Is Earth special? A large fraction of the scientific community doesn’t think so. In fact, most have adopted the Copernican principle, believing that Earth’s capacity to support life is commonplace. However, a number of factors indicate that Earth may be rare (or possibly unique) in its capacity to support life—even among the 100 sextillion terrestrial planets in the observable universe, according to a recent paper.

In two decades, the exoplanet catalog has grown to over 2,000 known exoplanets. Using data from those planets and host stars, astronomers have developed models to determine information about planets not yet discovered. Based on those models, astronomers have estimated that the observable universe contains around 1020 terrestrial planets!1 For comparison, somewhere between 1022–1024 stars exist in the observable universe, so roughly one in a hundred stars have rocky planets. These models also allow astronomers to compare terrestrial exoplanets to Earth. Amidst the comparisons, Earth stands out in at least three ways.

1. Age: Earth is younger.

While most terrestrial exoplanets are between 8–8.4 billion years old, Earth is much younger, only 4.5 billion years old. Why is such a young planet habitable? This is probably because older planets (that formed earlier in the history of the universe) are subject to dynamical and radiation effects that diminish the possibility of hosting life.

2. Galaxy type: Most planets reside in the wrong galaxies.

The number of planets per star remains largely constant with galaxy size; so, most terrestrial planets reside in galaxies about twice the size of the Milky Way. However, the vast majority of galaxies this large are not spiral but elliptical. Consequently, most of the terrestrial planets in the universe reside in ellipticals, but research suggests that truly habitable planets must orbit stars in a spiral galaxy—such as the Milky Way.

3. “Dangerous” neighbors: Earth has none.

Most planets that orbit otherwise life-friendly stars might have any hypothetical life exterminated due to radiation from nearby supernovae, gamma-ray bursts, active galactic nuclei, or dark matter annihilation regions. Dynamical encounters with interstellar gas clouds or dark matter clumps could also disrupt the stability of potentially habitable planets.

One theological point warrants discussion. The Bible gives much information about God’s activity to bring about human life here on Earth, but it says nothing about whether He performed similar work somewhere else in the universe. Except for angelic beings (they have no physical body), the Bible leaves open the question of whether life exists elsewhere in the universe. However, it emphatically states that all things exist because of His divine action (see John 1:1–3).

It seems likely scientific discoveries will continue to provide a growing body of evidence that Earth’s habitability is the exception instead of the rule. Astronomers have much work to do before they have the capacity to determine whether life exists beyond Earth, but the search is interesting from both a theological and scientific perspective.

Food for Thought

Would finding life on a planet outside our solar system diminish the case for God? Visit TNRTB on Wordpress to comment with your response.

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About The Author

Jeff Zweerink

Since my earliest memories, science and the Christian faith have featured prominently in my life - but I struggled when my scientific studies seemed to collide with my early biblical training. My first contact with RTB came when I heard Hugh Ross speak at Iowa State University. It was the first time I realized it was possible to do professional work incorporating both my love of science and my desire to serve God. I knew RTB's ministry was something I was called to be a part of. While many Christians and non-Christians see the two as in perpetual conflict, I find they integrate well. They operate by the same principles and are committed to discovering foundational truths. My passion at RTB is helping Christians see how powerful a tool science is to declare God's glory and helping scientists understand how the established scientific discoveries demonstrate the legitimacy and rationality of the Christian faith. While many Christians and non-Christians see the two as in perpetual conflict, I find they integrate well. • Biography • Resources • Upcoming Events • Promotional Items Jeff Zweerink thought he would follow in his father's footsteps as a chemistry professor until a high school teacher piqued his interest in physics. Jeff pursued a BS in physics and a PhD in astrophysics at Iowa State University (ISU), where he focused his study on gamma rays - messengers from distant black holes and neutron stars. Upon completing his education, Jeff taught at Loras College in Dubuque, Iowa. Postdoctoral research took him to the West Coast, to the University of California, Riverside, and eventually to a research faculty position at UCLA. He has conducted research using STACEE and VERITAS gamma-ray telescopes, and currently works on GAPS, a balloon experiment seeking to detect dark matter. A Christian from childhood, Jeff desired to understand how the worlds of science and Scripture integrate. He struggled when his scientific studies seemed to collide with his early biblical training. While an undergrad at ISU, Jeff heard Hugh Ross speak and learned of Reasons to Believe (RTB) and its ministry of reconciliation - tearing down the presumed barriers between science and faith and introducing people to their personal Creator. Jeff knew this was something he was called to be a part of. Today, as a research scholar at RTB, Jeff speaks at churches, youth groups, universities, and professional groups around the country, encouraging people to consider the truth of Scripture and how it connects with the evidence of science. His involvement with RTB grows from an enthusiasm for helping others bridge the perceived science-faith gap. He seeks to assist others in avoiding the difficulties he experienced. Jeff is author of Who's Afraid of the Multiverse? and coauthor of more than 30 journal articles, as well as numerous conference proceedings. He still serves part-time on the physics and astronomy research faculty at UCLA. He directs RTB's online learning programs, Reasons Institute and Reasons Academy, and also contributes to the ministry's podcasts and daily blog, Today's New Reason to Believe. When he isn’t participating in science-faith apologetics Jeff enjoys fishing, camping, and working on home improvement projects. An enthusiastic sports fan, he coaches his children's teams and challenges his RTB colleagues in fantasy football. He roots for the Kansas City Chiefs and for NASCAR's Ryan Newman and Jeff Gordon. Jeff and his wife, Lisa, live in Southern California with their five children.

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