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Theory of Intelligent Design, the best explanation of Origins » Astronomy & Cosmology and God » FineTuning of the earth

FineTuning of the earth

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1 FineTuning of the earth on Sat 21 Dec 2013 - 21:06


FineTuning of the earth

Argument by ‘the position of our planet’
1. If the sun where closer to the earth, we would burn up; if farther away we would freeze. 
2. If the earth was not tilted at 23 degrees, the areas near the poles would be dark and cold all year long.
3. If it tilted too much, the seasons would be very extreme for example, on the planet Uranus the winter is 42 years of total darkness!
4. If Earth did not have a large revolving moon, we would have no tides, causing the ocean waters to grow stagnant and produce no oxygen for its creatures.
5. What we see is a planet that is perfectly balanced for our habitation. We see design in the perfect balance.
6. When we see a design we know there is a Designer.
7. The structure of the universe, which is also like a universal clock, can be designed only by a greatest person.
8. That greatest person to design such huge things as a universe can be only God.
10. God exists.

The Finely Tuned Parameters of the Earth include:
- the Earth's just-right ozone layer filters out ultraviolet radiation and helps mitigate temperature swings
- the Earth's surface gravity strength preventing the atmosphere from losing water to space too rapidly
- the Earth's spin rate on its axis provides for a range of day and nightime temperatures to allow life to thrive
- the atmosphere's composition (oxygen, nitrogren, etc.)
- the atmosphere's pressure enables our lungs to function and water to evaporate at an optimal rate to support life
- the atmosphere's transparency to allow an optimal range of life-giving solar radiation to reach the surface
- the atmosphere's capactity to hold water vaper providing for stable temperature and rainfall ranges  
- efficient life-giving photosynthesis depends on quantum physics, as reported in the journal PNAS
- to prevent runaway consumption of all plant life, no species were created that could metabolize cellulose
- the water molecule's astounding robustness results from finely balanced quantum effects. As reported by New Scientist, "Water's life-giving properties exist on a knife-edge. It turns out that life as we know it relies on a fortuitous, but incredibly delicate, balance of quantum forces. ... We are used to the idea that the cosmos' physical constraints are fine-tuned for life. Now it seems water's quantum forces can be added to this 'just right' list."
- water is an unrivaled solvent; its low viscosity permits the tiniest blood vessels; its high specific heat stabilizes biosphere temperatures; its low thermal conductivity as a solid insulates frozen-over lakes and as a liquid its high conductivity lets organisms distribute heat; its an efficient lubricant; is only mildly reactive; has an anomalous (fish-saving) expansion when it freezes; its high vapor tension keeps moisture in the atmosphere; and it tastes great too!
- carbon atomthe phenomenally harmonious water cycle
- the carbon atom's astounding capabilities. As Cambridge astronomer Fred Hoyle wrote: "Some super-calculating intellect must have designed the properties of the carbon atom, otherwise the chance of my finding such an atom through the blind forces of nature would be utterly minuscule. A common sense interpretation of the facts suggests that a superintellect has monkeyed with physics, as well as with chemistry and biology, and that there are no blind forces worth speaking about in nature. The numbers one calculates from the facts seem to me so overwhelming as to put this conclusion almost beyond question."
- etc., etc., etc.

The distance from the earth to the sun must be just right. Too near and water would evaporate, too far and the earth would be too cold for life. A change of only 2 per cent or so and all life would cease.  Surface gravity and temperature are also critical to within a few per cent for the earth to have a life-sustaining atmosphere – retaining the right mix of gases necessary for life. The planet must rotate at the right speed: too slow and temperature differences between day and night would be too extreme, too fast and wind speeds would be disastrous. And so the list goes on. Astrophysicist Hugh Ross[7] lists many such parameters that have to be fine-tuned for life to be possible, and makes a rough but conservative calculation that the chance of one such planet existing in the universe is about 1 in 10^30.

SIZE AND GRAVITY: There is a range for the size of a planet and it gravity which supports life and it is small. A planet the size of Jupiter would have gravity that would crush any life form, and any high order carbon molecules, out of existence.
WATER: Without a sufficient amount of water, life could not exist.
ATMOSPHERE: Not only must a planet have an atmosphere, it must have a certain percentage of certain gasses to permit life. On earth the air we breath is 78% nitrogen, 21% oxygen, and 1% argon and carbon dioxide. Without the 78% nitrogen to “blanket’ the combustion of oxygen, our world would ‘burn up’ from oxidation. Nitrogen inhibits combustion and permits life to flourish. No other planet comes close to this makeup of atmosphere.
OXYGEN: The range of oxygen level in the atmosphere that permits life can be fairly broad, but oxygen is definitely necessary for life.
RARE EARTHS MINERALS: Many chemical processes necessary for life are dependent on elements we call ‘rare earth’ minerals. These only exist as ‘trace’ amounts, but without which life could not continue.
THE SUN: Our sun is an average star in both composition and size. The larger a star is the faster it burns out. It would take longer for life to develop than those larger stars would exist. Smaller stars last longer but do not develop properly to give off the heat and radiation necessary to sustain life on any planets that form. The smaller the star the less likely it will form a planetary system at all.
DISTANCE FROM THE SUN: To have a planet with a surface temperature within the bounds for life, it must be within the ‘biosphere’ of a star, a temperate zone of a given distance from the source of radiation and heat. That would depend on the size of the star. For an average star the size of our sun, that distance would be about 60 to 150 million miles.
RADIOACTIVITY: Without radioactivity, the earth would have cooled to a cold rock 3 billion years ago. Radioactivity is responsible for the volcanism, and heat generated in the interior of the earth. Volcanism is responsible for many of the rare elements we need as well as the oxygen in the air. Most rocky planets have some radioactivity.
DISTANCE AND PLACEMENT FROM THE GALACTIC CENTER: We receive very little of the x-rays and gamma rays given off from the galactic center, that would affect all life and its development on earth. We live on the outer rim of the Milky Way, in a less dense portion of the galaxy, away from the noise, dust, and dangers of the interior.
THE OZONE LAYER: Animal life on land survives because of the ozone layer which shields the ultraviolet rays from reaching the earth’s surface. The ozone layer would never have formed without oxygen reaching a given level of density in the atmosphere. A planet with less oxygen would not have an ozone layer.
VOLCANIC ACTIVITY: Volcanic activity is responsible for bringing heaver elements and gasses to the surface, as well as oxygen. Without this activity, the planet would never have sustained life in the first place.
EARTH’S MAGNETIC FIELD: We are bombarded daily with deadly rays from the sun, but are protected by the earth’s magnetic field.
SEASONS: Because of the earths tilt, we have seasons, and no part of the earth is extremely hot or cold. The seasons have balancing effect of the temperature on the surface and cause the winds and sea currents which we and all life depend on for a temperate climate.

Visible light is also incredibly fine-tuned for life to exist Though visible light is only a tiny fraction of the total electromagnetic spectrum coming from the sun, it happens to be the "most permitted" portion of the sun's spectrum allowed to filter through the our atmosphere. All the other bands of electromagnetic radiation, directly surrounding visible light, happen to be harmful to organic molecules, and are almost completely absorbed by the atmosphere. The tiny amount of harmful UV radiation, which is not visible light, allowed to filter through the atmosphere is needed to keep various populations of single cell bacteria from over-populating the world (Ross; The size of light's wavelengths and the constraints on the size allowable for the protein molecules of organic life, also seem to be tailor-made for each other. This "tailor-made fit" allows photosynthesis, the miracle of sight, and many other things that are necessary for human life. These specific frequencies of light (that enable plants to manufacture food and astronomers to observe the cosmos) represent less than 1 trillionth of a trillionth (10^-24) of the universe's entire range of electromagnetic emissions. Like water, visible light also appears to be of optimal biological utility (Denton; Nature's Destiny).

Distance of the earth from the sun : Malcolm Bowden says, "If it were 5% closer, then the water would boil up from the oceans and if it were just 1% farther away, then the oceans would freeze, and that gives you just some idea of the knife edge we are on."

The carbon dioxide level in atmosphere  If greater: runaway greenhouse effect would develop.  If less: plants would be unable to maintain efficient photosynthesis

Oxygen quantity in atmosphere If greater: plants and hydrocarbons would burn up too easily.  If less: advanced animals would have too little to breathe

Nitrogen quantity in atmosphere If greater: too much buffering of oxygen for advanced animal respiration; too much nitrogen fixation for support of diverse plant species.  
If less: too little buffering of oxygen for advanced animal respiration; too little nitrogen fixation for support of diverse plant species.

Atmospheric pressure: If too small: liquid water will evaporate too easily and condense too infrequently; weather and climate variation would be too extreme; lungs will not function. If too large: liquid water will not evaporate easily enough for land life; insufficient sunlight reaches planetary surface; insufficient uv radiation reaches planetary surface; insufficient climate and weather variation; lungs will not function

Atmospheric transparency:If smaller: insufficient range of wavelengths of solar radiation reaches planetary surface . If greater: too broad a range of wavelengths of solar radiation reaches planetary surface

stratospheric ozone quantity:If smaller: too much uv radiation reaches planet’s surface causing skin cancers and reduced plant growth . If larger: too little uv radiation reaches planet’s surface causing reduced plant growth and insufficient vitamin production for animals

Requirements Related to Planet Earth

Correct planetary distance from star
Correct inclination of planetary orbit

Correct axis tilt of planet

This has had important ramifications for life on the Earth as major and frequent shifts in this obliquity would have led to significant and rapid changes in the Earth's climate due to changes in insolation values at the poles and equator. A similar mechanism has been suggested to explain the apparent contradictions in the climate record of Mars.

The current relatively moderate axial tilt of the Earth ensures that the difference in heating between the poles and equator is sufficient to promote a healthy and diverse range of climatic zones without veering from one extreme to another (e.g. Snowball Earth hypothesis). In particular, the stability of the Earth's axial tilt produced by the Moon, coupled with the break up of the Pangean supercontinent in the late Mesozoic, produced a diverse set of climate zones (with their associated ecological niches) compared with what had gone before during the time of the dinosaurs. This helped set the stage for the rise of the mammals, including Man.

Correct rate of change of axial tilt
Correct period and size of axis tilt variation
Correct planetary rotation period
Correct rate of change in planetary rotation period
Correct planetary revolution period
Correct planetary orbit eccentricity
Correct rate of change of planetary orbital eccentricity
Correct rate of change of planetary inclination
Correct period and size of eccentricity variation
Correct period and size of inclination variation
Correct precession in planet’s rotation
Correct rate of change in planet’s precession
Correct number of moons
Correct mass and distance of moon
Correct surface gravity (escape velocity)
Correct tidal force from sun and moon
Correct magnetic field
Correct rate of change & character of change in magnetic field
Correct albedo (planet reflectivity)
Correct density density of interstellar and interplanetary dust particles in vicinity of life-support planet
Correct reducing strength of planet’s primordial mantle
Correct thickness of crust
Correct timing of birth of continent formation
Correct oceans-to-continents ratio
Correct rate of change in oceans to continents ratio
Correct global distribution of continents
Correct frequency, timing, & extent of ice ages
Correct frequency, timing, & extent of global snowball events
Correct silicate dust annealing by nebular shocks
Correct asteroidal & cometary collision rate
Correct change in asteroidal & cometary collision rates
Correct rate of change in asteroidal & cometary collision rates
Correct mass of body colliding with primordial Earth
Correct timing of body colliding with primordial Earth
Correct location of body’s collision with primordial Earth
Correct position & mass of Jupiter relative to Earth
Correct major planet eccentricities
Correct major planet orbital instabilities
Correct drift and rate of drift in major planet distances
Correct number & distribution of planets
Correct distance of gas giant planets from mean motion resonances
Correct orbital separation distances among inner planets
Correct oxygen quantity in the atmosphere
Correct nitrogen quantity in the atmosphere
Correct carbon monoxide quantity in the atmosphere
Correct chlorine quantity in the atmosphere
Correct aerosol particle density emitted from the forests
Correct cobalt quantity in the earth’s crust
Correct arsenic quantity in the earth’s crust
Correct copper quantity in the earth’s crust
Correct boron quantity in the earth’s crust
Correct cadmium quantity in the earth’s crust
Correct calcium quantity in the earth’s crust
Correct flourine quantity in the earth’s crust
Correct iodine quantity in the earth’s crust
Correct magnesium quantity in the earth’s crust
Correct nickel quantity in crust
Correct phosphorus quantity in crust
Correct potassium quantity in crust
Correct tin quantity in crust
Correct zinc quantity in crust
Correct molybdenum quantity in crust
Correct vanadium quantity in crust
Correct chromium quantity in crust
Correct selenium quantity in crust
Correct iron quantity in oceans
Correct tropospheric ozone quantity
Correct stratospheric ozone quantity
Correct mesospheric ozone quantity
Correct water vapor level in atmosphere
Correct oxygen to nitrogen ratio in atmosphere
Correct quantity of greenhouse gases in atmosphere
Correct quantity of greenhouse gases in atmosphere
Correct rate of change in greenhouse gases in atmosphere
Correct poleward heat transport in atmosphere by mid-latitude storms
Correct quantity of forest & grass fires
Correct quantity of sea salt aerosols in troposphere
Correct soil mineralization
Correct quantity of anaeorbic bacteria in the oceans
Correct quantity of aerobic bacteria in the oceans
Correct quantity of anaerobic nitrogen-fixing bacteria in the early oceans
Correct quantity, variety, and timing of sulfate-reducing bacteria
Correct quantity of geobacteraceae
Correct quantity of aerobic photoheterotrophic bacteria
Correct quantity of decomposer bacteria in soil
Correct quantity of mycorrhizal fungi in soil
Correct quantity of nitrifying microbes in soil
Correct quantity & timing of vascular plant introductions
Correct quantity, timing, & placement of carbonate-producing animals
Correct quantity, timing, & placement of methanogens
Correct phosphorus and iron absorption by banded iron formations
Correct quantity of soil sulfur
Correct ratio of electrically conducting inner core radius to radius of the adjacent turbulent fluid shell
Correct ratio of core to shell (see above) magnetic diffusivity
Correct magnetic Reynold’s number of the shell (see above)
Correct elasticity of iron in the inner core
Correct electromagnetic Maxwell shear stresses in the inner core
Correct core precession frequency for planet
Correct rate of interior heat loss for planet
Correct quantity of sulfur in the planet’s core
Correct quantity of silicon in the planet’s core
Correct quantity of water at subduction zones in the crust
Correct quantity of high pressure ice in subducting crustal slabs
Correct hydration rate of subducted minerals
Correct water absorption capacity of planet’s lower mantle
Correct tectonic activity
Correct rate of decline in tectonic activity
Correct volcanic activity
Correct rate of decline in volcanic activity
Correct location of volcanic eruptions
Correct continental relief
Correct viscosity at Earth core boundaries
Correct viscosity of lithosphere
Correct thickness of mid-mantle boundary
Correct rate of sedimentary loading at crustal subduction zones
Correct biomass to comet infall ratio
Correct regularity of cometary infall
Correct number, intensity, and location of hurricanes
Correct intensity of primordial cosmic superwinds
Correct number of smoking quasars
Correct formation of large terrestrial planet in the presence of two or more gas giant planets
Correct orbital stability of large terrestrial planet in the presence of two or more gas giant planets
Correct total mass of Oort Cloud objects
Correct mass distribution of Oort Cloud objects
Correct air turbulence in troposphere
Correct quantity of sulfate aerosols in troposphere
Correct quantity of actinide bioreducing bacteria
Correct quantity of phytoplankton
Correct hydrothermal alteration of ancient oceanic basalts
Correct quantity of iodocarbon-emitting marine organisms
Correct location of dislocation creep relative to diffusion creep in and near the crust-mantle boundary (determines mantle convection dynamics)
Correct size of oxygen sinks in the planet’s crust
Correct size of oxygen sinks in the planet’s mantle
Correct mantle plume production
Correct average rainfall precipitation
Correct variation and timing of average rainfall precipitation
Correct atmospheric transparency
Correct atmospheric pressure
Correct atmospheric viscosity
Correct atmospheric electric discharge rate
Correct atmospheric temperature gradient
Correct carbon dioxide level in atmosphere
Correct rates of change in carbon dioxide levels in atmosphere throughout the planet’s history
Correct rates of change in water vapor levels in atmosphere throughout the planet’s history
Correct rate of change in methane level in early atmosphere
Correct Q-value (rigidity) of planet during its early history
Correct variation in Q-value of planet during its early history
Correct migration of planet during its formation in the protoplanetary disk
Correct viscosity gradient in protoplanetary disk
Correct frequency of late impacts by large asteroids and comets
Correct size of the carbon sink in the deep mantle of the planet
Correct ratio of dual water molecules, (H2O)2, to single water molecules, H 2O, in the troposphere
Correct quantity of volatiles on and in Earth-sized planet in the habitable zone
Correct triggering of El Nino events by explosive volcanic eruptions
Correct time window between the peak of kerogen production and the appearance of intelligent life
Correct time window between the production of cisterns in the planet’s crust that can effectively collect and store petroleum and natural gas and the appearance of intelligent life
Correct efficiency of flows of silicate melt, hypersaline hydrothermal fluids, and hydrothermal vapors in the upper crust
Correct efficiency of ocean pumps that return nutrients to ocean surfaces
Correct sulfur and sulfate content of oceans
Correct orientation of continents relative to prevailing winds
Correct infall of buckminsterfullerenes from interplanetary and interstellar space upon surface of planet
Correct quantity of silicic acid in the oceans
Correct heat flow through the planet’s mantle from radiometric decay in planet’s core
Correct water absorption by planet’s mantle

Factors Necessary for a Habitable Planet Supporting Complex Life
Liquid Water
Within galactic habitable zone
Circumstellar Habitable Zone
Orbiting main sequence G2 dwarf star
Protected by gas giant planets
Nearly circular orbit
Oxygen rich atmosphere
Correct mass
Orbited by large moon
Magnetic field
Plate tectonics
Ratio of liquid water and continents
Terrestrial planet
Moderate rate of rotation
Probability of every factor randomly coinciding at the same time? 10-15th That’s 1/1,000,000,000,000,000 Or one-one-thousandth of one-one-trillionth… By comparison, there are 100 billion stars in our galaxy. Certainly a large number, but the probability is so small that it makes a habitable planet very unlikely.
Additionally, habitability does not mean life exists necessarily, or is even probable, only that it could be possible.
What are the odds?
What would you think if you were flipping a coin with a friend and it came up heads over and over?
What are the odds of flipping a coin and getting heads 50 times in a row?
1 in a Quadrillion
A quadrillion is a MILLION BILLION 10,000,000,000,000,000 That is 10 to the 15th

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2 Re: FineTuning of the earth on Mon 23 Jan 2017 - 13:57


The Earth…its size is perfect. The Earth’s size and corresponding gravity holds a thin layer of mostly nitrogen and oxygen gases, only extending about 50 miles above the Earth’s surface.If Earth were smaller, an atmosphere would be impossible, like the planet Mercury. If Earth were larger, its atmosphere would contain free hydrogen, like Jupiter.(4) Earth is the only known planet equipped with an atmosphere of the right mixture of gases to sustain plant, animal and human life.The Earth is located the right distance from the sun. Consider the temperature swings we encounter, roughly -30 degrees to +120 degrees. If the Earth were any further away from the sun, we would all freeze. Any closer and we would burn up.Even a fractional variance in the Earth’s position to the sun would make life on Earth impossible. The Earth remains this perfect distance from the sun while it rotates around the sun at a speed of nearly 67,000 mph. It is also rotating on its axis, allowing the entire surface of the Earth to be properly warmed and cooled every day.

And our moon is the perfect size and distance from the Earth for its gravitational pull. The moon creates important ocean tides and movement so ocean waters do not stagnate, and yet it restrains our massive oceans from spilling over across the continents.

Water…colorless, odorless and without taste, and yet no living thing can survive without it. Plants, animals and human beings consist mostly of water (about two-thirds of the human body is water). You’ll see why the characteristics of water are uniquely suited to life…It has an unusually high boiling point and freezing point. Water allows us to live in an environment of fluctuating temperature changes, while keeping our bodies a steady 98.6 degrees.Water is a universal solvent. Take a full glass of water, add a cup of sugar, and nothing spills over the edge; the water simply absorbs the sugar. This property of water means that thousands of chemicals, minerals and nutrients can be carried throughout our bodies and into the smallest blood vessels.(6)Water is also chemically inert. Without affecting the makeup of the substances it carries, water enables food, medicines and minerals to be absorbed and used by the body.Water has a unique surface tension. Water in plants can therefore flow upward against gravity, bringing life-giving water and nutrients to the top of even the tallest trees.
Water freezes from the top down and floats, so fish can live in the winter.Ninety-seven percent of the Earth’s water is in the oceans. But on our Earth, there is a system designed which removes salt from the water and then distributes that water throughout the globe. Evaporation takes the ocean waters, leaving the salt, and forms clouds which are easily moved by the wind to disperse water over the land, for vegetation, animals and people. It is a system of purification and supply that sustains life on this planet, a system of recycled and reused water.

The energy coming in from the Sun must be returned to space to keep Earth from overheating. In fact, the Earth sends exactly as much heat out to space as it receives from the Sun (plus a tiny bit more corresponding to Earth's own heat production, from radioactive decay). About 30 percent of the incoming radiation is simply reflected. The reflectivity of a planet is called its "albedo". Venus has a very high albedo (that is why that planet is so brilliant), while Earth has an intermediate one. Clouds and snowfields are especially efficient in reflecting sunlight. What is not reflected (70 percent) is absorbed in the atmosphere and on the ground, and is then re-radiated to space by the warmed objects, in the infrared portion of the spectrum (that is, as heat radiation). How is this balance maintained? Earth warms up to exactly the temperature that is necessary to re-radiate exactly the right amount of energy. 3


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3 Re: FineTuning of the earth on Tue 20 Jun 2017 - 10:03


Continents, essential for advanced life on earth 1

A carbon cycle, at least the planetary variety, needs both continents and oceans. Continents serve as a mixing bowl for minerals and water at the surface, where energy-rich sunlight is available. The continents began to appear about one billion years after Earth formed. As they grew, they and the crust they ride on extracted potassium, thorium, and uranium from the mantle. Because these radioisotopes have been the primary sources of heat in Earth’s interior over most of its history, siphoning them from the convecting mantle weakens tectonic activity. If the continents and crust had grown more rapidly, they would have drawn more heat-producing elements from the mantle. This would have slowed down mantle convection and tectonic activity in recent times, resulting in poorer climate feedback. Plate tectonics plays another life-essential role: it maintains dry land in the face of constant erosion. A large rocky planet like Earth wants to be perfectly round, with erosion eventually wearing down the mountains and even the continents, creating a true “waterworld.” Its interior must continuously supply energy to keep it from getting bowling-ball smooth. Without geological recycling, such a place would probably become lifeless, since it would lack a way to mix all the life-essential nutrients in its sunlight- drenched surface waters.

1. A privileged planet, Gonzalez, page 57

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4 Re: FineTuning of the earth on Tue 20 Jun 2017 - 10:24


The  Earth’s Magnetic Field

The earth’s magnetic field is critically important for at least two reasons:

it provides protection for life from high-energy particles originating from both cosmic rays and from our sun, and  it provides a shield preventing the depletion of our atmosphere from bombardment by the stream of charged particles ejected from the sun. 5 Because Earth rotates once every 24 hours, this motion causes its iron core to generate a strong magnetic field. This magnetic field shields Earth from cosmic rays, in addition to protecting Earth’s atmosphere from the solar wind. 6

Geologist hypothesize that the core of Earth is composed of a solid iron core and liquid iron outer core. Now two things are important about the cores' composition that makes it magnetic: 1. it is composed of iron and 2. it has a liquid outer core. As you likely know iron is a magnetic element. From physics we know a magnetic field can be induced when a charged ion moves in space. Think of it like electricity the power lines have flowing electrons in them as they move from the power plant to your home they actually induce a magnetic field in the power line. Now for Earth's liquid iron outer core, it is so hot the iron exists in a liquid, ionically charged state. So when the charged liquid iron moves about in the outer core the material induces Earth's magnetic field. Earth's magnetic field allows all life to exist as we know it today. Without our magnetic field Earth would be much like Mars, the magnetic field extends into outer space beyond our atmosphere and deflects high energy particles emitted by the sun. If these high- energy particles were not deflected they would strip Earth's atmosphere, all the oceans would evaporate into space, it would get very cold below freezing, and destroy all life as we know it. 11

At the center of the Earth is the core, which has two parts. The solid, inner core of iron has a radius of about 760 miles (about 1,220 km). It is surrounded by a liquid, outer core composed of a nickel-iron alloy. It is about 1,355 miles (2,180 km) thick. The inner core spins at a different speed than the rest of the planet. This is thought to cause Earth's magnetic field. 12

To develop and maintain a strong, steady magnetic field presents a challenge. Everything depends on the planet’s internal composition. For a rocky planet to maintain a sufficiently strong and enduring magnetic field, its internal composition must closely resemble Earth’s. In particular, it must have a liquid iron outer core surrounding a solid iron inner core and highly specified viscosity and magnetic diffusivity values at the inner-outer core and outer core–mantle boundaries. 9 A team of scientists has measured the melting point of iron at high precision in a laboratory, and then drew from that result to calculate the temperature at the boundary of Earth's inner and outer core — now estimated at  6,000 C (about 10,800 F). That's as hot as the surface of the sun.

The difference in temperature matters, because this explains how the Earth generates its magnetic field. The Earth has a solid inner core surrounded by a liquid outer core, which, in turn, has the solid, but flowing, mantle above it. There needs to be a 2,700-degree F (1,500 C) difference between the inner core and the mantle to spur "thermal movements" that — along with Earth's spin — create the magnetic field. 10

The evidence of the plasma shield
1. In Science Magazine, a team of geophysicists found another way that the earth’s magnetosphere protects life on the surface.  When high-energy ions in the solar wind threaten to work their way through cracks in the magnetosphere, Earth sends up a “plasma plume” to block them. The automatic mechanism is described on New Scientist as a “plasma shield” that battles solar storms.
2. Joel Borofsky from Space Science Institute says, “Earth doesn’t just sit there and take whatever the solar wind gives it, it can actually fight back.”
3. Earth’s magnetic shield can develop “cracks” when the sun’s magnetic field links up with it in a process called “reconnection.”  Between the field lines, high-energy charged particles can flow during solar storms, leading to spectacular auroras, but also disrupting ground-based communications.  But Earth has an arsenal to defend itself.  Plasma created by solar UV is stored in a donut-shaped ring around the globe.  When cracks develop, the plasma cloud can send up “tendrils” of plasma to fight off the charged solar particles.  The tendrils create a buffer zone that weakens reconnection.
4. Previously only suspected in theory, the plasma shielding has now been observed. As described by Brian Walsh of NASA-Goddard in New Scientist:
“For the first time, we were able to monitor the entire cycle of this plasma stretching from the atmosphere to the boundary between Earth’s magnetic field and the sun’s. It gets to that boundary and helps protect us, keeps these solar storms from slamming into us.”
5. According to Borofsky this observation is made possible by looking at the magnetosphere from a “systems science” approach.  Geophysicists can now see the whole cycle as a “negative feedback loop” – “that is, the stronger the driving, the more rapidly plasma is fed into the reconnection site,” he explains.  “…it is a system-wide phenomenon involving the ionosphere, the near-Earth magnetosphere, the sunward boundary of the magnetosphere, and the solar wind; and it involves diverse physical processes such as ionospheric outflows, magnetospheric transport, and magnetic-field-line reconnection.”
6. The result of all these complex interactions is another level of protection for life on Earth that automatically adjusts for the fury of the battle:
“The plasmasphere effect is indicative of a new level of sophistication in the understanding of how the magnetospheric system operates. The effect can be particularly important for reducing solar-wind/magnetosphere coupling during geomagnetic storms. Instead of unchallenged solar wind control of the rate of solar-wind/magnetosphere coupling, we see that the magnetosphere, with the help of the ionosphere, fights back.”
7. Because of this mechanism, even the most severe coronal mass ejections (CME) do not cause serious harm to the organisms on the surface of the Earth.
8. The necessary timings when this system should be activated and the whole complex, very important protection system of plasma shield, battling the solar storms is an evidence of intelligent design, for the purpose of maintaining the life of the living entities on the earth planet.
9. This intelligent designer, the creator of such a great system, best explains its existence.

The Creation of the Earth’s Magnetic Field. 1
The iron catastrophe turned out to be a blessing in disguise for the life that was to eventually emerge on Earth. It was one of a myriad number of factors that would later help to ensure the survival of life on the planet, "As the liquid iron swirled around it produced an invisible force that even today helps keep us alive: the Earth’s magnetic field. Convection currents inside the liquid core behaved like a dynamo and generated electric currents. These transformed our planet into a giant magnet with north and south magnetic poles." "Without the liquid iron core the early atmosphere would have been stripped away and life could never have evolved on our planet. That’s because space is lethal. It’s full of highly dangerous solar particles that can be ten times more deadly than the radiation from a nuclear explosion. These particles originate from the sun when it spews out massive solar flares. A devastating solar wind streams towards the Earth at 250 miles per second. That’s a million miles an hour. If it ever reached the surface of our planet it would strip away the atmosphere in a few thousand years. But the Earth’s magnetic field creates a protective shield and deflects the solar particles. Without the molten core, today our planet would be a sterile rocky sphere with little or no atmosphere. The tragic fate that befell our neighboring planet, Mars."

A terrestrial planet with plate tectonics is also more likely to have a strong magnetic field since both depend on convective overturning of its interior. And a strong magnetic field contributes mightily to a planet’s habitability by creating a cavity called the magnetosphere, which shields a planet’s atmosphere from direct interaction with the solar wind. If solar wind particles— consisting of protons and electrons—were to interact more directly with Earth’s upper atmosphere, they would be much more effective at “sputtering” or be stripping it away (especially the atoms of hydrogen and oxygen from water). For life, that would be bad news, since the water would be lost more quickly to space. Just as Star Trek’s Enterprise uses a force field to protect it from incoming photon torpedoes, Earth’s magnetic field serves as the next line of defense against galactic cosmic ray particles, after the Sun’s magnetic field and solar wind deflect the lower-energy cosmic rays. These cosmic ray particles consist of high-energy protons and other nuclei, which, together with highly interacting subatomic particles called mesons, interact with nuclei in our atmosphere. These secondary particles can pass through our bodies, causing radiation damage and breaking up nuclei in our cells.

Invisible hissing doughnut is Earth’s radiation shield 3

The rainbow ring the picture above is full of tiny radioactive missiles traveling close to the speed of light, shown as yellow and blue streaks.  Far above Earth, this high-energy radiation from space can damage satellite electronics and pose serious health risks to astronauts. The particles also constantly charge towards the planet’s surface, but luckily an invisible shield of plasma bent into a doughnut shape by Earth’s magnetic field, shown in green, keeps radiation at bay. There is an absolute limit on how close it can get – a comfortable 11,000 kilometers from the surface. A phenomenon called “plasmaspheric hiss” seems to be responsible: very low-frequency electromagnetic waves just inside the boundary of the plasma shield that sound like hissing static when played through a speaker. “It’s a very unusual, extraordinary, and pronounced phenomenon,” says Foster. “What this tells us is that if you parked a satellite or an orbiting space station with humans just inside this impenetrable barrier, you would expect them to have a much longer lifetime. That’s a good thing to know.”

Protective shield 8
Data gathered by the probes also showed that the radiation belts shield Earth from high-energy particles. "The barrier for the ultrafast electrons is a remarkable feature of the belts," study lead author Dan Baker, of the University of Colorado in Boulder, said in a statement.

In January 2016, scientists revealed that the shape of the belts depends on what type of electron is being studied. This means the two belts are much more complex; depending on what is being observed, they can be a single belt, two separate belts or just an outer belt (with no inner belt at all.)  
Two giant swaths of radiation, known as the Van Allen Belts, surrounding Earth were discovered in 1958. In 2012, observations from the Van Allen Probes showed that a third belt can sometimes appear. The radiation is shown here in yellow, with green representing the spaces between the belts.
Earth is surrounded by giant donut-shaped swaths of magnetically trapped, highly energetic charged particles. These radiation belts were discovered in 1958 by the United States' first satellite, Explorer 1. The discovery was led by James Van Allen at the University of Iowa, which eventually caused the belts to be named after him.
Van Allen's experiment on Explorer 1, which launched Jan. 31, 1958, had a simple cosmic ray experiment consisting of a Geiger counter (a device that detects radiation) and a tape recorder. Follow-up experiments on three other missions in 1958 — Explorer 3, Explorer 4 and Pioneer 3 — established that there were two belts of radiation circling the Earth.
This simple picture of the radiation belts persisted for decades until 2012, when a pair of probes was launched to study them in detail. This was the first time that two spacecraft simultaneously studied the radiation belts, trading information with each other to build a bigger picture.

Early probe findings
Part of the interest in the Van Allen belts comes from where they are located. It is known that the belts can swell when the sun becomes more active. Before the probes launched, scientists thought the inner belt was relatively stable, but when it did expand its influence extended over the orbit of the International Space Station and several satellites. The outer belt fluctuated more often.
The Van Allen Probes (formerly known as the Radiation Belt Storm probes) have several scientific goals, including discovering how the particles — ions and electrons — in the belts are accelerated and transported, how electrons are lost and how the belts change during geomagnetic storms. The mission was planned to last two years, but as of August 2016 the probes were still operating at double the expected mission lifetime.
Usually, scientists take a few months to calibrate their instruments, but a team with the Relativistic Electron Proton Telescope asked that their instrument be turned on almost immediately (three days after launch). Their reasoning was they wanted to compare observations before another mission, SAMPEX (Solar, Anomalous, and Magnetospheric Particle Explorer), de-orbited and entered Earth's atmosphere.
"It was a lucky decision," NASA said in February 2013, noting that a solar storm had already caused the radiation belts to swell as soon as the instrument was turned on. "Then something happened no one had ever seen before: the particles settled into a new configuration, showing an extra, third belt extending out into space," the agency added. "Within mere days of launch, the Van Allen Probes showed scientists something that would require rewriting textbooks."

Protective shield
Data gathered by the probes also showed that the radiation belts shield Earth from high-energy particles. "The barrier for the ultrafast electrons is a remarkable feature of the belts," study lead author Dan Baker, of the University of Colorado in Boulder, said in a statement.
"We're able to study it for the first time, because we never had such accurate measurements of these high-energy electrons before." [Gallery: NASA's Van Allen Probes]

Complex configuration
This new information helped scientists model the belts' changes. But there was more information to come. In January 2016, scientists revealed that the shape of the belts depends on what type of electron is being studied. This means the two belts are much more complex; depending on what is being observed, they can be a single belt, two separate belts or just an outer belt (with no inner belt at all.)
"The researchers found that the inner belt — the smaller belt in the classic picture of the belts — is much larger than the outer belt when observing electrons with low energies, while the outer belt is larger when observing electrons at higher energies," NASA wrote at the time. "At the very highest energies, the inner belt structure is missing completely. So, depending on what one focuses on, the radiation belts can appear to have very different structures simultaneously."
What is still poorly understood, however, is what happens when particles from the sun hit the belts during a geomagnetic storm. It is known that the number of electrons in the belts changes, either decreasing or increasing depending on the situation. Also, the belts eventually return to their normal shape after the storm passes. NASA said it isn't clear what kind of storm will cause a specific type of belt configuration. Also, the agency noted, any previous observations were done only with electrons at a few energy levels. More work needs to be done.
Luckily, scientists got the chance to observe a storm up close in March 2015, when one of the Van Allen probes happened to be situated inside the "right" spot in Earth's magnetic field to see an interplanetary shock. NASA describes such shocks as similar to when a tsunami is triggered by an earthquake; in this case, a coronal mass ejection of charged particles from the sun creates a shock in specific areas of the belts.
"The spacecraft measured a sudden pulse of electrons energized to extreme speeds — nearly as fast as the speed of light — as the shock slammed the outer radiation belt," NASA wrote at the time. "This population of electrons was short-lived, and their energy dissipated within minutes. But five days later, long after other processes from the storm had died down, the Van Allen probes detected an increased number of even higher energy electrons. Such an increase so much later is a testament to the unique energization processes following the storm."

Van Allen Probes Spot an Impenetrable Barrier in Space 7

The Van Allen belts are a collection of charged particles, gathered in place by Earth’s magnetic field. They can wax and wane in response to incoming energy from the sun, sometimes swelling up enough to expose satellites in low-Earth orbit to damaging radiation. The discovery of the drain that acts as a barrier within the belts was made using NASA's Van Allen Probes, launched in August 2012 to study the region. A paper on these results appeared in the Nov. 27, 2014, issue of Nature magazine.

“This barrier for the ultra-fast electrons is a remarkable feature of the belts," said Dan Baker, a space scientist at the University of Colorado in Boulder and first author of the paper. "We're able to study it for the first time, because we never had such accurate measurements of these high-energy electrons before." Understanding what gives the radiation belts their shape and what can affect the way they swell or shrink helps scientists predict the onset of those changes. Such predictions can help scientists protect satellites in the area from the radiation. The Van Allen belts were the first discovery of the space age, measured with the launch of a US satellite, Explorer 1, in 1958. In the decades since, scientists have learned that the size of the two belts can change – or merge, or even separate into three belts occasionally. But generally the inner belt stretches from 400 to 6,000 miles above Earth's surface and the outer belt stretches from 8,400 to 36,000 miles above Earth's surface. A slot of fairly empty space typically separates the belts. But, what keeps them separate? Why is there a region in between the belts with no electrons? 

Enter the newly discovered barrier. The Van Allen Probes data show that the inner edge of the outer belt is, in fact, highly pronounced. For the fastest, highest-energy electrons, this edge is a sharp boundary that, under normal circumstances, the electrons simply cannot penetrate. "When you look at really energetic electrons, they can only come to within a certain distance from Earth," said Shri Kanekal, the deputy mission scientist for the Van Allen Probes at NASA's Goddard Space Flight Center in Greenbelt, Maryland and a co-author on the Nature paper. "This is completely new. We certainly didn't expect that." The team looked at possible causes. They determined that human-generated transmissions were not the cause of the barrier. They also looked at physical causes. Could the very shape of the magnetic field surrounding Earth cause the boundary? Scientists studied but eliminated that possibility. What about the presence of other space particles? This appears to be a more likely cause. This animated gif shows how particles move through Earth’s radiation belts, the large donuts around Earth. The sphere in the middle shows a cloud of colder material called the plasmasphere. New research shows that the plasmasphere helps keep fast electrons from the radiation belts away from Earth.

 The radiation belts are not the only particle structures surrounding Earth. A giant cloud of relatively cool, charged particles called the plasmasphere fills the outermost region of Earth's atmosphere, beginning at about 600 miles up and extending partially into the outer Van Allen belt. The particles at the outer boundary of the plasmasphere cause particles in the outer radiation belt to scatter, removing them from the belt. This scattering effect is fairly weak and might not be enough to keep the electrons at the boundary in place, except for a quirk of geometry: The radiation belt electrons move incredibly quickly, but not toward Earth. Instead, they move in giant loops around Earth. The Van Allen Probes data show that in the direction toward Earth, the most energetic electrons have very little motion at all – just a gentle, slow drift that occurs over the course of months. This is a movement so slow and weak that it can be rebuffed by the scattering caused by the plasmasphere. This also helps explain why – under extreme conditions, when an especially strong solar wind or a giant solar eruption such as a coronal mass ejection sends clouds of material into near-Earth space – the electrons from the outer belt can be pushed into the usually-empty slot region between the belts. "The scattering due to the plasmapause is strong enough to create a wall at the inner edge of the outer Van Allen Belt," said Baker. "But a strong solar wind event causes the plasmasphere boundary to move inward." A massive inflow of matter from the sun can erode the outer plasmasphere, moving its boundaries inward and allowing electrons from the radiation belts the room to move further inward too.

An impenetrable barrier to ultrarelativistic electrons in the Van Allen radiation belts 4
Here we analyze an extended data set that reveals an exceedingly sharp inner boundary for the ultrarelativistic electrons. Additional, concurrently measured data reveal that this barrier to inward electron radial transport does not arise because of a physical boundary within the Earth’s intrinsic magnetic field and that inward radial diffusion is unlikely to be inhibited by scattering by an electromagnetic transmitter wave fields. Rather, we suggest that exceptionally slow natural inward radial diffusion combined with weak, but persistent, wave–particle pitch angle scattering deep inside the Earth’s plasmasphere can combine to create an almost impenetrable barrier through which the most energetic Van Allen belt electrons cannot migrate.

2. A privileged planet, Gonzalez, page 57
9. Improbable planet, Hugh Ross, page 57

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5 The earth's size and mass on Tue 20 Jun 2017 - 17:09


The earth's size and mass, fine tuned for life 1

Also vitally important is a planet’s mass. A planet’s habitability depends on its mass in many ways; terrestrial planets significantly smaller or larger than Earth are probably less habitable. Because its surface gravity is weaker, a less massive Earth twin would lose its atmosphere more quickly, and because of its larger surface-area-to-volume ratio, its interior might cool too much to generate a strong magnetic field. Smaller planets also tend to have more dangerously erratic orbits. In contrast, without getting more habitable, a more massive Earth-twin would have a larger initial inventory of water and other volatiles, such as methane and carbon dioxide, and would lose less of them over time. Such a planet might resemble the gas giant Jupiter rather than our terrestrial Earth. In fact, Earth may be almost as big as a terrestrial planet can get. While life needs an atmosphere, too much atmosphere can be bad. For example, high surface pressure would slow the evaporation of water and dry the interiors of continents. It would also increase the viscosity of the air at the surface, making it more difficult for big-brained, mobile creatures like us to breathe. In addition, more surface gravity would create less surface relief, with smaller mountains, and shallower seas. Even with more vigorous tectonic churning, rocks could not support mountains as high as those we enjoy. The planet probably would be covered by oceans and too mineral-starved at the surface (and too salty throughout) to support life. Even a gilled Kevin Costner, cast as a lone mariner, would find such a water world unappealing. 

To add insult to injury, the surface gravity of a terrestrial planet increases with mass more rapidly than you might guess. Intense pressures compress the material deep inside, so that a planet just twice the size of Earth would have about fourteen times its mass and 3.5 times its surface gravity. This higher compression would probably result in a more differentiated planet; gases like water vapor, methane, and carbon dioxide would tend to end up in the atmosphere. Earth has kept dry land throughout its history, in part, because some of its water has been sequestered in the mantle; in contrast, a more massive planet would probably have degassed more than Earth. Maybe you’re still pining away for some adventure on a sci-fi–inspired giant terrestrial planet, but there’s another problem with larger planets— impact threats. To put it simply, they’re bigger targets. Asteroids and comets have a really hard time avoiding larger planets, so these planets suffer more frequent high-speed collisions. While their bigger surfaces distribute the greater impact energy over more area, this doesn’t compensate for the larger destructive energy, since surface area increases slowly with mass for terrestrial planets more massive than Earth. Not only would both smaller and larger terrestrial planets probably be less livable than Earth, but they would also offer poorer overall platforms for discovery. While smaller planets would have taller mountains, providing a better view of the stars, they would have fewer earthquakes, delaying discoveries in geophysics. Smaller planets also provide a smaller, less effective platform for VLBI (very long baseline interferometry) radio observations— which require distant telescopes on different continents—and a smaller “lowest rung on the distance ladder,” which we’ll discuss later. A planet larger than Earth would probably have more tectonic activity, but it would have smaller mountains and a thicker atmosphere, which would hinder astronomy. On Earth, the atmosphere is not an insurmountable problem. Mountain observatories equipped with large optics, like the Keck telescopes on Mauna Kea or the Very Large Telescope in South America, can achieve a spatial resolution rivaling that of the Hubble Space Telescope. From their home on Earth’s surface, scientists can learn about Earth’s interior and the distant stars more efficiently than would observers on planets of quite different sizes.

Planetary Mass and the Evaporation of the Atmosphere 2
It is important for the existence of life that a planet has the right mass. Planets can be divided into three broad classes: Terrestrial planets are Earth-size objects which occupy the inner regions of a planetary system. They have masses roughly like that of the Earth (1/10–5 ME, where ME  is the mass of the Earth). The large Jupiter-like jovian planets consist mostly of hydrogen and have masses of 10–4000 ME. Finally, the Kuiper belt objects are small planetary bodies and comet nuclei with masses less than 1/1000 ME that orbit the Sun at large distances, beyond the belt of the jovian planets. Planet formation theories  provide estimates of the distances of the three types of planets around stars. These distance ranges for stars of different masses.  The very massive jovian planets are completely covered by oceans of liquid molecular hydrogen (plus small amounts of helium). They are inhospitable to life, because any organic or inorganic compound would sink to the bottom of such an ocean, due to the very low specific weight of hydrogen. There, it would become entrapped in the region in which hydrogen becomes metallic.  This leaves only terrestrial planets as possible seats of life. However, not every terrestrial planet is suitable. As for the planets with a large mass, those with too little mass must also be excluded. This is because every life-bearing planet or moon must be able to retain an atmosphere. If the gravitational attraction is too small to hold an atmosphere, a planet in the habitable zone would lose its oceans by evaporation and eventually show only a solid surface similar to that of the Moon. This does not mean that, under unusual circumstances, an ocean might not be retained. Jupiter’s moon Europa probably has an ocean under a surface
layer of ice, in which primitive life might possibly exist.

1. A privileged planet, Gonzalez
2. Intelligent life in the universe, page 91

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Orbit speed of the earth, fine-tuned for life 1

Earth revolves around the sun at a speed of roughly 29 kilometers per second. If Earth were to slow down to, say, 10 kilometers per second – all living things would burn. If the Earth’s orbit around the sun was faster, say, 60 kilometers per second – our planet would deviate from its course into the cold outer space, and all life would soon become extinct. Earth completes a single rotation per day, ensuring that we don’t burn during the day or freeze during the night. It rotates about its axis at a speed of 1,670 kilometers per hour. If it were to rotate any slower, every form of life on Earth would cease to exist, as it would either freeze at night or burn from the heat throughout the day. If, for example, Earth would rotate at a pace of 167 kilometers per hour, the days and nights would have been 10 times longer. The heat during the summer would rise to the point that would not allow the existence of any living things. The temperatures throughout the winter time would drop hundreds of degrees below zero and no life form would be able to survive. In fact, if the average annual temperature on Earth would either rise or drop, even by only a few degrees, most life forms would cease to exist. The change would disturb the ratio of the water quantities and areas to the amount of ice, and lead to devastating consequences. 2

rotating planets have a weak Coriolis force and long daytime illumination, which promotes strong convergence and convection in the substellar region. This produces a large area of optically thick clouds, which greatly increases the planetary albedo. In contrast, on rapidly rotating planets a much narrower belt of clouds form in the deep tropics, leading to a relatively low albedo. A particularly striking example of the importance of rotation rate suggested by our simulations is that a planet with modern Earth’s atmosphere, in Venus’ orbit, and with modern Venus’ (slow) rotation rate would be habitable. This would imply that if Venus went through a runaway greenhouse, it had
a higher rotation rate at that time.

As it orbits the sun once a year the earth travels at a speed of about 66,600 miles an hour. That speed is just right to offset the gravitational pull of the sun and keep the earth at the proper distance. If that speed were decreased, the earth would be pulled toward the sun. In time, Earth could become a scorched wasteland like Mercury, the planet closest to the sun. Mercury's daytime temperature is over 600 degrees Fahrenheit. However, if Earth's orbital speed were increased, it would move farther away from the sun and could become an icy waste like Pluto, the planet whose orbit reaches farthest from the sun. Pluto's temperature is about 300 degrees below zero Fahrenheit. 1


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7 Re: FineTuning of the earth on Fri 23 Jun 2017 - 1:07


Pressure of the atmosphere, fine-tuned for life 1

Viewed from Earth’s surface, the atmosphere seems homogeneous, constantly mixed by winds and convection. In fact, the first 83 kilometers above Earth is called the homosphere because the air is kept evenly mixed. Half of the mass of the atmosphere lies less than 6 kilometers above Earth. Even this diffuse veil has differences that reflect variations in solar radiation, heating by Earth’s surface, gravity, evaporation and incoming cosmic radiation. Thus, for example, gravity holds the heavier elements closer to the ground, while lighter ones, such as helium, are found in greater relative abundance at extreme altitudes. The lowest level of the homosphere is the troposphere, where life is found and weather occurs. It averages 11 kilometers above Earth but is 8 kilometers at the poles and 16 kilometers above the equator. Above the troposphere is the stratosphere (11 to 48 kilometers above Earth), where gases become thinner; this region contains the ozone layer, between 16 and 48 kilometers above Earth. Above the stratosphere lies the mesosphere, 48 to 88 kilometers above Earth.

Earth’s air pressure is highly anomalous. A planet’s primordial atmosphere is determined by its surface gravity, its distance from its host star, and its host star’s effective temperature. 2

Diagrams of Earth’s wind belts remind us of the importance of differences in air pressure existing from one location to another. Wind belts result from the tendency of air to flow from high to low pressure. A large portion of earth’s population exists in wind belts termed prevailing westerlies or northeast/southeast trade winds. Wind belts converge or diverge in their effort to equalize pressure conditions. In terms of our healthy, dynamic weather system, these effects are necessary. Absence of differences in pressure would result in the absence of wind, the absence of precipitation-producing storm systems and the absence of a mechanism for distributing life giving water where it is needed. It is not difficult to imagine that earth life would be very different if it would exist at all. 3


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Earth is slightly tilted on its axis at a 23.4-degree angle

This tilt helps balance the amount of radiation emitted by the sun. If for example, it had been tilted at an 80-degree angle, we wouldn’t have four seasons in a year. Without the seasons, life would vanish. The North and South Pole would be shrouded in perpetual twilight. Water vapor from the oceans would be carried by the wind towards the north and the south, and freeze as they approach the Poles. Over time, giant continents made of snow and ice would form around the Poles and cause most of Earth’s surface to become deserts. Eventually, the oceans would vanish entirely and the rains would stop. The weight of the ice accumulating at the Poles would cause the equator to expand and, as a result, the Earth’s spin would drastically change, leading to further negative effects on all of Earth’s existing life forms.

A large moon stabilizes the rotation axis of its host planet, yielding a more stable, life-friendly climate. Our Moon keeps Earth’s axial tilt, or obliquity—the angle between its rotation axis and an imaginary axis perpendicular to the plane in which it orbits the Sun— from varying over a large range.6 A larger tilt would cause larger climate fluctuations. 7 At present, Earth tilts 23.5 degrees, and it varies from 22.1 to 24.5 degrees over several thousand years. To stabilize effectively, the Moon’s mass must be a substantial fraction of Earth’s mass. Small bodies like the two potato-shaped moons of Mars, Phobos and Deimos, won’t suffice. If our Moon were as small as these Martian moons, Earth’s tilt would vary not 3 degrees but more than 30 degrees. That might not sound like anything to fuss over, but tell that to someone trying to survive on an Earth with a 60- degree tilt. When the North Pole was leaning sunward through the middle of the summer half of the year, most of the Northern Hemisphere would experience months of perpetually scorching daylight. High northern latitudes would be subjected to searing heat, hot enough to make Death Valley
in July feel like a shady spring picnic. Any survivors would suffer viciously cold months of perpetual night during the other half of the year. But it’s not just a large axial tilt that causes problems for life. On Earth, a small tilt might lead to very mild seasons, but it would also prevent the wide distribution of rain so hospitable to surface life. With a 23.5-degree axial tilt, Earth’s wind patterns change throughout the year, bringing seasonal monsoons to areas that would otherwise remain parched. Because of this, most regions receive at least some rain. A planet with little or no tilt would probably have large swaths of arid land. 1

1. Gonzalez, a privileged planet, page 6

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9 Liquid Water Habitable Zone on Fri 23 Jun 2017 - 15:16


Liquid Water Habitable Zone 1

The liquid water habitable zone is that region about a star wherein liquid water can exist on a planetary surface. For water to remain, of course, requires an appropriate level of atmospheric pressure. (Where pressure is low, such as on Mars, a drop of water would evaporate in a second.) The liquid water habitable zone may also be called the temperature habitable zone. At least some part of a planetary surface must range between 0–100°C (32–212°F)—assuming a surface air pressure similar to Earth’s—to retain liquid water. Whether or not any part of a planet’s surface stays at a temperature that permits the existence of liquid water depends on three factors:

(1) the host star’s luminosity, or total energy output;
(2) the planet’s atmospheric pressure; and
(3) the quantity of heat-trapping gas in the planet’s atmosphere.

At the Sun’s current luminosity level, the liquid water habitable zone lies between 95 and 137 percent of the Earth’s distance from the Sun. A planet orbiting closer than 95 percent Earth’s distance from the Sun would experience a runaway evaporation. Increased heat from the Sun would evaporate more of the water, and because water vapor is a greenhouse gas, this added water vapor would trap more heat, which would cause more water to evaporate and, thus, trap still more heat, and so on until no liquid water remained.

A planet at or beyond 137 percent Earth’s distance from the Sun would experience the opposite, a runaway freeze-up. Less heat from the Sun would mean more snowfall and more frozen surface water, both of which would reflect heat, causing, even more, snow to fall and more water to freeze, and so on, until no liquid water remained. Cloud cover or atmospheric haze could possibly mitigate the cooling effects of reflection from snow and ice. Or, if the planet’s albedo (surface reflectivity) is more like that of the Moon, which reflects only 7 percent of incident radiation at visible wavelengths than that of the Earth, which reflects 30–35 percent of incident radiation, then less of the Sun’s heat would be reflected away. These additional factors push the possibility of liquid water (on a planet) out to 167 percent of Earth’s distance from the Sun. More recent studies of newly derived water vapor and carbon dioxide absorption coefficients show the inner limit of the liquid water habitable zone at 99 percent of Earth’s distance from the Sun.

Our revised model predicts that the moist greenhouse limit for our Sun, which defines the inner edge of the HZ, is at 0.99 AU.

This narrowing of the zone so troubled extraterrestrial life enthusiasts as to spur development of a new model for the liquid water habitable zone. This model invokes planets that are much drier than Earth, and with surface rocks significantly more reflective than Earth’s. Researchers showed that if these desert worlds were to possess thin atmospheres with humidity levels no greater than 1 percent and a rotation axis tilt near 0° and a distance from their star roughly equal to the orbital distance of Venus, then a runaway water vapor greenhouse effect could possibly be avoided. These models further require that the tiny amounts of liquid water be restricted to the host planet’s high latitudes. One extreme model showed that if no water transport between one region and any other were to occur, runaway water vapor evaporation could be avoided even for planets as close to their star as Mercury is to the Sun (just 39 percent of Earth’s distance from the Sun). Extraterrestrial life enthusiasts have also proposed an extension to the outer boundary of the liquid water habitable zone. Models show that water worlds (planets with water covering their entire surface) would have much higher surface temperatures than planets with at least some dry land. Geothermal hot spots could potentially heat pools of water to life-sustaining temperatures on planets more distant from their host star than 167 percent of Earth’s distance from the Sun. These enthusiasts claim the outer limit can be pushed out to 225 percent Earth’s distance from the Sun, well beyond Mars’ distance. A major challenge, however, comes from the fact that carbon dioxide would freeze at such a distance. So, its potential greenhouse warming effect would be lost. The notion of an extremely wide habitable zone gives rise to bold assertions, such as the claim that 40+ billion Milky Way planets could potentially be “home” to life. But these terms need clarification. If one defines “life habitable zone” as a region where the most primitive conceivable unicellular lifeform could survive for a very brief time, it may be a bit wider than Kasting’s early calculations indicated—but only if life requires only a certain minimal amount of liquid water and not much more and if it really does arise spontaneously from nonlife under such conditions. For a long history of life, one that includes the possibility of advanced life, the liquid water habitable zone by itself would be much narrower than the narrowest limits described above. Advanced life requires more than merely a stable supply of liquid water. As ongoing research tells us, it requires a habitat in which frozen water, liquid water, and water vapor exist simultaneously over long time periods. It also requires a habitat in which water transitions efficiently from one of its states to the other two. What’s more, water represents only one of life’s requisites. Other essentials exist in their distinct zones, which may or may not overlap.

1. Improbable Planet, Hugh Ross, page 53

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10 Ultraviolet light, essential for life on Sun 25 Jun 2017 - 20:22


Ultraviolet light, essential for life

Scientists find ultraviolet light may create life-essential chemicals 1

Life exists in a myriad of wondrous forms, but if you break any organism down to its most basic parts, it's all the same stuff: carbon atoms connected to hydrogen, oxygen, nitrogen and other elements. But how these fundamental substances are created in space has been a longstanding mystery.

Now, astronomers better understand how molecules form that are necessary for building other chemicals essential for life. Thanks to data from the European Space Agency's Herschel Space Observatory, scientists have found that ultraviolet light from stars plays a key role in creating these molecules, rather than "shock" events that create turbulence, as was previously thought. Scientists studied the ingredients of carbon chemistry in the Orion Nebula, the closest star-forming region to Earth that forms massive stars. They mapped the amount, temperature and motions of the carbon-hydrogen molecule (CH, or "methylidyne" to chemists), the carbon-hydrogen positive ion (CH+) and their parent: the carbon ion (C+). An ion is an atom or molecule with an imbalance of protons and electrons, resulting in a net charge.

"On Earth, the sun is the driving source of almost all the life on Earth. Now, we have learned that starlight drives the formation of chemicals that are precursors to chemicals that we need to make life," said Patrick Morris, first author of the paper and researcher at the Infrared Processing and Analysis Center at Caltech in Pasadena.

In the early 1940s, CH and CH+ were two of the first three molecules ever discovered in interstellar space. In examining molecular clouds -- assemblies of gas and dust -- in Orion with Herschel, scientists were surprised to find that CH+ is emitting rather than absorbing light, meaning it is warmer than the background gas. The CH+ molecule needs a lot of energy to form and is extremely reactive, so it gets destroyed when it interacts with the background hydrogen in the cloud. Its warm temperature and high abundance are therefore quite mysterious.

Why, then, is there so much CH+ in molecular clouds such as the Orion Nebula? Many studies have tried to answer this question before, but their observations were limited because few background stars were available for studying. Herschel probes an area of the electromagnetic spectrum -- the far infrared, associated with cold objects -- that no other space telescope has reached before, so it could take into account the entire Orion Nebula instead of individual stars within. The instrument they used to obtain their data, HIFI, is also extremely sensitive to the motion of the gas clouds.

One of the leading theories about the origins of basic hydrocarbons has been that they formed in "shocks," events that create a lot of turbulence, such as exploding supernovae or young stars spitting out material. Areas of molecular clouds that have a lot of turbulence generally create shocks. Like a large wave hitting a boat, shock waves cause vibrations in material they encounter. Those vibrations can knock electrons off atoms, making them ions, which are more likely to combine. But the new study found no correlation between these shocks and CH+ in the Orion Nebula.

Herschel data show that these CH+ molecules were more likely created by the ultraviolet emission of very young stars in the Orion Nebula, which, compared to the sun, are hotter, far more massive and emit much more ultraviolet light. When a molecule absorbs a photon of light, it becomes "excited" and has more energy to react with other particles. In the case of a hydrogen molecule, the hydrogen molecule vibrates, rotates faster or both when hit by an ultraviolet photon.

It has long been known that the Orion Nebula has a lot of hydrogen gas. When ultraviolet light from large stars heats up the surrounding hydrogen molecules, this creates prime conditions for forming hydrocarbons. As the interstellar hydrogen gets warmer, carbon ions that originally formed in stars begin to react with the molecular hydrogen, creating CH+. Eventually the CH+ captures an electron to form the neutral CH molecule. "This is the initiation of the whole carbon chemistry," said John Pearson, researcher at NASA's Jet Propulsion Laboratory, Pasadena, California, and study co-author. "If you want to form anything more complicated, it goes through that pathway."

Scientists combined Herschel data with models of molecular formation and found that ultraviolet light is the best explanation for how hydrocarbons form in the Orion Nebula.

The findings have implications for the formation of basic hydrocarbons in other galaxies as well. It is known that other galaxies have shocks, but dense regions in which ultraviolet light dominates heating and chemistry may play the key role in creating fundamental hydrocarbon molecules there, too.
"It's still a mystery how certain molecules get excited in the cores of galaxies," Pearson said. "Our study is a clue that ultraviolet light from massive stars could be driving the excitation of molecules there, too."

Sunlight as an Energetic Driver in the Synthesis of Molecules Necessary for Life 2

Life is an inherently high-energy, out-of-equilibrium enterprise, and both the evolution and continuation of life require the input of energy to the system. Living organisms obtain energy autotrophically, chemotrophically, or heterotrophically, and then, through metabolism, create and replicate the complex biomolecules needed for their survival. Likewise, under prebiotic conditions without enzymatic assistance, the synthesis of such biomolecules from simpler organic molecules also requires energy from an external source. Light from the Sun is the single largest energy source on both the ancient and modern Earth. Even considering the lower luminosity of the early Sun, the amount of solar energy available on Earth was orders of magnitude greater than that provided by electrical discharges, shockwaves from impacts, radioactivity, volcanoes, and geothermal sources combined.
Additionally, in the absence of atmospheric oxygen and ozone, which shields the surface of the Earth from ultraviolet photons today, there would have been more of this chemically useful high energy light available on the surface of the prebiotic Earth. It stands to reason, then, that photochemical reaction may have played an important role in the development of larger, more complex molecules during the chemical evolution of biomolecules that eventually led to life.

Incoming solar radiation reaches Earth with high energy and low entropy, but is degraded into heat, motion, and ultimately thermal energy, which is re-radiated to space. This energy dispersal generates entropy, which can then drive large-scale processes such as weather systems, ocean currents, and life. The low entropy energy provided by a star is, therefore, different from thermal sources of energy (geothermal, volcanic, hydrothermal vents, etc.) considered in origin of life scenarios. Excitation initiated by thermal sources causes energy to be distributed randomly throughout molecules. It, therefore, requires very high temperatures for any significant fraction of molecules to have sufficient energy to react. Photochemistry, on the other hand, relies on the absorption of a photon, which excites a specific molecule, localizing a great deal of energy while still allowing
the temperature of the system to remain low. These characteristics lead to a great contrast between thermal chemistry and photochemistry; under conditions required for reaction, thermal chemistry always moves toward thermodynamic equilibrium, but photochemistry can move away from it. Photochemistry, therefore, allows for the direct generation of high-energy compounds and/or non-equilibrium systems without the need to invoke environmental changes, such as wet-dry cycles, as are required for thermal chemistry.

Furthermore, photochemistry is inherently molecule-specific because electronic and vibrational states are quantized and depend uniquely on the structure of the molecule. The functional groups of a molecule determine the shape of its potential energy surfaces, including the energy spacing between states, and govern the accessible reaction pathways. These potential energy surfaces are often affected by the molecule’s environment (e.g. solvent conditions). Different environments can often alter reaction mechanisms and, at times, change the final products. Thus, photochemistry is not only molecule-specific but is also quite environment specific.  

The early atmosphere contained very little oxygen or other species that are generated by reactions with molecular oxygen, such as ozone. The exact composition of the atmosphere during the Hadean has been controversial, though most agree that it was not oxidizing. Yet, while many concur that it was likely reducing during the Hadean, some argue that the global atmosphere was neutral at the advent of life, perhaps with locally reducing environments (e.g. near volcanoes). The dominant species in the atmosphere were most likely nitrogen N2 and carbon dioxide CO2. Some have considered that there might have been up to 100 bar of CO2 during this period, but it is more commonly assumed that the overall atmospheric pressure was close to the 1 bar of today. Additionally, constraints from paleosols39, 40 and banded iron formations suggest that upper limit to the mixing ratio of CO2 during the Archean was somewhere between 3 to 50 times the present atmospheric level. Using these constraints, the early Earth’s atmosphere has been modeled with mixing ratios of N2 and CO2 of roughly 0.9 and 0.1, respectively, with other minor trace gases included. Methane has the potential to be another key component of the early atmosphere. Some have proposed a relatively high concentration of CH4, which would create organic hazes that may have formed as an early UV shield. However, this requires a ratio of CH4/CO2 ratio of 0.1, which is a very high ratio considering there would be no biotic sources of methane. Instead, it is more likely that only trace amounts of methane existed and has been modeled with concentrations between 0 and 1 ppm. Other trace gases with significance for prebiotic photochemistry include HCN, NH3, H2S, and volatile organics, such as aldehydes and ketones. The expected prebiotic mixing ratios of these species are not well-constrained. The amount of HCN, for example, is dependent on assumptions about the concentration of CH4. Regardless, while these are important feedstock species for further chemistry, the expected steady state mixing ratios of these trace gases would be very small. Following periods of significant volcanic activity, SO2 outgassing from magma and lava would have also been an important constituent of the atmospheric mixture.  Although, given its reactivity,  the steady-state mixing ratio was likely relatively small. Water vapor is also outgassed by magma, and, while the majority of it was rapidly condensed to liquid, H2O was likely a significant component of the atmosphere, just as it is today. The specific mixing ratio of water in the atmosphere, however, is, and would have been, heavily temperature and therefore altitude dependent.

Ultraviolet Habitable Zone 5
Ultraviolet radiation is needed for the synthesis of many biochemical compounds that are essential for physical life. Therefore, if the ultraviolet radiation from a host star is too weak, no life is possible on that planet. On the other hand, if the ultraviolet radiation falling upon a planet’s surface is too strong, DNA and other life-critical biomolecules will be damaged to a degree that wipes out all life. The ultraviolet habitable zone is the area where the ultraviolet radiation from a star is neither too weak nor too strong for the existence of life. For host stars with an effective temperature more than 7,100 K (7,100 °C above absolute zero) or less than 4,600 K, even for just microbes, a team of four Chinese astronomers showed that the liquid water and ultraviolet habitable zones will not overlap.1 This may seem like a fairly wide effective temperature range, but it is narrow enough to eliminate all but 3 percent of the Milky Way Galaxy’s stars.

The ultraviolet habitable zone is that region about a star where incident UV radiation arriving on a planet’s surface is neither too strong nor too weak to provide for life’s needs. UV radiation is a double-edged sword. 3 Without it several essential biochemical reactions and the synthesis of many life-essential biochemical compounds (such as DNA repair and vitamin D manufacturing) cannot occur. Too much of it, however, will damage or destroy land-based life. Both the quantity and the wavelength of incident UV radiation must fall within a certain range for life to survive, and an even narrower range for life to flourish. The acceptable range of UV radiation seems especially narrow for human beings. Skin exposure to UV radiation serves as the primary source of vitamin D production in human bodies.

Vitamin D: The “sunshine” vitamin  4
Vitamin D insufficiency affects almost 50% of the population worldwide. An estimated 1 billion people worldwide, across all ethnicities and age groups, have a vitamin D deficiency (VDD). This pandemic of hypovitaminosis D can mainly be attributed to lifestyle (for example, reduced outdoor activities) and environmental (for example, air pollution) factors that reduce exposure to sunlight, which is required for ultraviolet-B (UVB)-induced vitamin D production in the skin. High prevalence of vitamin D insufficiency is a particularly important public health issue because hypovitaminosis D is an independent risk factor for total mortality in the general population.

Vitamin D helps grow strong bones, prevents many kinds of cancer, and maintains the immune response system. UV radiation exposure stimulates the pineal gland, which helps elevate positive moods. It can also help alleviate skin conditions such as psoriasis and eczema. However, only slightly more UV radiation exposure than the minimum levels required for these health benefits would raise the incidence of skin cancer and damage our eyesight. Still, more would generate life-threatening melanoma and blindness. Although the UV zone may prove relatively wide for the sake of more primitive life-forms, it may not be wide enough even then to overlap with the liquid water habitable zone. For host stars with effective temperatures less than 4,600 kelvin (K)—that’s the number of Celsius degrees above absolute zero—the outer edge of the UV habitable zone falls closer to the star than the inner edge of the liquid water habitable zone. For host stars with effective temperatures greater than 7,100 K, the inner edge of the UV habitable zone sits farther from the host star than the outer edge of the liquid water habitable zone. For older stars that have completed their hydrogen-burning phase, the UV habitable zone appears about ten times more distant from the host star than the liquid water habitable zone. As a basis for comparison, the Sun has an effective temperature of 5,778 K. The fact that the liquid water and UV habitable zones must overlap for the sake of life eliminates most planetary systems as possible candidates for hosting life. This requirement effectively rules out all the M-dwarf and most of the K-dwarf stars, as well as all the O-, B-, and A-type stars. All that remains are F-type stars much younger than the Sun, G-type stars no older than the Sun, and a small fraction of the K-type stars. Only stars at a certain distance from the galactic core can be considered candidates for life support. In the MWG, some 75 percent of all stars residing at this appropriate-for-life distance are older than the Sun. Once these and other noncandidate stars are ruled out, only 3 percent of all stars in our galaxy remain as possible hosts for planets on which primitive life could briefly survive.

2. Sunlight as an Energetic Driver in the Synthesis of Molecules Necessary for Life
3. Hugh Ross, Improbable Planet, page 54

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11 Photosynthetic Habitable Zone on Tue 27 Jun 2017 - 21:41


Photosynthetic Habitable Zone 4
The photosynthetic habitable zone refers to the range of distances from a host star within which a planet could possibly possess the necessary conditions for photosynthesis to occur. While some lifeforms can exist in the absence of photosynthesis, such life exhibits metabolic rates from hundreds to millions of times lower than those of photosynthetic life. In other words, without photosynthesis, large-bodied warm-blooded animals would not be possible.
Photosynthetic life requires much more demanding constraints on the quantity, stability, and spectral light range available on a planet’s surface. Limited photosynthetic activity is possible for a planet where the UV and liquid water habitable zones overlap. However, for the scope of photosynthetic activity advanced life requires to endure and thrive, these seven factors must fall within highly specific ranges:

1. Light intensity
2. Ambient temperature
3. Carbon dioxide concentration
4. Seasonal variation and stability
5. Mineral availability
6. Liquid water quantity
7. Atmospheric humidity (for land-based life)

Photosynthesis Requires the Right Kind of Star 1
Where can photosynthesis occur?  The answer depends on the energy of starlight, the atmosphere, the amount of water vapor, and the organisms equipped to harvest it. A new kind of photosynthetic bacterium was just discovered in a Yellowstone hot spring. 2 Exciting as this is (and the discoverer felt he had struck gold), the new species is just another tally among the bacteria and plants with the amazing ability to harvest light and produce energy for food and growth.  Some bacteria produce chemical energy from light in one step; plants and algae utilize light in two stages (photosystem I and II), and liberate oxygen in the process – an energy-intensive process.  They couldn’t do it, though, if Earth orbited most stars. John Raven took a look at this coupling between starlight and photosynthesis in Nature.  He reviewed some recent studies on how light energy penetrates atmospheres and bodies of water.  Water is an efficient absorber of solar energy; that’s why plants and seaweed are restricted to the photic zone of lakes and oceans, or to the land surface.  “This biological dark side of water – its absorption of solar electromagnetic radiation – creates habitats that restrict or eliminate the roles of solar radiation in supplying energy for photosynthesis and information to sensory systems,” Raven noted. What is the minimum energy required to trigger photosynthesis?  And what is the wavelength of the peak energy reaching the photic zone?  These questions yield answers about habitats on planets around other stars.  The “longest wavelength that has sufficient energy per photon to bring about the appropriate photochemical reaction (in which photon energy is converted into chemical energy)” sets physical constraints on photosynthesis, and thus on astrobiology.  Raven considered the likelihood that the plentiful M-type (red dwarf) stars could host life:

John Raven took a look at this coupling between starlight and photosynthesis in Nature :

He reviewed some recent studies on how light energy penetrates atmospheres and bodies of water.  Water is an efficient absorber of solar energy; that’s why plants and seaweed are restricted to the photic zone of lakes and oceans, or to the land surface. “This biological dark side of water – its absorption of solar electromagnetic radiation – creates habitats that restrict or eliminate the roles of solar radiation in supplying energy for photosynthesis and information to sensory systems,” Raven noted.   What is the minimum energy required to trigger photosynthesis?  And what is the wavelength of the peak energy reaching the photic zone?  These questions yield answers about habitats on planets around other stars.  The “longest wavelength that has sufficient energy per photon to bring about the appropriate photochemical reaction (in which photon energy is converted into chemical energy)” sets physical constraints on photosynthesis, and thus on astrobiology.  Raven considered the likelihood that the plentiful M-type (red dwarf) stars could host life:

Putative planets associated with stars of the M spectral type are commonly taken to be locations where life might occur, given the abundance of these stars and their longevity.  Photosynthetic organisms on an Earth-like planet orbiting an M star would experience stellar radiation with maximum photon fluxes at wavelengths in the infrared spectrum.  The ‘average’ photon would have a lower energy content, and there would also be a much greater absorption by water, than for solar radiation on Earth. Significant photosynthesis could nonetheless occur on such a planet.  But there would be energetic problems in using the relatively low-energy photons to reduce carbon dioxide with electrons from water, with production of oxygen.  The mechanism on Earth relies on two photochemical reactions in series; on planets orbiting an M star more than two reactions in series would be required.  On any such planet, the longer wavelengths at which photosynthetic pigments would absorb would have implications for the remote sensing of pigments by reflectance spectroscopy as an indicator (with appropriate caveats) of photosynthesis, and hence life.

Speaking of pigments, Freeman Dyson speculated in an article for the New York Review of Books about why plants are green instead of black. He writes :

If the natural evolution of plants had been driven by the need for high efficiency of utilization of sunlight, then the leaves of all plants would have been black.  Black leaves would absorb sunlight more efficiently than leaves of any other color.  Obviously plant evolution was driven by other needs, and in particular by the need for protection against overheating.  For a plant growing in a hot climate, it is advantageous to reflect as much as possible of the sunlight that is not used for growth.  There is plenty of sunlight, and it is not important to use it with maximum efficiency.  The plants have evolved with chlorophyll in their leaves to absorb the useful red and blue components of sunlight and to reflect the green.  That is why it is reasonable for plants in tropical climates to be green.  But this logic does not explain why plants in cold climates where sunlight is scarce are also green.  We could imagine that in a place like Iceland, overheating would not be a problem, and plants with black leaves using sunlight more efficiently would have an evolutionary advantage.  For some reason which we do not understand, natural plants with black leaves never appeared.  Why not?  Perhaps we shall not understand why nature did not travel this route until we have traveled it ourselves.

From there, Dyson speculated about how humans may some day improve on photosynthesis.2  But perhaps he is right; plants know something we don’t.  They are obviously very good at making use of the light falling on “God’s green Earth” as Michael Medved calls it when signing off his radio program each day.  God’s black Earth somehow wouldn’t sound as nice.

Solar radiation is also just the right energy for the transitions in rhodopsin in our retinas that allow us to see the green plants.

4. Ross, Improbable Planet, page 55

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12 Ozone Habitable Zone on Wed 28 Jun 2017 - 3:29


Ozone Habitable Zone

The ozone habitable zone describes that range of distances from a star where an ozone shield can potentially form. When stellar radiation impinges upon an oxygen-rich atmosphere, it produces a quantity of ozone in that planet’s atmospheric layers. This ozone, in turn, affects the amount of radiation reaching the planetary surface. Ozone, a molecule composed of three oxygen atoms, forms in a planet’s stratosphere as short wavelength UV radiation and, to a lesser degree, stellar X-ray radiation react with dioxygen (O2). Meanwhile, its reaction with atomic oxygen in the stratosphere destroys ozone (O3 + O →2O2). The quantity of ozone in the stratosphere at any given time depends on the status of this balancing act. Currently, ozone in Earth’s stratosphere absorbs 97–99 percent of the Sun’s short wavelength (2,000–3,150 Å), life-damaging UV radiation while allowing much of the longer wavelength (3,150+Å), beneficial radiation to pass through to Earth’s surface. What makes this life-favoring scenario possible is the combination of three main factors:

(1) the necessary quantity of oxygen in Earth’s atmosphere;
(2) the just-right intensity of UV radiation impinging on Earth’s stratosphere; and
(3) the relatively low variability of this UV radiation bath.

For the level of stellar UV emission to be sufficiently stable for life’s sake, the host star’s mass must be virtually identical to the Sun’s. Stars more massive than the Sun exhibit more extreme variation in UV emission. So do stars less massive than the Sun. The host star’s age also must be virtually the same as the Sun’s  and for the same reason—limited variability. Given that the quantity of oxygen in a planet’s atmosphere must also fall within a limited range, especially for advanced life, only a narrow range of distances from a host star allows for a planet’s stratospheric ozone to remain at appropriate levels for life. For life protection purposes, the ozone quantity in a planet’s troposphere (the atmospheric layer extending from the surface up to a certain distance, in Earth’s case, from sea level to six miles up) must amount to about 10 percent of that in the stratosphere. Too much ozone in the troposphere would hinder respiration for large-bodied animals while also reducing crop yields and wiping out many plant species. Insufficient tropospheric ozone would lead to an ever-increasing buildup of biochemical “smog” particles emitted by tree-like vegetation. These factors place additional constraints on a host star’s UV radiation intensity and stability, and on the host planet’s distance from the star, especially given that ozone production in a planet’s troposphere receives a boost from lightning.

1. Improbable Planet: How Earth Became Humanity's Home

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13 Tidal Habitable Zone on Wed 28 Jun 2017 - 19:59


Tidal Habitable Zone 1

The tidal habitable zone refers to the distance range from a host star where the planet is near enough for life-essential radiation but far enough to prevent tidal locking. Due to gravity, a star exerts a stronger pull on the near side of its surrounding planets than on the far side. Tidal force describes the difference between the near-side tug and the far-side tug, a difference that carries great significance. The tidal force a star exerts on a planet is inversely proportional to the fourth power of the distance between them. Thus, shrinking the distance by one half increases the tidal force by 16 times. If a planet orbits too close to its star, it becomes tidally locked (as the Moon is tidally locked with Earth), which means one hemisphere faces permanently toward its star. As a result of tidal locking, one face of the planet would receive an unrelenting flow of stellar radiation while the opposite side would receive none.

On a tidally locked planet, then, the only conceivable place where life could exist would be in the twilight zone––that narrow region between permanent light and permanent darkness. If such a planet happened to reside in the liquid water habitable zone and possess an atmosphere, water would move via atmospheric transport from the day side to the night side, where it would become permanently trapped as ice. So, no liquid water would exist anywhere on its surface. For life to exist on a tidally locked planet, it would have to be unicellular, exhibit extremely low metabolic rates, and reside below the surface. Tidal locking takes time to develop. A planet’s initial rotation rate gradually slows to equal its rate of revolution. The rate at which a planet becomes tidally locked to its star is inversely proportional to the sixth power of its distance from the star. For example, if Earth were to orbit ever so slightly nearer to the Sun, it would experience so much rotational slowing as to approach tidal locking and its consequences.

The Sun’s tidal contribution to this rotation rate decrease is about half the Moon’s. Given the mass of the Moon, the just-right level of tidal braking requires a Sun neither more nor less massive than it is and neither more nor less distant than it is. A star’s tidal force also erodes its planets’ rotation axis tilt. If a planet orbits too close to its star, tidal force would drive its rotation axis tilt to less than 5° and, consequently, prevent the occurrence of seasons there. The lack of seasons would radically shrink the planet’s habitable area. Food crops would be rare to impossible while any existent pathogens would potentially thrive. Intelligent life likely would be constrained to small populations with few means to advance beyond Stone Age technology. The star’s mass also comes into play in erosion of a nearby planet’s rotation axis tilt. To avoid such erosion and maintain the necessary tilt —while also remaining in both the water habitable and UV habitable zones—the mass of the star around which the planet orbits must fall within a precise range. 2

The bottom end of that range is 0.9 times the mass of the Sun. For a planet to maintain stable seasons and provide a secure foundation for intelligent life, the mass of the host star must be no less than that of the Sun. For stars more massive than the Sun, the habitable zones move out to greater distances. Such distances eliminate the possibility of catastrophic tidal effects, but these more massive stars burn up more rapidly and with more radical luminosity variations during their existence. They also emit more UV radiation. A star more massive than the Sun would possess a UV habitable zone only when that star is much younger than the Sun. Such a star could conceivably host a planet on which unicellular life would be able to survive for a relatively brief time, but not a planet on which life persists and becomes the foundation for more advanced life. The Sun’s mass proves just right for life on other counts, beyond applying tidal forces to ensure Earth’s just-right rotation rate at the just-right time for the benefit of human life. The complex interaction of both solar and lunar tidal effects permits Earth to sustain an enormous biomass and biodiversity at its seashores and on its continental shelves. The tides on Earth are optimal for recycling nutrients and wastes. They provide the potential for a rich and abundant ecology.

To move the Earth toward the Sun could be quite dangerous since this would strongly increase the tidal forces exerted by the Sun on our planet. Tidal forces owe their existence to the fact that gravitational forces vary with distance. On the Earth, it is the Moon that produces the largest tides. Figure 5.6 shows (exaggerated) the various forces exerted by the Moon on the Earth.

Since gravity varies with the square of the distance, the gravitational force (dashed) is much larger on the side of theE arth closest to the Moon. The gravitational force is smaller at the Earth’s center and even less on the far side of the Earth. The Moon and the Earth both orbit around their common center of mass, whereby centrifugal forces are created that prevent the two bodies from crashing into one another. These centrifugal forces (dotted) have the same magnitude everywhere on the Earth and balance the gravitational forces. When they are subtracted from the gravitational forces, they cancel at the Earth’s center but produce residual forces called tidal forces at the Earth’s near and far sides (Fig. 5.6, solid arrows), which pull oceans and landmasses in opposite directions relative to the Earth’s center. As the response of the oceans to the tidal forces takes time to build up, the observed maximum of the tidal bulge at a given point lags behind the culmination direction of the Moon. The deformation of land and the displacement of water in the oceans both use up energy, which slows the Earth’s rotation (an effect called tidal braking) and increases the distance to the Moon. Because of tidal braking, the rotation rate of the Earth has decreased from about a 5-hour day, four billion years ago, to the present 24-hour day. This increase of the length of the terrestrial day has caused the Moon (due to the law of angular momentum conservation) to move away from a distance of about 22 000 km (Chap. 3) at its formation to one of 380 000 km today.

1. improbable planet, Hugh Ross, page 58
2. Intelligent life in the universe, page 106

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14 Earth's plate tectonics essential for life on Fri 30 Jun 2017 - 19:54


Earth's plate tectonics essential for life

Plate tectonic activity generates continents, which together with the oceans, recycle nutrients and steadily remove potentially destructive greenhouse gases from the atmosphere 2

Earth is not just a vessel for life; the planet itself is alive. But its geological metabolism – and especially the dynamism of its tectonic plates – is also responsible for making it a habitable world. If the planet were a cold, dead, and inert space rock, life as we know it probably could not exist. At least on today's Earth, geology and biology go hand in hand. Of all planets, Earth is the only one known to have plate tectonics. It is also the only one known to harbour life. 1 Still, geological activity alone is not the same as plate tectonics. Earth is the only planet in the Solar System with an outer crust broken into several plates like a cracked eggshell. These rigid tectonic plates, extending a couple of hundred kilometres deep at most, float on the more malleable mantle below. On Earth, tectonic plates shift and slide, constantly renewing the surface. At mid-ocean ridges, rising magma forms new crust as it pushes two plates apart.

Sometimes, like in the Himalayas, continental plates thrust themselves into each other, and with nowhere to go but up, they build mountains. This is all essential for life on Earth. These processes carry carbon in and out of Earth's interior, and by doing so, regulate the amount of carbon dioxide in the atmosphere. Carbon dioxide is a greenhouse gas: too much of it, and the atmosphere traps too much heat. "The surface temperature increases and Earth eventually becomes a planet like Venus," says Jun Korenaga, a geophysicist at Yale University, US. Too little, and all the heat would escape, leaving Earth inhospitably cold. The carbon cycle therefore acts as a global thermostat, regulating itself when needed.   A warmer climate also results in more rain, which helps extract more carbon dioxide out of the atmosphere.

The gas is dissolved in raindrops, which fall on exposed rock. Chemical reactions between the rainwater and rock release the carbon and minerals like calcium from the rock. The water then flows through rivers and streams, eventually reaching the ocean, where the carbon forms carbonate rocks and organic objects like seashells. The carbonate settles on the bottom of the ocean, on a tectonic plate that gets subducted, carrying the carbon into Earth's interior. Volcanoes then belch the carbon back into the atmosphere as carbon dioxide. Plate tectonics plays a part in every aspect of this cycle. Not only does subduction deliver carbon back into Earth's mantle, but tectonic activity brings fresh rock to the surface. That exposed rock is crucial for the chemical reactions that release minerals. Mountains, formed from plate tectonics, channel air upward, where it cools, condenses, and forms raindrops – which help extract carbon from the atmosphere.

Then there are the volcanoes. "Plate tectonics helps keep volcanism active for a long time. "If we didn't have volcanism sending back carbon dioxide into the atmosphere, then the planet could get very cold. It would freeze over."  Maintaining a warm climate is key for a habitable planet. But plate tectonics contributes other things as well. For example, research has suggested that erosion and weathering processes remove elements like copper, zinc, and phosphorous from rock and carry them to the sea. These elements are important nutrients for organisms like plankton. By moving continents around, plate tectonics could also have created diverse environments. Continents drift across Earth's surface, going from one climate zone to another. Without plate tectonics, Earth would not have its diverse geography, which provides a wide range of habitats. Plate tectonics is also responsible for hydrothermal vents on the ocean floor. Near a plate boundary, seawater can seep into cracks, where magma heats it to hundreds of degrees, ejecting the hot water back into the ocean. Hydrothermal vents, discovered in the late 1970s, are home to diverse ecosystems, and some scientists have suggested that similar vents gave rise to the first life on Earth.

The constant plate motions may even play a role in Earth's magnetic field. The field might have acted as a shield that prevented the solar wind from stripping away the atmosphere – another possible requirement for life. The engine that generates the magnetic field is a churning, molten core of iron. Those turbulent motions are due to a process called convection, in which the hotter liquid rises while the cooler stuff sinks. Whether or not convection takes place in Earth's core – and so whether it creates a magnetic field – depends on the planet's cooling rate. "If you have plate tectonics, then that tends to cool the interior faster than if you didn't have it," says Peter Driscoll, a geophysicist at the Carnegie Institution of Washington. A faster cooling rate allows for convection and, in turn, a magnetic field. Mars and Venus, for example, do not have plate tectonics. Nor do they have liquid cores, magnetic fields, or life – that we know of, anyway. But while plate tectonics is important for life on Earth today, what about extraterrestrial life?

Plate tectonics provides our planet’s global thermostat by recycling chemicals crucial to keeping the volume of carbon dioxide in our atmosphere relatively uniform, and thus it has been the single most important mechanism enabling liquid water to remain on Earth’s surface. Plate tectonics is the dominant force that causes changes in sea level, which, it turns out, are vital to the formation of minerals that keep the level of global carbon dioxide (and hence global temperature) in check. Without plate tectonics, Earth might look like a watery world, with only isolated volcanic islands dotting its surface. Or it might look even more inimical to life; without continents, we might by now have lost the most important ingredient for life, water, and in so doing come to resemble Venus. Plate tectonics makes possible one of Earth’s most potent defense systems: its magnetic field. 3

2. Improbable Planet, Hugh Ross, page 18
3. RARE EARTH Why Complex Life Is Uncommon in the Universe, page 193

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15 The crust of the earth fine tuned for life on Thu 6 Jul 2017 - 12:33


The crust of the earth fine tuned for life

For 30 years, the late-veneer hypothesis has been the dominant paradigm for understanding Earth’s early history, and our ultimate origins, a theory which suggests that all of our water, as well as several so-called “iron-loving” elements, were added to the Earth late in its formation by impacts with icy comets, meteorites and other passing objects, but the hypothesis may not be the only way of explaining the presence of certain elements in the Earth’s crust and mantle.   The Earth has an iron-rich core that accounts for about one-third of its total mass. Surrounding this core is a rocky mantle that accounts for most of the remaining two-thirds, with the thin crust of the Earth’s surface making up the rest. 4  According to the late-veneer hypothesis, most of the original iron-loving, or siderophile, elements” -- those elements such as gold, platinum, palladium and iridium that bond most readily with iron -- would have been drawn down to the core over tens of millions of years and thereby removed from the Earth’s crust and mantle. The amounts of siderophile elements that we see today, then, would have been supplied after the core was formed by later meteorite bombardment. This bombardment also would have brought in water, carbon and other materials essential for life, the oceans and the atmosphere.

To test the hypothesis,  experiments were conducted at Johnson Space Center in Houston and the National High Magnetic Field Laboratory in Tallahassee. A massive 880-ton press to expose samples of rock containing palladium was used -- a metal commonly used in catalytic converters -- to extremes of heat and temperature equal to those found more than 300 miles inside the Earth. The samples were then brought to the magnet lab, where a highly sensitive analytical tool known as an inductively coupled plasma mass spectrometer was used, to measure the distribution of palladium within the sample.

At the highest pressures and temperatures,  palladium was found in the same relative proportions between rock and metal as is observed in the natural world. The distribution of palladium and other siderophile elements in the Earth’s mantle can be explained by means other than millions of years of meteorite bombardment.

The authors of the paper write :
The late veneer might not be sufficient for explaining the highly siderophile elements  ( HSE )  concentrations in the primitive terrestrial mantle.  The late veneer is not required for any of the HSE concentrations in the primitive terrestrial mantle. 5

The potential ramifications of this research result are significant. They will have important consequences for geologists’ thinking about core formation, the core’s present relation to the mantle, and the supposed bombardment history of the early Earth. It should lead to rethinking the origins of life on Earth.

Earth is sulfur poor 6
especially in the sulfur compounds most hazardous to life. Too much sulfur on a planet is deadly to life. 7  The Martian mantle contains at least three to four times as much sulfur as does Earth’s and that volcanic gas emissions during the late stages of Mars’ history are ten to a hundred times richer in sulfur and sulfur compounds than similar emissions on Earth. Mars’ atmosphere was tenuous (just one bar or less) during the late stages of its history. Such a thin atmosphere implies that the sulfuric volcanic gases Mars retains are dominated by heavier sulfur dioxide rather than by hydrogen sulfide. This sulfur dioxide can penetrate any existing persistent water layer on Mars, making such water much too acidic for the origin of life or for the maintenance of anything other than the most extreme acidophilic bacterial species. Too much sulfur on a planet is deadly to life. Sulfur ranks as the tenth most abundant element in the universe.  In Earth’s crust, sulfur ranks as only the seventeenth most abundant element. Relative to iron and magnesium, sulfur is fifty times less abundant in Earth’s crust than it is in the universe.

The abundances of volatile elements in the Earth’s mantle have been attributed to the delivery of volatile-rich material after the main phase of accretion. However, no known meteorites could deliver the volatile elements, such as carbon, nitrogen, hydrogen, and sulfur, at the relative abundances observed for the silicate Earth. Alternatively, Earth could have acquired its volatile inventory during accretion and dierentiation, but the fate of volatile elements during core formation is known only for a limited set of conditions 8

The chlorine abundance of Earth: Implications for a habitable planet 1
Earth is uniquely endowed in many overlooked ways with a fine-tuned abundance of chlorine and its many compounds. Sodium chloride is known as table salt. All known organisms need such salt in small quantities. It is crucial for metabolism, for maintaining essential fluid and pH balances, and for electrical signaling in nervous systems. Too much or too little salt in the diet causes muscle cramps, dizziness, electrolyte disturbances, neurological malfunctions, and/or death. 2

For several decades, astronomers have recognized that Earth possesses a superabundance of chlorine. Compared to magnesium and iron, Earth’s crust contains about three times as much chlorine as the rest of the Milky Way Galaxy. Earth’s oceans add nearly an equal quantity of chlorine as exists in the crust. However, relative to the proportion of chlorine in chondritic meteorites (remnants of the raw material from which supposedly Earth formed) and in the Sun, Earth is depleted by a factor of ten. It is similarly depleted in bromine and iodine.  This “missing” chlorine has perplexed geophysicists and geochemists. Until now, the only proposed solution was that chlorine somehow was dragged into the deep interior of Earth by the metals that form Earth’s core. Chlorine is just one of Earth’s exceptional elemental abundances. Twenty must exist at fine-tuned abundance levels for advanced life to be possible.

Halogens or halogen elements are a group in the periodic table consisting of five chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). 3  

Implications of halogen depletion on Earth 1
It is interesting to speculate on the conditions if Chlorine concentration of Earth would be 10 times its present value. There would be dramatic consequences for our planet. Today, Chlorine (Cl) is strongly partitioned into the oceans. Assuming that the ocean/mantle partitioning of Cl is independent of total concentration, our modern oceans should be at or close to halite saturation. Salinities would be similar to the modern Dead Sea, where only extremely limited life forms (green algae and halophilic archaeobacteria) exist. Life would most probably not have appeared on Earth. A hypersaline ocean would also limit oxygenation, so that multicellular eukaryotic organisms would be much less likely to emerge. Even if life did appear on Earth, it would unlikely to be the complex panoply of organisms that we see today. A high-salinity ocean would also limit precipitation on the continents. The equilibrium vapor pressure over hypersaline water is 80% of typical seawater and observed vapor pressures over the Dead Sea are reduced by half. Under such conditions, precipitation would be dramatically reduced or eliminated, making migration of life to the continents nearly impossible. The reduced level of precipitation would also limit continental erosion and the return of nutrients to the ocean, further retarding conditions for life and evolution in the oceans. Without Cl removal from early giant impacts, it is likely that Earth would be a ‘halogen-poisoned’ planet, one that would not be supportive of life as we know it. Martian meteorites appear to be chlorine-rich and water-poor relative to Earth, with predicted enrichments of at least 300%. The scientific explanation is that  for a planetary system similar to our own, a necessary condition for life may be the removal of halogens by late, giant impacts. Or maybe such divergent abundance levels demonstrate that Earth clearly is not an accident of nature, but was carefully planned and designed to contain the right amount of halogens.

If there were more iron in the crust, iron exposed on the surface would consume the free oxygen in the atmosphere.


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