1 The Privileged Planet Guillermo Gonzalez and Jay Richards So far the talks have been very complementary to what we're going to say and in fact, they lead into some of our material very nicely. First of all let me just start off by saying that we're not going to discuss cosmological issues. We're going to get far away from the Planck era and come to the nearby universe and discuss some local astronomical phenomena that can be quantified empirically. This talk will be entirely based on empirical observational astronomy evidence. Here's our basic thesis: we'll present evidence to show that the degree of measurability of the universe correlates with the degree of habitability over many decades and size and time scales, it's an empirical argument. We also claim that our habitable environment is an exceptional compromise of diverse and sometimes conflicting conditions for measurability ranging from cosmology and galactic astronomy to geophysics. We are not however arguing that every condition for measurability is individually and uniquely optimized for earth's surface. And so I'm going to try to present this case. Unfortunately this really requires about two hours of proper development because we have two separate issues that we are joining. We have an issue of the habitability of a place in the universe or life and we have a second issue and that is the ability to do measurements of the universe and to measure the laws of nature and determine them. Again it was very nice to have Polkinghorne discuss some of the requirements for doing science, and also Hodgson this morning discuss the minimum requirements for science. Well, one of these minimum requirements is actually the ability to measure the universe, that's often taken for granted by scientists, but in fact it's something that could have easily been otherwise. And most people don't realize just how optimized our environment is from measuring the most diverse aspects of the universe. So that's what we'll discuss. So here's a brief outline of my talk. So first, very briefly define what I mean by habitable, and of course I can't give you every detail so I'm just going to point you to some resources. Secondly, I'll discuss how I first came upon this correlation. First of all let me tell you I didn't set out to find this correlation between habitability and measurability. I just stumbled upon it completely by accident. And that first example is solar eclipses. And then I’m going to give more specific examples that I encountered after I discovered this correlation of eclipses and I found in fact, this is a general property of the universe. And so, there are five different specific examples discussed all relating to the solar system. If I had more time I would also discuss other areas in astrophysics where it appears that this correlation holds, stars, our place in the Milky Way, and finally our time in the universe. But I’ll have to leave that for another talk. So, what do I mean by a habitable planet? First of all, since the idea of measurement is really only meaningful with complex conscious beings like ourselves, what I mean by life from now on is complex conscious life, something like ourselves. And in fact, I can make more constraints on that, aerobic or oxygen breathing life. And there are also some very basic requirements that you Seattle Pacific University Transcriptions 2 can really say with certainty are required even for simple life. In fact Polkinghorne alluded to that in his talk. And a few of the other talks, carbon was mentioned. And the remarkable "coincidence" that you have this nuclear energy resonance in the nucleus of the carbon atom that is at just the right place to allow stars to create carbon in high abundance. but that's not the end of the story actually, you need to have it fine tuned both on the lower end of the resonance and at the higher end on the order of about 1% so you can have roughly equal numbers of carbon and oxygen in the universe. If you are far from that resonance one side or the other, either you'd have all carbon and no oxygen or oxygen and no carbon. We live in a universe with roughly equal amounts of carbon and oxygen. And so that's the whole story. So it's even more remarkable than Polkinghorne remarked. And the reason carbon and oxygen are particularly important for life is because first of all carbon is really the only atom you can build life on. Now there have been science fiction stories about silicon and other things, I don't have time to get into that so I'm just going to point you in a direction where you can find very nice information on this. The Anthropic Cosmological Principle by Barrow Tipler, Nature's Destiny by Michael Denton, I think there are copies of this book up there actually, and finally Worlds Without End by John Lewis who's a planetary scientist. And also water is another important requirement. You may not realize this but water, which is such a common compound in the universe, is in fact, quite extraordinary in its properties. And again I refer you to these references to learn just how extraordinary water is as the universal solvent for life. Water contains oxygen and hydrogen and that's where carbon and oxygen come in their importance. Carbon and oxygen come in as the bare minimum requirements for the building blocks of life, any conceivable kind of life in the universe. And many scientists are now coming to accept this. Finally, a terrestrial like planet and a circumstellar habitable zone is required to maintain liquid water. This is a concept that was developed over forty years ago and has been refined over the years by many scientists such as James Casting in Pennsylvania and other astrobiologists and it continues to be refined. You can't just have a planet at any orbit at any place in the solar system to maintain liquid waters stably for long periods of time on the surface. Finally, there is an idea that I am developing with my colleagues, Don Brownlee and Peter Ward at the University of Washington, called the galactic habitable zone. It's somewhat analogous to the circumstellar habitable zone around stars, but it takes into account long term after physical processes such as the production of the elements in supernovas, the position in the galaxy and the dynamics in the galaxy etcetera. If you want to see some details on this, you can find our paper on the web, it's called, The Galactic Habitable Zone on the Astro PH Archive, for those of you who know about that. And there's a very brief sort of lay level description in the book, Rare Earth by Don Brownlee and Peter Ward, but that's a concept we're continuing to work on. And finally, the other way that you can discuss or figure out what the requirements for life is to appeal to the anthropic principle in an empirical sense, not the cosmological sense, but the local astronomical sense in that if we compare the sun and the solar system and its properties to other stars and other planetary systems, then we see that the sun is quite different in one particular property. Then we can infer that particular property is an important property for habitability. So it's a way for at least suggesting possible parameters of Seattle Pacific University Transcriptions 3 the sun or the solar system that are important for habitability and then you can continue to pursue that through further research. And I'm doing some work in that area too, so there's a reference I provide there. This is literally just the background for what I mean by habitable. I guess complex life, conscious life based on carbon and water and about thirty other chemical elements. Okay so I grew up as an amateur astronomer so I've always been fascinated by eclipses, solar eclipses, lunar eclipses. I finally got to see, in India in 1995, a total eclipse of the sun. And I was inspired to write a research paper after that comparing the properties or the requirements for eclipses as viewed from the surface of the earth compared to other planets in the solar system. So of course, I'm sure all of you know how eclipses are produced, right? You need three bodies in a straight line in space, a luminous light source, an eclipsing body, and finally an observer platform all in a straight line in space. And they have to be constrained such that the eclipsing body, in our case the moon, it has a slightly larger apparent size than the eclipsed luminous body, therefore, blocking the entire light from the photosphere. Here is a picture from the 1995 eclipse and I superimposed the disk of the sun which you cannot see in an eclipse, but just to show you the very close relative sizes between the sun and the moon during an eclipse and also the very nice circularity of the lunar profile. You can see the solar corona during an eclipse and shown in red on either side, you can see the range of the apparent size of the moon relative to the sun in modern times. And notice that the average size is almost exactly the same.