Saturday, May 31, 2014

Shafts of Sunlight

Shafts of sunlight, sometimes mythologized as God rays, Ropes of Maui, Jacob's Ladder, or Fingers of God, are atmospheric optics known as crepuscular rays.

Crepuscular rays are shafts of sunlight that stream through gaps in atmospheric clouds.

The shafts appear to radiate from a point in the sky, but are are nearly parallel. The convergence to a point in the sky observed on the ground, is actually a perspective effect analogous to how parallel train rails appear to converge at a distance.
“When you come right down to it all you have is yourself. The sun is a thousand rays in your belly. All the rest is nothing.”
Pablo Picasso (1881-1973)

Crepuscular is derived from the Latin word crepusculum meaning twilight. Crepuscular rays frequently appear during the high contrast twilight hours of dawn or dusk.
“The human understanding is like a false mirror, which, receiving rays irregularly, distorts and discolors the nature of things by mingling its own nature with it”
Francis Bacon (1561-1626)


Saturday, May 24, 2014

It Goes On

Model of L-serine molecule
Moments after the Big Bang, the universe contained hydrogen, helium, and trace amounts of lithium. Once stars coalesced, carbon and oxygen were produced.

Carbon and oxygen are synthesized when helium burns inside red giant stars.
Carbon in the universe is traceable to stars

Carbon-based Life

Carbon is the essential ingredient of life-sustaining organic molecules: carbohydrates; proteins; nucleic acids; and lipids.

Carbon allows for bonds that form three-dimensional molecular structures likened to, and modeled by, rings and chains. Such complex molecular structures provide the building blocks of life.
“In three words I can sum up everything I've learned about life: it goes on.”
Robert Frost

Earth's Carbon

Earth is largely comprised of oxygen and silicon with comparatively little carbon.

Earth exhibits an observable and measurable carbon cycle analogous to a bookkeeper's columnar ledger of debits and credits. Carbon is exchanged between these reservoirs:
  • Biosphere - sum of all ecosystems, or life zone;
  • Pedosphere - outermost layer of Earth comprised of soil and soil formation;
  • Geosphere - solid parts of Earth including, but not limited to, the lithosphere;
  • Hydrosphere - combined mass of water on and under the surface of Earth; and
  • Atmosphere - layer of gases surrounding Earth retained by Earth's gravity.
Earth's carbon cycle is a model for the ongoing flows between each of the reservoirs. Some carbon flows are slow (e.g., on the order of hundreds of millions of years), while others are fast:
  • Slow Carbon Cycle - Over the span of geologic time (100 - 200 million years), chemical reactions, tectonic events, and volcanic events occur that transfers carbon between rocks, soil, ocean, and atmosphere.
  • Fast Carbon Cycle - Plants, and phytoplankton in the ocean, absorb carbon dioxide (CO2) from the atmosphere into their cells via photosynthesis, then return CO2 via cellular respiration and microbial decomposition.

Fast carbon cycle depicting exchange of carbon between reservoirs

“Originally, the atoms of carbon from which we’re made were floating in the air, part of a carbon dioxide molecule. The only way to recruit these carbon atoms for the molecules necessary to support life—the carbohydrates, amino acids, proteins, and lipids—is by means of photosynthesis. Using sunlight as a catalyst the green cells of plants combine carbon atoms taken from the air with water and elements drawn from the soil to form the simple organic compounds that stand at the base of every food chain. It is more than a figure of speech to say that plants create life out of thin air.”
Michael Pollan, The Omnivore's Dilemma: A Natural History of Four Meals

Monitoring Earth's Carbon

NASA will launch the Orbiting Carbon Observatory-2 satellite in July 2014. It will record atmospheric CO2 from space. The data will be used to map CO2 sources and sinks and to provide insight into its variability over seasonal cycles.

You will die but the carbon will not; its career does not end with you. It will return to the soil, and there a plant may take it up again in time, sending it once more on a cycle of plant and animal life.
Jacob Bronowski


Saturday, May 17, 2014

Earth's Interior

Earth's interior reveals itself from probing and prodding at the surface, by making inferences from the composition of meteorites, and by other indirect means.

Earth's core has been widely imagined and fantasized in fiction.

Science fiction stories like:
launch from the vast unknown that is Earth's interior into tales of adventure where characters encounter the unexpected.
"Is the Master out of his mind?' she asked me
I nodded.
'And he's taking you with him?'
I nodded again.
'Where?' she asked.
I pointed towards the center of the earth.
'Into the cellar?' exclaimed the old servant.
'No,' I said, 'farther down than that."
Jules Verne, Journey to the Center of the Earth
The Cutaway

Idealized depictions of a cutaway section of Earth's interior lure us to the false comfort that knowledge is set in stone. Knowledge of Earth's interior is a working model.

Knowledge is a working model because it is meant to undergo revisions as new information is discovered, analyzed, corroborated, and peer-reviewed.

For example, the hydrophilic mineral ringwoodite recently discovered from Earth's mantle, indicates there could be a vast subterranean water repository as large as the world's oceans (see Hydrous mantle, Nature). With evidence to corroborate this discovery, our working model might eventually undergo revision.
"Science, my lad, is made up of mistakes, but they are mistakes which it is useful to make, because they lead little by little to the truth."
Jules Verne, Journey to the Center of the Earth
What We Know

We know what we know about Earth's interior from various direct and indirect sources, including:
  • Rocks - By examining rocks erupted from great depths via volcanoes, we make inferences about the composition of Earth's mantle.
  • Meteorites - From the composition of meteorites that have struck Earth we make inferences about the composition of its interior. If we assume that meteorites originated from protoplanets that underwent a similar genesis to Earth, we make deductions about the composition of Earth's core and lithosphere. Stony meteorites are believed to be similar to Earth's lithosphere, while meteorites composed of iron and nickel are believed to be similar to Earth's core.
  • Seismology - Analyzing earthquake-generated waves, the mechanical disturbances that travel great depths into the interior, we make inferences about Earth's interior structure from changes in velocity of p-waves and s-waves.

"This lucid explanation of the phenomena we had witnessed appeared to me quite satisfactory. However great and mighty the marvels of nature may seem to us, they are always to be explained by physical reasons. Everything is subordinate to some great law of nature."
Jules Verne, Journey to the Center of the Earth


Saturday, May 10, 2014

A Charged Sky

Ancient peoples had a more vivid view of the night sky than we have. Our forebearers created colorful mythologies to explain the light shows known as Auroras, but we hemispherically-centric people in the northern hemisphere call the Northern Lights.

Northern Lights over Lyngen fjord, March 2012.

Auroras occur because of solar winds. Solar winds are highly charged electrons blown from the Sun toward the Earth. Streams of charged particles, called plasma, escape the Sun's gravity because of their high energy (1.5 to 10 KeV).
“A man is a very small thing, and the night is very large and full of wonders.”
Lord Dunsany
Solar winds flow at supersonic speeds outward from the Sun covering great distances and creating geomagnetic storms in the Earth's magnetosphere.
Depiction of solar wind particles interacting with Earth's magnetosphere.

When the highly charged electrons enter the Earth's upper atmosphere they encounter oxygen and nitrogen at various altitudes. Color in Northern Lights is determined by whether oxygen or nitrogen atoms are struck first and at what altitude.

Color Gas Alt. (km) Alt. (miles)
above 240
above 150
up to 240
up to 150
above 97
above 60
up to 97
up to 60

Shifting combinations of charged particles encountering atmospheric gases at various altitudes make the Northern Lights undulate and dance in the night sky.

The core and the surface
Are essentially the same,
Words make them seem different
Only to express appearance.
If name be needed, wonder names them both:
From wonder into wonder
Existence opens.
Lao Tzu, translated by Witter Bynner


Saturday, May 3, 2014


Following dawn and dusk, an earthly envelope of twilight fills us with emotions like hope and melancholy. Phases of sunlight move our circadian clock forward on the arrow of time.

When dawn surrenders to sunrise we are bathed in twilight.
“What breaks in daybreak? Is it the night? Is it the sun, cracked in two by the horizon like an egg, spilling out light?”
Margaret Atwood
That same twilight covers us from dusk until sunset. Twilight is refracted sunlight that reaches us after the sun slips below Earth's horizon.

Sunrise over the South Pacific Ocean
International Space Station, 5 May 2013

Categories of Twilight
Humans revel and take comfort in naming what we observe.

Naming lets us categorize and individuate experience. Thus we call out categories of twilight.
“Twilight drops her curtain down, and pins it with a star.”
Lucy Maud Montgomery
Objectifying observations is the silhouette of reverence.