Transcript Evidence for Design: Earth & Solar System

Evidence for design: earth and solar system
1. Introduction – two conflicting viewpoints
2. Factors that make the earth habitable
3. Quantifying – is the earth one in a million,
one in a trillion?
How exceptional is the Earth?
The Copernican principle vs
the anthropic coincidences
The Copernican principle
"However we are not able to make cosmological models without some
admixture of ideology. In the earliest cosmologies, man placed himself
in a commanding position at the centre of the universe. Since the time of
Copernicus we have been steadily demoted to a medium sized planet
going round a medium sized star on the outer edge of a fairly
average galaxy, which is itself simply one of a local group of galaxies.
Indeed we are now so democratic that we would not claim that our
position in space is specially distinguished in any way. We shall,
following Bondi (1960), call this assumption the Copernican principle.”
Hawking, S.W. and Ellis, G.F.R., The Large Scale Structure of SpaceTime, Cambridge University Press, Cambridge, p. 134, 1973.
How exceptional is the Earth?
“Most of the Universe is too cold, too hot, too dense, too
vacuous, too dark, too bright, or not composed of the right
elements to support life. … of all the known celestial
bodies, Earth is unique in both its physical properties and
its proven ability to sustain life….”
“From the biased viewpoint of Earthlings, however, it does
appear that Earth is quite a charmed planet.”
P. Ward and D. Brownlee, Rare Earth, 2000, p 37.
How exceptional is the Earth?
“The Earth is a precious jewel in space possessing a rare
combination of qualities that happen to make it almost
perfect for life. … Personally, I no longer have doubts.
The evidence points towards the Earth being a very
peculiar place; perhaps the only highly-habitable planet we
will ever find.
David Waltham, Lucky Planet, 2013, p 1,2.
Probability of another habitable planet
~ 1011 planets in our galaxy
1
1012
1
1
1
1
1
1
x
x
x
x
x
100
100
100
100
100
100
( )( )( )( )( )( ) =
If 6 finely-tuned factors exist, then we have no right to expect another
earth-like planet in the entire galaxy!!
~ 1022 planets in the observable universe
1
1
1
1
1
1
1
1
1
1
1
(100 )x (100 )x(100 )x (100 )x(100 )x (100 )x(100 )x (100 )x (100 )x (100 )x(100 ) =
1
1022
If 11 finely-tuned factors exist, then we have no right to expect another
earth-like planet in the entire observable universe!!
The probability of a planet
suitable for supporting complex life
(Hugh Ross)
The probability of a planet
suitable for supporting complex life
The probability of a planet
suitable for supporting complex life
Earth’s orbit around the sun
Freezing and
boiling of
water set
conservative
limits
Earth’s orbit around the sun
“One of Earth’s most basic life-supporting
attributes is indeed its location, its seemingly
ideal distance from the sun.”
Rare Earth, p 16.
“Astrobiologists James Kasting and his
colleagues … estimated in 1993 that the width
of the CHZ is from 0.95 to 1.15 AU.”
(1 AU = distance from the Earth to the Sun)
Rare Earth, p 19.
Orbital characteristics of extra solar planets
The Privileged Planet
pg 95
Earth’s tilt about spin axis
“Although our viewpoint
is certainly biased, our
planet’s tilt axis seems
to be “just right”.
Rare Earth, p 224.
+/- 1 deg for several thousand yrs
larger tilt - temperature extremes
smaller tilt - rain not distributed
Privileged Planet, p 5.
Earth’s tilt about spin axis
“Constancy of the tilt angle is a factor that provides long-term
stability of the Earth’s temperature. If the polar tilt axis had
undergone wide deviations from its present value, Earth’s
climate would have been much less hospitable…..
Rare Earth, p 224.
These results show that the situation of the Earth is very
peculiar. The common status for all the terrestrial planets is to
have experienced very large scale chaotic behavior for their
obliquity, which in the case of the Earth and in the absence of
the Moon, may have prevented the appearance of evoluted
forms of life. We owe our exceptional climate stability to an
exceptional event - the presence of the moon.
Jacques Laskar, quoted in Rare Earth p 224.
The Moon
Just right size and distance from the Earth to
-stabilize tilt
-slow Earth’s rate of rotation
“our moon is somewhat of a freak because of its large size in
comparison to its parent planet.”
Rare Earth p 222.
“Without the moon it is … likely that no birds, redwoods, whales,
trilobites, or other advanced life would ever have graced Earth. …
Although there are dozens of moons in the solar system, the
familiar ghostly white moon that illuminates our night sky is
highly unusual, and its presence played a surprisingly important
role …”
Rare Earth p 222.
The Moon
“We owe our present climate stability to an exceptional event:
the presence of the Moon.”
Jacques Laskar, quoted in Rare Earth p 224.
Produced by a “just right” collision?
“to produce such a massive moon, the impacting body had to be
the right size, it had to impact the right point on the Earth, and
the impact had to have occurred at just the right time in the
Earth’s growth process.”
Rare Earth p 231.
The Moon
itability requires a stabilizing large satellite, like our Moon?
small it would happen twice. Could instead
catastrophic destruction of both bodies as shown below. “a very freakish event”
Simulation of lunar formation event
Typical: catastrophic destruction
orlds collide:ofFinal
stages of planet formation
both bodies
vie of this simulated collision of two planetesimals can be
nd in the Links portion of the textbook web site
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Probability from data
In a recent survey of debris disks nearby newly forming stars, 1 star
in 400 showed a hot dense debris disk that likely was the result of a
large collision.
Gorlova et al, The Astrophysical Journal 2007, 670, 516
Just right collision to form a moon that is large and close like ours,
must be << 1/400
Earth’s size
“Earth’s size is just about right - not too small that its
gravity was too weak to hold the atmosphere and not so
large that its atmosphere would hold too much atmosphere
including harmful gases …
F. Press and R. Siever, Earth, 1986, p 4. Quoted in
Nature’s Destiny p 92
Earth’s size is also important for a sufficiently strong magnetic field
Earth’s atmosphere
“… differs greatly from those of other terrestrial planets,
which range from essentially no atmosphere (Mercury) to a
CO2 atmosphere a hundred times denser (Venus) and a CO2
atmosphere a hundred times less dense (Mars).”
Ward and Brownlee, Rare Earth, p 52.
“It is difficult to see how the actual concentrations of these
gases could be very different from what they are in any
atmosphere supporting a carbon-based biosphere.”
M. Denton, Nature’s Destiny, p 55.
Earth’s atmosphere
Oxygen is essential for the energy generating reactions of
life, its reactivity is fine-tuned.
“Oxygen is basically a very
dangerous reactive substance and is
highly toxic to life at levels above
those normally encountered in
nature. … Oxygen is fit because its
chemical reactivity is attenuated at
ambient temperatures (below 50 oC),
allowing living systems to utilize this
awesome energy source in a
controlled and efficient manner.”
M. Denton, Nature’s Destiny 123,
125
min. pressure is
required to retain
liquid water
M. Denton, Nature’s Destiny
Earth’s atmosphere
Oxygen is essential for the energy generating reactions of
life, its reactivity is fine-tuned.
“This key reaction (oxidation of hydrocarbons) provides
many times more energy than any of the multitude of
alternative energy-generating reactions. … Could our
atmosphere contain more oxygen and still support life? No!
… the current percentage of oxygen in the atmosphere, 21
%, is close to the upper limit of safety for life at ambient
temperatures.”
M. Denton, Nature’s Destiny, p 120.
“the present oxygen level is at a point where risk and benefit
nicely balance.”
J. E. Lovelock, Gaia, 1987, p 71.
Earth’s atmosphere
“Oxygen is … the only element in the most appropriate
physical state, with a satisfactory solubility in water and
with desirable combinations of kinetic and thermodynamic
properties.”
A. Naqui, B. Chance, E. Cadenas Ann. Rev. of
Biochemistry 1986, 55, 137.
“It turns out that the solubility of oxygen is just sufficient
to allow organisms to utilize oxidation as a means of energy
production. … Between 0 and 50 oC in an atmosphere
containing about 21% oxygen, sufficient oxygen dissolves in
water to support oxidative metabolism”
M. Denton, Nature’s Destiny p 123, 126.
Earth’s atmosphere
“ It
is surely a coincidence of
enormous significance that several
essential conditions are satisfied in this
one tiny region of space of all possible
atmospheres.
Fire is possible, but
runaway combustion is avoided, oxygen
toxicity is relatively low, the solubility
of oxygen is sufficient to support
oxidative metabolism, and the density is
sufficiently low that the work of
breathing during strenuous exercise is
not prohibitive.”
min. pressure is
required to retain
liquid water
M. Denton, Nature’s Destiny p 128.
M. Denton, Nature’s Destiny
Earth’s elemental composition
Earth’s elemental composition
number mass
46.6% O
35% Fe
27.7% Si
30% O
8.1% Al
15% Si
5.0% Fe
13% Mg
3.6% Ca
2.4% Ni
2.8% Na
1.1% Ca
2.1% Mg
1.1% Al
Relative abundance of elements in the sun
Earth’s elemental composition
If too much water - all land is covered
0.1% water
“with even twice as much water, Earth would have ended up
as an abyssal planet entirely covered with deep blue water a true “water world” …”
Ward and Brownlee Rare Earth, p 47
“thus the planet’s remarkable mixture of land and oceans is
a balancing act. … This fortuitous combination may be
the most important factor that ultimately made life possible.
Ward and Brownlee Rare Earth, p 53.
If too little water - global temperatures would fluctuate too
much
Ward and Brownlee Rare Earth, p 264
Earth’s elemental composition
“Discovering how Earth acquired its supply of water is one
of the most critical concerns of the new field of astrobiology.
As we pointed out in an earlier chapter, water was not
abundant in the inner regions of the solar system when
planets formed. There was far more water in the outer
regions of the solar system than among the inner planets.
Where did our water come from?”
Still subject of debate, comets - heavy bombardment?
Ward and Brownlee Rare Earth, p 261.
Earth’s elemental composition
“An enigma of Earth’s formation is its composition and particular
location in the solar system…. A grand paradox of terrestrial planets
is that if they form close enough to the star to be in its habitable
zone, they typically end up with very little water and a dearth of
primary life-forming elements such as nitrogen and oxygen,
compared with bodies that formed in the outer solar system. In
other words, the planets that are in the right place, and thus have
warm surfaces, contain only minor amounts of the ingredients
necessary for life”.
“the origin of biogenic elements is a subject of considerable
speculation.”
from “asteroidal and cometary debris” ?
Rare Earth, p 45, 48.
Earth’s elemental composition
If too much water - all land is covered
If too much carbon, CO2 will cause runaway
greenhouse effect
0.05 % carbon
Earth’s elemental composition
If too much water - all land is covered
If too much carbon, CO2 will cause runaway
greenhouse effect
Enough Fe in core for a magnetic field
35 % iron
Earth’s elemental composition
If too much water - all land is covered
If too much carbon, CO2 will cause runaway
greenhouse effect
Enough Fe in core for a sufficient magnetic field
Enough radioactive metals for long-lived furnace
(uranium, thorium, potassium)
Just right composition for thin crust - enables plate
tectonics
Earth’s elemental composition
Enough metal for iron- and nickel-rich liquid core
Enough radioactive elements for long period of radioactive heating
(uranium, thorium, potassium)
Composition allowed very thin outer crust of low density - plate tectonics
“The thickness, and stability of the Earth’s core, mantle, and crust could have
come about only through the fortuitous assemblage of the correct elemental
building blocks”.
Ward and Brownlee, Rare Earth, p 51.
Earth’s elemental composition
“… the Earth’s interior is a delicately balanced heat engine fueled by
radioactivity … were it running too slowly … the continents might not
have evolved to their present form… Iron may never have melted and
sunk to the liquid core, and the magnetic field would never have
developed…. If there had been more radioactive fuel, and therefore a
faster running engine, volcanic dust would have blotted out the Sun, the
atmosphere would have been oppressively dense, and the surface would
have been racked by daily earthquakes and volcanic explosions.”
F. Press and R. Siever, Earth, 1986, p 4.
radioactive elements:
uranium 238 – 0.0004% (by mass)
thorium 232 – 0.0012%
potassium 40 – 0.0028%
Earth’s cycles
Hydrological cycle
Plate tectonics (earth, but nowhere else in solar system)
Ensure the physical and chemical constancy of our environment
-regulates greenhouse gases
-builds continents
-global thermostat (5 C - 40 C)
-magnetic field (T difference across core, convection cells)
“Like two gigantic cogwheels engineered to fit perfectly together, these
two great cycles have turned together in perfect unison … ensuring the
continual turnover and essential recycling of the vital elements of life.”
M. Denton, Nature’s Destiny, p 84.
Design aspects
orbital distance
orbital eccentricity
tilt angle
moon (size and proximity)
planet size
amount of atmosphere
amount of O2 in atmosphere
amount of CO2 in atmosphere
amount of water
amount of radioactive elements
amount of Fe and nickel
crustal composition
plate tectonics
The sun
The sun
(G-type, main sequence)
Just-right size:
bigger - hotter, burns faster, more erratic
smaller - cooler, habitable zone closer in, its
gravity would slow a planet’s
rotation too much
5% of stars in our galaxy are similar to our sun
80% are red dwarf stars (highly unlikely to support habitable planets)
Hertzsprung-Russel StarData.png
main sequence stars:
fusing hydrogen to
helium
The sun
Temp range of stars:
The sun:
30,000 oC - 1000 oC
5500 oC
M stars: Habitable Zone = tidally locked
M-type stars - thousand or million times more active ( flares) than sun
Jupiter and outer planets
Jupiter: just-right size and location:
Jupiter and outer planets
Jupiter: just-right size and location:
“without a large planet positioned precisely where Jupiter is, the
earth would have been struck a thousand times more frequently in
the past by comets and meteors and other interplanetary debris.”
“…we wouldn’t be around to study the solar system.”
G. W. Wetherill, Nature 1995, 373: 470; Discover 1993, p 15.
However, if Jupiter were too large, or too close, it would perturb
Earth’s orbit.
Jupiter and outer planets
Gas giants: Jupiter, Saturn, Uranus, Neptune
Orbits:
-on the same horizontal plane
-almost circular (avg eccentricity = 0.06 Priv. Planet p 96)
Slight deviations
would be catastrophic
for Earth
Our position in the Milky Way
Some ways in which certain locations in our Galaxy might have low
probabilities of planet formation or might be hazardous for life.
Our position in the Milky Way
Our position in the Milky Way
Moreover, the Sun's circular orbit about the galactic center is just right;
through a combination of factors it manages to keep out of the way of
the Galaxy's dangerous spiral arms. Our solar system is also far enough
away from the galactic center to not have to worry about disruptive
gravitational forces or too much radiation. …
More than 95 percent of stars in the Galaxy, says Gonzalez, wouldn't be
able to support habitable planets simply because their rotation is not
synchronized with the rotation of the galaxy's spiral arms. Add all the
other factors involved in keeping a solar system habitable, and it seems
that the odds of finding another solar system in a Galactic Habitable
Zone are close to impossible.
Galactic Habitable Zones, Astrobiology Magazine, May 18, 2001
Recent headlines or articles:
Two Billion Earthlike Planets in the Milky Way: How Many Will Prove to
Support Advanced Life?
Found: An Earthlike Planet, at Last
Earth-like planets pile up
Time
Nature.com
Sept 2010
Newsblog Aug 19, 2011
What does it take to make a habitable planet?
Nature 470, 5, 2011
What does it take to make a habitable planet?
Nature 470, 5, 2011
What does it take to make a habitable planet?
Nature 470, 5, 2011
What does it take to make a habitable planet?
~ 1011 planets in our galaxy
1
1012
1
1
1
1
1
1
x
x
x
x
x
100
100
100
100
100
100
( )( )( )( )( )( ) =
If 6 finely-tuned factors exist, then we have no right to expect another
earth-like planet in the entire galaxy!!
1
8
1
1
1
1
1
1
1
1
1
1
(200 ) x (100 ) x (100 ) x ( 2 ) x ( 10 ) x (104 ) x (100 ) x (100 ) x (100 ) x (100 ) x (100 ) x (100 ) x
earthG-type, galactic rocky
sized
main habitable
in
sequence zone
Habitable
star
(Icarus 152
185-200,
Zone
(Nature 470,
27-29, 2011)
2001; the
physics
arXiv blog)
circular
orbit
moon
(large,
close)
….
magnetic
Jupiter
plate
right
right
field(liqui
(right
tectonics right
amount
amount
d iron
location,
atmosphere
of
of water
core)
(Venus and radioactive circular
Mars)
elements orbit)
What does it take to make a habitable planet?
Isaiah 45:18
For this is what the LORD says - he who created the
heavens, he is God; he who fashioned and made the earth, he
founded it; he did not create it to be empty, but formed it
to be inhabited - he says: I am the LORD and there is no
other.
Recent discoveries of exoplanets
Method 1 (HARPS): Doppler spectroscopy – shift in a star’s spectral
lines as it wobbles around a mutual center of gravity with a planet
sampling bias – only able to detect large planets (but getting better)
Method 2 (Kepler): change in brightness as a planet passes in front of its
star
-orbital size from period of transit and mass of star
-radius of planet from drop in brightness and size of star
-atmosphere if close enough
Kepler is sensitive enough to detect earth-sized planets in
earth-like orbits
“How is it that hardly any major religion has looked at science and
concluded, “This is better than we thought! The Universe is much bigger
than our prophets said, grander, more subtle, more elegant?” Instead they
say, “No, no, no! My god is a little god, and I want him to stay that way.” A
religion, old or new, that stressed the magnificence of the Universe as
revealed by modern science might be able to draw forth reserves of
reverence and awe hardly tapped by the conventional faiths.”
Carl Sagan, Pale Blue Dot: A Vision of the Human Future in Space
methods
Recent discoveries of exoplanets
Kepler’s region of study
Recent discoveries of exoplanets
Kepler’s region of study
Recent discoveries of exo-planets
Kepler:
-sensitive enough to detect earth-sized planets in earth-like orbits
-designed for 3-4 yr mission – could confirm an earth-like orbit
-fixed field of view – 150,000 stars in Cygnus and Lyra constellations
-unable to determine planet mass and composition
“The goal of Kepler is to find an Earth-sized planet in the habitable zone [where
life could arise], with a one-year orbit. Proving that such an object really is a
planet is very difficult [with current technology]. When we find what looks to be
a habitable Earth, we’ll have to use a validation process, rather than a
confirmation process. We’re going to have to make statistical arguments.”
Bill Cochran, Kepler Co-Investigator
Recent discoveries of exoplanets
Kepler discoveries:
-1100 planets candidates (Feb 2011)
-40 candidates smaller than twice earth’s size
-5 estimated to be within star’s habitable zone
Kepler 4-10, 11
Kepler10b:
-mass from
ground based
measurements
-4.6 x earth’s
mass
-1.4 x earth’s
radius
-0.84 day orbit
-Kepler’s first
rocky planet
Kepler11:
“five planets
packed into a
region that’s
smaller than
mercury’s orbit
around the sun”
Kepler16
Kepler16: binary star system, planet 16b confirmed to
orbit both stars
http://www.nasa.gov/multimedia/videogallery/index.html?col
lection_id=14471&media_id=111565131
Kepler18
10% larger than the sun, 97% of sun’s
mass
HD 85512b and Gliese 581d
Both likely to be
tidally locked!
DiscoveryNews
HD 85512b and Gliese 581d
Both likely to be
tidally locked!
DiscoveryNews