James Mackey

Constraints on a Chance Universe & The Anthropic

Principle

Physical Science 410James Mackey

James Mackey

ASSUMPTIONS

In all of the following discussion, it is assumed that life is carbon based.

While silicon based life has been discussed by a few individuals, the length of amino acid chains based on silicon are no more than a few hundred at the most - insufficient for the complexity required for life as we know it.

James Mackey

Additionally, boron has been advocated as an alternate basis for life; however, boron is relatively rare in the universe compared to carbon or silicon, which would make life even less probable than it is.

James Mackey

Boron 7.0 X 10-7 2 x 10-9

James Mackey

It is also assumed that physical laws, as best as we understand them, operate the same at all places and times in the evolution of the universe. No unknown physical laws can be postulated to explain currently unexplainable phenomena.

James Mackey

It is possible for something to be so improbable that even in the possible time span of the universe, 13.6 Billion years or about 4.3x1017 seconds, it will never happen.

Any argument from design is usually faith strengthening not

faith producing!

James Mackey

The Universe possesses narrowly defined

characteristics that permit the possibility of a suitable

habitat for humanity

The Anthropic Principle

James Mackey

“[There] is for me powerful evidence that there is something going on behind it all…It seems as though

somebody has fine-tuned nature’s numbers to make the Universe…The

impression of design is overwhelming.” The Cosmic Blueprint (New York,

Simon & Schuster, 1988) p203

Physicist Paul Davies

This principle has been recognized by numerous scientists in recent years, and has been increasingly publicly stated.

James Mackey

“The medieval theologian who gazed at the night sky through the eyes of Aristotle and saw angels moving the spheres in harmony has become the modern cosmologist who gazes at the same sky through the eyes of Einstein and sees the hand of God not in angels but in the constants of nature.......

Theoretical Physicist Tony Rothman in a popular article wrote:

James Mackey

....When confronted with the order and beauty of the universe and the strange coincidences of nature, it’s very tempting to take the leap of faith from science into religion. I am sure many physicists want to. I only wish they would admit it.”

"A ‘What You See is What You Beget ‘ Theory," Discover (May 1987) p99

James Mackey

“One would have to conclude either that the features of the universe

invoked in support of the Anthropic Principle are only coincidences or that the universe was indeed tailor made

for life. I will leave it to the theologians to ascertain the identity of

the tailor!”"The Anthropic Principle and the Structure of the Physical World," Nature 278 (1979) p53

Cosmologist Bernard Carr

Studied relativity and cosmology under Stephen Hawking at the Institute of Astronomy in Cambridge and at Caltech. Prof. of Math & Astronomy at Queen Mary College

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“The exquisite order displayed by our scientific understanding of the physical world calls for

the divine”Cosmos, Bios, and Theos, Margenau & Varghese, ed. (LaSalle Il,Open Court,1992) p52

Physicist Vera Kistiakowlsky, past president of Association of Women in Science

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“Amazing fine-tuning occurs in the laws that make this

[complexity] possible. Realization of the complexity

of what is accomplished makes it very difficult not to use the word ‘miraculous’

without taking a stand as to the ontological status of that

word”

George Ellis, a colleague of Stephen Hawking and Roger Penrose

”The Anthropic Principle : Laws and Environments,” in The Anthropic Principle, Bertola & Curi, ed. (New York, Cambridge University Press,1986) p30

James Mackey

• The fine tuning of the universe provides prima facie evidence of deistic design. • Take your choice: blind chance that requires a multitude of universes or design that requires only one… • Many scientists, when they admit their views, incline toward the theological or design argument.”Masks of the Universe (New York, Collier Books,1985) pp252,263 (emphasis mine)

Cosmologist Edward Harrison

• “Here is the cosmological proof of the existence of God – the design argument of Paley – updated and refurbished.

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“If we need an atheist for a debate, I go to the philosophy department. The physics department isn’t much use.””Cease Fire in the Laboratory,” Christianity Today, 3 April 1987, p18

Mathematical Physicist Robert Griffiths

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Planet hunters Geoff Marcy and Paul ButlerIn discussing the 33 (at that time) known planets discovered orbiting other star systems, the authors observe that most such systems are dominated by highly elliptically orbit giant planets.• "The predominance of elliptical orbits implies that planetary systems with circular orbits may be the exception rather than the norm. • Apparently our nine planets were just far enough apart and low enough in mass to avoid this chaos [referring to the tendency of giant planets to slingshot neighbors out of their systems]. •The nine planets do perturb one another, but not enough to cause close passages.

James Mackey

• If our solar system is unusual in its circular orbits, we humans would seem to be extraordinarily lucky to be here. • After all, the circular orbit of earth keeps solar heating nearly constant, minimizing temperature fluctuations. •Perhaps biological evolution would not have proceeded to intelligence if Earth's temperature were fluctuating widely.

•The planetary house of cards that we call our solar system may be one of the rare systems that remains just barely stable.

James Mackey

•It may be that Darwinian evolution towards complex organisms is enhanced by circular orbits. If so, we owe our existence to Earth's stable orbit."

Astronomy, March 2000, "Planets Beyond" by Geoff Marcy and Paul Butler, page 45

Despite the fact there are currently 1079 extrasolar planets, these conclusions are still perfectly applicable

James Mackey

• wed

James Mackey

In an article, “Exploring Our Universe and Others”, in Scientific American’s The Once and Future Cosmos, Martin Rees observed..

“Our universe could not have become structured if it were not expanding at a special rate. If the big bang had produced fewer density fluctuations, the universe would have remained dark, with no galaxies or stars… ..If our universe had more than three spatial dimensions, planets could not stay in orbits around stars.”

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continuing

“If gravity were much stronger, it would crush living organisms of human size and stars would be small and short-lived. If nuclear forces were a few percent weaker, only hydrogen would be stable: there would be no periodic table, no chemistry and no life.

Some would argue that this fine-tuning of the universe, which seems so providential, is nothing to be surprised about, because we could not exist otherwise.”

James Mackey

“The more the universe is comprehensible, the more it also seems pointless.” Steven Weinberg, The First Three Minutes

“The usual approach of science of constructing a mathematical model cannot answer the questions of why there should be a universe for the model to describe.Why does the universe go to all the bother of existing?”Stephen W Hawking

Always keep in mind, the opposite side of this viewpoint..

James Mackey

To serve as an introduction to the problem of the probability of intelligent life having arisen by purely chance means, we will look at a famous equation, The Drake Equation, and its implications for the existence of intelligent “communicating” life in our galaxy.

A highly recommended resource is Rare Earth, by Peter Ward and Donald Brownlee (Copernicus Books, Springer, Feb. 2000)

James Mackey

Originally postulated by astronomer Frank Drake in the 1950s to predict how many civilizations might exist in our galaxy in order to estimate the likelihood of our detecting radio signals from other technologically advanced civilizations.N = N* fs fp ne fi fc fl L

The Drake Equation

James Mackey

N* = stars in the Milky Way galaxy (or often R* = avg. rate of star formation in galaxy)fs = fraction of sun-like starsfp = fraction of stars with planetsne = number of planets in a star’s habitable zonefi = fraction of habitable planets where life does arisefc = fraction of planets inhabited by intelligent beingsfl = % of lifetime of a planets with a civilization capable of communicationL = length of time civilization survives

where

James Mackey

For example, Carl Sagan assumed that ALL stars had 10 planets. The results of these assumptions were an estimate of perhaps one million civilizations of creatures in our galaxy capable of interstellar communication at this time!

The initial assumptions made for the terms in this equation (whose values, except for N*, were very poorly known) were exceedingly optimistic.

Without doubt this is a totally unrealistic estimate!

James Mackey

Fairly common assumptions made by SETI supporters are listed as follows:N* - the number of stars in the Milky Way galaxy is probably fairly well known at 200 to 300 billion. This is normally based on measures of the mass of the galaxy, and the mass of an average star (assumed ~ 1 M0). The actual average size star in the Milky Way is an M class star about 50% of Sun’s mass

James Mackey

fp - the fraction of stars that have planets around them - Current estimates range from 20% to 100%.

ne - number of planets per star that are capable of sustaining life

For each star that has a planetary system, how many planets are capable of sustaining life? Estimates range from 1 to 2.

James Mackey

fl - the fraction of planets in ne where life evolves:On what percentage of the planets that are capable of sustaining life does life actually evolve? Current estimates are 100% (where life can evolve it will) . fi - the fraction of fl where intelligent life evolves

On the planets where life does evolve, what percentage evolves intelligent life? Estimates are 50 – 100 %

James Mackey

What percentage of intelligent life forms have the means and the desire to communicate? Estimates are 10 % to 20%

fc - the fraction of fi that communicate

L - fraction of a planet's life during which - communicating civilizations may survive For each civilization that does communicate, for what fraction of the planet's life does the civilization survive? This is the most vague question.

James Mackey

How long can our civilization survive without destroying ourselves as some predict or will we beat our problems and survive indefinitely? If doomsday came today this figure would be 10-9. If we survive for 10,000 more years this figure would be 10-6.

Using the Earth as our model, the expected lifetime of our Solar System is approximately 10 billion years. Already communication by radio has been for less than 100 years.

James Mackey

N = 200 billion (1/4) 2 (1/2) (1/10) (1/10) (1/100 million)

N ~ 50 technological civilizations in just the Milky Way Galaxy!

Since there are billions of galaxies, the assumption is then that there are billions of technological civilizations capable of radio communication in

the universe!

N = N* fs fp ne fi fc L

James Mackey

The Delimma!

Where are they?

(Known as the Fermi paradox)

If there are/have been highly technological and long-lived civilizations in our Galaxy, why haven’t we seen them or their effects?

James Mackey

RARE EARTH EQUATION

N = N* fpm fp ne ng fi fc fl fm fj fme

Considering some of the terms in this equation, let’s try to arrive at a reasonable estimate based on current discoveries and understanding. If we rewrite the equation in more modern terms, and rename the modified Drake Equation as the:

James Mackey

N* = stars in the Milky Wayfp = fraction of stars which have planets similar to earthfpm = fraction of metal-rich planetsne = planets in a star’s AHZng = stars in a Galactic HZfi = fraction of planets where life (of any kind) arisesfc = fraction of planets where complex

metazoans arise

where

James Mackey

fl = % of planet’s lifetime that is marked by Complex metazoansfm = fraction of planets with a single large moonfj = fraction of solar systems with Jupiter- sized planetsfme = fraction of planets with a critically low number of mass extinction events.

James Mackey

Animal Habitable Zones (AHZ) - regions about the parent star where complex life can arise. This is more restrictive than the simple HZ.

Habitable Zones (HZ) - regions about a parent star where conditions are conducive to the development & survival life of any form:

i.e. temps that allow liquid water

Some Definitions

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What makes a planet habitable?• Located at an optimal distance from

the Sun for liquid water to exist.

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• Large enough for geological activity to release & retain water and atmosphere.

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Galactic Habitable Zones (GHZ) regions in the galaxy where solar systems and planets can safely form without appreciable danger from catastrophic events in the galaxy.

James Mackey

N* - the number of planets in the Milky Way galaxy is probable fairly well known at about 400 billion. This is normally based on measures of the mass of the galaxy, and the mass of an average star.

James Mackey

fp - the fraction of stars that have planets similar to Earth

Based on the most recent successes in finding extrasolar planets orbiting distant stars, it would seem that the value of the first ½ of this factor would be rather high. Optimists placing its value at 1.0 and pessimists at 0.1 (about 10% of surveyed stars reveal the presence of planets).A reasonable value for this alone would be 0.5.

However the “similar to Earth” is vastly more restrictive, of 1771 planets (3/14/2014) ~ 15 are similar IN SIZE to Earth… prob ~ 0.008

James Mackey

Exoplanet mass as function of semi-major axisRed lines locate the Earth at 1 AU and mass 0.00314 MJ

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These can be ruled out because their HZ (habitable zones - where surface temperatures would be conducive to life) are uninhabitable for other reasons… increased radiation exposures increased tidal effects

likelihood of no moon

The most common stars in our galaxy are M stars, which are fainter than the sun and probably about 100 times more numerous.

Not one of the Earth size planets has an orbit even close to 1 AU

James Mackey

To be in its HZ, a planet must be so close to these small stars that tidal effects would lock these stars into synchronous rotation with one side always facing the star and the other side always permanently dark. A real life example would be the planet Mercury. If the stars are much more massive than the sun, their stable lifetimes are only a few billion years - inadequate time for the development of advanced life and the evolution of an ideal atmosphere.

James Mackey

The evidence for the importance of metal-rich stars comes indirectly from the planet search program.Spectroscopic studies of the stars about which we have been able to identify planets shows that they, like our own sun, are rich in metals. Yet general surveys of stars in our neighborhood show that the metal content of our sun is abnormally large.

fpm - the fraction of metal-rich planets

James Mackey

Sun’s metallicity is 0

Based on Extrasolar planets as of 3/14/2014

James Mackey

The elements so important to life as we know it are exceedingly rare in the universe – in a sense human beings are trace elements in the universe. A very conservative estimate of the fraction of stars that are sufficiently metal-rich like the sun would be ~ 0.5

It would seem to be impossible for complex life to develop on a planet formed in the nebula of a metal-poor star.

James Mackey

The fraction of planets in a star’s habitable zone can be reasonably estimated from our own solar system. If we take the sun’s HZ to be 1.0 AU 0.3 AU in a solar system ranging out to more than 40 AU, we can estimate the fraction as 1.3/40 or ~ 0.027.

ne - the fraction of planets in a star’s AHZ

However, as we will see our solar system is not common, so a smaller value is likely

James Mackey

Of the 1771 planets discovered about other stars, only 3 are close to Earth’s mass (smallest is PSR-1257 12b ~ME /50) with KOI-52c at 2/3 ME and Kepler 42 c ~ ME though none of these few orbit within 20% of 1 AU

James Mackey

a b c d e

Mercury a = .00017

Venus b = .00256

Earth c = .00315

Mars d = .00034

Jupiter e = 1.0

Solar system masses in terms of Jupiter mass

Our solar system

6 x MEI would weigh more than 900 pounds

James Mackey

AN EXTRASOLAR AN EXTRASOLAR SYSTEMSYSTEM

Unlike our solar system, the Upsilon Andromedea System has large planets orbiting close to the star.

The orbits of the inner planets in our solar system compared to those of the Upsilon Andromedea System

225 Me 600 Me 1200 Me

James Mackey

It is more difficult to estimate the Galactic Habitable Zone’s percentage for our solar system. Based purely on our physical location in the Milky Way galaxy, one could assign a fraction of ~0.2. If the solar system were much closer toward the galactic center, the probability of dangerous radiation from supernova or magnetar, etc. events would escalate dramatically.

ng - stars in a galactic HZ

James Mackey

James Mackey

If we were much further away from the center, we would be near the edge of the solar nebula as the solar system developed and the concentration of heavy elements (heavier than helium) would be too low.Heavy metals are necessary for dense metallic cores which are necessary for a planetary magnetic field and all of its protective effects and for the radiation heat stemming from the planet’s interior that helps drive plate tectonics

James Mackey

Again, it should be observed that there is convincing evidence that GHZs may be drastically reduced as our knowledge of more catastrophic events, such as merging neutron stars, and better estimates for the frequencies of such events improves.

James Mackey

Based on current ideas, the probability of simple forms of life existing on a planet is very high. Very simple life is considered ubiquitous by many. This is based on recent findings that have demonstrated that life can exist under conditions previously thought to make life impossible.

fI - fraction of planets where life arises

James Mackey

Such organisms have been found in sea ice, in highly acidic pools, in deep sea hydrothermal vents, in environments exceeding 80 C, and at depths exceeding 2.7 km below ground in basaltic rock.

Microorganisms that can survive under extreme conditions have been dubbed “extremophiles”.

James Mackey

Since life CAN exist under such conditions, many astrobiologists believe that life WILL exist under similar conditions which are found many places in our solar system. If we accept these ideas, we would assign a fraction of at least 0.5 for the probability that simple life would exist on a life-capable planet.

James Mackey

The fraction of planets where complex metazoans (multicellular organisms) arise is a very different quantity than fi.

In contrast to the high probability assigned to fi, the probability for fc based on current understanding would be extremely small.

fc - fraction of planets with complex metazoans

James Mackey

While simple organisms are able to survive rapidly changing environments and fairly large extinction events, multicellular organisms are much more susceptible to extinction from significant climatic changes (unless they have progressed to the point of extensive diversity). The history of the Earth shows evidence of several extinction events in the past

James Mackey

Based on the data presented by David Raup, the probability of extinction for species (the so called ‘kill curve’), is essentially negligible over a 100,000 year times scale,

perhaps 5% to 10% over a million year scale,

approximately 30% over a 10 million year time frame, and rises to over 70% on the 100 million year level.

“kill” curve

James Mackey

In the book Extinction: Bad Genes or Bad Luck, published in 1990, he estimated that extinctions of a level sufficient to exterminate all life should have an average spacing of 2 billion years.

James Mackey

The well publicized 65 million year old impact event at Chicxulub that killed the dinosaurs is an example of an extinction event that killed many species, but not all. Had the impacting object been only twice the estimated size, it could possibly have sterilized the Earth.Estimated value ~ 0.001

If life has existed for 4 billion years on Earth, then we may be pushing our luck.

The significance of such extinctions will be discussed again under fme

James Mackey

fl - fraction of planet lifetime with complex metazoans

This is a very controversial value again depending upon how optimistic one is about the nature of complex life.

Based on the Earth alone, which may NOT be a good example, one could estimate 6x108 animal life/4.5x109 life of Earth for ~ 0.13.

This value leans strongly towards the highly optimistic side.

James Mackey

Based on the available information from the 1771 or so planetary systems discovered as of the present, one would assign a rather large fraction to this number, realizing that as techniques improve and develop that enable astronomers to identify smaller rocky planets orbiting other stars, this number may have to be re-evaluated. Chosen value 0.5

fj - fraction of systems with Jupiter-like planet

James Mackey

If, however, Jupiter-like means a Jupiter sized planet orbiting close to 5 AU, this drops the probability significantly – only 2 of the 1096 extrasolar planetary systems has a single Jupiter size planet in an approx. 5 AU orbit (ups And e @5.24 Au, Mass =1.06 MJ; and HD

154345 b @4.2 AU, Mass = 1.0 MJ)

2/1771 = 0.0011

James Mackey

Computer simulations by Fred Rasio and Eric Ford (MIT), among others, show that Earthlike planets are probably unable to survive the gravitational tug-of-war in a system with two (or more) massive, Jupiterlike giants.

They would be slung out of the solar system or sent careening into the central star.

Why is such a Jupiter like planet Important?

James Mackey

Computer simulations by George Wetherill (Carnegie Institution of Washington) indicate that Jupiter acts as the solar system's gravitational vacuum cleaner, efficiently thinning out the population of hazardous comets that venture into Earth-crossing orbits. (Wetherill died in 2006)

On the other hand, systems with no giant planets at all might also have dire consequences for life-bearing planets.

James Mackey

Without a Jupiter the current impact rate of comets would be 1,000 times higher, says Wetherill* , with truly catastrophic collisions (like the one 65 million years ago) happening about once every 100,000 years. *1997, he received the National Medal of Science, the nation's highest scientific award. This would surely frustrate any slow evolutionary progress from simple life forms to higher intelligences.

James Mackey

fm - fraction of planets with Earth-like moon

With our sample size of one (only our own solar system), only 1 planet of 9 has the requisite large and close (but not too close!) moon. Chose a value of 0.08

However, it is well argued that this is a highly optimistic number based on considerations of the Earth-moon system.

James Mackey

The current accepted explanation for the existence of our Moon is the Impact Model, in which it is assumed that early in Earth’s history, it was struck by a large object in a glancing impact that blew off larges amounts of the Earth’s outer layers. This debris ultimately reformed into our Moon.This is based primarily on the similarity between the elements found on the moon and those in the Earth’s surface layers along with the dearth of heavy metals on the Moon

James Mackey

Dynamical studies by Jacques Laskar and Philip Robutel (Bureau des Longitudes, Paris) have shown that rocky, Earthlike planets show chaotic variations in orbital tilt that could lead to drastic climate changes.Fortunately, Earth's chaotic tendencies are damped by tidal interaction with the Moon.

James Mackey

“Laskar's work has thus been fundamental in helping to reveal the chaotic nature of the solar system. In the course of such studies, Laskar developed a new tool based on frequency analysis to discriminate regular orbits from chaotic ones that is today widely used for a variety of problems in conservative dynamics. He and his collaborators have also made important contributions to the study of planetary spin axis dynamics. They expanded on previous works to show that the evolution of the Martian spin axis is chaotic and that the motion of Earth's spin axis would be chaotic without the Moon. Laskar and his student, Correia, have also demonstrated that the current retrograde spin of Venus could be obtained from almost any initial condition when the perturbations of Venus's orbit by the other planets, and plausible models for its atmospheric tides and core-mantle interactions, are accounted for. “ (emphasis mine)

Jacques Laskar: 2006 AAS Brouwer Award Winner

James Mackey

This would cause extreme variations in the patterns of the seasons. According to one analysis of planet formation, a world like Earth has only about a 1 in 12 chance of ending up with a nice, mild axial tilt that is safely stabilized by a large moon.

Without a relatively large satellite, Earth might have experienced variations in axial tilt similar to those of Mars, possibly as large as 20 ° to 60 °.

James Mackey

• Contributes to stability of the spin axis of the Earth•Existence of plate tectonics to recycle CO2------ and O2 in the atmosphere. This has stopped -- atmospheric loss or a runaway greenhouse effect•Significant volcanic activity to release

atmospheric gases•Production of continental land masses

The existence of large single moon (a very low probability system based on the impact formation model of the origin of the Moon).

James Mackey

Examination of the fossil record reveals that extinction events have occurred several times in the discernable history of the Earth.There are several extinction mechanisms that can create planetary disasters (some have occurred and some, to the best of our knowledge, have not). A partial list would be:

fme - fraction of planets with low extinction rates

James Mackey

Some sources of Extinction Events

Changing a planet's spin rate

Moving out of the AHZ (animal habitable zone)

Changing energy output of the star

Nearby Supernova

Impact of a comet or asteroid

Large gamma ray sources

Cosmic ray jets and gamma ray explosions

Catastrophic climactic change:Icehouse and Runaway Greenhouse Effect

James Mackey

Six archaeologically identified extinction events in Earth’s history

since the Cambrian.

James Mackey

• The 24 hr spin rate of the Earth is anomalous when compared to the other planets in our solar system except Mars. • The Jovians tend to spin much faster, while Mercury and Venus spin more slowly

• slowly enough that they are 'tidally locked' to the sun as they orbit, with one side always facing the sun or with the length of a solar day being longer than an orbital year.

Changing a planet's spin rate

James Mackey

Many astronomers believe that many of the planets have undergone serious rotation shifts in their history, due to chance encounters with large masses or general chaotic tendencies, e.g. Venus, NeptuneSuch shifts would definitely be detrimental to any form of evolving organisms.

James Mackey

Liquid water is a requirement for complex animal life, and consequently any shift in orbital radius would move the Earth out of the liquid water zone with deleterious effects on any animal life. Such perturbations are believed to be fairly common in solar systems with either close orbiting massive planets or Jupiter-like planets with highly elliptical orbits.

Moving out of the AHZ (animal habitable zone)

James Mackey

Any significant change in the energy of the parent star of a habitable planet would likely be disastrous to animal life or its prospects for evolution. In addition to dramatic changes that would occur around an unstable star, even stable main sequence stars such as the sun experience a gradual increase in energy output as Hydrogen is consumed in the core and converted to Helium.

Changing energy output of the star

James Mackey

On the Earth, the temperature has been maintained at a relatively constant value by a gradual reduction in greenhouse gases as the energy output of the sun has increased.What causes this reduction? probably plate tectonics

James Mackey

Astronomer's calculations have estimated that a supernova occurring within 10 parsecs (32.6 light years) would produce energy fluxes of Electromagnetic and charged particle radiation sufficient to destroy Earth's ozone layer in 300 years or less.

Nearby Supernova

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VELA Supernova Remnant

About 800 light-yrs

James Mackey

Based on the number of stars within 30 light years of Earth and the rates of supernova explosion among stars, it is highly likely that one or more such events have occurred within 30 lys of Earth during the last 500 million years. The probability of such explosions would be much higher closer to the galactic center.

James Mackey

All planetary systems are full of debris left over from planetary formation. In the early years of solar system life, all planets were heavily bombarded by this debris making the development of life impossible until the bombardment frequency decreases.

Impact of a comet or asteroid

James Mackey

The following chart illustrates the rate of meteor impacts at the top of Earth's atmosphere as a function of size:

Mass Extinctions and the Rare Earth Model

However, even at the present, the probability of such impacts is not zero. approximately 65 million years ago a large impact killed off the dinosaurs and many other species living near the end of the Mesozoic Era.

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Chixulub

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According to the Earth Impact Database there are 182 verified impact craters on Earthhttp://www.passc.net/EarthImpactDatabase

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Tunguska meteorite exploded about 300 m above the uninhabited Siberian countryside in 1908.

Because it was so isolated, it was several years before any outsiders observed the site. The picture seen next is the first picture taken at the site almost 10 years later.

Impacts are still occurring!

James Mackey

James Mackey

View of the Impact Site after more than 20 years

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Peekskill Meteorite

Peekskill, N.Y. 10/9/92: Car trunk, floor, pierced by meteorite.

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November 30th, 1954 Sylacauga, Alabama. Elizabeth Anne

Hodges

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•Chelyabinsk meteorite 2/15/2013

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Gamma ray satellites have detected numerous sudden bursts of gamma radiation from various galaxies. While the origin and mechanism for these bursts is not established, they would be extremely lethal to life on any nearby planetary systems.

Large gamma ray sources

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1998 event

20,000 yrs ago while Mammoths, Mastodons, etc. roamed North America - a distant neutron star in constellation Aquila (SGR 1900+14, ~45000 light-yrs) underwent an unknown type of cataclysm..

A violent explosion propelled a sphere of hard radiation out at the speed of light.

For 20,000 years this sphere expanded until on Aug. 27, 1998 it hit the Earth over the Pacific Ocean and then passed on through space.

James Mackey

For about 5 minutes Earth was bombarded by a high level of gamma rays & X-rays.Even after 20,000 lyrs the energy level sent radiation sensors on 7 satellites to max. or off scale. Two of these satellites shut down to avoid burnout.

The radiation penetrated to within 30 miles from the Earth’s surface. The first time ever such an event from outside our solar system had a measurable effect on the atmosphere of Earth.

James Mackey

In recent years astronomers have postulated that the merger or collapse of neutron stars would generate massive cosmic rays jets and gamma ray bursts potentially lethal to nearby galaxies. Gamma-ray Bursts: These events are the most powerful in the Universe. Over a few seconds a gamma-ray bust can release most energy than our Sun will during its entire lifetime

Cosmic ray jets and gamma ray explosions

James Mackey

Annis says that giant gamma-ray bursts (GRBs) occur in every galaxy, including ours, from time to time. Such explosions, he says, emit so much radiation that they probably wipe out almost all the life in the whole galaxy. If so, intelligent life forms might not usually have time to evolve to the space-faring stage before being exterminated.

One of the latest proposals (1999) has been offered by James Annis, an astrophysicist at Fermilab near Chicago, Illinois.

He calculates a rate of such events as about 1 burst every few hundred million years.

James Mackey

Should such an event occur in the Milky Way, and the energy from such an event strike the Earth, it would kill all life on our planet, even if the event were at the galactic center.

It is also argued that such events would have been much more likely in the earlier history of the universe.

James Mackey

Catastrophic climactic change:Icehouse and Runaway

Greenhouse EffectUnder certain conditions, radical climactic changes can cause mass extinction. Major glaciations and greenhouse heating are examples, with both depending upon the amount of CO2 or other greenhouse gases. These are the killing mechanisms produced by reduction or increase in stellar output or by alteration of the planet's orbit.

James Mackey

Are considerations of such catastrophic events and possible extinctions reasonable?

There is some geological & paleontological evidence for a number of "mass" extinctions in Earth's past. An abbreviated list of these events and their approximate date are given as follows:

James Mackey

The bombardment extinctions : 4.6 to 3.8 billion years ago

This period of intense bombardment of all the planets from residual solar system debris would have sterilized the Earth's surface at least several times.

James Mackey

The advent of oxygen - : 2.5 to 2.2 billion years

The rise of oxygen in the Earth's atmosphere would certainly have doomed most anaerobic bacterial species existing on Earth at that time. Beyond this general idea, there is no other information known.

James Mackey

Beyond geological evidence of massive glaciation, even as far as the equator, we know little of these events, whether there were many such glaciations and corresponding extinctions, or only a few is not known. It is probable that in such extensive ice ages, even the oceans were frozen to significant depths. There is some fossil evidence of extinctions of stromatolites and other planktonic organisms.

"Snowball Earth" : 750 to 600 million years ago

James Mackey

ICE-ALBEDO FEEDBACK: For any imposed cooling (or warming), the resulting higher (or) lower albedo will cause further cooling (or warming). Thus, ice advance is self-stabilizing.RUNAWAY ICE ALBEDO: If ice lines close to within ~30° of the equator, the ice albedo feedback becomes unstoppable and ice quickly covers the tropics.

PLANETARY ALBEDO: The fraction of incoming radiation that is reflected back to space.[sea water ~0.1; bare land ~0.3; sea ice ~0.6; fresh snow ~0.9]

James Mackey

Earth’s ice ages end as oceans freeze over and volcanoes release CO2 into the atmosphere

Snowball Earth and the CO2 cycle

James Mackey

Much work has been done on this hypothesis in the last 5 years, and a great deal of supporting evidence has been presented. Interestingly is a connection between the effects of a “Snowball earth” and the Cambrian “explosion” occurring after the end of the ice coverage.For much more detail about this idea, see the article “Snowball earth” listed on my 410 website, and if you search “Snowball Earth” on YouTube or the web you will several BBC documentaries on the topic.

James Mackey

This is the most enigmatic and important of the extinction events. During this brief time in which a large number of phyla apparently disappeared from the Earth, we also see the appearance of all the animal phyla still existing on Earth. Since this event, no new phyla have appeared.

The Cambrian mass extinctions : 560 to 500 million years ago

James Mackey

James Mackey

There are a number of extinctions suggested by scientists around this period, however the cause of the major Cambrian extinctions and others of that time period remains an enigma. The explosion of animal life since this event suggest that this extinction may have had very positive benefits for more complex organisms.

James Mackey

During this period (Paleozoic era) these two major mass extinctions apparently destroyed the majority of sea species. The causes of these extinctions are not known, though a number of suggestions (anoxia, temperature change, seal level change, etc.) have been advanced, as well as a possible impact event.

The Ordovician & Devonian extinctions : 440 & 370 million years

James Mackey

On most measures of extinction (% of existing species, genera, or families eliminated worldwide) this is the most catastrophic of all mass extinctions that have occurred on the Earth. Specialists in compiling extinction records point out that more than 50 % of marine families died out, and anywhere from 80 to 90 % of all species went extinct. During this event, the majority of the plant and animal life on Earth disappeared.

The Permo-Triassic event : 250 million years ago

James Mackey

The end-Permian mass extinction event ranks as the most devastating to terrestrial faunas in the history of the Earth.

Marking the end of the great Paleozoic era, it saw to the death of about 95% of marine species and land families. This is the most extensive extinction event ever, the closest that metazoans have come to being exterminated in the 600 million years since they first evolved in the Cambrian radiation.

James Mackey

The following diagram shows the number of organism species present on Earth since the Cambrian radiation. The mass extinctions can be seen when this plot has sharp declines. There have been 5 major mass extinctions, of which it can be seen that the drop of families at the Permo-Triassic boundary has been the greatest.

James Mackey

This event has been extensively studied, and currently it is believed that a combination of things contributed to its severity.

The most important of these was a short time outgassing of CO2 from the ocean floors during unusually severe volcanic eruptions about 250 million years ago. The sudden release of large quantities of CO2 directly killed many marine organisms by carbon dioxide poisoning.

James Mackey

The largest eruption of the 20th century, Mt Pinatubo is tiny compared to the Siberian Traps but caused a 0.5 degree drop in global temps the year after it erupted. The largest eruption in historic memory occurred on Iceland in 1783-84 spewing out 12 km3 of lava onto the island (the Siberian Traps erupted about 3 million km3). The poisonous gases given out are recorded as killing most of the islands crops and foliage and lowering global temps by about 1 degree. If events this size can affect temperatures and large areas then the effects of a large scale flood basalt are incomprehensible.

Could such events cause or add to a mass extinction event?

James Mackey

The sudden increase in greenhouse gases produced a large increase in the amount of heat trapped by the atmosphere.

This produced a heat spike of 5 to 10 degrees persisting for 10 to 100 thousand years which killed off large amounts of terrestrial life.

James Mackey

Currently this event is believed to be a double or triple cause event spread over nearly 100,000 years. A CO2 increase caused by the silurian traps volcanic activity, a possible impact added to the problem of ~ 5 degree temp. increase, causing an ocean temp increase that released huge amounts of Methane (a strong greenhouse gas) producing a addnt 5 degree for a total of 10 degree increase – sufficient to kill most organisms on land or sea.

James Mackey

This was a significant event eliminating about 50 % of genera, especially destructive to marine life. This was thought by many to have been an impact event, but there is currently no identified impact site associated with this event. The Manicouagan Crater in Quebec is about 100 km in diameter and of the correct size, however it is currently dated at 214 million years, which is too early. There are environmental changes associated with this period, but nothing of a severity to produce the observed effect. Its probable cause remains unknown.

The end-Triassic mass extinction : 202 million years

James Mackey

This mass extinction event, resulting in the death of the dinosaurs, is one of the most well known extinction events. A team of scientists directed by Luis Alvarez proposed that this was an impact event occurring about 65 million years ago. This was based on evidence of large iridium concentrations found at several sites around the world, and an association with high iridium concentrations in many meteorites.

The Cretaceous/Tertiary boundary event : 65 million years

James Mackey

Based on this, and other evidence, it is widely accepted that an approximately 10 km diameter comet or asteroid struck the ocean off the coast of Yucatan blasting a crater between 180 to 300 km wide and precipitating a chain of events exterminating the dinosaurs and over 50% of other species on Earth at that time. The impact, in addition to shock waves and massive fires, produced major and long lasting climactic changes.

James Mackey

Based on all of this information one would assign a very small fraction to fme since the evidence indicates that significant mass extinctions are not uncommon in a planet’s history. A value of 0.000001 will be assumed, i.e. a one in a million chance!

James Mackey

If we assume ~ 400 billion stars in the Milky Way galaxy, and assume 4 planets per star, then the likelihood of finding a planet with all of the requisite requirements for complex life to develop, evolve, and survive would be.....

(4x1011)*.003*.01*.027*.2*.5*.001*.13*.08*.005*1x10-6 or about 0.0000000017 =1.7x10-9 in our Milky Way galaxy.

Based on extremely optimistic values for the various factors in the Rare Earth Equation.

James Mackey

Even assuming ~ 1012 galaxies and and 4 planets per star yields

6.7 x 103 planets out of 1.6x1024

planets or 1 part of 4,000,000,000,000,000,000,000

for the probability of the correct system arising by chance!What reasonable conclusion should one make?

James Mackey

Recall that the estimates made by supporters of SETI are much more optimistic and generous......yielding much larger numbers..

One such estimate gave 100,000 radio communicating civilizations currently active in the Milky Way galaxy.

James Mackey

That figure of 100,000 would mean there is one radio-emitting civilization right now per 4 million stars -- reason enough to tune in on the heavens and start hunting for them. If they were scattered at random throughout the Milky Way, the nearest one would probably be about 500 light-years from us. A two-way conversation would require a time equal to a good part of recorded human history, but a one-way broadcast might be audible.

James Mackey

However, 50 years of SETI have failed to find anything, even though radio telescope apertures, receiver techniques, and computational abilities have improved enormously since the early 1960s.

Granted, the "parameter space" of possible radio signals (the possible frequencies, locations on the sky, signal strengths, on-off duty cycles, etc.) is vastly larger than the tiny bit that has yet been searched.

James Mackey

But we have discovered, at least, that our galaxy is not teeming with powerful alien transmitters continuously broadcasting near the 21-centimeter line. No one could say this in 1961!

James Mackey

According to many life scientists, it is naive to suppose that the evolution on another planet should necessarily result in intelligence as we know it.

In his bestseller Wonderful Life, paleontologist Stephen Jay Gould (Harvard University) asserts, "We probably owe our own existence to . . . good fortune. Homo sapiens is an entity, not a tendency."

James Mackey

“..if we could rewind the tape of biological evolution on Earth and start over, it is impossible that humans would again appear on the scene. We are the result of too long a chain of chance flukes and happenstance.”

Evolution is unpredictable and chaotic. Gould has pointed out again and again that..

James Mackey

Our notion that the increase of biological diversity is necessarily accompanied by an increase of mental capabilities may be dead wrong. If some recently evolved animals are bigger and smarter than any earlier ones, that could just be a fluke. Human levels of planning and technology may be even more so. There are no firm indications that increased intelligence is an inevitable product of biological evolution.

Gould notes that there is no overall pattern in evolution, no preferred direction.

James Mackey

Contrary to popular belief, the fact that intelligence has arisen once tells us absolutely nothing about how often it happens -- for the simple reason that we ourselves are the one case! We are a self-selected sample. Even if intelligent life is so improbable that it appears just a single time in one remote corner of the universe, we will necessarily find ourselves right there in that corner observing it, because we are it.

James Mackey

"Physicists still tend to think more deterministically than biologists," wrote Mayr in the May 1996 issue of The Planetary Report.

"They tend to say that if life has originated somewhere, it will also develop intelligence in due time. The biologist, on the other hand, is impressed by the improbability of such a development."

James Mackey

Based on almost any reasonable criteria that one could devise, the existence of intelligent life on Earth

and perhaps in the Universe as well

is an ENIGMA....

without GOD

James Mackey

Based on political events of the last few years, this is a good

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