As a child, the deep end of the swimming pool terrified me. At the shallow end, I could stand on the bottom with my head still safely above the surface. I swam with confidence and pleasure. The deep end, however, was a different matter. Lettering painted on the rim of the pool -- say, 9' 6" -- filled me with dread. Down by more than double my height, the pool drain possessed, I imagined, a gravitational sucking force. Were I to swim over it, surely, it would drag me under, as irresistibly as if pulled beneath by the tentacles of an octopus. A watery death awaited, my toes caught and entangled in the drain's grates. Of that, the child I was had no doubt.
The pool's deep end was for me an abyss. In its etymology, the word "abyss" derives from Greek words "a-" (without) and "byssos" (depth), thus bottomless and limitless. Usually it refers to watery, oceanic depths, but it might also suggest a crevasse, chasm, or other terrestrial void. Abyss has a connotation of terror, one coming, I suspect, from the implication that what is bottomless must also be inescapable. Moreover, it is a bottomless below, suggesting a grave, the underworld of Hades or Tartarus, and the oblivion coming with death. Few who visit there ever return to the world of the living on earth's sunny surface [1]. The related word "abysmal" has had, since the early 19th century [2], the additional connotation of a wretchedness into which one falls, for example, "the abysmal conditions of those living on the street." For the Chinese, abyss appears as an interpretation of the water over water, or Pit, hexagram of the I Ching. Other interpretations of that hexagram involve darkness, risk, and concealed danger. Fear of bottomless depths is, evidently, not strictly Western.
I am now reading Claude C. Albritton's book, The Abyss of Time (WH Freeman, 1980). A geologist, Albritton provides a history of the geological discovery of the vastness of earth's time. We might simply call such vastness "deep time". The discovery came slowly, in the successive discoveries made by geologists and others over several hundred years. Time gathered its depth (or, expanse) as these discoveries pushed out estimates of the age of the earth from 6000 years (a date derived nonscientifically by analysis of the Jewish scriptures, Genesis in particular) to today's estimate of 4.6 billion years. This increase of more than 750,000-fold has required adjustment in how we, as mortal humans, understand ourselves as existing in the matrix of time.
Albritton's title, "the abyss of time", originates in the discoveries of James Hutton, one of geology's founders. Hutton came to understand geological processes as slow and inexorable. Given sufficient time, these processes -- no different from those active at this present time -- can raise mountains and cut vast canyons. No Biblical floods or other catastrophic events are needed [3]. Instead, only time, in vast amounts, is required. Consequently, "we find no vestige of a beginning - no prospect of an end," wrote Hutton (Albritton, p. 96). Moreover, "the mind seemed to grow giddy by looking so far into the abyss of time" (Albritton, p. 103) wrote John Playfair, Hutton's collaborator and biographer. Playfair wrote this at Siccar Point, Scotland, the site of a geological unconformity that provided Hutton with his most important insights. But why describe time with the word "abyss" considering it terrifying connotation?
In its new-found vastness, geological time seems to deny our stories of time's beginning, be it the Genesis story or the Big Bang, as well as of time's ending, say, the return of Christ or nuclear winter. Time without beginning and without end consequently loses its unfolding progressive character, becoming more nearly circular and repetitious. Sisyphus, eternally rolling his boulder up the mountain only to have it roll back down, graduates from mere metaphor and mythology. He is a man punished by the gods with futility and imprisoned in the realm of circular time. His fate and its futility are what makes understanding geological time an abyss [4].
Endnotes
1. Greek and Roman mythology give special attention to those few mortals who have visited and later returned from the Underworld. These special mortals include Odysseus, Aeneas, Sisyphus, and Orpheus. (Eurydice, beloved by Orpheus, almost made the list.)
2. See "abysmal" in The Oxford Dictionary of Word Histories, edited by Glynnis Chantrell, 2002.
3. This doctrine now goes by the name Uniformitarianism.
4. Albert Camus, for one, disagreed. In his essay "The Myth of Sisyphus" (ca. 1942), he presented Sisyphus as the modern absurd hero, ending his essay with the words "one must imagine Sisyphus happy". His Sisyphus defies both the gods and the circularity of time. He knows time but not the abyss. I wonder how much Camus knew about geological time.
posted: 2020-03-09, last edited: 2020-03-10 (rewritten)
Showing posts with label history of universe. Show all posts
Showing posts with label history of universe. Show all posts
Monday, March 9, 2020
Thursday, February 20, 2020
How old is old?
What is the oldest thing found on earth?
Rocks, right? Some of the oldest rock formations are found in northern and eastern Canada and date back about four billion years. Immensely, unimaginably old they are, and yet the earth itself is older, dated to about 4.54 billion years. On earth, rocks are continuously recycled, broken down by weathering and erosion, and moved by water, wind, and gravity. And rocks are also built back up, reformed by sedimentation and remelting, pushed up again by our earth's ever-moving crust. Original rocks, present when our newly-created, molten planet had cooled and solidified, are likely long since recycled and remade by our dynamic living planet.
So how about meteorites, the rocky remains of "shooting star" reaching the earth's surface still intact? They are older still. At the local New Mexico Museum of Natural History and Science is found an iron-nickel meteorite collected from South America and dated to 4.55 billion years ago. "PLEASE TOUCH" says the sign by the meteor. Awed, I place my hand on its rusty metallic surface and try to feel the vastness of time that my rational mind cannot comprehend. "This may be the oldest rock you will ever touch" suggests the sign. Indeed.
Earth, sun, and the seven planets [1] of our solar system all originated together about 4.57 billion years ago. Originally part of rocky objects smaller than Earth but still part of the solar system, rocks that would become meteorites cooled faster and solidified sooner than Earth. Thereby they are older.
But can we go even farther back in time? Can we find even more ancient mineral-based substances on earth? Until recently I thought not. But now, I stand corrected.
Older matter ought to exist somewhere. Old as Earth and the solar system are, we are but recent arrivals. As the Big Bang creation is dated to about 13.7 billion years ago, some two-thirds of the universe's history had already passed before our solar system was created. Generations upon generations of stars and galaxies predate us and our sun. The vastness of earth's history therefore contacts to something termed "recent". Absurd! My mind rebels at this absurdity and this monstrosity. I am a trained experimental scientist. I do believe these ages. Still, I need something solid, something tangible, something to touch and feel, if only with scientific instruments, so that I can also believe in my heart and marrow as I believe in my brain. I need more evidence.
Late last month a scientific paper [2] appeared providing some of that evidence. The paper's title is instructive: "Lifetimes of interstellar dust from cosmic ray exposure ages of presolar silicon carbide". The words "presolar" and "interstellar" suggest matter older than the solar system and originating outside of it. "Dust" suggests solid matter, and "silicon carbide" is a particular type of mineral, one of the first minerals to form in the history of the universe [3]. Presolar grains are not new. What this paper contributes is a new method of dating them. The grains they dated are derived from the Murchison meteorite that landed in Australia in 1969. While most of the meteorite's matter dates from just after the formation of the solar system, embedded within it are trace grains of far older matter, matter containing the mineral silicon carbide (SiC). The oldest grains date to 1 to 5 billion years prior to the solar system's formation, or 5.6 to 9.6 billion years ago. As I touched the meteorite at the local museum, might my hand have come into contact with similar ancient presolar grains [4]?
Should we believe this paper? Key to answering that question is considering carefully the methods used. The authors face two challenges: (1) convincing us that the SiC grains came from outside the solar system and (2) establishing a date for their formation. For (1) the authors relied on a well-established method: demonstrating by mass spectroscopy isotopic anomalies characteristic of matter originating outside of the solar system. For (2) the authors developed a new dating method based on cosmic ray exposure. They had to. As they note in their paper, "Dating of interstellar dust directly with astronomical methods is not possible. Neither is dating based on the decay of long-lived radioactive nuclides, due to current analytical limitations and unknown initial isotopic compositions."
But can we go back even further in time?
Yes, we can go almost all of the way back, back more than 13.6 billion years, if we relax one key assumption. Up to this point, this blog post has been written from a geologist's point of view. What counts to the geologist are minerals, those underlying chemical components of terrestrial rocks, meteorites, and presolar grains. Key to the definition of mineral is the requirement that atoms continuously exist in an intact, regular, and solid structure. Recycling of rocks on earth's surface, for example, reshuffles this structure, thereby resetting a mineral's age to the most recent episode of (re)mineralization.
Chemists, in contrast, see things differently. They are more willing to let go of the requirement that dating apply to elements in their mineral form. What matters is only the elements themselves, and not their chemical neighborhood and bonding partners. All hydrogen, some helium, and traces of lithium were created in the Big Bang and predate even the first stars. Cosmologists estimate that by 379,000 years after the Big Bang, the expanding universe had cooled enough for the nuclei of the hydrogen, helium, and lithium to combine with electrons forming the first atoms.
I sip some tea, and in the water composing it, I taste and consume hydrogen dating back nearly to the Big Bang 13.7 billion years ago. Oh the places that hydrogen has been!
NOTES
1. Missing from the list of eight planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune) is Pluto. Based on its small mass and the aberrant characteristics of its orbit (specifically, its eccentricity and large deviation from the ecliptic), Pluto was reclassified in 2006 from a "planet" to a "dwarf planet", the same status shared by Ceres, one of the larger known asteroids.
2. The article is by Philipp R. Heck et al. and was published on 28 January 2020 in the Proceedings of the National Academy of Science, 117(4): 1884-1889. The original article is available here at no cost.
3. See Professor Robert Hazen's course, "The Origin and Evolution of Earth" (The Great Courses, 2013), especially lectures four and five. See also the Wikipedia entry on "presolar grains".
4. I am doubtful. The Murchison meteorite, a carbonaceous chondrite, has a composition distinctly different from iron-nickel meteorite displayed at the NM Museum of Natural History and Science.
ACKNOWLEDGMENT
Professor Carol Hill, her course "Planetary Geology" (now being taught at the University of New Mexico), and my fellow classmates motivated and informed this blog post.
posted: 2020-02-20, last modified: 2020-02-20
Rocks, right? Some of the oldest rock formations are found in northern and eastern Canada and date back about four billion years. Immensely, unimaginably old they are, and yet the earth itself is older, dated to about 4.54 billion years. On earth, rocks are continuously recycled, broken down by weathering and erosion, and moved by water, wind, and gravity. And rocks are also built back up, reformed by sedimentation and remelting, pushed up again by our earth's ever-moving crust. Original rocks, present when our newly-created, molten planet had cooled and solidified, are likely long since recycled and remade by our dynamic living planet.
So how about meteorites, the rocky remains of "shooting star" reaching the earth's surface still intact? They are older still. At the local New Mexico Museum of Natural History and Science is found an iron-nickel meteorite collected from South America and dated to 4.55 billion years ago. "PLEASE TOUCH" says the sign by the meteor. Awed, I place my hand on its rusty metallic surface and try to feel the vastness of time that my rational mind cannot comprehend. "This may be the oldest rock you will ever touch" suggests the sign. Indeed.
 |
| Iron-nickel meteorite at the New Mexico Museum of Natural History and Science |
Earth, sun, and the seven planets [1] of our solar system all originated together about 4.57 billion years ago. Originally part of rocky objects smaller than Earth but still part of the solar system, rocks that would become meteorites cooled faster and solidified sooner than Earth. Thereby they are older.
But can we go even farther back in time? Can we find even more ancient mineral-based substances on earth? Until recently I thought not. But now, I stand corrected.
Older matter ought to exist somewhere. Old as Earth and the solar system are, we are but recent arrivals. As the Big Bang creation is dated to about 13.7 billion years ago, some two-thirds of the universe's history had already passed before our solar system was created. Generations upon generations of stars and galaxies predate us and our sun. The vastness of earth's history therefore contacts to something termed "recent". Absurd! My mind rebels at this absurdity and this monstrosity. I am a trained experimental scientist. I do believe these ages. Still, I need something solid, something tangible, something to touch and feel, if only with scientific instruments, so that I can also believe in my heart and marrow as I believe in my brain. I need more evidence.
 |
| Timeline of the Universe |
Late last month a scientific paper [2] appeared providing some of that evidence. The paper's title is instructive: "Lifetimes of interstellar dust from cosmic ray exposure ages of presolar silicon carbide". The words "presolar" and "interstellar" suggest matter older than the solar system and originating outside of it. "Dust" suggests solid matter, and "silicon carbide" is a particular type of mineral, one of the first minerals to form in the history of the universe [3]. Presolar grains are not new. What this paper contributes is a new method of dating them. The grains they dated are derived from the Murchison meteorite that landed in Australia in 1969. While most of the meteorite's matter dates from just after the formation of the solar system, embedded within it are trace grains of far older matter, matter containing the mineral silicon carbide (SiC). The oldest grains date to 1 to 5 billion years prior to the solar system's formation, or 5.6 to 9.6 billion years ago. As I touched the meteorite at the local museum, might my hand have come into contact with similar ancient presolar grains [4]?
Should we believe this paper? Key to answering that question is considering carefully the methods used. The authors face two challenges: (1) convincing us that the SiC grains came from outside the solar system and (2) establishing a date for their formation. For (1) the authors relied on a well-established method: demonstrating by mass spectroscopy isotopic anomalies characteristic of matter originating outside of the solar system. For (2) the authors developed a new dating method based on cosmic ray exposure. They had to. As they note in their paper, "Dating of interstellar dust directly with astronomical methods is not possible. Neither is dating based on the decay of long-lived radioactive nuclides, due to current analytical limitations and unknown initial isotopic compositions."
But can we go back even further in time?
Yes, we can go almost all of the way back, back more than 13.6 billion years, if we relax one key assumption. Up to this point, this blog post has been written from a geologist's point of view. What counts to the geologist are minerals, those underlying chemical components of terrestrial rocks, meteorites, and presolar grains. Key to the definition of mineral is the requirement that atoms continuously exist in an intact, regular, and solid structure. Recycling of rocks on earth's surface, for example, reshuffles this structure, thereby resetting a mineral's age to the most recent episode of (re)mineralization.
Chemists, in contrast, see things differently. They are more willing to let go of the requirement that dating apply to elements in their mineral form. What matters is only the elements themselves, and not their chemical neighborhood and bonding partners. All hydrogen, some helium, and traces of lithium were created in the Big Bang and predate even the first stars. Cosmologists estimate that by 379,000 years after the Big Bang, the expanding universe had cooled enough for the nuclei of the hydrogen, helium, and lithium to combine with electrons forming the first atoms.
I sip some tea, and in the water composing it, I taste and consume hydrogen dating back nearly to the Big Bang 13.7 billion years ago. Oh the places that hydrogen has been!
NOTES
1. Missing from the list of eight planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune) is Pluto. Based on its small mass and the aberrant characteristics of its orbit (specifically, its eccentricity and large deviation from the ecliptic), Pluto was reclassified in 2006 from a "planet" to a "dwarf planet", the same status shared by Ceres, one of the larger known asteroids.
2. The article is by Philipp R. Heck et al. and was published on 28 January 2020 in the Proceedings of the National Academy of Science, 117(4): 1884-1889. The original article is available here at no cost.
3. See Professor Robert Hazen's course, "The Origin and Evolution of Earth" (The Great Courses, 2013), especially lectures four and five. See also the Wikipedia entry on "presolar grains".
4. I am doubtful. The Murchison meteorite, a carbonaceous chondrite, has a composition distinctly different from iron-nickel meteorite displayed at the NM Museum of Natural History and Science.
ACKNOWLEDGMENT
Professor Carol Hill, her course "Planetary Geology" (now being taught at the University of New Mexico), and my fellow classmates motivated and informed this blog post.
posted: 2020-02-20, last modified: 2020-02-20
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