbit space. The orbit is not big enough for the likes of competition. Earth’s competitor we’ll name Theia for the Titan goddess who gave birth to the moon.
Theia crashes into Earth. Theia is obliterated. The explosion of impact sends a combination of Earth’s stuff and Theia’s stuff out in to Earth’s orbit. Earth’s gravity gathers this stuff and eventually it becomes the moon.
This brand new moon is close to Earth about 15,000 miles. Earth rotates fast on its axis. Instead of 24 hours each day is five hours. Over the course of 4.5 billion years the moon has gradually moved away from Earth. Today the moon is about 239,000 miles from Earth. They have done measurements since the 1970s and found the moon is moving away from Earth about an inch and a half a year. It doesn’t sound like much but over the course of 4.5 billion years, it eventually gets there.
As the moon moves further away it causes Earth to spin more slowly. Like a skater who brings her arms in to spin faster and slows the spin by bringing her arms out, so the moon by moving further and further away slows the spin of Earth. The moon always faces us as she orbits us. Earth and moon always look lovingly into one another’s eyes. Isn't science romantic?
Another result of the impact of Theia on Earth was to tilt Earth on its axis. It spins about 23 degrees off center. Which is convenient for the change in seasons we enjoy today. The Big Thwack theory explains best the relative compositions of Earth and moon, the rotation of Earth, the 23 degree angle and the presence of the moon itself. It didn’t have to happen this way. Had Theia thwacked Earth at a different angle things would have turned out differently.
If you were to land on Earth at that time, you wouldn’t last long. Earth at this time is thousands of degrees at the surface. From space it would look black because of the basalt crust with red stripes of volcanic magma. All the time, Earth is being pelted by meteorites. The moon from Earth would look huge as it is only 15,000 miles away. It would take up a vast portion of the sky. It would be hot and volcanic too.
Another couple of hundred million years pass. See how that goes? Long periods of time, then an event like The Big Thwack that change everything, then long periods of time. Earth’s infancy is really a mystery. It is theoretical. No rocks or minerals survive from that Hadean time. The word Hadean comes from the words Hades, that is hot.
After this period Earth cooled and the oceans began to form. Enter water.
Water is one of the most abundant chemicals in the cosmos. Oceans cover 71% of earth’s surface today. At some early point water covered the whole surface of Earth. Earth was a beautiful blue ball. Water has some important and unique properties. It dissolves things. It freezes weirdly, from top to bottom as opposed to other liquids. Its solid form, ice, is less dense than its liquid form. So it floats. This serves to protect what is underneath the layer of ice. Water has a high surface tension allowing it to form drops rather than remain a gaseous mist.
On Earth we know of no life whatsoever that does not require water. Some living things don’t appear to require much, but all living things need water. When theKepler telescope set its eyes on one region in the galaxy it was looking for planets that would be in the “Goldilocks” zone. That is a temperature zone that would allow for the possibility of liquid water.
One hundred million years or more following The Big Thwack, not that long in deep time, Earth was a blue ball of water with an ocean a mile deep and a few volcanoes poking above the waves.
At around that time enter granite, the foundation stone of the continents. How did Earth move from black basalt to granite continents? It is fairly recently that the concept of plate tectonics has been accepted. According to Robert Hazen the maxim is this:
Granite floats, basalt sinks: that’s the key to the origins of the continents.” P. 124.
Granite floats, basalt sinks: that’s the key to the origins of the continents.” P. 124.
Volcanoes blow up cinders and ash on to the surface that forms granite islands that are less dense than the basalt. These granite islands form and link and actually shift and move, thus the origin of the popular song by Carole King, “I Feel the Earth Move Under My Feet.”
You can put together the puzzle pieces of the most recent continental shifts, if you allow for “recent” to be 300 million years. If you look at a globe you can see how Africa and South America were once one. They spooned together. But all of the continents at one time were one. Species of living things that existed in that time before the drift have commonalities on the various continents. That isn’t even the beginning. That is 300 million years ago only. We are still at four billion years ago. Over the course of our four billion year history the floating islands of granite come together and separate.
If you were able to time travel to 500 million years after The Big Thwack, to about four billion years ago, you would visit a blue and gray Earth. You could bring your towel and lie on a beach. Nothing green. No trees, no grass, no fishies. It would be quite beautiful though. You would have to do without breathing. There would be no oxygen in the atmosphere. The nitrogen and carbon dioxide would suffocate you in a minute. But other than that it would be nice. A blue-gray lifeless Earth waiting for another random event.