Our solar system comes with planets of all sorts of sizes and compositions. Not long ago, it was possible to debate if there were any other planets in the Universe other than those of our solar system. Now, there doesn’t seem to be any question that other planets, called exoplanets, do exist. The question now is how many and what do they look like?
These questions are becoming increasingly possible to answer. The first planets identified were massive gas giants like Jupiter and Saturn but with ever more precise instruments the identification of planets in the so-called habitable zone around stars has become possible. The habitable zone refers to the region of space that is neither too close or too far away from a sun/star for earth-like conditions to exist.
Yesterday NASA announced the discovery of a solar system with seven earth-sized planets, three of which reside in orbits that could enable them to have earth-like characteristics. This solar system is not far away and it is expected that further analyses and soon-to-be new telescopes will be able to probe the atmospheres of these exoplanets in unprecedented detail. It could be that we will discover that these planets have barren rocky surfaces but this new discovery confirms that exoplanets are far from rare and as such it raises the possibility that some planets could be very much like our own.
How many earth-sized planets in “habitable” zones are there?
In 2013 an analysis of data from stars systems that had been studied and reasonable assumptions about how to extrapolate from those studies allowed an estimate of how many earth-like planets exist in the universe. The authors concluded that 22% of sun-like stars in our galaxy have planets in the “habitable” zone. That would mean that there are 8 to 10 billion planets 1-2 times the size of earth in this zone around stars just in our own Milky Way galaxy. Extrapolating that out to a Universe yields 80 to 400 quintillion earth-sized planets. Writing that out to show how mind-boggling big that number is you get: 400,000,000,000,000,000,000 planets. There would probably be 10 times as many total planets that are more like Mercury or Saturn that Earth-sized planets thus giving us an estimated 4 sextillion total in the Universe give or take a few sextillion.
Rather than being exceedingly unlikely that other planets exist, it now almost certain that there are more planets than stars in the universe making our planet and solar system seem – to put it mildly – a whole lot less unique.
Septillions of stars and planets, that we are part of just one galaxy among millions, and the great distances between stars and galaxies brought challenges to those in the past that believed the earth was the physical center of God’s creation. How special could man be as part of that creation? Initially there was denial of the physical shape of the universe but over hundreds of years Christians came to see the universe once again as attesting to the majesty of God’s creation. Rather than the expanse of the Universe making man look like a mere speck of dust, man could be understood as the center of God’s interest in creation, and thus in a way even more special in comparison to the rest of a large universe.
God has given us a vast playground to explore with wonders that will never cease to amaze. The further we look the more we see! Despite its size, God had man in mind when he created the universe. He has cared for him and has created man in his image out of all the things in his entire creation. The more we discover the more amazing this fact should be.
Unfortunately, many challenges to Christian doctrines have been self-inflicted. It has not been uncommon for man to say that Scriptures require much more than is actually there. Our human nature presses us to want answers to all questions and believing the Scriptures have the answers to all questions we quickly read our desired answers into scripture and consider all other avenues of inquiry closed. As a result we have placed the earth at the physical center of the universe or the center of the solar system and taught that this is required of all “true” Christians. We have interpreted the Scriptures to say that the earth does not move and thus the continents could not move. With respect to the universe we have emphasized our special place among the stars and said that the Earth is absolutely unique and specially made for man. While I believe the latter to be true, has God actually told us everything we about His creation or only what we need to know? Do we know that only place in the Universe life exists is here on Earth? Is that revealed to us in the scriptures?
Man at the Center of the Universe?
Today some Christians are again faced with making another paradigm shift because they have put themselves into another self-inflicted interpretive box. By putting man at the center and/or pinnacle of God’s creation, even if they have now given up having him at the physical center of creation, many have still assumed that our solar system and our planet in particular is a very special place. A common strictly literalist reading of the creation account in Genesis seems to suggest God created the entire Universe in an instant and then took one piece of that creation, a formless and void chunk of matter, and formed it into a suitable habitat for man. By inference then, the earth must be a special place with properties that would not be expected to be found anywhere else in His creation. This fine-tuning argument has been around for hundreds of years. And because this is the only place made for living things, it is proposed that we can find evidence of God’s design by comparing this world to all other worlds. But what if there are septillions of other similar worlds and what if God created – by supernatural or natural means – life there as well?
Sometimes Christians have had a tendency to act as if all of creation was made specifically for man. This results from the dominion mandate and the attention God places on man’s creation in the second creation account which places man at the center of attention. That account tells us of a creation of a being that can reflect upon God’s creation and appreciate it for what it really is: the handiwork of God.
We are a created being that can be a creative force via our being made in his image. We are also given the duty to protect and tend to the rest of creation. But man has taken these truths and distorted them, putting himself on a pedestal seeking to worship himself as the ultimate pinnacle of creation. Man has been tempted to want to see all of creation as being for man. But did God create the vastness of the Universe for us and for his own glory? Probably both.
Consider a tiny moon circling a planet that circles a star that we can’t even see today on the other side of the Universe. Has this been created for us or with us in mind? Much of the universe will pass without any person ever setting their eyes upon it or being aware of its existence. Even on earth, there are species that have lived in the depths of the ocean that have gone extinct before man even had the capacity to find them and they will never be known to man because they have left no trace of their existence.
Billions of other earth’s?
It has been to God’s good pleasure that he created a Universe via means that have resulted in the formation of solar systems very much like our own. It has been my impression that many Christians have long resisted the idea that there could be other planets in the Universe other than those that are in our solar system. I don’t not sure why. Maybe because it seems to strike against the feeling that our solar system must be special?
Maybe it’s because the scriptures do not speak of other worlds. But this is an argument from silence and our knowledge of the solar system should give us pause to how we read into scripture a message about exoplanets. Mars and the other planets of the solar system are not mentioned in the creation account either but they would be counted as visible points of light or “stars” in that account. Yes, I am aware that John 10:16 which speaks of Jesus having sheep that are not of this pen and that he must bring them to him as well has been interpreted by some as a reference to life on other planets but I don’t think there is any merit to this interpretation of that passage.
Some Christians have found the fine-tuning argument for the existence of the Universe and out planet as promoted by astronomer Fred Hoyle in 1959 (in Religion and the Scientists) to be compelling. This argument suggests that only earth has formed (or been created from nothing) with specific attributes that are exactly right for earth. Earth has been thought by many Christians to be so perfectly created that there could not be another earth because life was formed here on Earth and there would be no need for such conditions anywhere else. For these people, the existence of septillions of earth-sized planets circling other stars certainly could be disconcerting.
So then, what do we make of all these planets – 8 to 10 billion planets like earth just in our galaxy alone!? How do Christians respond? As a said earlier, some have assumed – ether hopefully or based on their preferred reading of Scripture – that there would be no other planets.
For the most part, Christians have come to accept the reality of vast numbers of exoplanets. Of course the more sensitive theological issue is that of life on other planets be that in our solar system or on exoplanets. For now, let me say I don’t know if there is life on these other planets. I won’t say there can’t be and I won’t say there must be. I don’t believe that the Scriptures can be used to argue definitely one way or the other, although I do believe a strong argument can be made that man, created in the image of God, is unique in the Universe. If evidence of life, similar to that here on Earth, is found to exist elsewhere it will not shake the foundations of my faith because I have not tied my faith to an expectation of exactly how God created life and the Universe. I am not denying that God hasn’t told us some very explicit things about his creation, He has. What I’m emphasizing here is that I am trying not to hold my fellow Christians to articles of faith that aren’t explicitly taught in the Scriptures. Rather than be bound by the baggage of expectations for what the Universe must look like, this frees me to express my amazement at His creation rather than be in constant fear of what scientist might find next. Scientific exploration of the Universe is not a threatening exercise but one which takes us to greater and greater appreciation for this temporal-physical place we call home.
I hesitate to stop here but I also hesitate to continue. This is a complex topic and I don’t wish to over simplify it. For now I would have you observe that the discovery of planets outside our solar system should not be any more challenging to the Christian worldview than the first realization that any of the points of light in our sky were not stars but rather planets in our own solar system. That discovery presented many of the same challenges that any planet orbiting another star does today.
J.W. Wartick has written an article that explores some of the issues I have brought up here in more depth: Theological Reflections on Life on Other Planets. He does a better job than I of framing some of the theological issues.
This is an updated and revised version of an article I wrote in 2013.