Soil Underfoot

16th century polymath Leonardo da Vinci observed, "We know more about the movement of celestial bodies than about the soil underfoot."

That da Vinci recognized our existential blindspot five hundred years ago is remarkable given soil scientists now warn us that Earth's soil is disappearing at a greater rate than it can be replenished.

A cloak of loose, soft material, held to the earth’s hard surface by gravity, is all that lies between life and lifelessness.
― Wallace H. Fuller

Soil profile
source: USDA

Humus

The word human arrived into the English-speaking lexicon from the Latin humus which translates to earth and ground.

The modern word humus describes organic material resulting from the biodegradation of plants and animals that are transformed into fertile soil. Plants drop leaves, seeds, twigs, and other materials to the ground which, over time, decay into rich, dark humus that becomes topsoil.

The soil is the great connector of lives, the source and destination of all. It is the healer and restorer and resurrector, by which disease passes into health, age into youth, death into life. Without proper care for it we can have no community, because without proper care for it we can have no life.
― Wendell Berry

Soil Loss

The United Nations designated 2015 as the International Year of Soils. The UN cautions that more than a third of Earth's soil is at risk.

Wallace Fuller's cloak of organic material ― all that lies between life and lifelessness ― is undergoing rapid loss or degradation because of water erosion, wind erosion, pollution, acidification and nutrient depletion.

We might say that the earth has the spirit of growth; that its flesh is the soil.
― Leonardo da Vinci

Germination
source: USDA

Humility

Humility is from humus,
meaning from-the-earth.
We are pinholes of light
delayed by nothing and
arriving unannounced
like the tiny sounds
of before and after

REFERENCES

• Earth Could Lose a Third of Its Topsoil, by Patrick J. Kiger, Discovery, 15 October 2015.
• Soils of the Desert Southwest, by Wallace H. Fuller, University of Arizona Press, 1975.
• Humility, by Bob MacNeal, Buckets of Wisdom, 8 June 2013, Saint Paul.
• Spotlighting humanity’s ‘silent ally,’ UN launches 2015 International Year of Soils, UN News Centre, 5 December 2014.
• The Unsettling of America: Culture and Agriculture, by Wendell Berry, Counterpoint 2004.

The Forest Primeval

The first stanza of Longfellow's poem Evangeline sets the stage for a primal forest:

This is the forest primeval. The murmuring pines and the hemlocks,
Bearded with moss, and in garments green, indistinct in the twilight,
Stand like Druids of eld, with voices sad and prophetic,
Stand like harpers hoar, with beards that rest on their bosoms.

As ancient fossil forests are unearthed, scientists gather clues about nascent plant life and the prevailing climatic conditions of the time.

Fossilized forests discovered around the world, dated as far back as 380 million years ago, provide insights into Earth's ever-changing atmospheric composition and the corresponding climate changes on Earth.

During the Devonian some 420 to 360 million years ago, the atmosphere underwent a 15-fold decline in carbon dioxide. The decline is thought to be primarily attributable to carbon sequestration caused by the evolutionary emergence of large forest trees.

Carbon sequestration rates vary by forest age, composition, and location, but today we know that a single tree can absorb carbon dioxide at a rate of 48 lb. per year.

The decline in atmospheric carbon during the Devonian period is posited to have spawned large-scale global cooling that led to a period of glaciation.

Sketch of the forest floor in ancient fossil forest near Gilboa, New York
Frank Mannolini, New York State Museum

Fossil plant-life discovered in Schoharie County, New York in the 1850s, in 1920, and again in 2010, included the Gilboa stumps cited as Earth's oldest trees.

It was like discovering the botanical equivalent of dinosaur footprints. But the most exciting part was finding out just how many different types of footprints there were. The newly uncovered area was preserved in such a way that we were literally able to walk among the trees, noting what kind they were, where they had stood and how big they had grown."
― William Stein, Binghamton University, 2010

Researchers have unearthed another forest with fossilized tree stumps preserved in place in Svalbard, a Norwegian archipelago in the Arctic Ocean. 380 million years ago, Svalbard was located near the equator.

Reconstructed drawing
Fossil forest, Svalbard

Since the Devonian period, plate tectonics has transported Svalbard to its current location in the arctic ocean.

"These fossil forests shows us what the vegetation and landscape were like on the equator 380 million years ago, as the first trees were beginning to appear on the Earth."
― Chris Berry, Cardiff University

By the phenomena of carbon sequestration, trees absorb structure-forming carbon from atmospheric carbon dioxide through photosynthesis.

"The evolution of tree-sized vegetation is the most likely cause of this dramatic drop in carbon dioxide because the plants were absorbing carbon dioxide through photosynthesis to build their tissues, and also through the process of forming soils."
― Chris Berry

Svalbard is also in the forefront of preserving plant diversity. One of the northernmost inhabited villages on Earth, Svalbard is the site chosen by the Norwegian government in 2008 for the Global Seed Vault. Secured in the permafrost, the Svalbard seed vault is the largest seed storage in the World.

"In some mysterious way woods have never seemed to me to be static things. In physical terms, I move through them; yet in metaphysical ones, they seem to move through me."
― John Fowles

REFERENCES

• Ancient fossil forest unearthed in Arctic Norway, Phys.org, 19 November 2015.
• Cardiff uni researchers help unearth ancient forest, BBC News, 19 November 2015.
• Evangeline, A Tale of Acadie, Henry Wadsworth Longfellow, 1847.
• Floor of Oldest Forest Discovered in Schoharie County, NY, New York Geological Survey, 1 March 2012.
• Lycopsid forests in the early Late Devonian paleoequatorial zone of Svalbard, Christopher M. Berry1 and John E.A. Marshall, Geology, 19 November 2015.
• Svalbard Global Seed Vault, Norwegian Government, February 2008.

Earthly Rotation

Like a whirligig Earth rotates on its own axis.

Primitive observers from the inhabited middle latitudes of Earth would've have mused about something we rarely contemplate:

The Sun rises in the East
The Sun sets in the West

Like most celestial phenomena, Sunrises and Sunsets occur over a repeatedly observable and predictable cycle. During one day, the Sun appears to follow a half-circular arc through the sky.

As observers of the night sky our ancestors would've also noticed that stars moves along a similar circular path.

Our ancestors might have reasonably believed that the bespeckled night sky was an extraterrestrial backdrop that rotates.

"Before we invented civilization our ancestors lived mainly in the open out under the sky." ― Carl Sagan

Whirling Southern Star Trails over ALMA by ESO

Ancient ancestral astronomers might have hypothesized a stationary Earth centered about a rotating backdrop of stars.

"Mortal as I am, I know that I am born for a day. But when I follow at my pleasure the serried multitude of the stars in their circular course, my feet no longer touch the earth."
― Ptolemy, Almagest, a 2^nd century astronomical treatise

Today we know it's the Earth that's rotating on its axis that creates this illusion. How might we devise a model that matches our observations and proves the Earth is rotating?

Supporting Model

Foucault pendulum
at the North Pole
by Theresa Knott

A less intuitive but valid hypothesis is that the Earth is rotating on its own axis. Of course we know now that Earth rotates on its own axis, but we were helped by a model to clinch the deal of corroborating what others had observed for generations.

The classic model that helped prove Earth is rotating on its own axis is a simple experiment with a pendulum known as the Foucault pendulum.

Foucault Pendulum

The Foucault pendulum (pronounced foo-koh) was introduced in 1851 to visually demonstrate Earth's rotation. The experiment is named after French physicist Léon Foucault.

An experimental Foucault pendulum, commonly suspended 39–98 feet and freely swinging back and forth, will be visibly affected by Earth’s rotation.

Simulated pendulum rotation
by Dominique Toussaint

The affect is not visible after a few swings, rather becomes gradually visible by a matter of degrees over the course of a day.

To maintain the bob of a pendulum swinging in museum demonstrations, an electromagnetic or other drive is used, or the pendulum is manually restarted.

A pendulum day is the time needed for the plane of a Foucault pendulum to complete 360 degree rotation. The duration of a pendulum day is one day divided by the sine of the latitude.

"I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth." ― Umberto Eco

REFERENCES

• But it moves! How we know the Earth rotates, Ethan Siegel,17 September 2010.
• Foucault pendulum, Wikipedia.
• Pale Blue Dot: A Vision of the Human Future in Space, Carl Sagan, Random House 1994.

Increasingly Earlier Life

Every creature inhabiting Earth, including newcomers like humans, represents an unbroken line to primitive carbon-based life present on Earth nearer and nearer to the planet's probable inception some 4.54 billion years ago.

Gnat encased in amber

"What we normally think of as 'life' is based on chains of carbon atoms, with a few other atoms, such as nitrogen or phosphorus."
— Stephen Hawking, from a 2008 lecture

Chains of carbon atoms are common to all living things.

Biogenic Substances

Biogenic substances contain carbon which is a recognized marker for living organisms. Such substances, in the form of constituents, or as secretions from plants or animals, embody biomolecules which are the building blocks of life.

coal & oil	geologic-age constituents that have undergone changes
chalk & limestone	geologic-age secretions (e.g., marine animal shells)
grass & wood	contemporary constituents
pearls, silk & ambergris	contemporary secretions

Improbable Life

That life-forming elements came from dying stars in the far reaches of the universe make life on Earth nearly incomprehensible, if not improbable.

I tell my students, with a feeling of pride that I hope they will share, that the carbon, nitrogen, and oxygen that make up ninety-nine per cent of our living substance were cooked in the deep interiors of earlier generations of dying stars. Gathered up from the ends of the universe, over billions of years, eventually they came to form, in part, the substance of our sun, its planets, and ourselves. Three billion years ago, life arose upon the earth. It is the only life in the solar system.
— George Wald, Harvard Biochemist ⁽¹⁾

olive-green zircon crystal
by Rob Lavinsky

Earliest Biogenic Substances

The earliest recorded biogenic substances on Earth gets incrementally pushed back as scientists find and analyze new artifacts.

Until recently, graphite detected in rock dated 3.8 billion years ago was the earliest known biogenic residue of life.

UCLA geochemists recently identified specks of biogenic carbon encased in undisturbed, crack-free zircon crystals from Western Australia.

This discovery pushes back the earliest biogenic residue some 300 millions years to 4.1 billion years ago. Thus it places the probable earliest life closer to the time when Earth was formed 4.54 billion years ago.

"Life on Earth may have started almost instantaneously. With the right ingredients, life seems to form very quickly."
— Mark Harrison, UCLA geochemist

REFERENCES

• 4.1 Billion Year Old Australian Zircon Contains Graphite of Biological Origin, Sci-News.com 20 October 2015.
• Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon, Elizabeth A. Bella, Patrick Boehnkea, T. Mark Harrison, and Wendy L. Maob, PNAS, 10.1073/pnas.1517557112, 14 October 2015.

⁽¹⁾ From speech given at an anti-war teach-in at the Massachusetts Institute of Technology, (4 Mar 1969) 'A Generation in Search of a Future', as edited by Ron Dorfman for Chicago Journalism Review, (May 1969)