What do you need in order to have a planet that supports complex life? First, you need liquid water at the surface of the planet. But there is only a narrow range of temperatures that can support liquid water. It turns out that the size of the star that your planet orbits around has a lot to do with whether you get liquid water or not. A heavy, metal-rich star allows you to have a habitable planet far enough from the star so the planet can support liquid water on the planet’s surface while still being able to spin on its axis. The zone where a planet can have liquid water at the surface is called the circumstellar habitable zone (CHZ). A metal-rich star like our Sun is very massive, which moves the habitable zone out further away from the star. If our star were smaller, we would have to orbit much closer to the star in order to have liquid water at the surface. Unfortunately, if you go too close to the star, then your planet becomes tidally locked, like the moon is tidally locked to Earth. Tidally locked planets are inhospitable to life.
Circumstellar Habitable Zone
Here, watch a clip from The Privileged Planet: (Clip 4 of 12, full playlist here)
But there’s more.
The Galactic Habitable Zone (GHZ)
So, where do you get the heavy elements you need for your heavy metal-rich star?
You have to get the heavy elements for your star from supernova explosions – explosions that occur when certain types of stars die. That’s where heavy elements come from. But you can’t be TOO CLOSE to the dying stars, because you will get hit by nasty radiation and explosions. So to get the heavy elements from the dying stars, your solar system needs to be in the galactic habitable zone (GHZ) – the zone where you can pickup the heavy elements you need but not get hit by radiation and explosions. The GHZ lies between the spiral arms of a spiral galaxy. Not only do you have to be in between the arms of the spiral galaxy, but you also cannot be too close to the center of the galaxy. The center of the galaxy is too dense and you will get hit with massive radiation that will break down your life chemistry. But you also can’t be too far from the center, because you won’t get enough heavy elements because there are fewer dying stars the further out you go. You need to be in between the spiral arms, a medium distance from the center of the galaxy.
Like this:
Galactic Habitable Zone and Solar Habitable Zone
Here, watch a clip from The Privileged Planet: (Clip 10 of 12, full playlist here)
The GHZ is based on a discovery made by astronomer Guillermo Gonzalez, which made the front cover of Scientific American in 2001. That’s right, the cover of Scientific American. I actually stole the image above of the GHZ and CHZ (aka solar habitable zone) from his Scientific American article (linked above).
These are just a few of the things you need in order to get a planet that supports life.
Here are a few of the more well-known ones:
a solar system with a single massive Sun than can serve as a long-lived, stable source of energy
a terrestrial planet (non-gaseous)
the planet must be the right distance from the sun in order to preserve liquid water at the surface – if it’s too close, the water is burnt off in a runaway greenhouse effect, if it’s too far, the water is permanently frozen in a runaway glaciation
the solar system must be placed at the right place in the galaxy – not too near dangerous radiation, but close enough to other stars to be able to absorb heavy elements after neighboring stars die
a moon of sufficient mass to stabilize the tilt of the planet’s rotation
plate tectonics
an oxygen-rich atmosphere
a sweeper planet to deflect comets, etc.
planetary neighbors must have non-eccentric orbits
By the way, you can watch a lecture with Guillermo Gonzalez explaining his ideas further. This lecture was delivered at UC Davis in 2007. That link has a link to the playlist of the lecture, a bio of the speaker, and a summary of all the topics he discussed in the lecture. An excellent place to learn the requirements for a suitable habitat for life.
Let’s start with an example of a famous battle in the long war between science and religion.
Canadian science writer Denyse O’Leary writes about the history of cosmology at Evolution News.
Excerpt:
What help has materialism been in understanding the universe’s beginnings?
Many in cosmology have never made any secret of their dislike of the Big Bang, the generally accepted start to our universe first suggested by Belgian priest Georges Lemaître (1894-1966).
On the face of it, that is odd. The theory accounts well enough for the evidence. Nothing ever completely accounts for all the evidence, of course, because evidence is always changing a bit. But the Big Bang has enabled accurate prediction.
In which case, its hostile reception might surprise you. British astronomer Fred Hoyle (1915-2001) gave the theory its name in one of his papers — as a joke. Another noted astronomer, Arthur Eddington (1882-1944), exclaimed in 1933, “I feel almost an indignation that anyone should believe in it — except myself.” Why? Because “The beginning seems to present insuperable difficulties unless we agree to look on it as frankly supernatural.”
One team of astrophysicists (1973) opined that it “involves a certain metaphysical aspect which may be either appealing or revolting.” Robert Jastrow (1925-2008), head of NASA’s Goddard Institute for Space Studies, initially remarked, “On both scientific and philosophical grounds, the concept of an eternal Universe seems more acceptable than the concept of a transient Universe that springs into being suddenly, and then fades slowly into darkness.” And Templeton Prize winner (2011) Martin Rees recalls his mentor Dennis Sciama’s dogged commitment to an eternal universe, no-Big Bang model:
For him, as for its inventors, it had a deep philosophical appeal — the universe existed, from everlasting to everlasting, in a uniquely self-consistent state. When conflicting evidence emerged, Sciama therefore sought a loophole (even an unlikely seeming one) rather as a defense lawyer clutches at any argument to rebut the prosecution case.
Evidence forced theorists to abandon their preferred eternal-universe model. From the mid 1940s, Hoyle attempted to disprove the theory he named. Until 1964, when his preferred theory, the Steady State, lost an evidence test.
Here is a a quick summary of some of the experimental evidence that emerged in the last few decades that caused naturalists to abandon the eternal universe that they loved so much when they were younger.
The importance of having a narrative
Now I want to make a very, very important point about Christianity and the progress of science. And that point is that it is very important that Christians present the evidence in exactly the way that Denyse presented it in that article – in its historical context, featuring the conflict between naturalists and the experimental evidence.
All Christians should be familiar with the following basic pieces of evidence which fit the war between science and naturalism narrative:
The origin of the universe
The cosmic fine-tuning
The origin of life (biological information)
The sudden origin of the Cambrian phyla
The habitability/observability correlation
When you talk about these evidences as a Christian theist to non-Christians, you have to have cultivated a genuine interest in reconciling your beliefs with science. You have to accept that there are two books that reveal God’s character and attributes. The book of nature, and the book of Scripture. And you need to be flexible about getting these two books to fit together. The book of nature gives us natural theology (see Romans 1). It tells us that God is Creator and Designer. The book of Scripture tells us that God stepped into history as a man to save us by taking the punishment for our headlong rush away from God, which the Bible calls sin. Science is one way that humans can recover some of basic knowledge about God. Knowledge that is only possible because God created and designed the universe (and us) in such a way that we are capable of making discoveries, and that the universe is capable of being explored and understood.
It’s very important to present these five basic evidences to non-Christians in the historical context. And here is the story you must tell: “In the beginning, there was the naturalism, and the naturalism tried to argue from ignorance that God was not Creator and God was not Designer. And then came the science, and now people have to give up their naturalism in order to not be crazy and irrational”. That’s the narrative you use when talking to non-Christians about science.
In the beginning was the naturalism:
In pre-scientific times, atheists maintained that the universe was eternal
In pre-scientific times, atheists maintained that a life-permitting universe was as likely as a life-prohibiting universe
In pre-scientific times, atheists maintained that the cell was a simple blob of jello that could spontaneously emerge in some warm pond
In pre-scientific times, atheists maintained that the sudden origin of the Cambrian phyla would be explained by subsequent fossil discoveries
In pre-scientific times, atheists maintained that there was nothing special about our galaxy, solar system, planet or moon
But then science progressed by doing experiments and making observations:
Scientists discovered redshift and the cosmic microwave background radiation and more!
Scientists discovered the fine-tuning of gravity and of the cosmological constant and more!
Scientists discovered protein sequencing and exposed the myth of “junk DNA” and more!
Scientists discovered an even shorter Cambrian explosion period and the absence of precursor fossils and more!
Scientists discovered galactic habitable zones and circumstellar habitable zones and more!
And now rational people – people who want to have true beliefs about reality – need to abandon a false religion (naturalism).
Now naturally, science is in a state of flux and things change. But you have to look at the trend of discoveries, and those trends are clearly going against naturalism, and in favor of Christian theism. No one is arguing for a deductive proof here, we are simply looking at the evidence we have today and proportioning our belief to the concrete evidence we have today. People who are guided by reason should not seek to construct a worldview by leveraging speculations about future discoveries and mere possibilities. We should instead believe what is more probable than not. That’s what a rational seeker of truth ought to do. Proportion belief to probabilities based on current, concrete knowledge.
It is very important that Christians keep abreast of the progress of science, and give proper respect to science when forming our worldviews, and keep in mind what is really going on with atheism. There is a lot of loud worshiping of science by people like Dawkins and Atkins and Krauss, but if you dig into things a little, you’ll find that they are actually filled with rage and enmity against what science has revealed about nature. And not just in one area, but in many, many areas.
Atheism, as a worldview, is not rooted in an honest assessment about what science tells us about reality. Atheism is rooted in a religion: naturalism. And the troubling thing we learn from looking at the history of science is that this religion of naturalism is insulated from correction from the progress of science. Nothing that science reveals about nature seems to be able to put a dent in the religion of naturalism, at least for most atheists. Their belief in naturalism is so strong that it repels all scientific evidence that falsifies it. Atheists simply don’t let science inform and correct their worldview.
It falls to us Christian theists, then, to hold them accountable for their abuse and misrepresentation of science. And that means telling the story of the progress of science accurately, and accurately calling out the religion of naturalism for what it is – a religion rooted in blind faith and ignorance that has been repeatedly and convincingly falsified by the progress of science in the modern era.
Basically, there was an atheist who challenged the idea that nature is designed because there are things in nature which cause suffering, like earthquakes and volcanoes.
Now the first thing to note is that atheists commonly think that God’s job is to make humans happy. If he doesn’t make humans feel happy – regardless of their knowledge of him and relationship with him – then he is a big failure. Many atheists think that, it is one of the most common reasons why people become atheists. But of course anyone who reads the Bible and reads the story of Jesus knows that the purpose of life on God’s view is for humans to know him and to be disciples of a suffering Messiah who sacrifices himself in order to obey God the Father. So that’s the first thing to say – purpose of life not happiness, but knowledge of God and being a disciple of Jesus. This may involve all kinds of suffering, and that’s to be expected.
Second, there is a response to the problem of evil based on the necessity of natural laws. The argument goes that you can’t have genuine morality without a predictable, knowable system of natural laws.
But I want to talk about something different in this post. In the video, Dr. Rana thinks that many of the things that cause suffering in the natural world are actually necessary for life to exist at all. He provides the example of plate tectonics in his video above, and I want to take that one and add to it the example of heavy element production and the stellar lifecycle. These are both from a book called “Rare Earth”, which is written by two non-Christians – Peter Ward and Donald Brownlee, but I’ll link to web sites to make the case.
Plate tectonics.
Here’s an article from Reasons to Believe by Dr. David Rogstad, who has a PhD in physics from Caltech – the top school for experimental science. The article not only goes over the basic plate tectonics to carbonate-silicate cycle connection, but it adds a newer discovery to boot.
Excerpt:
Earthquakes are a byproduct of plate tectonics, a theory in geology developed in recent years for explaining motions near the surface of the Earth. One of the benefits from plate tectonics is that Earth maintains the right levels of carbon dioxide (CO2) in the atmosphere to compensate for the Sun’s increasing luminosity. This is accomplished by what is called the carbonate-silicate cycle. CO2 is removed from the atmosphere through weathering. The weathered products are eventually drawn into the Earth’s interior via plate tectonics. Processes inside the Earth’s interior release the CO2 back into the atmosphere via volcanoes. While all aspects of this mechanism are not yet fully understood, it has been instrumental in providing a stable environment for life on the Earth for billions of years.
New research provides yet another component that appears fine-tuned for life. In a letter in the September 27, 2007 issue of Nature together with a corresponding news release from the University of Bonn, Arno Rohrbach and his colleagues have discussed another mechanism similar to the carbonate-silicate cycle. It also depends on plate tectonics but, in this case, the mechanism controls the amount of oxygen on the surface of the Earth.
Oxygen becomes bound up in various oxides which are then drawn into the Earth’s interior, where various processes result in its being incorporated into an exotic mineral called majorite. The results reported in this letter established that majorite functions as a kind of “reservoir” for oxygen, and when the majorite ascends nearer to the surface of the Earth it breaks down and releases its oxygen. Some of this oxygen also binds with hydrogen released from the interior of the Earth to form water. The authors have referred to the whole process as an “oxygen elevator.”
They go on to say that “without the ‘oxygen elevator’ in its mantle the Earth would probably be a barren planet hostile to life. According to our findings, planets below a certain size hardly have any chance of forming a stable atmosphere with a high water content.”
This research confirms the existence of one more finely tuned mechanism that depends on plate tectonics and contributes to an environment that can support life. It also gives humans one more reason to be appreciative rather than dismayed when we experience an earthquake that breaks some precious possessions beyond repair.
Astronomer Dr. Hugh Ross who has a PhD in Astronomy from the University of Toronto and did a 5-year post-doctoral work at Caltech, adds to this with another discovery.
Excerpt:
In the December 2007 issue of Astrobiology Stanford University geophysicists Norman H. Sleep and Mark D. Zoback note that the higher tectonic activity during Earth’s early history could have played a key role in cycling critically important nutrients and energy sources for life. The production of numerous small faults in the brittle primordial crust released trapped nutrients. Such faults could also release pockets of methane gas and molecular hydrogen. The methane and hydrogen could then provide crucial energy sources for nonphotosynthetic life. Finally, the production of faults could bring water to otherwise arid habitats, such as rocks far below Earth’s surface.
Faulting, generated by active and widespread tectonics, allowed a youthful Earth to support diverse and abundant life. This enhanced diversity and abundance of life quickly transformed Earth’s surface into an environment safe for advanced life. Also, the buildup of biodeposits for the support of human civilization occurred more rapidly due to active tectonics.
The more rapid preparation of Earth for humanity is critical. Without such rapid preparation, humans could not come upon the terrestrial scene before the Sun’s increasing luminosity would make their presence impossible (due to excessive heat).
So that’s the science behind earthquakes. So that’s a brief look at why we need plate tectonics for life, and we just have to buck up and take the earthquakes with it. It’s not God’s job to give us happiness and health. That’s not his plan. People who complain about earthquakes have to show how God could get the life-permitting effects of earthquakes without wrecking his ability to succeed in his plan to make people know him and follow him. But how can an atheist do that? They can’t. I think that people just need to realize that humans are not in charge here and we have to live with that. We have to accept that we didn’t make the universe, and we don’t get to decide what purpose it has. God decides.
On to star formation.
Star formation
Atheists often complain that the universe is too big or too old (which is actually the same thing, since the more time passes, the more it expands). The fact of the matter is that life appeared the earliest it could appear – we needed the universe to be a certain age before it could support life.
The second parameter of the universe to be measured was its age. For many decades astronomers and others have wondered why, given God exists, He would wait so many billions of years to make life. Why did He not do it right away? The answer is that, given the laws and constants of physics God chose to create, it takes about ten to twelve billion years just to fuse enough heavy elements in the nuclear furnaces of several generations of giant stars to make life chemistry possible.
Life could not happen any earlier in the universe than it did on Earth. Nor could it happen much later. As the universe ages, stars like the sun located in the right part of the galaxy for life (see chapter 15) and in a stable nuclear burning phase become increasingly rare. If the universe were just a few billion years older, such stars would no longer exist.
The trick for getting from helium to the generation of planets, and ultimately to life, was the formation of carbon, the key element for the success of life and for the production of heavy elements in stars. Carbon could not form in the early moments following the Big Bang, because the density of the expanding mass was too low for the necessary collisions to occur. Carbon formation had to await the creation of giant red stars, whose dense interiors are massive enough to allow such collisions. Because stars become red giants only in the last 10% of their lifetimes (when they have used up much of the hydrogen in their cores), there was no carbon in the Universe for hundreds of millions to several billion years after the Big Bang—and hence no life as we know it for that interval of time.
[…]The sequence of element production in the Big Bang and in stars provided not only the elements necessary for the formation of Earth and the other terrestrial planets but also all of the elements critical for life—those actually needed to form living organisms and their habitats.
[…]The processes that occurred during the billions of years of Earth’s “prehistory” when its elements were produced are generally well understood. Elements are produced within stars; some are released back into space and are recycled into and out of generations of new stars. When the sun and its planets formed, they were just a random sampling of this generated and reprocessed material. Nevertheless, it is believed that the “cosmic abundance” mix of the chemical elements—the elemental composition of the sun—is representative of the building material of most stars and planets, with the major variation being the ratio of hydrogen to heavy elements.
[…]Many stars are similar in composition, but there is variation, mainly in the abundance of the heavier Earth-forming elements relative to hydrogen and helium. The sun is in fact somewhat peculiar in that it contains about 25% more heavy elements than typical nearby stars of similar mass. In extremely old stars, the abundance of heavy elements, may be as low as a thousandth of that in the sun. Abundance of heavy elements is roughly correlated with age. As time passed, the heavy-element content of the Universe as a whole increased, so newly formed stars are on the average more “enriched” in heavy elements than older ones.
[…]The matter produced in the Big Bang was enriched in heavier elements by cycling in and out of stars. Like biological entities, stars form, evolve, and die. In the process of their death, stars ultimately become compact objects such as white dwarfs, neutron stars, or even black holes. On their evolutionary paths to these ends, they eject matter back into space, where it is recycled and further enriched in heavy elements. New stars rise from the ashes of the old. This is why we say that each of the individual atoms in Earth and in all of its creatures—including us—has occupied the interior of at least a few different stars.
What he’s saying is that heavy elements are created gradually because of the star formation lifecycle. The first generation of stars are metal-poor. The next generation of stars is better. And so on until we get to stars that can support life by providing a steady, stable amount of energy – as well as other benefits like planets with an atmosphere. Our planet is 4.5 billion years old, and the universe is about 14 billion years old. Simple life appears about 4 billion years ago on Earth. That means we got life practically immediately, given that we had to develop the heavy elements needed to make a life-supporting star, a life-supporting planet and us.
UPDATE: Sean from ReligioPolitical Talk pointed out this related post out to me:
Another examples is that hurricanes help to regulate the earths temperature, and cause “sea deserts” to bloom… assisting in many ways earth’s climate:
“Some parts of the ocean are like deserts, because there isn’t enough food for many plants to grow. A hurricane’s high winds stir up the ocean waters and help bring nutrients and phytoplankton to the surface, where they get more sunlight, allowing the plants to bloom,” Babin said. (NASA)
….”Most certainly,” says Steve DiMarco, a Texas A&M University oceanography professor who for 16 years has studied the Gulf of Mexico, which has a “dead zone” where oxygen-depleted water can kill marine life.
In early July, most of the Texas-Louisiana shelf from Freeport, Texas, to the Mississippi River Delta was hypoxic – meaning the salt water has lost large amounts of oxygen. Later in July, Hurricane Dolly disrupted the dead zone and re-oxygenated the shallow waters south of Louisiana and the entire shelf off Texas. Oxygen levels started to drop again within days after the storm.
In early August, Hurricane Eduard re-oxygenated the Louisiana shelf, but by mid-August oxygen concentrations dropped to hypoxic levels.
And guess what?
Hurricane Ike re-oxygenated the shelf when it made landfall Sept. 12 in Texas. The latest data collected in October showed oxygen concentrations nearly all at normal levels, DiMarco said….
WINTERY KNIGHT 