Fine-Tuning For Life On Earth
2004 June Update
by Hugh Ross
© 2004 Reasons To Believe
Evidence for the Fine-Tuning of the Galaxy-Sun-Earth-Moon System for Life Support
The environmental requirements for life to exist depend quite strongly on the life form in question. The conditions for primitive life to exist, for example, are not nearly so demanding as they are for advanced life. Also, it makes a big difference how active the life form is and how long it remains in its environment. On this basis there are six distinct zones or regions in which life can exist. In order of the broadest to the narrowest they are as follows:
for unicellular, low metabolism life that persists for only a brief time period
for unicellular, low metabolism life that persists for a long time period
for unicellular, high metabolism life that persists for a brief time period
for unicellular, high metabolism life that persists for a long time period
for advanced life that survives for just a brief time period
for advanced life that survives for a long time period
Complicating factors, however, are that unicellular, low metabolism life (extremophiles) typically is more easily subject to radiation damage and it has a low molecular repair rate. The origin of life problem is far more difficult for low metabolism life (H. James Cleaves II and John H. Chambers, “Extremophiles May Be Irrelevant to the Origin of Life,” Astrobiology, 4 (2004), pp. 1-9).
The following parameters of a planet, its planetary companions, its moon, its star, and its galaxy must have values falling within narrowly defined ranges for physical life of any kind to exist. References follow the list.
galaxy cluster type
if too rich: galaxy collisions and mergers would disrupt solar orbit
if too sparse: insufficient infusion of gas to sustain star formation for a long enough time
galaxy size
if too large: infusion of gas and stars would disturb sun’s orbit and ignite too many galactic eruptions
if too small: insufficient infusion of gas to sustain star formation for long enough time
galaxy type
if too elliptical: star formation would cease before sufficient heavy element build-up for life chemistry
if too irregular: radiation exposure on occasion would be too severe and heavy elements for life chemistry would not be available
galaxy mass distribution
if too much in the central bulge: life-supportable planet will be exposed to too much radiation
if too much in the spiral arms: life-supportable planet will be destabliized by the gravity and radiation from adjacent spiral arms
galaxy location
if too close to a rich galaxy cluster: galaxy would be gravitationally disrupted
if too close to very large galaxy(ies): galaxy would be gravitationally disrupted
if too far away from dwarf galaxies: insufficient infall of gas and dust to sustain ongoing star formation
decay rate of cold dark matter particles
if too small: too few dwarf spheroidal galaxies will form which prevents star formation from lasting long enough in large galaxies so that life-supportable planets become possible
if too great: too many dwarf spheroidal galaxies will form which will make the orbits of solar-type stars unstable over long time periods and lead to the generation of deadly radiation episodes
hypernovae eruptions
if too few not enough heavy element ashes present for the formation of rocky planets
if too many: relative abundances of heavy elements on rocky planets would be inappropriate for life; too many collision events in planetary system
if too soon: leads to a galaxy evolution history that would disturb the possibility of advanced life; not enough heavy element ashes present for the formation of rocky planets
if too late: leads to a galaxy evolution history that would disturb the possibility of advanced life; relative abundances of heavy elements on rocky planets would be inappropriate for life; too many collision events in planetary system
supernovae eruptions
if too close: life on the planet would be exterminated by radiation
if too far: not enough heavy element ashes would exist for the
formation of rocky planets
if too infrequent: not enough heavy element ashes present for the
formation of rocky planets
if too frequent: life on the planet would be exterminated
if too soon: heavy element ashes would be too dispersed for the
formation of rocky planets at an early enough time in cosmic history
if too late: life on the planet would be exterminated by radiation
white dwarf binaries
if too few: insufficient flourine would be produced for life chemistry to proceed
if too many: planetary orbits disrupted by stellar density; life on planet would be exterminated
if too soon: not enough heavy elements would be made for efficient
flourine production
if too late: flourine would be made too late for incorporation in protoplanet
proximity of solar nebula to a supernova eruption
if farther: insufficient heavy elements for life would be absorbed
if closer: nebula would be blown apart
timing of solar nebula formation relative to supernova eruption
if earlier: nebula would be blown apart
if later: nebula would not absorb enough heavy elements
number of stars in parent star birth aggregate
if too few: insufficient input of certain heavy elements into the solar
nebula
if too many: planetary orbits will be too radically disturbed
star formation history in parent star vicinity
if too much too soon: planetary orbits will be too radically disturbed
birth date of the star-planetary system
if too early: quantity of heavy elements will be too low for large rocky planets to form
if too late: star would not yet have reached stable burning phase; ratio of potassium-40, uranium-235 & 238, and thorium-232 to iron will be too low for long-lived plate tectonics to be sustained on a rocky planet
parent star distance from center of galaxy
if farther: quantity of heavy elements would be insufficient to make rocky planets; wrong abundances of silicon, sulfur, and magnesium relative to iron for appropriate planet core characteristics
if closer: galactic radiation would be too great; stellar density would disturb planetary orbits; wrong abundances of silicon, sulfur, and magnesium relative to iron for appropriate planet core characteristics
parent star distance from closest spiral arm
if too large: exposure to harmful radiation from galactic core would be too great
z-axis heights of star’s orbit
if more than one: tidal interactions would disrupt planetary orbit of life support planet
if less than one: heat produced would be insufficient for life
quantity of galactic dust
if too small: star and planet formation rate is inadequate; star and planet formation occurs too late; too much exposure to stellar ultraviolet radiation
if too large: blocked view of the Galaxy and of objects beyond the Galaxy; star and planet formation occurs too soon and at too high of a rate; too many collisions and orbit perturbations in the Galaxy and in the planetary system
number of stars in the planetary system
if more than one: tidal interactions would disrupt planetary orbit of life support planet
if less than one: heat produced would be insufficient for life
parent star age
if older: luminosity of star would change too quickly
if younger: luminosity of star would change too quickly
parent star mass
if greater: luminosity of star would change too quickly; star would burn too rapidly
if less: range of planet distances for life would be too narrow; tidal forces would disrupt the life planet’s rotational period; uv radiation would be inadequate for plants to make sugars and oxygen
parent star metallicity
if too small: insufficient heavy elements for life chemistry would exist
if too large: radioactivity would be too intense for life; life would be poisoned by heavy element concentrations
parent star color
if redder: photosynthetic response would be insufficient
if bluer: photosynthetic response would be insufficient
galactic tides
if too weak: too low of a comet ejection rate from giant planet region
if too strong too high of a comet ejection rate from giant planet region
H3+ production
if too small: simple molecules essential to planet formation and life chemistry will not form
if too large: planets will form at wrong time and place for life
flux of cosmic ray protons
if too small: inadequate cloud formation in planet’s troposphere
if too large: too much cloud formation in planet’s troposphere
solar wind
if too weak: too many cosmic ray protons reach planet’s troposphere causing too much cloud formation
if too strong: too few cosmic ray protons reach planet’s troposphere causing too little cloud formation
parent star luminosity relative to speciation
if increases too soon: runaway green house effect would develop
if increases too late: runaway glaciation would develop
surface gravity (escape velocity)
if stronger: planet’s atmosphere would retain too much ammonia and methane
if weaker: planet’s atmosphere would lose too much water
distance from parent star
if farther: planet would be too cool for a stable water cycle
if closer: planet would be too warm for a stable water cycle
This is just 30 of 154 of these parameters.
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