> Current Issues > Science & Medicine

The Anthropic Principle

May 9, 2009 | by Prof. Nathan Aviezer

Scientists call it the "Goldilocks" story. Alone among planets, earth supports human life, because it is "not too hot and not too cold, not too hard and not too soft, but just right".

In recent years, it has become clear to many scientists that the universe appears as if it were specifically designed for the existence and well-being of human beings. This phenomenon, which has attracted considerable scientific attention, has become known as the "Anthropic Principle" -- from the Greek word anthropis, meaning "man."

The Anthropic Principle expresses itself in two ways:

  1. even very slight changes in the laws of nature would have made it impossible for life to exist, and
  2. human life would not have been possible were it not for the occurrence in the past of a large number of highly improbable events.

Whereas the secular scientist sees such a sequence of occurrences as mere "lucky accidents," the believing Jew sees in them the guiding hand of the Creator.

Let us look at some of them.


Because of the extreme conditions present in the interior of the sun, a proton may occasionally transform spontaneously into a neutron, which like the proton is a fundamental particle of nature. The resulting neutron can combine with another proton to form a composite particle known as a deuteron. These deuterons "burn" via a thermonuclear reaction and this "burning" provides the intense heat and brilliant light of the sun. Thus, deuterons constitute the solar fuel that generates the energy of the sun which enables life to exist on earth. A very important feature of solar "burning" is that it occurs very gradually.

The possibility of proton-neutron combination and the impossibility of proton-proton combination both depend on the strength of the "nuclear force," one of the fundamental forces in nature. (The other fundamental forces include the familiar force of gravity and the electromagnetic force.) Detailed calculations of the nuclear force have demonstrated the following results:

  • If the nuclear force were only a few percent weaker, then a proton could not combine with a neutron to form a deuteron. If this were the case, no deuterons would be formed in the sun and hence no solar fuel would exist. As a result, the sun would not shine ("burn"), but would merely be a cold ball of inert gas -- precluding the possibility of life on earth.

  • If the nuclear force were only a few percent stronger, then each proton would rapidly combine with another proton with explosive results. If this were the case, the sun would soon explode and thus cease to "burn," once again precluding the possibility of life on earth.

It is an extraordinary fact that the strength of the nuclear force just happens to lie in the narrow range in which neither of these two catastrophes occurs.


It is not necessary to elaborate on the necessity of water and air for the existence of life. The earth has an abundant supply of both, permitting life to flourish here, while our two neighboring planets, Venus and Mars, are both devoid of water and air, and hence are devoid of life. These facts may not seem particularly noteworthy, but we shall see just how remarkable they really are.

Our neighboring planets, Venus and Mars, are both devoid of water and air, and hence are devoid of life.

It was recently discovered that, shortly after they were formed, all three planets -- Earth, Venus and Mars -- had large amounts of surface water. The deep channels that are observed today on the surface of Mars were carved out long ago by the copious fast-flowing Martian primordial surface waters. Similarly, Venus was once covered by deep oceans which contained the equivalent of a layer of water three kilometers deep over its entire surface.

However, in the course of time, all surface waters on Mars and Venus disappeared. How did earth escape this catastrophe?

The answer is that earth escaped this catastrophe by sheer "accident!"

Earth just happens to be sufficiently distant from the sun that our surface water neither evaporated nor decomposed, as happened on Venus. Moreover, earth just happens to be sufficiently near the sun that the temperature remains high enough to prevent all the oceans from freezing permanently, as happened on Mars.

The same balance rules the earth’s atmosphere.

Recent studies of the carbonate-silicate geo-chemical cycle have shown that the planetary atmosphere involves the subtle interplay of many factors. This interplay is so delicate that if the earth were only a little closer to the sun, surface temperatures would be far higher than the boiling point of water, precluding all possibility of a life-sustaining atmosphere.

Similarly, if earth were only a little farther from the sun, the concentration of carbon dioxide would become so high that the atmosphere would not be breathable by human beings. Fortunately, the orbit of our planet just happens to lie at the crucial distance from the sun that permits the formation of a life-sustaining atmosphere.

This remarkably fortunate coincidence is known among scientists as "the Goldilocks problem of climatology." Recall the children's story in which Goldilocks found the various items of Baby Bear to be "not too hot and not too cold, not too hard and not too soft, but just right." In that vein, scientists refer to the existence of water and air on earth as another example of the Anthropic Principle.


After being the undisputed masters of our planet, all the dinosaurs worldwide suddenly became extinct. This sudden destruction of all the dinosaurs, together with most other animal species, is the most famous of a number of such mass extinctions that have occurred periodically in the history of our planet, each time abruptly wiping out the majority of animal species.

The sudden disappearance of the dinosaurs has baffled scientists for many years. What could have caused the abrupt demise of these extremely successfully animals after they had enjoyed such a long period of dominance? What occurred to suddenly wipe them out?

After years of debate, the riddle of what caused the sudden and total destruction of the dinosaurs was finally solved in 1980 by Nobel laureate Luis Alvarez and his son Walter. The two showed that a giant meteor from outer space had collided with the earth, causing a worldwide catastrophe. This explanation for this and other mass extinctions -- that is, the impact of meteors or comets colliding with the earth -- has become known as the "impact theory." The scientific evidence in favor of the impact theory accumulated rapidly, and by 1987, Professor Alvarez could point to 15 different pieces of scientific data that supported the theory.

In recent years, it has become clear to many scientists that the universe appears as if it were specifically designed for the existence and well-being of human beings.

The point of central importance to our discussion is that the collision between a meteor and the earth was a matter of sheer luck. This has been repeatedly stressed by the leading paleontologists. For example, Professor David Raup, past president of the American Paleontological Society, has taken precisely this point as the central theme of his famous article (since expanded into a book with same title), "Extinctions: Bad Genes or Bad Luck?" Raup emphasizes the role played by "luck" in mass extinctions:

The extinction of a given species or higher group is more bad luck than bad genes. Pure chance would favor some biologic groups over others.

Professor David Jablonski of the University of Chicago, a world authority on the subject of mass extinctions, echoes this opinion:

When a mass extinction strikes, it is not the "most fit" species that survive; it is the most fortunate. Species that had been barely hanging on ... inherit the earth.

These leading paleontologists are emphasizing that if a giant meteor suddenly falls from the sky and wipes out some species, while permitting other species to survive and ultimately to flourish, then the latter species were blessed with good luck -- the occurrence of an extremely improbable and totally unexpected event.

The Darwinian principle of "the survival of the fittest" is irrelevant in such a process.


Why is the sudden destruction of all the dinosaurs worldwide a dramatic example of the Anthropic Principle?

As long as the dinosaurs dominated the earth, there was no possibility for mammals to exist. Only after the dinosaurs were wiped out could the mammals flourish and become the dominant fauna.

This intimate connection between human beings and the dinosaurs was emphasized by Professor Alvarez, who ends his article about the abrupt destruction of all the world's dinosaurs, with the following stirring words:

From our human point of view, that impact [of a meteor] was one of the most important single events in the history of our planet. Had it not taken place, the largest mammals alive today might still resemble the rat-like creatures that were then scurrying around trying to avoid bring devoured by dinosaurs.

But there is even more to the story. For human beings to exist today, it was not sufficient merely that such an impact with the meteor occurred. The impact had to have occurred with the right strength.

As Professor Alvarez explains:

If the impact had been weaker, no species would have become extinct; the mammals would be subordinate to the dinosaurs, and I wouldn't be writing this article. If the impact had been stronger, all life on this planet would have ceased, and again, I wouldn't be writing this article. That tells me that the impact must have been of just the right strength [to ensure that] the mammals survived, while the dinosaurs didn't.


A few years ago, I wrote a book on Biblical creation and science, titled "In the Beginning," showing that current scientific evidence is in remarkable agreement with the Biblical account of the origin and development of the universe. My book has enjoyed a measure of success, and has been reprinted ten times and translated into Hebrew, Russian, French, Spanish,Portuguese and Norwegian.

However, the book was not to everyone's taste. Professor Raphael Falk, a geneticist at the Hebrew University and a militant secularist, was so outraged by my book that he published a 10-page article devoted solely to attacking both my book and me personally.

It is important to explain what is wrong with Falk's argument, because his error is not immediately obvious and, in fact, has been repeated by many other writers.

A rare, extremely improbable event occurs if one defines the conditions before knowing what will happen.

For example, he writes: "I pull a $1 note from my wallet and observe its serial number to be G65538608D ... [probability for occurrence] was less than 1 in 10 billion. Thus, undeniably, I am faced here with an extremely rare event ... but I am not surprised. What is essential is to make the crucial distinction between improbable events that are genuinely surprising and those that are not..."

What is wrong with this reasoning?

There was a probability was not 1 in 10 billion but 100 percent that the dollar note pulled from the wallet had G65538608D for its serial number! Why? Because this number was chosen by looking at the serial number on the $1 note. In other words, one was simply asking, "What is the probability that the serial number on the note is the serial number on the note?" And the answer to this question, clearly, is 100 percent. Since the event was not improbable at all -- but certain -- there is no reason whatever to be surprised by its occurrence...

A rare, extremely improbable event occurs if one defines the conditions before knowing what will happen.

For example, if one chooses a serial number before pulling the $1 note from the wallet, and then find that the number chosen is exactly the same as the number on the note, we would all be absolutely astonished -- and with good reason!


Among the popular national lotteries in Israel is "Lotto." Say, for example, that one million people buy a Lotto ticket each week. If I am informed that this week's winner is Chaim Cohen from Afula, I will certainly not get very excited about it. But why not? The chances that Chaim Cohen would be the winner were only 1 in 1 million -- and it happened!

The reason for my lack of excitement is the following. I could not care less if the Lotto winner is Chaim Cohen from Afula, Sarah Levi from Beer Sheva, or Shmerel Berel from Ramat Gan. In other words, each of the 1 million Lotto players is completely equivalent in my eyes to Chaim Cohen from Afula. (The technical term for this in statistics is "equivalent microstates.")Although the chances were only 1 in 1 million that the winner would be Chaim Cohen from Afula, there exist 1 million "equivalent" Chaim Cohens. Therefore, the substance of what I heard is that someone won the Lotto this week. And the chances for that event happening -- someone winning -- are 100 percent. Hence, I have no reason to be surprised.

Now consider a slightly different scenario. If I were informed the following week that Chaim Cohen from Afula again won the Lotto, I would most certainly be amazed, and so would anyone else. But why? The chances of Chaim Cohen winning Lotto the second week were exactly the same as his chances of winning the first week. The answer is that the context is entirely different.

In the first week, Chaim Cohen was just 1 out of 1 million equivalent Lotto players. But in the second week, he has become a unique individual -- the fellow who won last week. In other words, in the second week, there exists only one Chaim Cohen -- only one previous week's winner. When such a rare event occurs, we are all genuinely surprised.

Finally, if we were to learn that Chaim Cohen from Afula had again won the Lotto for the third consecutive week, it is clear that suspicion, not surprise, would be the natural reaction. Indeed, there is little doubt that the fraud division of the police department would soon be paying Chaim Cohen a visit to discuss with him just how it happen that Chaim won the Lotto for three consecutive weeks.

But why? The chances of Chaim Cohen winning Lotto in the third week were exactly the same as his chances of winning first week. The answer again lies in the context of the event. In the third week, Chaim Cohen is an extremely unusual individual -- the fellow who has already won the Lotto for two weeks running. The chances that same person will win the Lotto again are easily shown to be one in a million-millions. Such events so rare that they simply do not occur. Therefore, the police department directly suspects that a guiding hand behind Chaim Cohen's triple win.

A guiding hand in the creation of the universe means the intercession of Almighty, but a guiding hand in "determination of the Lotto winner" means five years in prison!


We shall next consider card games, beginning our discussion with the game poker -- in particular, five-card poke without a draw. In this game, each player is dealt five cards from the deck and these cards form a combination (such as a pair, three-of-a-
kind, a flush, etc.). Each combination has an agreed ranking, and the game is won by player whose cards form the highest-ranking combination.

The highest-ranking combination cards in poker is the straight flush. A straight flush is so rare that one can play poker all day, every day of his life, and never see one. And if a poker player should ever get a straight flush, he will never forget
it. It's the dream of every poker player!

We now turn to a different card game: bridge. In this game, each player is dealt 13 cards, but we will consider only the first five cards to enable us to make a comparison with poker. If a bridge player's first five cards were to be the combination that constitutes a straight flush in poker, he would probably not even be aware of it because, in bridge, a "straight flush" has no value or meaning whatever.

A "straight flush" -- prized in poker -- is meaningless in bridge.

This combination of cards is not even defined in bridge, hence I put quotation marks around the words "straight flush." Thus, we see that the exact same combination of cards is considered a wondrous combination in poker because of its rarity and value,but is considered a meaningless combination in bridge, despite its rarity, because it has no value.

The preceding examples and discussion pave the way for the answer to our central question: What conclusions may one draw from the Anthropic Principle?

The answer depends on one's views regarding the significance of human beings. In our example about poker and bridge, we explained why the extremely rare straight flush is a wondrous event in a poker game, but a meaningless event in a bridge game. In other words, the same rare event can be either wondrous or meaningless: it all depends on the importance that one attributes to the event itself.

Returning to the subject of our article -- human beings -- we saw that many extremely unlikely events ("a staggeringly improbable series of events ... quite unrepeatable" in the words of Stephen Jay Gould) had to "occur" to make possible the appearance of human beings on earth.

Thus, the extreme rarity of the events leading to human existence is well established. Indeed, that is the scientific content of the Anthropic Principle. But before we can decide on the meaning of these events, we must first decide on the meaning of the end product -- human beings.

If humans are assumed to be just another species in the animal kingdom (as the secularists believe), not more important than any other of the approximately two million species discovered so far, then the Anthropic Principle has no meaning. We have seen that rarity by itself is not significant. It is a "straight flush" in bridge, rare and interesting, but without any meaning.

If, however, one believes that human beings are the most important species in the world and that humanity is the entire reason for the creation of the universe -- as the Torah and the Sages of the Talmud repeatedly emphasize -- then the Anthropic Principle is of the utmost significance. It is a straight flush in poker, the most meaningful of occurrences.

In summary, the scientists have discovered that, in the existence of human beings, the universe has dealt out the extremely rare straight flush. Everyone agrees with that -- the Anthropic Principle has become a scientifically established fact.

If a non-believer is "playing bridge," the Anthropic Principle means nothing to him.

By contrast, the believing Jew is "playing poker" and therefore the Anthropic Principle is yet another example of the harmony that exists between modern science and words of the Torah.


Leave a Reply

🤯 ⇐ That's you after reading our weekly email.

Our weekly email is chock full of interesting and relevant insights into Jewish history, food, philosophy, current events, holidays and more.
Sign up now. Impress your friends with how much you know.
We will never share your email address and you can unsubscribe in a single click.
linkedin facebook pinterest youtube rss twitter instagram facebook-blank rss-blank linkedin-blank pinterest youtube twitter instagram