A couple of weeks ago, there was a widely-disseminated news story about the discovery of seven “Earth-like” planets orbiting a distant star, Trappist-1, which supposedly proves that there is nothing special about man or the earth, which supposedly proves the existence of alien life, which supposedly proves that there is no Creator and the Bible is false. This is not the first time a discovery of an “Earth-like” planet has been announced; such announcements, complete with bogus “artist’s concepts,” have been coming out for about ten years now, with some of the more recent being Kepler 452b, Proxima b, and Kepler 186f. The first supposed “Earth-like” planet was Gliese 581c, whose discovery was announced in 2007; within a couple of months, astronomers realized that Gliese 581c could not support life, but they found another planet in the same system, Gliese 581d, that they said was just right for life; after Gliese 581d proved to be too cold to support life, the discovery of the better-situated Gliese 581g was announced in 2010, with one astronomer telling the press that “the chances of life on this planet are almost 100 percent.” Further investigation, however, showed by 2014 that both Gliese 581d and Gliese 581g were mere illusions and do not even exist. News stories about the discovery of planets where life could possibly exist date back to 1996, shortly after the first extrasolar planets were discovered. The two planets heralded at that time were not Earth-like and proved to have serious problems for habitability; the one deemed most suitable for life was estimated to have a surface temperature of 185°F, and is a gas giant eight times the mass of Juipter.
Though the latest planets were discovered through a telescope in Chile, many of the new planetary discoveries have been made using NASA’s Kepler spacecraft, which was built expressly to look for Earth-like planets in hopes of finding evidence for alien life. Many of the missions of NASA and the European Space Agency now have a theological aim—specifically, the aim of supporting atheism. The director of astrophysics at NASA said when Kepler was launched, “Kepler will answer a profound and fundamental question about our place in the universe”—a theological question. The meaning of this statement is that NASA wants to use Kepler to support their deeply held belief that life and the universe were not the product of special creation, the earth is not unique, and the same processes which led to the formation of the earth and the evolution of life on the earth led to the formation of innumerable other earths with life elsewhere in the universe.
It may be asked, however, does the discovery of “Earth-like” planets imply that there is life outside the earth? The answer is a resounding “No!”—first of all, because the earth is uniquely designed for life (hence, these planets are not truly “Earth-like”); and, secondly, because life cannot arise by evolutionary processes.
The earth is the ideal size to produce the perfect gravitational force necessary for life. Studies of astronauts have shown how zero-gravity impairs human health; presumably gravity that is too low or too high would also be harmful to human health. In addition, a planet that is too small, like Mercury, will not have enough gravity to hold an atmosphere in place; gases will simply escape into outer space. And an atmosphere is needed not only to have breathable air, but also to provide pressure to hold liquid water in place and prevent it from escaping; the low atmospheric pressure on Mars causes water to boil away. A planet that is too large, such as Jupiter, will trap light gases that are poisonous to life. A thick atmosphere and strong gravity will also create surface air pressures that are oppressive for life. For these reasons, scientists look for planets that are similar in size to the earth when searching for extraterrestrial life. The seven recently-discovered planets do, indeed, appear to be similar in size to the earth.
Venus is similar in size to the earth, but its atmosphere consists mainly of greenhouse (polyatomic) gases which render its surface temperatures unbearably hot for life. The earth’s atmosphere, by contrast, has exactly the right composition for life. It has just the right oxygen/nitrogen ratio to maintain suitable air temperatures and support life processes. It also has just the right amounts of carbon dioxide, water vapor, and ozone for life to exist. It contains just the right amount of greenhouse gases (less than 1%), so as to retain some warmth but not too much. The atmosphere sustains life, regulates the climate, and protects life from harmful radiation. There is no other known planet with abundant free oxygen. With regard to the seven newly-discovered planets, the authors of the study concluded that they probably formed far away from Trappist-1 and then migrated closer to the star, which means that their composition is probably more similar to planets like Jupiter, Saturn, Neptune, and Uranus, than to the earth—in other words, they likely do not have abundant oxygen.
Not just the composition of the earth’s atmosphere is important, but also the composition of the its crust. The earth’s crust contains minerals such as iron, calcium, and sodium that are essential for life; other planets lack one or more essential minerals.
The earth has the ideal axis of rotation to have the widest possible zone of habitability between the poles. It has the ideal rotation period for the length of the day and night, keeping nights from getting too cold, and days from getting too hot. And the earth has the ideal period of revolution around the sun, so that its seasons are the perfect length (winters and summers are neither too long nor too short). Critically, its orbit is close to being circular; if its orbit were strongly elliptical, temperatures would be too hot for part of the year and too cold for part of the year. While the earth’s orbit takes it slightly closer to the sun during fall and winter in the northern hemisphere, the climactic effect is offset by the greater amount of water in the southern hemisphere.
The most striking feature of the earth, from a scientific point of view, is its abundant liquid water at the surface. Temperature and atmospheric conditions must be just right, and also very stable, in order for water to exist in liquid form. Further, just the right amount of water is present so that the earth is neither too dry nor completely covered with water, and land surfaces receive regular rainfall though the hydrologic cycle. Liquid water has not been observed as presently existing in significant quantities anywhere else in the universe. This is significant, because scientists believe life cannot exist without water. The search for extraterrestrial life is therefore a search, first and foremost, for a planet or moon with the right conditions for liquid water to exist. But not only does the earth have water, its water is suitable for life because the earth’s crust has the right blend of minerals (e.g., the oceans are not too saline for life to exist).
Having a planet with abundant water, of just the right size, just the right atmosphere, the ideal axis of rotation, the ideal rotation period, and the ideal period of revolution is not enough to support life. Life on the earth is dependent upon the sun’s energy to provide warmth and to allow organisms to convert sunlight into food through the process of photosynthesis. The earth is situated an ideal distance from the sun to keep it the perfect temperature for life (i.e., a temperature where liquid water exists in abundance and is not too hot). The case of Trappist-1, the star which the seven newly-discovered planets were found orbiting, is much different. Trappist-1 is a dwarf star, only one-twelfth the size of the sun. Scientists believe that at least some of the seven planets are the right distance from Trappist-1 to potentially have liquid water (i.e., the surface temperature may be between the freezing point and the boiling point). However, the surface temperature of a planet is determined not just by its distance from a star, but also by the composition of its atmosphere. Since scientists have never found a planet with a diatomic atmosphere like the earth’s, speculation that the newly-discovered planets may have such an atmosphere has no basis in observational science.
The sun, crucially, provides abundant light for life on the earth. However, the light from Trappist-1 on the newly-discovered planets is only about 1/200th the strength of the sun’s light on the earth—something similar to a permanent twilight, and certainly not enough light to support the earth’s ecosystems. The light from Trappist-1 is also much redder than the sun’s light, which results in even weaker photosynthesis. In addition, because the planets are so close to Trappist-1, they do not rotate, but rather are “gravitationally locked” or “tidally synchronized,” meaning that one side is always facing the star and the other side is always facing away. The result is a very uneven distribution of temperature, with half of the planet being very cold and very dark, the brightest part of the planet being very hot, and only a dim sliver of the planet with a pleasant temperature. However, that small zone with a pleasant temperature would likely be constantly beset by powerful winds.
A larger problem with dwarf stars like Trappist-1 is that they are usually variable stars whose energy output is very inconsistent. This means that a planet orbiting one those stars would alternate from being frozen solid (when the star’s energy output wanes) to being burning hot (when the star’s energy output increases). In addition, M-dwarf stars (the type where most of the new planets are being discovered) periodically emit powerful flares of far greater intensity than any solar flare. Since planets have to be very close to dwarf stars in order to have surface temperatures which could allow for liquid water, the effect of these flares would be absolutely devastating to life on those planets (if it existed). The sun, by contrast, is not just another star; it differs from every other known star in that it has an extremely consistent energy output, creating the stable conditions needed for life. The sun is also just the right size to give the earth the perfect balance of warmth and light.
While the earth relies on the sun to produce the light and heat needed for life, the sun also produces damaging radiation. The earth has a magnetic field of the ideal strength to keep radiation from the sun (and other celestial bodies) from damaging life. Also, without a magnetic field, solar radiation would strip the earth of its atmosphere over time. This magnetic field is created by electrical currents within the earth. While the earth’s magnetic field has weakened considerably since Creation (electrical currents encounter resistance), it still exists at a strength which gives good protection to life. But while life cannot exist without a magnetic field to protect it, a magnetic field that is too strong would create catastrophic physical damage (e.g., melting the earth). A magnetic field must exist at the right strength to be right for life. As for the seven recently-discovered planets, they are gravitationally locked, and gravitationally locked planets likely do not have magnetic fields, meaning that they cannot protect their atmospheres or their surfaces against radiation.
Not just the sun, but also the moon plays an important role in supporting life on the earth. The moon is the perfect size, composition, and distance from the earth. It is 400 times smaller than the sun, but also 400 times closer to the earth than the sun, so that it appears exactly the same size as the sun in the sky. It gives enough light to keep nights from being completely dark, but it is not so bright as to make sleep difficult. The moon moves about 1.5 inches further away from the earth each year (lunar recession), but basically stays in the same place over time on a biblical timescale (though it would have moved off into space long ago on an evolutionary timescale). Critically, the moon stabilizes the earth’s rotation, keeping the poles consistently at about 23.5 degrees, which in turn stabilizes the earth’s climate and produces seasons. This stabilization occurs because the moon orbits the earth in the same plane as the earth orbits the sun and is relatively large in comparison to the earth. By contrast, the satellites of other planets are generally far smaller than the planets they orbit, and they orbit these planets around their axis of rotation (and thus do not provide stabilization).
Somewhat surprisingly, the other planets in the solar system are also necessary for life on the earth. The largest planet, Jupiter, is particularly helpful—it is too far away to pull the earth or the moon out of orbit, but its gravity deflects most of the asteroids and comets that come hurtling in our direction. It was for this reason that the scientific community got excited in 2002 over the possibility of extraterrestrial life when a “Jupiter-like” planet was discovered orbiting the star 55 Cancri. However, the orbit of this planet is much more elliptical than the planets in our solar system, meaning that it would cross the orbit of any “Earth-like” planet in the system, disrupting its orbit and thereby rendering conditions for life impossible. While the earth and other planets in the solar system have low orbital eccentricity (making the earth’s temperature and orbit stable), most exoplanets have high orbital eccentricity (i.e., are highly elliptical), except for the ones that are very close to the stars they orbit and are therefore gravitationally locked. In the case of the seven planets revolving around Trappist-1, Danny Faulkner notes, “Numerous simulations revealed that the system likely would disrupt within a half-million years” because of gravitational interactions among the planets. Obviously the evolutionary timescale requires far more than 500,000 years for life to evolve.
Finally, the Milky Way is an ideal galaxy for life, and the sun is in an ideal location within the Milky Way. Our night sky is just dark enough, with just the right number of visible stars, none of which is excessively bright, and which are distributed fairly evenly throughout the sky.
The earth has the perfect conditions for life to exist. These conditions are so specific, there is probably no other place in the universe that has these conditions—that is, there are no other earths. Speculating that planets which are barely detectable may have conditions suitable for life to exist is not scientifically responsible. But the conditions for life to exist are different than the conditions for life to evolve. In fact, it is absolutely impossible for life to evolve; one of the most basic principles of biology is that life only comes from other life. The most fundamental characteristic of the earth that makes it able to support life is that it already supports life, diverse life. Living things on the earth depend on other living things to survive and provide balance to the earth’s ecosystems; new life arises when existing life reproduces. The Bible teaches that all life is ultimately sourced in God the Creator, who not only created biological life, but also fine-tuned a planet and a universe to support it. The discovery of “Earth-like” planets, which in fact are not truly Earth-like, is not a discovery of extraterrestrial life and does not provide supporting evidence for Darwinian evolution.