Saturday, February 28, 2015

Worldly Photographs

Some experience the world with enduring curiosity.
I had been chipping at the world idly, and had by accident uncovered vast and labyrinthine further worlds within it.
— Annie Dillard, An American Childhood
Some discover the poetic allure of worldly phenomena by accident, others discover with intent. Attentiveness to sensual phenomena requires discipline. Attentiveness must be practiced and exercised like one might practice running, yoga, meditation, or tai chi.
Push it. Examine all things intensely and relentlessly.
— Annie Dillard, Pilgrim at Tinker Creek
Originating with the fine art photography movement in the 1890s, photographers have used the mental and physical act of curating visual input to tune and exercise the brain to visual receptiveness.

For many photographers, photographing is a discipline of
Attentiveness with intent
Erosion Spider above is one of the 2014 European Geosciences Union photo contest winners. The image was made by John Clemens in the Grand Canyon.
Toward the bottom of the Grand Canyon in Arizona, USA, lies the Middle Cambrian Bright Angel Shale, a variably coloured sequence of relatively soft sedimentary rocks, here sculpted by erosion into a spider-like outcrop decorated with small green desert shrubs.
John Clemens
The curated photographs of the annual European Geosciences Union photo contest are a feast for the senses. Photography is a visual medium curiously capable of transporting one to a place where the other senses come to life if only in one's imagination.
Art is always the replacement of indifference by attention.
Guy Davenport


Saturday, February 21, 2015

Earth Size

In 240 BC Eratosthenes estimated the circumference of the Earth to within 100 miles.
[Eratosthenes] ... is a mathematician among geographers, and yet a geographer among mathematicians; and consequently on both sides he offers his opponents occasions for contradiction.
Eratosthenes (276–194 BC)
Ancient Greeks knew Earth was spherical. How did Eratosthenes accurately estimate its circumference?

The answer lies in a tale of two cities: Syene and Alexandria. Syene was the ancient name of the city known today as Aswan.

Sun Straight up Syene

Eratosthenes heard that the sun could be observed straight overhead from the bottom of a well in Syene at noon during the summer solstice. No shadows would have been cast on the walls of the well. No shadows would have been cast by the style of an above-ground sundial.

The Alexandria Angle

At noon in Alexandria during a summer solstice, Eratosthenes observed a shadow cast by a column.

Using the height of the column (h) and the distance (d) of the edge of shadow from the column, Eratosthenes used the trigonometric functions tangent and arctangent to determine the shadow angle θ.

Since tan(θ) = d / h, Eratosthenes used the arc-tangent to find the angle.

The History of Geodesy, NOAA

θ = arctan(d / h)
Eratosthenes found the angle θ of the shadow cast by the column to be 7.2°.

Two Cities

Syene to Alexandria was an established trade route of camel-driven caravans. Eratosthenes knew the distance between Syene and Alexandria was about 4,400 stades.

stade is an ancient Greek unit of measurement equivalent to the distance of footraces in the ancient Olympic Games in Olympia.
1 stade ~ 600 feet
Using the 7.2° angle θ of the shadow and the distance between Alexandria and Syene, Eratosthenes used an arithmetic ratio. Expressed in words, he recognized
The shadow angle 7.2° is to 360° of the Earth as the 4,400 stades is to the circumferential distance C of the Earth. 
Expressed as a ratio:
7.2°=4,400 stades
Solving for circumferential distance C:
C=360°   x 4,400 stads  = 220,000 stads or 25,000 miles
Remarkably Eratosthene's estimate overshot the circumference of the Earth by a mere 99 miles.
25,000 miles24,901 miles


Saturday, February 14, 2015

Alpine Tree Line

The maximum elevation where trees survive in an alpine environment is called the tree line. Viewed from a distance the tree line appears abrupt.
Tree line below Wheeler Peak
One forgets that there are environments which do not respond to the flick of a switch or the twist of a dial, and which have their own rhythms and orders of existence. Mountains correct this amnesia.
Robert Macfarlane
What accounts for an alpine tree line?

High-elevation snow lingers before melting. Lingering snow shortens the growing season. New growth is inhibited because saplings do not have enough time to harden before the impending frost.
By speaking of greater forces than we can possibly invoke, and by confronting us with greater spans of time than we can possibly envisage, mountains refute our excessive trust in the man-made. They pose profound questions about our durability and the importance of our schemes. They induce, I suppose, a modesty in us.
Robert Macfarlane
High-elevation winds are another existential threat to new growth. The survival of a sapling depends its ability to bend and buttress itself against wind.
Those who travel to mountain-tops are half in love with themselves, and half in love with oblivion.
Robert Macfarlane
Alpine microclimates are determined by elevation and exposure. The higher the elevation the lower the temperature.

Tree line transition on the
Wheeler Peak summit trail
Ascending a peak in the Rocky Mountains, a traveler will lose about 3.5°F in temperature for every 1000 foot gain in elevation.

On the trail, there is a transition zone of scrub conifers between the full canopy forest below and the treeless tundra above.
The clearest way into the Universe is through a forest wilderness.
John Muir


Saturday, February 7, 2015

Great Ploughs

Glaciers are mechanical engines that grind, plough, and sculpt the earth. The 19th century natural historian Louis Agassiz wrote,
The glacier was God's great plough.
— Louis Agassiz, Geological Sketches, 1875.
Grey Glacier in the Southern Patagonian Ice Field, Chile

Glaciers leave a record of linear etchings, rubble, and deposited boulders from which we cobble the geologic narratives to reconcile what we see today.
The earth was covered by a huge ice sheet which buried the Siberian mammoths, and reached just as far south as did the phenomenon of erratic boulders. This ice sheet filled all the irregularities of the surface of Europe before the uplift of the Alps, the Baltic Sea, all the lakes of Northern Germany and Switzerland. It extended beyond the shorelines of the Mediterranean and of the Atlantic Ocean, and even covered completely North America and Asiatic Russia.
— Louis Agassiz, Études sur Les Glaciers, 1840, trans Albert V. Carozzi
Morteratsch glacier in the Bernina Range of the Bündner Alps, Switzerland
When the Alps were uplifted, the ice sheet was pushed upwards like the other rocks, and the debris, broken loose from all the cracks generated by the uplift, fell over its surface and, without becoming rounded, moved down the slope of the ice sheet.
— Louis Agassiz, Études sur Les Glaciers, 1840, trans Albert V. Carozzi
Mark Twain wrote of his experience visiting glaciers in The Alps. Twain wrote of feeling tolerably insignificant faced with the magnificence of The Alps, the new understanding of glaciers in the latter half of the 19th century that coincided with the burgeoning science of glaciology.
A man who keeps company with glaciers comes to feel tolerably insignificant by and by. The Alps and the glaciers together are able to take every bit of conceit out of a man and reduce his self-importance to zero if he will only remain within the influence of their sublime presence long enough to give it a fair and reasonable chance to do its work.
— Mark Twain, A Tramp Abroad, 1880.