(Roughly) Daily

Posts Tagged ‘earth

“To see a world in a grain of sand and a heaven in a wildflower”*…

Where, exactly is Heaven? Stephen Reid Case explains how a very concrete, physical answer to that question became much less concrete…

The Christian concept of heaven, so familiar today from popular depictions of clouds and haloed angels, was an invention – one that came about as early Christians interpreted their religious writings in the context of the Greek culture in which their movement grew up. Christian writers combined Plato’s ideas about the soul’s ascent to the sky at death with Aristotle’s understanding of the structure of the universe, a combination that allowed them to apply a cosmological framework to terms like ‘heaven of heavens’, as well as the ascents, described in the New Testament, of both Jesus and Paul. By the Middle Ages, anyone who uttered the words ‘Our Father, who art in heaven …’ had a clear spatial understanding of where heaven was: God dwelt in the third heaven, above the heaven of the air and the heaven of the stars. This third heaven, the empyrean, became an article of Christian faith – until the new cosmology of Copernicus and Galileo placed the Sun rather than Earth in the centre of the universe. This transformation from an Earth-centred to a Sun-centred universe did not simply displace Earth; it destroyed heaven as a place within the cosmos.

If I asked my astronomy students where heaven was located, I would no doubt receive a classroom full of bewildered stares, despite the fact that I teach at a Christian university – where the majority of students believe in both heaven and the afterlife. When pressed, they might offer thoughts about heaven being a different plane of reality or perhaps another dimension. They believe, but they don’t conceptualise heaven as a location; it is not a part of their spatial understanding of the universe. For most of the history of Christianity, though, the opposite was true…

For hundreds of years, Christians knew exactly where heaven was: above us and above the stars. Then came the new cosmologists: “Where God dwelt.”

* William Blake, “Auguries of Innocence” l. 1 (ca. 1803)

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As we muse on metaphor and morphology, we might recall that it was on this date in 1972 that the Apollo 17 mission launched; on their way to the moon, about 18,000 miles from the Earth, astronauts Harrison Schmitt and Ron Evans took the photo now known as “The Blue Marble”– one of the most reproduced images in history.

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Written by (Roughly) Daily

December 7, 2022 at 1:00 am

“Iteration, like friction, is likely to generate heat instead of progress”*…

A word of caution from the wondrous Randall Munroe (@xkcd): “Rotatation.”

* George Eliot, The Mill on the Floss

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As we resist repetition, we might send perpetual birthday greetings to Jean Bernard Léon Foucault; he was born on this date in 1819.  A physicist who made an early measurement of the speed of light, discovered eddy currents, and is credited with naming the gyroscope (although he did not invent it), Foucault is best remembered for the (eponymously-named) Foucault’s Pendulum– suspended from the roof of the Panthéon in Paris– demonstrating the effects of the Earth’s rotation.  Using a long pendulum with a heavy bob, he showed its plane was not static, but rotated at a rate related to Earth’s angular velocity and the latitude of the site.

In fact, essentially the same experimental approach had been used by Vincenzo Viviani as early as 1661; but it was Foucault’s work that caught the public imagination: within years of his 1851 experiment, the were “Foucault’s Pendulums” hanging– and attracting crowds–in major cities across Europe and America.

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Written by (Roughly) Daily

September 18, 2022 at 1:00 am

“To be ignorant of what occurred before you were born is to remain always a child”*…

There’s history… and then there’s deep history. C. Patrick Doncaster, a professor of ecology at Southampton University has created “Timeline of the human Condition- Milestones in Evolution and History.” Starting with the Big Bang (13.8 billion years ago) it marks significant events in Earth’s development, the evolution of life, and the development of human culture (science/technology, economics, politics, and art) all the way up to 2021.

It concludes with a trio of handy analogies…

Following the big bang 13.8 billion years ago, time passed two-thirds of the way to the present before the formation of the Sun 4.57 billion years ago. Rescaled to a calendar year, starting with the big bang at 00:00:00 on 1 January, the Sun forms on 1 September, the Earth on 2 September, earliest signs of life appear on 13 September, earliest true mammals on 26 December, and humans just 2 hours before year’s end. For a year that starts with the earliest true mammals, the dinosaurs go extinct on 17 August, earliest primates appear on 9 September, and humans at dawn of 25 December. For a year that starts with the earliest humans, our own species appears on 19 November, the first built constructions on 8 December, and agricultural farming begins at midday on 29 December.

Timeline of the Human Condition- Milestones in Evolution and History.” (via @Recomendo6)

See also: “How We Make Sense of Time.”

* Marcus Tullius Cicero

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As we prize perspective, we might spare a thought for James Hiram Bedford; he died on this date in 1967. A psychologist who wrote several books on occupational counseling, he is best remembered as the first person whose body was cryopreserved after legal death. He remains preserved at the Alcor Life Extension Foundation in Arizona.

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“Appearances are a glimpse of the unseen”

A shower of comets rains down on Earth while violent volcanic eruptions billow up from below. Both events may follow our planet’s passage through dark matter concentrated in the Milky Way’s plane and help to trigger extinction events.

Are we on the verge of understanding the upheavals that have shaped the earth?

Do geologists dream of a final theory? Most people would say that plate tectonics already serves as geology’s overarching idea. The discovery of plate tectonics 50 years ago was one of the great scientific achievements of the 20th century, but is the theory complete? I think not. Plate tectonics describes Earth’s present geology in terms of the geometry and interactions of its surface plates. Geologists can extrapolate plate motions both back in time and into the future, but they cannot yet derive the behavior and history of plate tectonics from first principles.

Although scientists can interpret the history through the lens of what they see today, an important question remains: Why did geologic events — such as hot-spot volcanism, the breakup of continents, fluctuations in seafloor spreading, tectonic episodes, and sea-level oscillations — occur exactly when and where they did? Are they random, or do they follow some sort of a pattern in time or space?

A complete theory of Earth should explain geologic activity in the spatial domain, as plate tectonics does quite well for the present (once you incorporate hot spots), but also in the time and frequency domains. Recent findings suggest to me that geology may be on the threshold of a new theory that seeks to explain Earth’s geologic activity in time and space in the context of its astronomical surroundings.

The solar system oscillates with respect to the midplane of the disk-shaped Milky Way Galaxy with a period of about 60 million years. The Sun’s family passes through this plane twice each period, or once every 30 million years or so. The solar system behaves like a horse on a carousel — as we go around the disk-shaped galaxy, we bob up and down through the disk, passing through its densest part roughly every 30 million years.

Surely, it is too much of a coincidence that the cycle found in mass extinctions and impact craters should turn out to be one of the fundamental periods of our galaxy. The idea seemed almost too pretty to be wrong. But people searching for cycles have been fooled before, and we still had to answer the question: How does this cycle of movement lead to periodic perturbations of the Oort Cloud comets?

The idea of a roughly 30 million-year rhythm in geologic events has a long history in the geological literature. In the early 20th century, W.A. Grabau, an expert on sedimentary strata, proposed that tectonic activity and mountain building drove periodic fluctuations in sea level with an approximately 30 million-year cycle. In the 1920s, noted British geologist Arthur Holmes, armed with a few age determinations from radioactive decay, saw a similar 30 million-year cycle in Earth’s geologic activity…

If the cycles are real, what could be driving these long-term changes in volcanism, tectonics, sea level, and climate at such regular, if widely spaced, intervals? At first, I thought that the periodic energetic impacts might somehow be affecting deep-seated geological processes. I suggested in a short note in the journal Nature that large impacts might so deeply excavate and fracture the crust — to depths in excess of 10 miles (16 km) — that the sudden release of pressure in the upper mantle would result in large-scale melting. This would lead to the production of massive flood-basalt lavas, which would cover the crater and possibly create a mantle hot spot at the site of the impact. Hot spots could lead to continental breakup, which can cause increased tectonics and changes in ocean-floor spreading rates, and in turn cause global sea levels to fluctuate. Unfortunately, no known terrestrial impact structure has a clear association with volcanism, although some volcanic outpourings on Mars seem to be located along radial and concentric fractures related to large impacts.

The potential key to resolving this geological conundrum may come from outer space. Remember that Randall and Reece suggested that Earth passes through a thin disk of dark matter concentrated along the Milky Way’s midplane every 30 million years or so. Astrophysicist Lawrence Krauss and Nobel Prize-winning physicist Frank Wilczek of Harvard University, and independently Katherine Freese, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, proposed that Earth could capture dark matter particles that would accumulate in the planet’s core. The number of dark matter particles could grow large enough so that they would undergo mutual annihilation, producing prodigious amounts of heat in Earth’s interior.

A 1998 paper in the journal Astroparticle Physics (which I am sure few geologists ever read) provided a potential missing link. Indian astrophysicists Asfar Abbas and Samar Abbas (father and son, respectively) at Utkal University also were interested in dark matter and its interactions with our planet. They calculated the amount of energy released by the annihilation of dark matter captured by Earth during its passage through a dense clump of this material. They found that mutual destruction among the particles could produce an amount of heat 500 times greater than Earth’s normal heat flow, and much greater than the estimated power required in Earth’s core to generate the planet’s magnetic field. Putting together the predicted 30 million-year periodicity in encounters with dark matter with the effects of Earth capturing this unstable matter produces a plausible hypothesis for the origin of regular pulses of geologic activity.

Excess heat from the planet’s core can raise the temperature at the base of the mantle. Such a pulse of heat might create a mantle plume, a rising column of hot mantle rock with a broad head and narrow tail. When these rising plumes penetrate Earth’s crust, they create hot spots, initiate flood-basalt eruptions, and commonly lead to continental fracturing and the beginning of a new episode of seafloor spreading. The new source of periodic heating by dark matter in our planet’s interior could lead to periodic outbreaks of mantle-plume activity and changes in convection patterns in Earth’s core and mantle, which could affect global tectonics, volcanism, geomagnetic field reversals, and climate, such as our planet has experienced in the past.

These geologic events could lead to environmental changes that might be enough to cause extinction events on their own. A correlation of some extinctions with times of massive volcanic outpourings of lava supports this view. This new hypothesis links geologic events on Earth with the structure and dynamics of the Milky Way Galaxy.

It is still too early to tell if the ingredients of this hypothesis will withstand further examination and testing. Of course, correlations among geologic events can occur even if they are not part of a periodic pattern, and long-term geological cycles may exist apart from any external cosmic connections. The virtue of the galactic explanation for terrestrial periodicity lies in its universality — because all stars in the galaxy’s disk, many of which harbor planets, undergo a similar oscillation about the galactic midplane — and in its linkage of biological and geological evolution on Earth, and perhaps in other solar systems, to the great cycles of our galaxy.

Dark matter’s shadowy effect on Earth“: Earth’s periodic passage through the galaxy’s disk could initiate a series of events that ultimately lead to geological cataclysms and mass extinctions. From Michael Rapino (@mrr1_michael)

For very different angle on the evolution of the earth, the wonderful Walter Murch: “Why Birds Can Fly Over Mount Everest.”

* Anaxagoras

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As we dig deep, we might spare a thought for Harlow Shapley; he died on this date in 1972. An astronomer known as “the Modern Copernicus,” he did important work first at the Mt. Wilson Observatory, and then as head of the Harvard College Observatory. He boldly and correctly proclaimed that the globulars outline the Galaxy, and that the Galaxy is far larger than was generally believed and centered thousands of light years away in the direction of Sagittarius: he discovered the center of our Galaxy, and our position within it.

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“Everything is in motion. Everything flows.”*…

(Roughly) Daily has looked at the related theories of plate tectonics and continental drift before (e.g., here and here). They are relatively young: proposed in the early twentieth century by Alfred Wegener, they weren’t widely accepted until 1960 or so. Now they’re fundamental– and allowing scientists to reconstruct the earth’s past. To wit, this animation looking at the Earth’s tectonic plate movement from 1 ga (geological time for 1 billion years ago) to the present-day (the video starts at time 1,000 ma [1,000 million years ago], and moves at the rate of about 25 million years every second)…

From Earthbyte

Here’s a even more ambitious project, looking back 3.3 billion years:

More on plate tectonics and the supercontinents that it formed (and unformed) at Visual Capitalist.

* William Hazlitt

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As we buckle up, we might recall that in the very late 50s, the Ohio Art Company– which had been pursuing a pair of business: toys (e.g., windmills and a climbing monkey) and custom metal lithography products for food container and specialty premium markets– found a way to merge the two.  It acquired the rights to French electrician André Cassagnes‘ L’Écran Magique (The Magic Screen)– a drawing toy that allowed users to spin knobs to create line drawings, which could be erased by by turning the device upside down and shaking it. Ohio Art renamed it the Etch A Sketch, and introduced it in this date in 1960.

At its launch, which was near the peak of the Baby Boom, the Etch A Sketch was priced at $2.99 (equivalent to $26 in 2020); the company sold 600,000 units that year … and went on to sell over 100 million units and to earn a place in the National Toy Hall of Fame.

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Written by (Roughly) Daily

July 12, 2021 at 1:00 am

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