Tag Archives: Astrobiology

New study: model of 700 quintillion terrestrial exoplanets suggests Earth is special

The Circumstellar Habitable Zone, where liquid water could potentially exist
The Circumstellar Habitable Zone, where liquid water could potentially exist

This is from Scientific American. (H/T William)

Excerpt:

More than 400 years ago Renaissance scientist Nicolaus Copernicus reduced us to near nothingness by showing that our planet is not the center of the solar system. With every subsequent scientific revolution, most other privileged positions in the universe humans might have held dear have been further degraded, revealing the cold truth that our species is the smallest of specks on a speck of a planet, cosmologically speaking. A new calculation of exoplanets suggests that Earth is just one out of a likely 700 million trillion terrestrial planets in the entire observable universe. But the average age of these planets—well above Earth’s age—and their typical locations—in galaxies vastly unlike the Milky Way—just might turn the Copernican principle on its head.

Astronomer Erik Zackrisson from Uppsala University and his colleagues created a cosmic compendium of all the terrestrial exoplanets likely to exist throughout the observable universe, based on the rocky worlds astronomers have found so far. In a powerful computer simulation, they first created their own mini universe containing models of the earliest galaxies. Then they unleashed the laws of physics—as close as scientists understand them—that describe how galaxies grow, how stars evolve and how planets come to be. Finally, they fast-forwarded through 13.8 billion years of cosmic history. Their results, published to the preprint server arXiv (pdf) and submitted to The Astrophysical Journal, provide a tantalizing trove of probable exoplanet statistics that helps astronomers understand our place in the universe.

Discover magazine, which is all in for Darwinism and aliens everywhere, says this about the study:

Zackrisson found that Earth appears to have been dealt a fairly lucky hand. In a galaxy like the Milky Way, for example, most of the planets Zackrisson’s model generated looked very different than Earth — they were larger, older and very unlikely to support life.

[…]Zackrisson’s work suggests an alternative to the commonly held assumption that planets similar to Earth must exist, based on the sheer number of planets out there.

[…]One of the most fundamental requirements for a planet to sustain life is to orbit in the “habitable zone” of a star — the “Goldilocks” region where the temperature is just right and liquid water can exist. Astronomers have, to this point, discovered around 30 exoplanets in the habitable zones of stars. Simply extrapolating that figure based on the known number of stars suggests that there should be about 50 billion such planets in the Milky Way alone. Probability seems to dictate that Earth-twins are out there somewhere.

But according to Zackrisson, most planets in the universe shouldn’t look like Earth. His model indicates that Earth’s existence presents a mild statistical anomaly in the multiplicity of planets. Most of the worlds predicted by his model exist in galaxies larger than the Milky Way and orbit stars with different compositions — an important factor in determining a planet’s characteristics. His research indicates that, from a purely statistical standpoint, Earth perhaps shouldn’t exist.

Time for me to list out some of the things that are required for a galaxy, solar system and planet to support complex embodied life. Not just life as we know it, but life of any conceivable kind given these laws of physics.

  • 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

It’s not easy to make a planet that supports life. For those who are interested in reaching out to God, he has left us an abundance of evidence for his existence – and his attention to detail.

Related posts

The importance of having a narrative when confronting the assumption of naturalism

Apologetics and the progress of science
Apologetics and the progress of science

How do you present theism as a rational belief to a person who thinks that the progress of science has removed the need for God?

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 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:

  1. The origin of the universe
  2. The cosmic fine-tuning
  3. The origin of life (biological information)
  4. The sudden origin of the Cambrian phyla
  5. 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:

  1. In pre-scientific times, atheists maintained that the universe was eternal
  2. In pre-scientific times, atheists maintained that a life-permitting universe was as likely as a life-prohibiting universe
  3. In pre-scientific times, atheists maintained that the cell was a simple blob of jello that could spontaneously emerge in some warm pond
  4. In pre-scientific times, atheists maintained that the sudden origin of the Cambrian phyla would be explained by subsequent fossil discoveries
  5. 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:

  1. Scientists discovered redshift and the cosmic microwave background radiation (evidence for a cosmic beginning) and more!
  2. Scientists discovered the fine-tuning of gravity and of the cosmological constant and more!
  3. Scientists discovered protein sequencing and exposed the myth of “junk DNA” and more!
  4. Scientists discovered an even shorter Cambrian explosion period and the absence of precursor fossils and more!
  5. 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.

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.

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.

Positive arguments for Christian theism

Michael Strauss: are Earth-like planets common in the universe?

Christianity and the progress of science
Christianity and the progress of science

Physicist Michael Strauss is one of my favorite speakers and scholars – he has a real love of experimental science which I find lacking in many Christian philosophers who seem to treat science (as opposed to naturalism) as the enemy.

Here is his latest blog post:

When scientists say that an Earth-like planet may have been discovered, they actually mean one of three things. Either (1) the planet is in such an orbit around its central star that allows the temperature on the planet to possibly harbor liquid water, or (2) the planet is about the same size as the earth, or (3) the planet is solid and rocky rather than gaseous. Of course any one of these criteria, or even all three, does not actually give us a true Earth-like planet. We know that our moon is in the correct location to contain liquid water, but it is not “Earth-like.” We know Venus is about the size of the earth, but it is not “Earth-like.” We know that Mercury is rocky and not gaseous, but it is not “Earth-like.” So none of these criteria really give an Earth-like planet. Headlines and sound-bites are not meant to be precise but to draw attention, and it is much more exciting to proclaim an “Earth-like” planet has been found rather than a “Venus-like” planet (if even that could be claimed).

[…]An enlightening book on this subject is Rare Earth: Why Complex Life Is Uncommon in the Universe by Peter D. Ward and Donald Brownlee, published in 2000. One of my favorite chapters in the book is titled “The Surprising Importance of Plate Tectonics” which documents why plate tectonics is required in order for complex life to survive. Having lived 23 years of my life in California, I am well acquainted with the consequences of plate tectonics, but had no idea that such activity was crucial for my survival. Ward and Brownlee document how plate tectonics not only forms and maintains continents, but promotes biological diversity, regulates global temperature, and helps maintain a planetary magnetic field. They write, “It may be that plate tectonics is the central requirement for life on a planet and that it is necessary for keeping a world supplied with water,” (p. 220).

The astrophysicist Hugh Ross has done a rough estimate of the probability of finding a single planet that could support even simple unicellular life for a sustained period of time. Including correlations and longevity factors, and assuming there are 10 billion trillion planets in the visible universe, he concludes that the probability of finding a single planet that could support unicellular life for a prolonged period of time is 1 in 10556, (see Part B of this document). If this informed estimate is even close to being correct, then there are no other planets in the visible universe that can support life.

Previously, I blogged about a few of the minimum requirements that a planet must satisfy in order to support complex life.

Here they are:

  • 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 planet has to be far enough from the star to avoid tidal locking and solar flares
  • 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
  • planet mass must be enough to retain an atmosphere, but not so massive to cause a greenhouse effect

That’s a lot of characteristics that need to be present. When you calculate the probabilities of each one and then multiply them (product rule) to get the odds of getting a planet with ALL of them present, you get a number far smaller than the maximum number of possible life sites in the universe. We are alone.