In a recent documentary Into the Universe With Stephen Hawking, British physicist Stephen Hawking claims that intelligent alien life forms almost certainly exist. However, he cautions that communicating with them could be dangerous, since they may be looking for new planets to conquer. More optimistic, Guy Consolmagno, the Pope's astronomer, suggested that aliens might have souls and could thus be baptized--if they were to request it.
Many people share Hawking’s belief in the existence of aliens. In 1992 the US space agency NASA launched a major project to search for extra-terrestrial intelligence. This project, called SETI (short for: Search for Extra-Terrestrial Intelligence) uses radio telescopes around the world to examine distant stars for signals that might be of artificial origin. Thus far the results have been completely negative. Discounting flying saucer reports, no signs of aliens have been detected.
The Scientific Case for Aliens
How strong is the scientific case for aliens? Estimates vary considerably.
The optimists assert that many stars have planets, that a good fraction of those planets are suitable for life, that life will in fact develop on a sizeable proportion of such inhabitable planets, and, finally, that a significant number of these life-bearing planets will produce intelligent societies. Even if the fraction in each step is on the small side (say, 1 out of 100), the huge number of stars in our Galaxy alone, estimated at about 300 billion, would still leave us with a potential of approximately 3000 intelligent civilizations in our Galaxy. Many of these are likely to be much more advanced than us.
On the other hand, the pessimists point out that all of the above factors are highly uncertain, that attaching numbers to them is no more than guessing, and that, in fact, some of the required steps in the chain seem to be extremely unlikely - if not impossible - on the basis of current scientific knowledge.
Although a number of stars have recently been found to have planets, few of these seem to be habitable. Just last week the discovery was announced of a just-right, Goldilocks planet. The planet orbits the star Gleise 581 and is said to have three times the mass of the earth, an orbital period of 37 days, a rocky sufrace, and a temperature hospitable to life. Dr Steven Vogt, the discoverer, believes "chances for life on this planet are 100 percent...It's pretty hard to stop life once you give it the right conditions." This claim is based on the supposition that water could exist in liquid form on the planet and that, on earth, life is always found where there is water.
Yet, it should be kept in mind that this planet has not been directly observed. All its properties are surmised from tiny wobbles found in the motion of the parent star. In particular, no actual rocky surface, liquid water or life-supporting atmosphere have been observed. The official research report in fact notes that the wobbles could be due to measurement errors and that the tentative conclusions must be confirmed by further research.
Contrary to Vogt's optimism, given a habitable planet--even with liquid water and all other conditions needed for life--the naturalist, chances for life to evolve are extremely improbable. Paul Davies (Are We Alone? 1995, p.28) estimates the odds against random permutations of molecules assembling DNA as about 104000 (1 followed by 4000 zeros) to one against! This is about the same as tossing a coin and getting heads 130,000 times in a row. At that rate Davies concludes that, over ten billion years, we wouldn't expect to find another DNA molecule in the observable universe.
What about the chances of life evolving into civilization? Stephen Webb [If the Universe is teeming with aliens -Where is everybody? 2002, p.239] contends that of the alleged 50 billion speciation events in the history of the earth only one led to language—which is the key to civilization. Hence Webb concludes that we must be alone in the universe.
Optimists, such as Jack Cohen and Ian Stewart (Evolving the Alien: The Science of Extraterrestrial Life 2002) argue that life may take on many different forms, beyond our imagination. Perhaps. However, given the above immense odds against the chance emergence of intelligent life, such considerations seem unlikely to reduce the odds sufficiently to favour the existence of aliens.
Motivation For Belief in Aliens
Given the lack of scientific evidence, why do so many people believe in aliens? The motivation seems to be primarily psychological and philosophical. Consider the words of Carl Sagan (Broca’s Brain 1979, p.276):
“The translation of a radio message from the depths of space...holds the greatest promise of both practical and philosophical benefits. In particular, it is possible that among the first contents of such a message may be detailed descriptions for the avoidance of technological disaster, for a passage through adolescence to maturity...”
Paul Davies (1995, p.136) comments:
“The interest in SETI among the general public stems in part, I maintain, from the need to find a wider context to their lives than this earthly existence provides. In an era when conventional religion is in sharp decline, the belief in super-advanced aliens...can provide some measure of comfort and inspiration...This sense of a religious quest may well extend to the scientists themselves, even though most of them are self-professed atheists.”
It is ironic that man, even after having rejected God, still searches the heavens for his salvation.
From a Christian perspective, should we expect aliens to exist?
It is certainly possible that God has directly created intelligent beings on other planets. Yet Scripture makes no mention the creation of intelligent beings beyond of the earth (except, of course, the angels). To this one might suggest that God my not have deemed it necessary to inform us of such creatures.
The foremost theological issue concerns Christ's incarnation. Was it unique? Or did it re-occur on other planets, as was postulated by theologian Paul Tillich? Augustine (354-430) already noted that the historical process of creation, fall, and redemption could occur only once. This seems clear from such biblical texts as "for Christ also has once suffered for sins" (I Peter 3:18) and "Christ being raised from the dead dies no more...he died unto sin once" (Romans 6:9-10).
John Jefferson Davis [1997, "Search for Extraterrestrial Intelligence and the Christian Doctrine of Redemption". Science & Christian Belief 9 (No.1): 21-34] suggests that Christ’s unique incarnation as a human nevertheless suffices for the redemption of all intelligent beings in the universe. However, Scripture makes a necessary connection between the first Adam and the second Adam, Christ. For Christ's sacrifice to be sufficient it was essential that Christ have a human nature:
Forasmuch then as the children are partakers of flesh and blood, he also himself likewise took part of the same...For verily he took not on him the nature of angels; but he took on him the seed of Abraham. Wherefore in all things it behoved him to be made like unto his brethren, that he might be a merciful and faithful high priest in things pertaining to God, to make reconciliation for the sins of the people. (Hebrews 2:14-17)
Aliens, like angels, are not descendants of Adam. They thus share neither his nature nor guilt. Hence Christ's sacrifice is of no avail to them. Man is the only creature to be thereby saved from the consequences of his sinfulness. Thus, if aliens exist, either they have not fallen from grace or, less happily, like the fallen angels, they cannot be redeemed.
Man has a special relation to God. Man alone was created in the image of God and appointed to rule over creation. Even stars were created primarily to serve as lights and signs for man. Finally, at the end of times, Christ returns to the earth, the abode of man, to judge living and dead. Man is to judge the angels (I Cor.6:3). The New Jerusalem comes down from heaven to earth. All this reinforces the special place of man in God's creation.
In conclusion we note that there is no scientific evidence in support of the belief in aliens. Indeed, there has been no sign of life of any form on any of our planets. Searches for interstellar life, scanning nearby stars for radio signals or noise indicative of civilization, have virtually ruled out the possibility of advanced civilized life within a hundred light years. To span greater distances even an extremely fast rocket travelling at a tenth of the speed of light would take longer than a millennium, and radio dialogues would have century-long gaps. Thus, for all practical purposes, communication with extra-terrestrial civilizations can be ruled out.
From an evolutionary perspective, the odds are so heavily stacked against the chance occurrence of life, particularly intelligent life. Theological considerations based on biblical revelation weigh very heavily against the presence of aliens, but not conclusively so.