The history of man is full of stories, myths, and speculations about life elsewhere in space. From Star Trek to Star Wars we have seen not only science fiction but reputable main-line science crank out story after story and speculation after speculation about life forms on other planets orbiting other stars. With the recent discoveries of hundreds of planets circling other stars there has been a lot of gasoline thrown on the fire of speculation as to whether there are other planets with other sentient beings asking the same questions that we are asking here on earth.

The question of life elsewhere has no direct implications for those of us who believe in the God of the Bible. The Bible has no direct mention of life or the lack of life elsewhere, and the message of Jesus Christ is directed to those living on this planet. Any mention of what that message might be for a “Mr. Spock” who lives on some other planet is purely speculative.

There has been a recent flood of mainstream articles in the media on planets like Gliese 581g which is claimed to be “the first extrasolar planet likely to be hospitable to life” (Science News, November 6, 2010, page 14). Some of these claims turn out to be premature, as did this one. On October 11 the Geneva Observatory in Switzerland announced it could find no evidence of that planet, and whether it is eventually found or not points out how desperate some seem to be to find a life-supporting planet. We once again want to emphasize that this issue has no biblical ramifications, and certainly such planets will eventually be found even if this one turns out to be a case of overzealous misinterpretation.

All of this posturing over life in space is rooted in an oversimplification of what it takes to have a place like Earth. The sole criterion for an earth-like planet in these scientific discussions is whether or not the planet in question has a “habitable zone.” It turns out a habitable zone is defined by these researchers as one where liquid water can be found. It may sound as though every planet would have a habitable zone, because if a star is very hot the planet can simply be farther from it to reduce the temperature or if the star is cooler the planet can just get closer to it and raise the temperature. The problem with that view is that there are other parameters affecting whether or not water can exist as a liquid. If a planet is too small, then it does not have enough gravity to hold the water. The reason there is virtually no hydrogen in the earth’s atmosphere is that our gravity is too weak to hold hydrogen and any hydrogen that is in our atmosphere will escape to outer space because of our weak gravity. A planet like Mercury has virtually no gases in its atmosphere because of its small mass. There are similar complications if a planet is too large. So the planet’s size is also a factor in the planet’s habitable zone.

The shape of the orbit of a planet around its star is also an issue. If the orbit of a planet is eccentric (very oval), then as it goes around its star the temperatures will vary radically. When the orbit is close to the star (perihelion) the temperatures will go very high and when it is at its greatest distance from the star (aphelion) the temperature will go very low. Most extrasolar planets have been found to have very elliptical orbits. The earth’s orbit is much more circular avoiding extremes in how much energy reaches the surface.

Articles in the mainstream media about life in space infer that if there is a habitable zone there will automatically be life on that planet. The fact is that there is a variety of other factors that must be carefully managed for life to exist on a planet. Stars give off a variety of very destructive radiations that are a product of the nuclear reactions that provide the energy of the star. Any planet that harbors life must have a series of defense systems to protect against the radiation. In the earth’s case there are several such defense systems. We have a strong magnetic field which deflects radiation if the particles are charged, as many of them are. The atmosphere is also a part of the defense of any planet that allows life to exist on it. The earth’s atmosphere not only has a thickness that absorbs some radiations, but it also has layers within the atmosphere that remove certain kinds of radiation. Most of us remember discussions of the ozone layer of our atmosphere which protects life on the planet from incoming ultraviolet radiation. The ozone layer is just one of as many as a dozen layers, each designed to handle a particular kind of radiation from reaching the surface of the earth.

In addition to radiation, a planet needs a shielding device to protect against incoming solid objects. As natural processes take place in space, there are chunks of rock ranging in size from hundreds of miles in diameter to micrometers. We have names to describe these objects such as meteoroids, asteroids and comets. These solid objects have to be intercepted to prevent them from having a negative impact on life forms on any planet. In the case of the earth we have an incredible system of planets placed at strategic distances and having carefully designed sizes so that their gravitational fields absorb debris coming in along the ecliptic which otherwise would pose a significant hazard to life forms on this planet. Neptune, Uranus, Saturn, Jupiter and the Moon all serve as shields to the earth. In the past few years we have witnessed Jupiter taking direct hits that otherwise might have posed a threat to the planet on which we live.

Having stable weather conditions on a planet is also a prerequisite to life. Neptune is a planet where we have seen lightning bolts the size of the state of Texas, and where wind velocities exceed 1,000 miles per hour. Weather conditions are controlled by many things — the tilt of the planet on its axis, how fast it spins, and the chemistry of its atmosphere are probably the three biggest factors. The 23 1/2 degree tilt of the earth on its axis allows a constant shifting of the maximum absorption areas of the surface of the planet. The fact that the Sun’s  direct rays move from day to day distributes the heat allowing stability and minimizing violent winds.

The spin rate of the planet is also critical. If the planet spins too slowly, the surface heats up to extreme values causing thermal movement of air creating violent conditions. If it spins too fast, the wind velocities become extreme. Jupiter’s spin rate is one revolution in less than ten hours causing wind velocities of hundreds of miles per hour. Having roughly 75 percent of the planet’s surface covered with water also has a positive effect upon how our planet handles heat imbalances, with hurricanes being our most common violent adjustment to heat imbalances. Venus, with large quantities of sulfuric acid in its atmosphere, will obviously be quite different.

This very brief and oversimplified picture should say to us that we see what we have on this planet as something very special, very fragile, very much worth taking care of. If God has chosen to do similar work elsewhere, we will perhaps eventually find out about it. What the creation should say to us now is “The heavens are telling the glory of God; the skies show forth the work of His hands. Day after day they speak, and night after night they reveal knowledge” (Psalm 19:1 – 2a, The Word: The Bible from 26 Translations).
--John N. Clayton

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