Today, thanks to developments in cosmology, we know more about the universe than any other era in human history. Extraordinary advances in ideas—from Einstein’s general relativity to particle phys-ics—and in instruments—from space telescopes to particle accelera-tors—have dramatically changed our conception of the physical world and the cosmos.1 The Hubble Telescope, for example, orbiting the earth for more than two decades now, has been able to gaze farther and deeper into the cosmos, disclosing to us a universe immensely large and incredibly old. We remain in utter awe and wonder before the infinity of the universe, so inconceivably large that distances can be measured only in light years. It is believed that the observable universe has a diameter of 93 billion light years (the speed of light being a whopping 186,411.4 miles per second) and contains hundreds of billions of galaxies, with a recent German supercomputer animation plugging the number at approximately 500 billion galaxies.2 A galaxy, like our own Milky Way, contains approximately 200 to 250 billion stars, with a medium star, like our sun, being a million times more massive than the earth. According to our current knowledge, the observable universe is said to contain 300 sextillion (3x1023) stars.3
It is also humbling to realize that the observable universe in terms of normal matter accounts for less than 5 percent of the mass of the universe (the stars and planets constituting a mere 0.5 percent and the rest being gas) while the bulk of the universe consists of dark
1 See Michael S. Turner, “Origin of the Universe,” Scientific American (Sep-tember 2009): 36.
2 For an account of the largest simulation experiment of the universe, the
“Millennium Run” carried out at the Max Planck Institute for Astrophysics, see V. Springel et al., “Simulations of the Formation, Evolution and Clustering of Galaxies and Quasars,” nature 435 (2005): 629–36.
3 See Pieter G. van Dokkumi and Charlie Conroy, “A Substantial Population of Low-Mass Stars in Luminous Elliptical Galaxies,” nature 468 (2010): 940–42.
This study almost tripled the previous estimates with regard to the total number of stars in the universe.
energy (68.3 percent) and dark matter (26.8 percent).4 The vastness of the universe and its amazing order have been a source of wonder for humans since ancient days and have inspired generations of poets, sages, and mystics down through the ages.
Equally marvelous and awe inspiring is the realization that in such an infinitely vast universe, stretching across billions of light years, our home planet is a unique place capable of harboring advanced and complex forms of life. We quiver at the thought that in an area to be measured in light years, if not in infinities of time and space, we are alone.5 The quest for extraterrestrial life has enthralled humanity since time immemorial, and the scientific exploration in this regard is only in its initial stages, having coincided with the onset of the space era. It would certainly be preposterous to rule out the possibility of life, even relatively advanced forms of it, elsewhere in the universe;
there could very well be such life, given the sheer immensity of the cosmos. But limiting ourselves to the earth within the solar system and to our immediate galactic neighborhood, we remain awestruck by the wonderful saga of how our single planet became a marvelous home where life evolved from single cells to conscious beings through com-plex processes that unfolded over millions and millions of years. The contemporary ecological crisis threatens precisely this capacity of the earth to be a home for living beings to flourish. Thus, it is important that we reflect on the stupendous miracle of the gradual fashioning of our home before dwelling at length on the crisis itself.
in the Beginning . . .
Recent discoveries in cosmology reveal how the saga of Earth be-coming a home is intricately linked to the wider cosmic epic of the origin, formation, and evolution of the universe. The building blocks necessary for the construction of our common home were originally created and gradually molded in the cosmic furnace of the universe over billions of years. So, in order to fathom the significance of the shaping of the earth as a home for life, we need to place our geologi-cal history in the larger cosmic odyssey of nearly 14 billion years.
The emergence of our planet, and ultimately our own existence, can
4 See Mark Peplow, “Planck Telescope Peers into the Primordial Universe,”
nature news (March 21, 2013).
5 See Paul Davies, the eerie Silence: Are We Alone in the universe? (Lon-don: Allen Lane, 2010); John Gribbin, Alone in the universe: Why our Planet is unique (Hoboken, NJ: Wiley, 2011).
be understood only by returning to the very dawn of creation, to the origin of the universe attributed to a singular moment called the Big Bang, and to the succession of events thereafter.
The most widely accepted scientific explanation for the origin of the universe is the Big Bang theory.6 It posits that the material universe originated from the violent explosion that occurred 13.82 billions of years ago7 and has expanded and cooled ever since. It is mind-boggling to realize that the initial point from which the universe blazed forth in a great flash, with an intensity never to be equaled again, would have occupied a tiny sphere 10-33 centimeters in diameter (trillions and trillions of times smaller than the head of a pin). The original sear-ing hot fireball of the Big Bang must have been a point of extremely high temperature, 1032 centigrade, which means inconceivable energy density, and the crucial early sequences of its evolution took place in mere billionths of a second.8 The initial moment of the Big Bang is itself shrouded in mystery. Time and space did not exist, because these came into existence only thereafter, and the four fundamental forces of nature—gravity, the strong and weak nuclear forces, and electro-magnetism—existed as a single unified cosmic force. Scientists seek to approximate this instance by referring to it as Planck’s limit-time.
At the end of the Planck limit-time, 10-43 second after the Big Bang, the first cosmic phase transition took place: gravity broke away to become a distinct entity, and space and time became well defined. At 10-35 second, the universe underwent a sudden inflation—
a super-rapid expansion of space—that prevented the embryonic universe from collapsing on itself. At this stage the strong nuclear force split away, leaving only electromagnetism and the weak nuclear force tied together. The expansion continued, while temperature and
6 The theory was originally proposed by the Belgian astronomer-priest Georges Lemaître in 1927, corroborated experimentally by Edwin Hubble’s observation of the constant expansion of the universe, recognized by renowned astronomers like Arthur Eddington, theoretically elaborated by George Gamow and others, and eventually accepted by prominent scientists of the day, including Albert Einstein. The Big Bang theory found acceptance in scientific circles because of two cornerstone astronomical observations: the abundance of light chemical elements and the discovery of cosmic microwave background radiation.
7 Peplow, “Planck Telescope Peers into the Primordial Universe.”
8 See Robert M. Hazen, the Story of earth: the first 4.5 billion years, from Stardust to living Planet (New York: Viking, 2012), 7–13; Brian Swimme and Thomas Berry, the universe Story: from the Primordial flaring forth to the ecozoic era: A celebration of the unfolding of the cosmos (London: Penguin Books, 1992), 7; Leonardo Boff, cry of the earth, cry of the Poor (Maryknoll, NY: Orbis Books, 1997), 44; Turner, “Origin of the Universe,” 36.
density gradually diminished. At 10-32 second, radiation and matter were created. The energy that drove inflation was transferred to the multitude of Higgs particles, which decayed, releasing the energy as radiation. Quantum processes caused the radiation to decay spon-taneously into subatomic particles of matter and antimatter, which annihilated each other. However, in the process a small imbalance in the laws of physics produced slightly more matter than antimat-ter. For every billion particles of antimatter, there were a billion and one particles of matter, which ensured that at the end of the process a small excess of matter remained. All the material content of the universe—including us—derives from this slight excess of matter.
At 10-10 second the electromagnetic and weak nuclear forces finally went their separate ways. At 10-5 seconds the quark particles, which formed shortly after inflation, bunched together to form protons and neutrons, the building blocks of atomic nuclei. At 100 seconds the temperature of the Big Bang fireball dropped enough to allow protons and neutrons to stick together, allowing the nuclei of the lightest chemical elements—hydrogen, helium, and a small amount of lithium—to be formed. It is only after 3,800,000 years, with the temperature having been lowered substantially to approximately 6000°C—about the same as the surface of the sun, that the atomic nuclei forged during the first 100 seconds were able to capture elec-trons and form the first whole atoms.9 Radiation streamed freely through space, and the universe became transparent. This moment in the evolution of the early universe has left a remarkable fossil relic in the form of the cosmic microwave background radiation that is still observable today.10 A phase of stability was reached as far as the particle interactions were concerned, and the four original interconnections of gravity, the electromagnetic force, and the strong and weak nuclear forces came into play throughout the universe.
A second phase began called the galactic phase. In the billion years that followed, the primordial gas of hydrogen and helium expanded and eventually cooled down, giving rise to the first condensations of matter—the proto-galaxies—which contracted under gravity’s effect.
9 Paul Parsons, the Big Bang (London: BBC, 2001), 42–44, 53; Turner, “Ori-gin of the Universe,” 39, 41.
10 The cosmic microwave background radiation is a residual echo of the hypo-thetical primordial explosion that allows cosmologists to deduce the conditions present in the early stages of the Big Bang and, in particular, helps account for the chemistry of the universe. See Peter Coles, cosmology: A Very Short introduction (Oxford: Oxford University Press, 2001), 61; Parsons, the Big Bang, 52.
It was from these gas nebulas in the grip of gravitational collapse that the first galaxies and stars were formed, depending on the fluctuations of density of matter that existed within the proto-galactic clouds.11 The stars lit up as the gravitational pressures within the gas nebulas increased the temperatures and ignited nuclear fires at their core.
Within the stars, nuclear reactions created ever heavier atomic ele-ments. Only the three lightest elements—hydrogen along with traces of helium and lithium—were created in the first few minutes after the Big Bang; all other elements were produced later in stars.12 In first-generation stars heavier elements like carbon—the chemical basis for life—nitrogen and oxygen were forged. Aging first-generation stars expelled them into space, which went on to form new generations of stars, accruing and producing ever heavier elements in the process.
A special role was played in this regard by the supernovas—massive stars that ran through the process of nucleosynthesis within relatively shorter periods—which spewed out into interstellar space heavier ele-ments in violent and spectacular explosions. This process continued for billions of years during which generations of stars, especially su-pernovas, created in their internal nuclear furnaces heavier elements like phosphorus, sulphur, iron, gold, and the rest of the elements in the periodic table. The stars disgorged these elements into space to become part of interstellar clouds from which newer solar systems—
and ultimately we—were formed. We are indeed stardust.
Nearly 5 billion years ago our solar system was formed in the pe-riphery of the Milky Way at a distance of nearly 27,000 light years from its center. It formed from a giant rotating cloud of gas and dust composed mostly of the residue of the explosion of a supernova. To be precise, the sun and the accretionary disk was formed 4.567 billion years ago.13 The sun, a medium-sized star, was formed at the center of this protoplanetary disk, having gathered to itself more than 99 percent of the original interstellar debris, while the remaining swirling portion went on to create the planetary bodies that spun around it: four ter-restrial planets—Mercury, Venus, Earth, and Mars—and four gaseous
11 Computer simulations reveal that stars and galaxies first emerged when the universe was about 100 million years old. See Turner, “Origin of the Universe,”
38.
12 See Michele Fumagalli et al., “Detection of Pristine Gas Two Billion Years After the Big Bang,” Science express (November 10, 2011): 1.
13 Alex N. Halliday, “In the Beginning,” nature 409 (2001): 144; Matthias Gritschneder et al., “The Supernova Triggered Formation and Enrichment of Our Solar System,” Astrophysical Journal 745 (January 20, 2012): 22.
ones—Jupiter, Saturn, Uranus, and Neptune.14 Most of the planets have their own satellites, like Earth’s moon, which was formed 4.53 billion years ago.15 The solar system is our immediate cosmic family.
Within the solar system, as the third planet in order of distance from the mother star, our home Planet Earth came into existence. The accretion of the earth with a metal core and primitive atmosphere was completed between 4.51 billion to 4.45 billion years ago.16 The formation of Earth marked the end of a long and stupendous voyage of cosmic evolution, a journey that began with the primordial flash of the Big Bang and took billions of years, while chemical elements neces-sary for life brewed in the cosmic furnaces of the supernovas. Earth was also destined to become the home for intelligent beings composed of the atoms of oxygen, hydrogen, and carbon that streamed out of stellar explosions of the distant past in the remote recesses of the universe, who would one day look back at the very cosmic process that brought them into being.
The vastness of the universe against which the drama of the forma-tion of our small home planet was played out fills us with a sense of profound awe. But we need to remember that such immense cosmic spatial and temporal scales were necessary to create a home like the earth, containing the proper chemical elements required for life. As John Polkinghorne reminds us:
Those trillions of stars have to be around if we are to be around also to think about them. In modern cosmology there is a direct correlation between how big a universe is and how long it has lasted. Only a universe as large as ours could have been around for the fifteen billion years it takes to evolve life—ten billion years for the first generation of stars to generate the elements that are the raw materials for life, and about a further five billion years to reap the benefit of that chemical harvest.17
14 The International Congress of Astronomers, gathered in Prague in August 2006, decided to declassify Pluto as a “nano planet.”
15 According to the Giant Impact hypothesis, the moon formed as a result of a collision between Earth and a Mars-size body called Theia. The impact caused a portion of the combined mantle of Earth and Theia to be expelled into space, eventually forming the moon.
16 Halliday, “In the Beginning,” 144.
17 John Polkinghorne, Beyond Science: the Wider human context (Cambridge:
Cambridge University Press, 1996), 84. Along similar lines Royal Astronomer Martin Rees argues that nothing as complex as humankind could have emerged in a smaller universe: “The cosmos is so vast because there is one crucially important
Such a propitious outcome was indeed accompanied by what Thomas Berry calls the “cosmic moments of grace,” for the fact that events so crucial to the development of a universe calibrated to sup-porting intelligent forms of life appear to have happened at almost zero probability.18 There were indeed several cosmic moments of grace in the story of the universe’s evolution from the simplicity of the quark soup to the complexity we see today in galaxies, stars, planets, and life. It is indeed startling to realize how the initial conditions of the universe were so very fine-tuned for the development of life, of which the Planet Earth was to become a privileged and unique oasis in the vast cosmic ocean.
earth—the “goldilocks” Planet
The earth has been rightly called the garden planet of the universe.19 Our home planet is indeed a unique home for life, a rare oasis in the barren cosmic ocean, where life has flourished in extraordinary abundance and variety.
However, the closer we study the geology, the chemistry, and the biology of the earth, we realize that it is also a “Goldilocks” planet, the “just right” place for life to have evolved. We enumerate a few of its unique features below, before going on to discuss a couple of them at length.
One factor that makes the earth hospitable for life is its location in the solar system. The earth is 93 million miles distant from the sun, a distance suitable for maintaining an optimal temperature that allows water to remain liquid, a fundamental requirement for life to exist and flourish. Its present position also guarantees the right gravitational pull from the sun, from its own moon—which keeps the earth spinning
huge number N in nature, equal to 1,000,000,000,000,000,000,000,000,000,000, 000,000. This number measures the strength of the electrical forces that hold atoms together, divided by the force of gravity between them. If N had a few less zeros, only a short-lived miniature universe could exist: no creatures could grow larger than insects, and there would be no time for biological evolution” (Martin Rees, Just Six numbers: the deep forces that Shape the universe [London: Phoenix, 2000], 2).
18 See Seán McDonagh, “The Story of the Universe: Our Story,” SedoS Bul-letin 41 (2009): 151. See also Seán McDonagh, to care for the earth: A call to a new theology (London: Geoffrey Chapman, 1986), 83.
19 Among the many who have done so, see the cry of the earth: A Pastoral reflection on climate change by the irish catholic Bishops” conference (2009), 7; McDonagh, to care for the earth, 84.
at the right speed and tilting at the right angle, factors that affect the present day-night cycle and the tides in the oceans—and even from a fellow planet like Jupiter, which curiously influences the stability of Earth’s orbit. The 23.5 degree inclination of the earth to the sun cre-ates the seasons and makes agriculture possible. The earth also has the right mass to possess the proper gravitational attraction, which in turn entitles it to have its own atmosphere, unlike the moon, which does not have one and where consequently life can never evolve as it did on Earth. Earth retains an atmosphere and water at its surface because of the protective magnetic field generated in its liquid iron/
nickel core. The magnetic field also acts as a protective shield from dangerous ionizing radiations from the solar wind, while the ozone layer in the upper layers of the atmosphere blocks out the harmful ultraviolet rays. The atmosphere on Earth has the right composition
nickel core. The magnetic field also acts as a protective shield from dangerous ionizing radiations from the solar wind, while the ozone layer in the upper layers of the atmosphere blocks out the harmful ultraviolet rays. The atmosphere on Earth has the right composition