[Home] [Site map] [Updates] [Projects] [Contents; 1. Introduction; 2. Philosophy (1), (2), (3), (4) & (5); 3. Religion (1) & (2); 4. History (1), (2) & (3); 5. Science; 6. Environment (1) & (3); 7. Origin of life (1), (2) & (3); 8. Cell & Molecular (1), (2) & (3); 9. Mechanisms (1), (2) & (3); 10. Fossil Record; 11. `Fact' of Evolution; 12. Plants; 13. Animals; 14. Man (1) & (2); 15. Social; 16. Conclusion; Notes; Bibliography A-C, D-F, G-I, J-M, N-S, T-Z]
"PROBLEMS OF EVOLUTION": 6. ENVIRONMENT (2) 1. Fitness of the environment for life 2. Universe's fitness for life 1. Physics 1. Constants 2. Laws 1. Maupertuis' principle of least action 2. Chemistry 1. Elements 1. Carbon 2. Water 3. Size of 4. Galaxy (Milky Way) 1. Special 1. Among the oldest 2. The right shape 2. Galactic Habitable Zone (GHZ) 3. Solar System's fitness for life 1. Unique? 2. Sun 3. Planets 1. Circular orbits 2. Jupiters 3. Number of Earth-like planets in the Universe 4. Asteroids 4. Earth's fitness for life
"PROBLEMS OF EVOLUTION": 6. ENVIRONMENT (2) 1. Fitness of the environment for life 2. Universe's fitness for life A leading evolutionist, the late John Maynard Smith, admitted that "The simplest interpretation" for the fact that "many substances such as water have precisely those properties required if life is to exist" is "that the Universe was designed by a creator who intended that intelligent life should evolve" (Maynard Smith & Szathmary, 1996, p.107)! Indeed, "the laws governing our Universe appear to be so finely tuned for our existence" that there are only "two possible explanations ... either the Universe was designed specifically for us by a creator or there is a multitude of universes" and "only in those universes in which the properties ... are right for life would any life arise to notice any fine-tuning" (Chown, 1998). But instead of accepting this simplest explanation on the normal scientific principle of Ockham's Razor, according to which science should prefer explanations with the least number of assumptions (Tegmark, 2003; Davies, 1983, p.173; Davies, 1994, p.53; Davies, 1995, pp.79-80; Koons, 1997; Barber, 1993; Gardner, 2001; Holder, 1993, p.171), creation is just ruled out in advance on the grounds that "This interpretation lies outside science" (Maynard Smith & Szathmary, 1996, p.107). In other words, evolutionists are less concerned with an explanation being true than that it conforms to their personal materialist/naturalist philosophy! [top] 1. Physics Evolutionist Richard Dawkins argues for a "Universal Darwinism" in which he claims "that all life, everywhere in the universe, would turn out to have evolved by Darwinian means" (Dawkins, 1989b, p.322; Dawkins, 1983, p.403; Dawkins, 1996c, p.202ff). But in doing so, Dawkins is relying on the fact that the universe must be just right for Darwinian mechanisms to work. As Dawkins himself stated in his book "The Blind Watchmaker," the USA edition of which was subtitled "Why the Evidence of Evolution Reveals a Universe Without Design," "the only watchmaker in nature is the blind forces of physics, albeit deployed in a very special way" (Dawkins, 1986, p.5. My emphasis). Dawkins is implicitly making the point that the cosmologist John Leslie makes explicitly, that "not just any universe would be one in which Darwinian evolution would work," for example, "If a tiny reduction in the early cosmic expansion speed would have made everything recollapse within a fraction of a second while a tiny increase would quickly have yielded a universe far too dilute for stars to form, then such changes would (presumably) have been disastrous to Evolution's prospects" (Leslie, 1989, p.108). Physicist Paul Davies notes that "As our understanding of the basic processes of nature advances, so it becomes increasingly clear that what we call scientific laws are not just any old laws, but are remarkably special in a number of intriguing ways." (Davies, 1994, p.45). The late Stephen Jay Gould cited approvingly the argument of "Henry Ward Beecher, America's premier pulpiteer during Darwin's century," that "Design by wholesale is grander than design by retail" (Gould, 1991, p.400). Now whether or not it would be "grander," the point is that "Design by wholesale" would still be design! So even if all the other problems of evolution were solved, evolutionists would still have the problem of explaining the ultimate "Design by wholesale." As Darwin's contemporary, theologian Robert L. Dabney, realised, "if the theory of the evolutionist were all conceded, the argument from designed adaptation would not be abolished but only removed one step backward. ... Who planned and adjusted these wondrous powers of development?" (Dabney, 1878, p.37; Livingstone, 1987, p.125) [top] 1. ConstantsA tweak of God's knobs: New research appears to put humankind back at the centre of the universe, The Guardian, Johnjoe McFadden, September 13, 2005. ... In The Hitchhikers Guide to the Galaxy the Deep Thought computer announced that the answer to the ultimate question of life, the universe and everything was 42. Contemporary physicists are finding themselves just as frustrated as the hyperintelligent race of beings who built Deep Thought after discovering that the ultimate answer to their questions turns out to be a set of meaningless numbers. Many scientists conclude that the answers are contingent on biology and the facts of life. Imagine if the values of one or two of nature's fundamental constants were slightly different, say the strengths of forces that hold atoms together. One consequence might be that the Earth's oceans would regularly freeze. Water - essential for life - is unique in being lighter as a solid than as a liquid. So ice sheets float and form an insulating layer that stops the deeper waters freezing. If water was more conventional then the primordial oceans would never have stayed liquid for long enough for life to evolve. But then of course we would not be here to ponder our good fortune. This is the point of the anthropic principle, which starts from the fact of our existence and then argues backwards to claim that the precise properties of the universe that emerged from the big bang had to be those that made the eventual emergence of humans inevitable. The unique properties of water depend on an exquisite level of fine tuning of the fundamental constants. So why are these constants just right? Because if they weren't we wouldn't be here. There are lots of other fine tunings. Carbon, also essential for life, is made in stars by the fusion of three helium atoms. It is only due to an extraordinary "coincidence" in the resonant energies of helium, beryllium and carbon that stars make lots of carbon. Change the resonant energy by just 0.0001% and no carbon. Proponents of the anthropic principle claim it is pointless looking for theoretical explanations for the precise values of the fundamental constants; they are what they are because if they weren't we wouldn't be here. Opponents claim that the principle betrays a lack of imagination for assuming that other forms of life wouldn't be possible. But this is harder to sustain when considering some of the more cosmic consequences of tweaking the constants. If the weak force that binds atomic nuclei had been just a bit weaker, all hydrogen would have turned to helium without making any of the heavier elements. If the strong force had been a bit stronger, the universe would not even have had any atoms. New research is making even the sceptics grudgingly accept the anthropic principle. A paper by Mario Livio and Martin Rees, the astronomer royal, explores the value of the cosmological constant, a measure of how much energy is contained in empty space. Without this value being tweaked to an extraordinary level of precision, the universe would be filled only with huge black holes or entirely empty of stars. But who's doing the tweaking? Another reason scientists are wary is that it seems to reverse the Copernican revolution and place humankind at the centre of the universe. Even worse, it could allow creationists to bring the G word back into science: a God to tweak all those knobs to make life possible. But if God is needed to tweak the universe's knobs then who was there to tweak God's knobs? Physicists such as Martin Rees and Stephen Hawking prefer another scenario whereby an infinite number of universes exist, each with different values of the fundamental constants. In just a few of them the constants have taken on the right values for the creation of stars, life and evolution. ..." [top]2. Laws 1. Maupertuis' principle of least action"All the great metaphysical `Arguments' which use aspects of the laws of Nature-the Design Argument, the Ontological Argument, the Cosmological Argument-are just arguments; that is they begin from some assumptions, and deduce a conclusion. That conclusion is worth no more and no less than the initial assumptions, and can never be independent of them. They are not disproved by counter-arguments of the Kantian sort, any more than they are proved by those of the Newtonians. Although, for example, the form of Newton's laws of motion excludes any teleological notions, and replaces final causes by initial causes and algorithms for computing the subsequent states which follow from them, one should not draw far-reaching metaphysical conclusions from this image. In 1748 Maupertuis showed that Newton's laws of motion could be derived by the application of a teleological principle. It is possible to define a mathematical quantity, the action, which involves the product of mass, velocity, and distance travelled by bodies. Maupertuis's Principle, which we now call the Principle of Least Action, was that `If there occurs some change in Nature, the amount of action necessary for this change must be as small as possible.'" (Barrow J.D. "The World Within the World," Oxford University Press: New York NY, 1988, pp.80-81. Emphasis original)"Maupertuis's Principle, which we now call the Principle of Least Action, was that `If there occurs some change in Nature, the amount of action necessary for this change must be as small as possible.' This elegant idea turns out to be equivalent to the Newtonian laws of motion (although it is more powerful in the sense that it can be used to derive the equations of motion in other areas of physics once the appropriate action is identified). But, unlike the formulation of Newton, it is teleological. It says that, of all the paths that could be taken by a body moving from A to B, it actually takes that path for which the associated action is a minimum. This path is therefore determined by both the initial and the final states. Maupertuis attached great metaphysical significance to this result, regarding it as a 'proof of existence of Him who governs the world'. Formerly, arguments of the sort that we lived in the `best of all possible worlds' were open to the objection that we did not know any other worlds with which to draw such a comparison, but Maupertuis claimed that the other worlds were those in which motion occurred with non- minimal action. Our world was optimal in this well-defined sense, and moreover there existed a teleological aspect to the laws of Nature ..." (Barrow J.D. "The World Within the World," Oxford University Press: New York NY, 1988, p.81)[top] 2. Chemistry 1. Elements"Astronomers have identified what could be one of the earliest stars formed in the Universe, Nature magazine reports. Scientists think the cosmic relic may consist largely of elements created in the hot gas that existed just 15 minutes after the Big Bang. The star has a very low iron content - an elemental signature that suggests it is made of fresh material that was never processed by an earlier star. But other such signatures are unusual for a very primitive stellar object. It's remarkable but apparently what we see in these stars is the tiny amount of lithium produced in the Big Bang Timothy Beers [said] ... The new star HE0107- 5240 and another star called HE1327-2326 have the lowest abundances of heavy elements known. About 13.7 billion years ago, the Universe consisted of a hot gas with a temperature high enough to produce the lightest chemical elements. The rapid expansion after the first 15 minutes of the Universe put an end to the synthesis of new elements by the process of nucleosynthesis. However, after about 200 million years, the Universe grew large enough for haloes of dark matter to form and this triggered the formation of the first stars. ... These first stars synthesised all the heavier elements, from carbon to uranium, that form the basis of solid planets and organic life. Over the past 25 years, astronomers have been scouring the skies for stars with a composition that reflects these first stellar objects. The new star HE1327-2326 has an unexpectedly low abundance of the metal lithium and an unexpectedly high amount of the metal strontium for such a primitive star. "The lithium problem is immediately more troublesome. Many of the primitive stars studied in the past have lithium abundances that are very similar to one another," said co-author Timothy Beers ... "It's remarkable but apparently what we see in these stars is the tiny amount of lithium produced in the Big Bang." "Yet in this star, it's not at that perfect value, so we're a bit confused as to why that might be." ( "Relic star poses cosmic puzzles," BBC, 14 April, 2005). [ [top]1. Carbon"From 1953 onward, Willy Fowler and I have always been intrigued by the remarkable relation of the 7.65 Mev energy level in the nucleus of 12C to the 7.12 Mev level in 16O. If you wanted to produce carbon and oxygen in roughly equal quantities by stellar nucleosynthesis, these are the two levels you would have to fix, and your fixing would have to be just where these levels are actually found to be. Another put-up job? Following the above argument, I am inclined to think so. 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." (Hoyle F., "The Universe: Past and Present Reflections," Annual Review of Astronomy and Astrophysics, Vol. 20, 1982, pp.1-35, p.16) [top]2. Water This sounds like yet another fine-tuned parameter of water!:"Planets were formed from sticky ice grown from interstellar gas, say researchers ... The mystery of how dust specks in the early solar system stuck together to form planets has been solved by US researchers. Dr Jim Cowin and team ...report[ed] ... The researchers have managed to test for the first time just how well the galaxy's ubiquitous icy dust grains stick together, the very first small steps towards building planets around stars. "Water is a complicated substance," says Cowin. The researchers made water ice from water vapour in a laboratory under low-pressure, frigid, spacelike conditions. When grown at low pressure on a surface from water vapor at -233°C, water ice is nothing like what we chip off our windshields here on Earth, says Colvin. Instead, water molecules do two very strange things. First, they create a loose, fluffy, crushable ice structure that takes up twice the volume of normal ice. That spacious ice structure works like a shock absorber during collisions with other particles and possibly keeps dust particles from eternally bouncing off each other and never getting together. The second thing is that water molecules might be aligning themselves electrically, molecule-by-molecule as they settle down to make ice, so that the entire dust particle they coat has a north and south electrical pole, like a tiny magnet. ..." (O'Hanlon L., Cool answer to planet formation," ABC/Discovery News, 21 March 2005) [top]3. Size of"In recent years, however, a much more important argument has gradually surfaced against this anthropocentric world view. It is concerned with the tremendous amount of time it took after the Big Bang for humans to appear and to rise to any degree of significance on this planet. In the words of Bertrand Russell, `If the purpose of the Cosmos is to evolve mind, we must regard it as rather incompetent in having produced so little in such a long time.' [Russell B., `Religion and Science,' Oxford University Press: New York, 1968, p 216] However, with the tremendous increase in our cosmological understanding in recent years, a devastating anthropocentric rebuttal to this objection has suddenly made itself known: carbon- based life forms intrinsically require a universe as big and as old as our own in order to exist, because they are physiologically dependent on an adequate supply of carbon and other heavy elements, which weren't in existence in any appreciable quantities immediately following the Big Bang. Instead, they had to be `cooked' for billions of years in the interiors of dying red giant stars, and then subsequently released into the cosmos via colossal supernova explosions. When this striking fact is taken into consideration (along with the other temporal stipulations on planetary and organic evolution), it turns out that ours is the youngest possible universe that could have evolved carbon-based life forms through natural evolutionary pathways. [Barrow J.D. & Tipler F.J., `The Anthropic Cosmological Principle,' Oxford University Press: New York, 1986, p.385] Furthermore, given the fact that the universe is expanding, ours is also the smallest possible universe that could have evolved life through these same natural pathways. [Ibid] Thus, it would take a universe as big and as old as the present one just to evolve a single race of intelligent beings. Accordingly, as long as we accept the stipulation that life must evolve through natural evolutionary pathways, the vast size and age of our universe is perfectly compatible with an anthropocentric world view." (Corey M.A., "Back to Darwin: The Scientific Case for Deistic Evolution," University Press of America: Lanham MD, 1994, pp.368-369. Emphasis original)"The Size of The Universe ... In several other places we have used the fact of the Universe's size as a striking example of how the Weak Anthropic Principle connects aspects of the Universe that appear, at first sight, totally unrelated. The meaning of the Universe's large size has provided a focus of attention for philosophers over the centuries. We find a typical discussion in Paradise Lost where Milton evokes Adam's dilemma: why should the Universe serve the Earth with such a vast number of stars ... if life and mind are important, or unique, why does their appearance on a single minor planet require a further 1022 stars as a supporting cast? ... However, the modern picture of the expanding universe that we have just introduced renders such a line of argument, at best, irrelevant to the question of Design. ... The size of the observable universe, ... is inextricably bound-up with its age ... These relations display explicitly the connection between the size, mass and age of an expanding universe. If our Universe were to contain just a single galaxy like the Milky Way, containing 1011 stars, instead of 1012 such galaxies, we might regard this a sensible cosmic economy with little consequence for life. But, a universe of mass 1011 [solar masses] ... would ... have expanded for only about a month. No observers could have evolved to witness such an economy-sized universe. ... A minimum time is necessary to evolve astronomers by natural evolutionary pathways and stars require billions of years ... to transform primordial hydrogen and helium into the heavier elements of which astronomers are principally constructed. Thus, only in a universe that is sufficiently mature, and hence sufficiently large, can `observers' evolve. In answer to Adam's question we would have to respond that the vastness of `Heaven's wide circuit' is necessary for his existence on Earth. (Barrow J.D. & Tipler F.J., "The Anthropic Cosmological Principle," [1986], Oxford University Press: Oxford UK, 1996, reprint, pp.384-385. Emphasis original)"All This for Us. Hawking also rejects the anthropic principle, which is the observation that the universe has all the necessary and narrowly defined characteristics to make human life possible. Hawking apparently finds it impossible to believe that "this whole 'vast construction [the universe] exists simply for our sake." [Hawking S.W., "A Brief History of Time," [1988] Bantam: New York, 1991, reprint, p.126] As support for his incredulity, he says that "there does not seem to be any need for all those other galaxies, nor for the universe to be so uniform and similar in every direction on the large scale." [Ibid, p.133] But, he ignores a growing body of research. The uniformity, homogeneity, and mass density of the universe all must be precisely as they are for human life to be possible at any time in the universe's history [Ross H.N., "The Fingerprint of God," [1989], Promise Publishing Co: Orange CA, Second edition, 1991, pp.124-128]" (Ross H.N., "The Creator and the Cosmos: How the Greatest Scientific Discoveries of the Century Reveal God," [1993], NavPress: Colorado Springs CO, 1994, Third printing, p.86)"The mass density determines how efficiently nuclear fusion operates in the cosmos. The mass density we measure translates into about a hundred-billion-trillion stars for the presently observable universe. As table 14.1 indicates (page 112), if the mass density is too great, too much deuterium (an isotope of hydrogen with one proton and one neutron in the nucleus) is made in the first few minutes of the universe's existence. This extra deuterium will cause the stars to burn much too quickly and erratically for any of them to support a planet with life. On the other hand, if the mass-density is too small, so little deuterium and helium are made in the first few minutes that the heavier elements necessary for life will never form in stars. What this means is that the approximately hundred-billion-trillion stars we observe in the universe -no more and no less- are needed for life to be possible in the universe." (Ross H.N., "The Creator and the Cosmos: How the Greatest Scientific Discoveries of the Century Reveal God," [1993], NavPress: Colorado Springs CO, 1994, Third printing, p.118)"For example, the mass density of the universe determines how efficiently nuclear fusion operates in the cosmos. ... if the mass density were too great, too much deuterium (a heavy isotope of hydrogen with one proton and one neutron in the nucleus) would be made in the first few minutes of the universe's existence. This extra deuterium will cause all the stars to burn much too quickly and erratically for any of them to support a planet with life upon it. On the other hand, if the mass density were too small, so little deuterium and helium would be made in the first few minutes that the heavier elements necessary for life would never form in the stars. What this means is that the approximately 100 billion trillion stars we observe in the universe, no more and no fewer, are needed for life to be possible in the universe. Evidently God cared so much for living creatures that he constructed 100 billion trillion stars and carefully crafted them throughout the age of the universe so that at this brief moment in the history of the cosmos humans could exist and have a pleasant place to live." (Ross H.N., "Astronomical Evidences for a Personal, Transcendent God," in Moreland J.P., ed., "The Creation Hypothesis: Scientific Evidence for an Intelligent Designer," InterVarsity Press: Downers Grove IL, 1994, p.164) [top]4. Galaxy (Milky Way) 1. Special 1. Among the oldest Our galaxy, the Milky Way, is no ordinary galaxy, but is in fact special in a number of ways. For example, the Milky Way is "an original member of the universe, having been born just about as early on as was possible", "The overall universe is about 13.7 billion years old" and the Milky Way's age is about 13.6 billion years" (Britt, 2004c). [top] 2. The right shape"[T]here are three basic types of galaxies in our universe. First, there are spiral galaxies like our own Milky Way. These are dominated by a central spherical bulge and a disk with `spiral arms' extending outward from the nucleus in a spiral pattern, resembling a celestial pinwheel. Second, there are elliptical galaxies, which are sort of egg-shaped. And, third, there are irregular galaxies, which appear disorganized and distorted. `... our type of galaxy optimizes habitability, because it provides safe zones,' ... But what about other types of galaxies? Might they also provide threat-free neighborhoods for life-populated planets? `What about elliptical galaxies?' ... `Elliptical galaxies look amorphous and are sort of egg-shaped, with stars having very random orbits, like bees swarming a beehive .... `The problem for life in these galaxies is that the stars visit every region, which means they'll occasionally visit the dangerous, dense inner regions, where a black hole may be active. In any event, you're less likely to find Earth-like planets in elliptical galaxies because most of them lack the heavy elements needed to form them.' This was an important point, because I knew that most galaxies fall into the elliptical category. `Most elliptical galaxies are less massive and luminous than our galaxy,' ... `Our galaxy is on the top one or two percent of the most massive and luminous. The bigger the galaxy, the more heavy elements it can have, because its stronger gravity can attract more hydrogen and helium and cycle them to build heavy elements. In the lowmass galaxies, which make up the vast majority, you can have whole galaxies without a single Earth-like planet. They just don't have enough of the heavy elements to construct Earths. Just like a globular cluster-you can have a whole globular cluster with hundreds of thousands of stars, and yet there won't be a single Earth. ... Thousands and thousands and thousands of galaxies-but zero Earths, because the heavier elements haven't built up enough yet.' ... With elliptical galaxies being unlikely sites for budding civilizations, I turned to the last category of galaxy, called irregulars. `What's their potential for life?' I asked. `Like the ellipticals, they also don't provide a safe harbor. In fact, they're worse. They're distorted and ripped apart, with supernovae going off throughout their volume. There are no safe places where there are fewer supernovae exploding, like we have between our spiral arms. ... Sometimes people claim you can be in any part of any galaxy. ... other regions-spiral arms, galactic centers, globular clusters, edge of disks-and no matter where it is, it's worse for life." (Gonzales & Richards, 2004b, pp.168-171. Emphasis in original) [top]2. Galactic Habitable Zone (GHZ) Astronomers are now coming to recognise that there is a "Galactic Habitable Zone (GHZ)" only within which there will be found Earth-like planets (Gonzalez & Richards, 2004a, p.152). To be considered "Earth- like" a planet would need to have permanent liquid water (Gonzalez & Richards, 2004a, p.152), amongst other conditions necessary for the long-term survival of life (Gonzalez & Richards, 2004a, p.152). [to be continued] [top] 3. Solar System's fitness for life 1. Unique? http://news.bbc.co.uk/1/hi/sci/tech/4205227.stm BBC ... 25 January, 2005 ... Cosmic birth theory gets support Our SolarSystem could have formed in a violent nebula New meteorite data lends support to a controversial theory that the violent explosion of a star was involved in the creation of the Sun and its planets. The primitive space rock contains signs that a short-lived, radioactive form of the element chlorine may have been present in the early Solar System. A US- Chinese team claims the most likely source of this "isotope" was a supernova - or exploding star. [More evidence that our Solar System is special]."Though researchers find more and more distant planets revolving around alien suns, the discoveries highlight that Earth and its solar system may be an exceptionally rare place indeed. That was the consensus ... among five planetary science experts who spoke at the 5th annual Isaac Asimov Memorial Panel Debate held at the American Museum of Natural History. ... Prior to the discovery of planets around stars other than our sun in the 1990 s, scientists thought that alien solar systems must look something like our own. They presumed that just like our solar system, there would be small rocky planets like as Earth close to their host stars and large, low density ones a little farther out. But what they discovered were solar systems unlike ours with big Jupiter-like planets close to their host star. Of the 150 alien planets found, none of them resemble our own. `So maybe it's not the enigma of other solar systems, it's the enigma of our solar system,' Tyson said in opening the debate' ... But with the vast majority of the alien planets found in eccentric orbits, Butler has a different view. `I think with the data at hand, we can say that our solar system is rare. Eccentricity dominates,' said Butler. `It's just a matter of how rare we are,' he added. And Benedict agrees. `The older I get, the less likely it seems to me there d be a bunch of places like our solar system,' he said. Or as Tyson added, `There's no place like home.'" (Goudarzi S., "Five Out of Five Researchers Agree: Earth's Solar System Special," SPACE.com, 31 March 2005) [top]2. Sun "life needs a star that can serve as an incubator ... by providing relatively stable temperatures for billions of years" (Naeye, 1996, p.39). "But only a small fraction of the Milky Way Galaxy's 200 billion stars fit the bill (Naeye, 1996, p.39). "One that fits it perfectly is the Sun (Naeye, 1996, p.39). "This middle-aged star has a slightly above-average size and mass, and it produces a steady energy output (Naeye, 1996, p.39). "But the Sun, unlike the majority of stars, has no stellar companion (Naeye, 1996, p.39). "Roughly two-thirds of Milky Way stars belong to binary or multiple star systems (Naeye, 1996, p.39). "In most multiple star systems, either planets won't form, or varying gravitational forces will yank planets into tortured, elongated orbits (Naeye, 1996, p.39). "At one point in its orbit a planet will come very close to a star's searing heat, causing liquid water to evaporate (Naeye, 1996, p.39). "At other times it will venture far, far away, and water will freeze as temperatures plunge to a few degrees above absolute zero. ... life could never evolve on such planets" (Naeye, 1996, p.39). 3. Planets Evidence is mounting that our solar system is unique (Ali, 2004a). Scientists are starting to openly question the `Copernican' mediocrity principle: "Ever since Copernicus displaced the Earth from the centre of the Universe, astronomers have tended to assume that there is nothing special about our place in the cosmos. But apparently our planetary system might not be so normal after all" (Ball, 2004b), and "Earth-like planets may be more rare than thought" meaning "We could be alone in the Universe after all" (Ball, 2004b). Of the "110 ... extrasolar planets" discovered to date, "they are all between about a tenth and ten times as massive as Jupiter" and "Most of them are ... much closer to their sun than Jupiter is to ours ... They also tend to have more elongated orbits than those of Jupiter and the Earth, both of which orbit the Sun on almost circular paths" (Ball, 2004b, Britt, 2004a). When "The core accretion model" is "run on a computer, Neptune and Uranus typically don't show up" (Britt, 2004a). Also, "observations reveal that Saturn has a solid core but Jupiter does not" (Britt, 2004a). The smallest extrasolar planet discovered to date is "a world about 14 times the mass of our own around a star much like the Sun" which it is speculated "could be a rocky planet with a thin atmosphere, a sort of `super Earth" (Britt, 2004b). "But this is no typical Earth. It completes its tight orbit in less than 10 days, compared to the 365 required for our year. Its daytime face would be scorched. ... we can expect it to be quite hot, given the proximity to the star.... around 1,160 degrees Fahrenheit" (Britt, 2004b). Even apart from this planet's orbit being most unEarth-like, "the surface gravity of a terrestrial planet increases with mass ... rapidly ... so that a planet just twice the size of Earth would have about fourteen times its mass and 3.5 times its surface gravity" (Gonzalez & Richards, 2004a, p.59). "This higher compression would probably result in a more differentiated planet" with more "gases like water vapor, methane, and carbon dioxide ... in the atmosphere" (Gonzalez & Richards, 2004a, p.59). Also, "there's another problem with larger planets impact threats. ... they're bigger targets. ... these planets suffer more frequent, high-speed collisions" (Gonzalez. & Richards, 2004a, p.60). [top] 1. Circular orbits"Try to imagine this, a scene unwitnessed by any thinking being, although it could play out every few weeks somewhere in the Milky Way: You are on the curdled, hot surface of a new-born world; an unknown cousin of Earth only a few millions of years old. The landscape is a sweltering, fulminating jumble of soft rock, as sterile as space itself. If anyone could gaze at the night sky, they would see a dark bowl riddled with hard, bright dots. The dots are sibling worlds - new planets in various stages of gestation, careening through the viscous disk of gas and lumpy dust that has given them substance and form. Suddenly, and by chance, a not- so-improbable encounter takes place. The trajectory of another object, a litter mate, crosses nearby. For several days, the second planet sails large across the sky: silent and dangerous. There is no actual collision; no cataclysmic shattering of nascent worlds. But gravitational interaction during this brief encounter changes the motion of both objects; speeding up one, and slowing the other. And now a dispiriting event unfolds, although this world has no eyes to see it. Ejected by chance from the solar system of its birth, the planet sideslips into deep space. Every hour, the sun that had promised to warm its surface for billions of years recedes by another fifty thousand miles. In a mere decade, the home star shrinks to a point of light, eventually indistinguishable from other stars of the sky. The planet’s surface cools, its atmosphere condenses, falls, and piles up in frozen drifts. This is an orphan world, wandering without destination in the numbing, frigid desert of deep space. Although it was kicked from the litter by accident, this planet’s involuntary exile may be a frequent fate for newborn worlds. Doug Lin, an astronomer at the University of California at Santa Cruz, says, "My sense is that orphan planets could be numerous. There’s already indirect evidence that Jupiter-sized worlds have been ejected from some of the extrasolar planetary systems we’ve discovered in the last decade. The clue is that large planets in these systems often have highly elliptical orbits." Giant worlds in egg-shaped orbits are, presumably, the objects that were left behind when a planetary fender-bender took place. "You don’t have that situation in our solar system. We’re lucky because Jupiter - which had a low-eccentricity orbit to begin with - has nudged the other planets into similar near- circular orbits, where they don’t get in one another’s way," notes Lin. ..." (Shostak S., "Orphan Planets: It's a Hard Knock Life," SPACE.com, 24 February 2005)BALTIMORE - Of the more than 130 planets found around distant stars, a large number have highly elliptical orbits, crazy oblong shapes that have surprised theorists who try to explain the configurations with near collisions or perturbing disks of gas. An elliptic orbit is characterized by the eccentricity, which is how much a planet's distance from its star varies as it carves out a year. Most of the planets in our solar system have relatively low eccentricities, less than about 5 percent .... By contrast, the average eccentricity of extrasolar planets is about 25 percent. And these are not Plutos. They are typically more massive than Jupiter. "The eccentricities are the most remarkable thing about these planets," said Geoff Marcy ... Some have eccentricities of 80 percent, which is as high as the crazy orbits of some comets in our solar system. Marcy and others detect extrasolar planets - most often by a wobble they induce in their host stars. This planet-star swing dance might seem to be more noticeable when the planets orbit is highly eccentric, but Marcy said that is not true. As more and more planets are found, it appears that high eccentricities are common, making our solar system more the exception than the rule. "This is surprising because massive planets would form in nearly circular orbits, and interactions with a gas disk would tend to keep the eccentricity low," said Phil Armitage... If there are multiple planets in the system and two of them lie in nearby orbits, they can interact with each other. "For the extremely high eccentricities, it is hard to imagine these being generated without planet interactions," Armitage said. The smaller mass planet will often get tossed out into space, while the lager planet survives in a highly elliptical orbit. "Earth-sized planets usually lose out in these interactions," said David Bennett ... (Schirber M., "Eccentric Worlds: Strange Orbits Puzzle Astronomers," SPACE.com, 10 May 2005)"Except for the fact that we call it home, for centuries astronomers didn't have any particular reason to believe that our solar system was anything special in the universe. But, beginning with the discovery 10 years ago of the first planet outside our solar system, evidence suggests that, as far as planetary systems go, the solar system might be special indeed. Instead of the nice circular orbits our nine planets enjoy, most of the more than 160 extrasolar planets detected in the last decade have eccentric orbits: so elongated that many come in very close to the central star and then go out much further away. In a paper to be published April 14 by the journal Nature, astrophysicists at Northwestern University are the first to report direct observational evidence explaining the violent origins of this surprising planetary behavior. `Our results show that a simple mechanism, often called 'planet-planet scattering,' a sort of slingshot effect due to the sudden gravitational pull between two planets when they come very near each other, must be responsible for the highly eccentric orbits observed in the Upsilon Andromedae system,' said Frederic A. Rasio, associate professor of physics and astronomy. `We believe planet-planet scattering occurred frequently in extrasolar planetary systems, not just this one, resulting from strong instabilities. So while planetary systems around other stars may be common, the kinds of systems that could support life, which, like our solar system, presumably must remain stable over very long time scales, may not be so common.' Verene Lystad ... and Eric B. Ford ... focused on, three huge Jupiter-like planets orbiting the central star Upsilon Andromedae, was the first extrasolar multiplanet system ever discovered by Doppler spectroscopy.... The inner planet, a `hot Jupiter' so close to the star that its orbit is only a few days, was discovered in 1996, and the two outer planets, with elongated orbits that perturb each other strongly, were discovered in 1999. As a result, the system now has been well studied for many years and offered the best and most accurate data for the research team's calculations. `In this system the two outer planets are in a very peculiar orbital configuration, which kept puzzling us for a long time,' said Rasio. To understand this better, Rasio and his collaborators developed a precise computer model of the orbits of the planets as they are today and then evolved them back tens of thousands of years. Their analysis showed that the system evolved over time exactly as would be expected if the initially stable system was suddenly perturbed, with the sudden disturbance affecting the outermost planet only. They showed that a fourth giant planet, which is no longer in the system, must have come in too close and scuffled with the outer planet in a gravitational feud, eventually kicking the outer planet into the middle one. The fourth planet -- the troublemaker -- was ejected into space. The abrupt kick sent the outer planet into an elliptical orbit, while the middle planet initially remained on a circular orbit. Over time, the outer planet eventually perturbed the middle planet's orbit enough to deform it slowly into an eccentric orbit as well, which is what is seen today, although every 7,000 years or so the middle planet returns gradually to a circular orbit. `This is what makes the system so peculiar,' said Rasio. `Ordinarily, the gravitational coupling between two elliptic orbits would never make one go back to a nearly perfect circle. A circle is very special.' `Originally the main objective of our research was to simulate the Upsilon Andromedae planetary system, essentially in order to determine whether the outer two planets lie in the same plane like the planets in the solar system do,' said Lystad .... `We were surprised to find that for many of our simulations it was difficult to tell whether the planets were in the same plane due to the fact that the middle planet's orbit periodically became so very nearly circular. Once we noticed this strange behavior was present in all of our simulations, we recognized it as an earmark of a system that had undergone planet-planet scattering. We realized there was something much more interesting going on than anyone had found before.' Understanding what happened during the formation and evolution of Upsilon Andromedae and other extrasolar planetary systems has major implications for our own. `In these newly discovered systems things have not remained stable for billions of years,' said Rasio. `While they may have formed like the solar system, after a while things went catastrophic. Our solar system, it appears, is rather peculiar in its long-term stability." ("Mystery of extrasolar planets' eccentric orbits," Northwestern University News Release, Spaceflight Now, April 19, 2005) [top]2. Jupiters"... recent theoretical modeling of the dynamics of solar systems suggest that a large gaseous planet occupying the same position as Jupiter does in our own solar system confers dynamical stability to the whole planetary system, ensuring that the orbits of the other smaller planets are stable over billions of years and ... because as planetary scientist George Wetherill points out, "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." (Wetherill G.W., "How Special is Jupiter?" Nature Vol. 373, 1995, p.470) Wetherill continues that if it were not for Jupiter "we wouldn't be around to study the origin of the solar system." [Wetherill G.W., "Our Friend Jove" Discover, July 1993, p.15]." (Denton M.J., "Nature's Destiny: How the Laws of Biology Reveal Purpose in the Universe," Free Press: New York NY, 1998, p.96)"JUPITER ... appears to have been Earth's guardian angel: it has protected our fragile, life-bearing globe from a deadly barrage of comets. George Wetherill, a planetary scientist at the Carnegie Institution of Washington, D.C., reached this conclusion after simulating the birth of solar systems on a desktop computer. ... Wetherill's simulations suggest that Jupiter flung trillions of comets out of our solar system within the first billion years after the sun formed, and that the planet is continuing to eject them today at a lower but steady rate. In systems lacking Jupiter size planets, however, the small inner worlds are relentlessly bombarded. Without a full-size Jupiter, Wetherill estimates, Earth would have been struck by comets at least 1,000 times more often, and catastrophic impacts of the kind that probably exterminated the dinosaurs would have occurred every 100,000 years or so instead of every 100 million. It may well be that if Jupiter weren't there, we wouldn't be here either,' says Wetherill. `Higher organisms require significant amounts of time to evolve. If this were happening every 100,000 years, you would hardly have a chance to evolve very much before you got wiped out again. I think there's a good chance we wouldn't be around to study the origin of the solar system." ("Our Friend Jove,' Discover, Vol. 14, No. 7, July 1993, p.15)"Jupiter also played a crucial role in purging the inner solar system of bodies left over from planet formation. Jupiter is 318 times more massive than Earth, and it exerts enormous gravitational influence. Its gravitational interactions very efficiently scatter bodies that approach it, and it has largely cleaned out stray bodies from a large volume of the solar system. In the early solar system, there were tremendous numbers of small bodies that had escaped incorporation into planets, but over half a billion years, most of the larger ones inside the orbit of Saturn disappeared. They were accreted by planets, ejected out of the solar system, or incorporated into the Oort cloud of comets. Jupiter was the major cause of this purging of the middle region of the solar system. The objects that still impact Earth today are planetesimals that managed to survive in three special ecological niches: the Oort comet cloud lie yond Pluto, the Kuiper belt of comets just beyond the outer planets, and the asteroid belt, that special refuge located between Mars and Jupiter. The current impact rate averages one 10-kilometer body every 100 million years The impact of just such a body occurred 65 million years ago, the time of the K/T extinction that ended the age of the dinosaurs. George Wetherill of the Carnegie Institute of Washington has estimated that the, flux of these 10-kilometer bodies hitting Earth might be 10,000 times higher if Jupiter had not come into being and purged many of the leftover bodies of the middle region of the solar system [Wetherill G.W., "Possible consequences of the absence of Jupiters in planetary systems," Astrophysics and Space Science, vol. 212, 1994, pp. 23-32; Wetherill G.W., "How Special Is Jupiter?" Nature, vol. 373, 9 February 1995, p.470]. If Earth had been subject to collisions with extinction causing projectiles every 10,000 years instead of every 100 million years, and fairly frequently with even larger bodies, it seems unlikely that animal life would have survived." (Ward P.D. & Brownlee D., "Rare Earth: Why Complex Life is Uncommon in the Universe," Copernicus: New York NY, 2000, pp.238-239)"JUPITER AND Saturn, the farthest planets the ancients knew, patrol the vast domain of the outer, solar system. .... As astronomers know today, these weighty names fit both worlds perfectly, for their most impressive property is not color or beauty but sheer mass. Together, the two gas giants harbor twelve times more mass than all the other planets combined. ... Although astronomers have assumed that other solar systems resemble ours and thus have worlds like Jupiter and Saturn, this need not be the case. `There are all sorts of ways you could mess up the formation of a Jupiter,' said George Wetherill, a planetary scientist at the Carnegie Institution of Washington, `and maybe nature just doesn't care whether it makes a Jupiter or not.' For this reason, most solar systems could lack such large planets. `If this is true,' said Wetherill, `it might be surprising that we happen to live in a planetary system which has a Jupiter and a Saturn. But maybe it's not so surprising, because perhaps if it weren't for Jupiter and Saturn, we wouldn't be here.' ... Wetherill's idea actually followed from theories of how the solar system formed. When the planets were developing, 4.6 billion years ago, countless comets roamed the solar system. Many of these collided with one another to form the cores of the four giant planets Jupiter, Saturn, Uranus, and Neptune-but the mighty gravitational force of Jupiter and Saturn tossed trillions of other comets away. As a consequence, few comets remain to hit the solar system's planets today, sparing Earth in particular from the devastating impacts that could have thwarted the development of intelligent life. ... If that idea is correct, however, it raises the stakes in the search for extrasolar giant planets. If astronomers examine other stars and fail to find Jupiters-the planets that are easiest to detect-those solar systems may possess no life at all, even if they have warm, wet planets like Earth. Conversely, if planets like Jupiter abound, they will boost the hope that life exists elsewhere." (Croswell, 1997, pp.161-163)"Today Wetherill uses a powerful desktop computer to simulate the formation of the Earth and the other planets. `What I think is of some relevance to the search for extrasolar planets,' he said, `is to try to develop a general theory for the formation of planetary systems, of which our solar system would be but one example and might be similar to others in some ways and different in other ways. There'd be no specific need for all planetary systems to develop in exactly the same way. So I've been looking into how variations of the initial conditions for the formation of a planetary system might lead to variations from one system to another.' Wetherill starts his model with small bodies orbiting a star. These bodies collide and grow into larger ones, which in turn become the planets of a solar system. Terrestrial planets-rocky worlds similar in mass to Earth- form near their star, where the disk of gas and dust orbiting the star is hot and only substances with high melting points, rock and iron, condense into solids. In 1991, Wetherill's work indicated that such planets are fairly easy for nature to produce, if nature operates the same way that his computer simulations do. Proponents of extraterrestrial life greeted Wetherill's result, since it meant that many if not most stars should have small planets like Earth. Wetherill even found that a typical simulation produced four terrestrial planets that match the pattern in our solar system: the first planet (e.g., Mercury) was small, the next two (Venus and Earth) were larger, and the final one (Mars) was again small. Also in 1991 came the stunning discovery of the first two pulsar planets, whose masses resemble Earth's and demonstrate that nature can indeed manufacture terrestrial-mass extrasolar planets- even in exotic locales. The story changed, though, when Wetherill turned to the giant planets. According to an idea that Japanese astronomer Hiroshi Mizuno and his colleagues published in the late 1970s, these planets formed in a more complicated way than did the terrestrial planets. Far from the star, the disk was cool, so ices of water (H2O), methane (CH4), and ammonia (NH3) condensed. These far outweighed the rock and iron, because the ices contained three of the most common elements in the universe-oxygen, carbon, and nitrogen joined with hydrogen, the most abundant element of all. Due to all this material and the large volume of the outer solar system, enormous objects of ice and rock formed that had roughly 10 times more mass than the Earth. In the case of Jupiter and Saturn, these objects formed quickly, and Mizuno said their gravitational pull grabbed huge quantities of the hydrogen and helium gas that pervaded the disk. Today, Jupiter has 318 times the mass of the Earth and Saturn 95 times, most of it hydrogen and helium. Uranus and Neptune, which today have only 15 and 17 Earth masses, grabbed little if any gas, presumably because their ice-rock cores formed later, after the Sun had blown away the hydrogen and helium gas in the disk. Mizuno's model for the formation of the giant planets explains why all four have similar cores. It also agrees with the planets' observed atmospheric abundances. For example, the theory correctly predicts that all four planets should have more carbon relative to hydrogen than the Sun. This is because their cores had methane, which contains carbon, and some of that leaked into the planets' atmospheres. Furthermore, the two planets that captured the least hydrogen and helium - Uranus and Neptune-have the greatest carbon-to-hydrogen ratios, just as the theory predicts, because their methane was least diluted by the infalling hydrogen and helium. In 1992, Wetherill ran his model on the computer-and it failed. `Instead of forming a system that looked like Jupiter and Saturn,' he said, `I usually got a large number of objects moving in highly eccentric orbits, and it's rather difficult for this to develop into the story we like to tell where a ten- Earth-mass core develops and starts to capture gas. So the possibility occurred to me that maybe it doesn't arise very often. Maybe Jupiter is a fluke, which actually did occur in some of my calculations, but only as a fluke rather than as a rule of thumb. `Now this is very egotistical: to think that just because I don't know how to make Jupiter implies that nature doesn't know how to make it. But this was at the same time that people were failing to find any Jupiter-like planets around other stars. It began to look-and I think it still does look-as if Jupiter is an unusual object. `So if that's the case, then that raised the question: why do we have a Jupiter? The possible answer was that our solar system may be a highly biased sample, biased by the fact that we're here to see it.' In contrast, a solar system that lacks a Jupiter and a Saturn is not self-observable, if it never gives birth to intelligent life." (Croswell K., "Planet Quest: The Epic Discovery of Alien Solar Systems, "Free Press: New York NY, 1997, pp.164-165, 167. Emphasis in original)"Long ago, Jupiter and Saturn cleaned the solar system of most cometary debris, including comets that may have been quite large, possibly as large as planets. Consequently, catastrophic impacts-such as the one that killed the dinosaurs and most other species living 65 million years ago-now occur only rarely. In the early solar system, said Wetherill, Jupiter and Saturn worked as a team, playing ball with comets and passing them back and forth from one planet to the other, boosting the comets' velocities. Most of the comets got cast clear out into interstellar space, while some were deposited in the Oort cloud, the vast comet reservoir that surrounds the solar system. Uranus and Neptune, which are smaller than Jupiter and Saturn, treated comets more gently. They transported comets toward Jupiter and Saturn, which then got rid of them. In 1994, the world witnessed a dramatic event that symbolized Jupiter's role as protector of terrestrial life: the planet took a direct hit from Comet Shoemaker-Levy 9, an impact that left Jupiter's atmosphere scarred for months. Had the planet not intervened, the comet might someday have collided with Earth. To see what would happen if Jupiter and Saturn did not exist, Wetherill tried simulations in which the two planets failed to accrete much hydrogen and helium. This could occur if a solar system lost its hydrogen and helium disk before the cores of Jupiter and Saturn captured much gas. Many solar systems may therefore have `failed' Jupiters and Saturns- planets with the masses of Uranus and Neptune, but located at the orbital positions of Jupiter and Saturn. Wetherill found that such planets are dangerous. `Failed Jupiters and Saturns are not really effective in removing material from the solar system,' said Wetherill, `but they're effective enough that they perturb this material over the lifetime of the solar system into orbits which come into the inner solar system, into the region of the Earth.' Comets would therefore bombard this hypothetical Earth as much as a thousand times more often than they do the real one. On the real Earth, devastating impacts occur roughly once every 100 million years, leaving long intervals of relative calm, during which life can evolve. On an Earth without the protective shield of a full-fledged Jupiter and Saturn, these catastrophes could strike every 100,000 years-a time shorter than Homo sapiens is old. Life might still originate on such a world, Wetherill said, but it might not develop into complex life. `Even on the Earth, it wasn't until around 600 million years ago that multicellular organisms became common,' he said. `So we went for 4 billion years without doing much; it might not take much more to prevent intelligent life from arising at all. Apparently, it's not really easy, even on a very nice planet like the Earth.' Without Jupiter and Saturn, the Earth might also be buried under water. Much of the water now on Earth came from comets, and even with Jupiter and Saturn protecting the planet, seawater covers 71 percent of the Earth's surface. If Jupiter and Saturn did not exist, and comets rained down on Earth more often, the Earth might be a completely water- covered world, and any life would forever remain in the sea-another situation that might have prevented the emergence of intelligent life. Although dolphins have a fair degree of intelligence, they have not developed a written language, preventing future generations of dolphins from studying and building on the knowledge of their ancestors." (Croswell, 1997, pp.167-168) [top]3. Number of Earth-like planets in the Universe It is easy for evolutionists to claim there are millions, if not billions, of `Earth-like' planets, as long as they are vague about the details of how truly Earth-like a planet is. The following is a webbed representation of a spreadsheet model I have now developed, as a first stage in identify Earth-like factors, with nominal estimates only assigned to them to illustrate how the model will work. I will over time refine this model and then start plugging in actual estimates of each factor in order to derive an estimate of how many truly Earth-like planets there are in the Universe.
| References and comments | |||
| Galaxies in universe | 1 followed by 11 zeros | ||
| Galaxies right size | |||
| Galaxies right shape | |||
| Galaxies right age | |||
| Galaxies no collision, etc | |||
| Stars in average galaxy | |||
| Stars in GHZ | Galactic habitable zone | ||
| Stars right type | |||
| Stars right age | |||
| Stars no collision, supernova, etc | |||
| Stars with planets | |||
| Planets in average solar system | |||
| Planets in CHZ | Circumstellar habitable zone | ||
| Planets in stable orbit | |||
| Planets in circular orbit | |||
| Planets no giant(s) in inner orbit | |||
| Planet right age | |||
| Planet right mass | |||
| Planet right type (e.g. rocky) | |||
| Planet large moon | |||
| Planet heavy core | |||
| Planet right water | |||
| Planet right atmosphere | |||
| Planet right axial tilt | |||
| Planet right rotation | |||
| Planet no life extinguishing event |
"Is there any room in this vast Universe of intelligent beings for the belief that God has chosen our planet to be the sole or even the primary object of His concern? The validity of the question depends upon our acceptance of the notion that intelligent life is common in the Universe. For my part, I am not so sure that intelligent life exists on other planets. The basic argument for this view is that each star offers life an opportunity, and there are 1022 (ten thousand million million million) stars and planets in the observable universe. Even if the chance of life evolving is as small as, say, one in a million, still there must be millions upon millions of inhabited planets in the Universe. Suppose, however, that twenty-two separate conditions must be met for intelligent life: the star must be single, it must produce visible and ultraviolet light; its planet must have an atmosphere that transmits light but not X rays or extreme ultraviolet; there must be liquid water, there must be carbon; the star must live a long time; its output of energy must not vary rapidly; the planet must be in a suitable zone of distances from its star, it must have land as well as water; it must not suffer excessive and prolonged bombardment by meteorites; and so on. These conditions would not be satisfied on every planet in the Universe. If each were satisfied on only 1 planet in 10, which is not an unreasonable estimate, then if the requirement; are really separate, the chance of finding a planet with all 22 conditions satisfied simultaneously would be one tenth multiplied by itself twenty-two times, or 1/1022. This would mean that only one planet in the Universe is likely to bear intelligent life. We know of one-the earth-but it is not certain that there are many others, and perhaps there are no others." (O'Keefe J.A., "The Theological Impact of the New Cosmology," in Jastrow R., "God and the Astronomers," [1978], W.W. Norton: New York NY, Second Edition, 1992, pp.122-23)While the above model is only concerned with the factors that contribute to a truly Earth-like planet, excluding life itself, even though life is one of the major factors that has made the Earth habitable for complex life (e.g. most of the Earth's oxygen has been produced by photosynthesis), this illustrates how by analogous reasoning there can be a hundred billion galaxies in the Universe each with a hundred billion stars on average and yet there still could be only one truly Earth-like planet in that Universe, if the conditions for being Earth-like turn out to be sufficiently stringent, independent and numerous. Again it is not claimed that there is only one Earth-like plenet in the Universe, Earth itself, but that there may be. [top] 4. Asteroids
"Our present-day Solar System is a quieter place, with impacts of the scale that killed the dinosaurs occurring only every 100 million years or so." HD69830, which lies in the northern constellation of Puppis, is probably just a couple of billion years younger than our Sun, and with a slightly lower power output. There are two other known distant asteroid belts, but they circle even younger and more massive stars. Constant bombardment The Spitzer team will have to do some further observations to be absolutely sure it has actually seen an asteroid belt. It is just possible that what has been detected is the dust trail of a giant comet, but the team says its current data makes this scenario unlikely. ...In pictures HD69830 is not known to have any planets in orbit around it, let alone small, rocky worlds like Earth. Current telescope technology is simply not good enough to see such detail. But if there is an Earth there, it could be an uncomfortable place. "The frequency of impacts from this massive asteroid belt would be much larger than we experience on the Earth and so extinctions would be extremely frequent and there is a valid question that could be asked about whether life could actually take hold and evolve on such a world," commented Dr Jonathan Lunine ... " (Dusty debris may be asteroid belt, BBC, 20 April, 2005) [More evidence of Earth's rare (if not unique) fitness for life. ...] [top]
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Created: 3 November, 2003. Updated: 24 January, 2006.