Geomagnetic Past

Convection currents of magma
in the outer core

With the paleomagnetic record as leading indicator, Earth's magnetic poles are poised to reverse within the next few thousand years.

Earth's Magnetic Field

A molten iron core generates Earth's magnetic field. Loosely analogous to an electrical generator, Earth's magnetic field is created by the convection of magma in its outer core.

The turbulent convection of molten iron is driven by radioactive heating. This movement produces electrical and magnetic energy. The currents cause the magnetic field surrounding the planet.

Geomagnetism is an ongoing and self-sustained process provided there is sufficient energy to convect flow in the outer core.

Geophysicists attribute shifting currents within the molten core as the cause for the drifting of the magnetic poles. Magnetic North drifts about 10 miles a year.

The positions of Magnetic North and Magnetic South appear destined to flip-flop as they have many times over the course of many millions of years.

What's past is prologue
— William Shakespeare, The Tempest.

Ancient Polarity

Geomagnetic reversals have occurred frequently over the past 169 million years. Paleomagnetic evidence is found in rocks on the ocean floor and in some lava flows.

Geomagnetic polarity is shown (image right) as time descends back in time from present day (top) to the Jurassic period (bottom). Polarity has flipped between the normal configuration we observe today (black stripes) and the reverse configuration we observe in the paleomagnetic record (white stripes).

The Cenozoic era ranges from present day to 66 million years ago. The Mesozoic era ranges from the beginning of the Cenozoic era to 252 million years ago. The Cenozoic, known also as the Age of Mammals, is derived from a composite of the Greeks words for new and life.

Conscience is our magnetic compass; reason our chart.
— Joseph Cook

REFERENCES

• Geomagnetic Reversal, Wikipedia.
• Geomagnetism Program, USGS.
• How does the Earth's core generate a magnetic field?, USGS.
• Understanding Ancient Geomagnetic Reversal, Phys.org Earth Sciences, 22 December 2014.

Earthly Naming

B-15

Massive icebergs are given names. Lesser icebergs remain nameless. B-15 is the largest recorded iceberg.

Naming is curious and profoundly human.

Icebergs are named when they exceed an arbitrary length threshold.

If an iceberg has one side at least 12 miles long, it is named and tracked by the U.S. National Ice Center.

The side-length naming threshold has the unintended consequence of leaving massive, roundish-shaped icebergs unnamed. An unnamed 64 square mile iceberg was spotted three weeks ago adrift in the South Atlantic Ocean.

Unnamed iceberg in the South Atlantic Ocean
NASA Operational Land Imager, 3 December 2014

This particular unnamed iceberg has the same surface area as an entity we've deemed name-worthy: Galveston Island.

Why does William Shakespeare's character Juliet ask Romeo what's in a name?

Juliet:

What's in a name? That which we call a rose By any other name would smell as sweet.

She asks what's in a name because the star-cross'd lovers are burdened with names from two warring families. Juliet laments a person's name is an artificial — and in their case, an irrelevant — convention.

Why do humans name things?

Naming is conventional and arbitrary. Naming objectifies. Naming gives us the illusion of control and the illusion of mastery over — or separateness from — the natural world.

Yet what would we do without naming? The negative aspects of objectifying things also grease the skids for interpersonal communication. Naming gives us a hand-hold on the abstract, the complex, and the poetic.

Naming gives us a handle to things. A personified handle is expressed in this passage from Anne of Green Gables:

Anne:	What is the name of that geranium on the window-sill, please?
Marilla:	That's the apple-scented geranium.
Anne:	Oh, I don't mean that sort of a name. I mean just a name you gave it yourself. Didn't you give it a name? May I give it one then? May I call it—let me see—Bonny would do—may I call it Bonny while I'm here? Oh, do let me!
Marilla:	Goodness, I don't care. But where on earth is the sense of naming a geranium?
Anne:	Oh, I like things to have handles even if they are only geraniums. It makes them seem more like people.
— Excerpt from Anne of Green Gables

Names have a historical narrative rarely considered. Some names are compounded from others, like iceberg.

Names move in and out of favor. Iceberg floated into existence.

REFERENCES

• Anne of Green Gables, by L. M. Montgomery, 1908.
• Iceberg B-15, Wikipedia
• Operational Land Imager, NASA.
• Unnamed Iceberg, Earth Observatory, 3 December 2014.

Original Water

More than two thirds of Earth's surface is covered by water.

The Asteroid Belt

If Earth's primordial water was boiled off from the intense heat during planetary cooling, where did Earth's abundant water originate?

The origin of Earth’s water remains a mystery.

A prevailing hypothesis is that Earth's water came later from collisions with water-bearing comets or proto-planets from the outer reaches of the Asteroid Belt

Recent analysis of the composition of water sampled on comet 67P suggest Earth's water might not have come from cometary collisions (Life from Comet Collisions).

Scientists suggest that one key to solving the mystery of Earth's abundant water is found in the D/H ratio or the flavor of water. The D/H ratio is the proportion of Deuterium (symbol D) to Hydrogen (symbol H). The ratio of these two hydrogen isotopes might provide clues to the origin of Earth's water.

Deuterium is a form of hydrogen (i.e., hydrogen isotope) that has an additional neutron not present in common hydrogen. There are about 6,420 hydrogen atoms for every deuterium atom found in the world's oceans.

Deuterium can replace hydrogen in water molecules. The properties of D₂O differ from H₂O (common water). D₂O is called heavy water because it's 10.6% denser than H₂O. D₂O is also more viscous than H₂O.

The current opinion that science and poetry are opposed is a delusion. On the contrary science opens up realms of poetry where to the unscientific all is a blank. Those engaged in scientific researches constantly show us that they realize not less vividly, but more vividly, than others, the poetry of their subjects.
― Herbert Spencer, Education, Intellectual, Moral, and Physical (1861)

Analysis of the composition of water sampled on comet 67P, along with previous D/H analysis of other comets show a range of ratios generally containing higher amounts of deuterium than Earth.

Deuterium to Hydrogen Ratio in the Solar System

Source: ESA

Of the deuterium to hydrogen ratios detected in the solar system, the European Space Agency reports:

Of the 11 comets for which measurements have been made, it is only the Jupiter-family Comet 103P/Hartley 2 that was found to match the composition of Earth’s water.

The D/H ratio of water sampled on comet 67P is three times greater than that of Earth's oceans.

Scientists are are turning their attention to asteroids. Meteorites from asteroids in the Asteroid Belt have a closer match to the D/H ratio of water on Earth. Meteorites have a much lower water content than comets. However multiple serious of meteorite bombardments could have produced Earth's oceans.

Water does not resist. Water flows. When you plunge your hand into it, all you feel is a caress. Water is not a solid wall, it will not stop you. But water always goes where it wants to go, and nothing in the end can stand against it. Water is patient. Dripping water wears away a stone.
― Margaret Atwood, The Penelopiad

REFERENCES

• A Comet's Tale, shared on Google Plus by Brian Koberlein, 11 Dec 2014.
• Origin of Water on Earth, Wikipedia.
• Rosetta Fuels Debate on Origin of Earth's Oceans, European Space Agency, 10 December 2014.

Gravity Potato

GRACE satellite data

As mass goes, so goes gravity.

The earthward acceleration of gravity varies by about 0.5% over the surface of the Earth because of unevenly distributed mass.

Exaggerated data visualizations depict the dissymmetrical variations in Earth's gravity field.

Time and Location

Gravitational pull varies by location because of unevenly distributed mass in the oceans, continents, and deep interior. Climate-related variables, like continental water balance, and the accumulation or ablation of glaciers, causes the distribution of mass to vary over time.

Measuring G-Force

The local gravitational field is measured using a gravimeter. A gravimeter is an accelerometer that measures the earthward acceleration of gravity or G-force.

Gravity Potato

Variations in Earth's gravity field is shown in an image known as the Potsdam Gravity Potato. The Potsdam Gravity Potato is derived from a gravity field model produced by the German Research Center for Geophysics (GFZ).

Geoid: The Potsdam Gravity Potato

Some 800 million observations support GFZ's gravity field model. Supporting data were obtained from:

• LAGEOS, GRACE , and GOCE satellites;
• Ground-based gravity measurements; and
• Satellite altimetry data.

Attraction Mystery

Gravity is a natural phenomenon wherein physical bodies attract each other. Gravity gives weight to physical objects and causes objects to fall when dropped.

Because there is a law such as gravity, the universe can and will create itself from nothing.
— Stephen Hawking

Gravity is one of four fundamental forces. Gravitation acts across the universe. Earth's gravitation is part of the human experience mediating nearly everything we do.

Most gravity has no known origin. Is it some exotic particle? Nobody knows.
— Neil deGrasse Tyson

REFERENCES

• Geoid, Wikipedia.
• Geoid: The Potsdam Gravity Potato, GFZ - German Research Centre for Geosciences.
• Grounded, GrokEarth, 12 April 2014.
• The Potsdam Gravity Potato Shows Variations in Earth’s Gravity, Matt Williams, Universe Today, 29 November 2014.