One of the unique aspects of Judaism is its far reaching universality. Not only does Judaism provide a lesson for every human being, its teachings extended to the very boundaries of the universe.
It is an axiom of Judaism that the entire universe was created for the sake of man. In one place, the Talmud reckons that there are some [10 to the 18th power] stars in the observable universe, and explicitly states that they were all created for the sake of man. It goes further to state that all the angels and spiritual worlds also only exist for this purpose.
Of course, this immediately raises a question that many find quite difficult. How is it possible that man, living on a dust mote called planet Earth, should be the center of the universe? Our Sages realized the vast number of stars in the universe, and also realized that many of them were many orders of magnitude larger than the earth. (Maimonides - Foundations of Torah 3:8)
...It should be quite simple to understand that size and quantity alone are meaningless to an infinite God. There is absolutely no question that the human brain is vastly more complex than the greatest galaxy, and furthermore, that it contains more information than the entire observable inanimate universe. Beyond that, man is endowed with a divine soul that towers over even the highest angels.
Although the creation of such a vast universe for the sake of man does not defy logic, we still need to seek out a reason for its necessity. Some sources state that by contemplating the greatness of the universe, one can begin to comprehend that of God, and thereby fear Him all the more (Maimonides - Foundations of Torah 2:2).
However, if we speak of the possibility of extra terrestrial life, we must explore the question somewhat further.
THE FREE WILL QUESTION
One of the first to discuss the question of extraterrestrial life in general was Rabbi Chasdai Crescas (Or Hashem 4:2). After a lengthy discussion, he comes to the conclusion that there is nothing in Jewish theology to preclude the existence of life on other worlds.
As possible evidence for extraterrestrial life, he quotes the Talmudic teaching (Avoda Zara 3b) that "God flies through 18,000 worlds." Since they require His providence, we may assume that they are inhabited.
Of course, this Talmudic quotation is by no means absolute proof, for it may be speaking of spiritual worlds, of which an infinite number were created.
One could also attempt to support this opinion from the verse (Psalms 145:13), "Your kingdom is a kingdom of all worlds." However, here, too, this may be speaking of spiritual universes.
The exact opposite opinion is that of Rabbi Yosef Albo, author of the "Ikkarim." He states that since the universe was created for the sake of man, no other creature can exist possessing free will. Since any extraterrestrial life would neither have free will nor be able to serve a creature having free will (as terrestrial animals and plants serve a terrestrial man), they would have no reason for existing and therefore be totally superfluous.
One could bring some support to the second opinion from the Talmudic teaching that every land where it was not decreed for man to live was never subsequently inhabited. However, here again, it is not absolute proof, since this may only refer to our planet.
THE STAR OF MEROZ
Between these two extremes, we find the opinion of the Sefer Habris who states that extraterrestrial life does exist, but that it does not possess free will. The latter is the exclusive possession of man, for whom the universe was created. The 18,000 worlds mentioned earlier, in his opinion, are inhabited physical worlds.
The proof that he brings for his thesis is most ingenious. In the song of Deborah, we find the verse, "Cursed is Meroz... cursed are its inhabitants" (Judges 5:23). In the Talmud, we find the opinion that Meroz is the name of a star. According to this opinion, the fact that Scripture states, "Cursed is Meroz... cursed are its inhabitants" is clear proof from the words of our Sages for extraterrestrial life.
Of course, even this proof is subject to refutation, for the Zohar also follows the opinion that Meroz is a star, yet states that "its inhabitants" refers to its "camp," that is, most probably, to the planets surrounding it. Nevertheless, the simple meaning of the verse seems to support the opinion of the Sefer Habris.
The Sefer Habris goes on to say that we should not expect the creatures of another world to resemble earthly life, any more than sea creatures resemble those of land.
He further states that although extraterrestrial forms of life may possess intelligence, they certainly cannot have freedom of will. The latter is an exclusive attribute of man, to whom was given the Torah and its commandments. He proves the latter thesis on the basis of the above-mentioned Talmudic teaching that all the stars in the observable universe were created for the sake of man.
WINGS TO ESCAPE THE EARTH
...The basic premise of the existence of extraterrestrial life is strongly supported by the Zohar. The Midrash teaches us that there are seven earths. Although the Ibn Ezra tries to argue that these refer to the seven continents, the Zohar clearly states that the seven are separated by a firmament and are inhabited. Although they are not inhabited by man, they are the domain of intelligent creatures.
We therefore find the basic thesis of the Sefer Habris supported by a number of clear-cut statements by our Sages. There may even be other forms of intelligent life in the universe, but such life forms do not have free will, and therefore do not have moral responsibility.
Freedom of will, however, is not at all an observable quantity. Even its existence in man has been hotly debated by the secular philosophers. Indeed the main proof that man does indeed have free will comes from the fact that God has given him moral responsibility, namely the Torah. It is in this sublime, yet unobservable quality, that man is unique.
However, if we assume this to be true, we would return to the basic question of Rabbi Yosef Albo, mentioned earlier: If such creatures never have any utility for man, what is their reason for existence?
We find a most fascinating answer to this question in the Tikunei Zohar. Speaking of the verse (Song of Songs 6:8), "Worlds without number," the Tikunei Zohar states: "The stars certainly are without number. But each star is called a separate world. These are the worlds without number."
The Tikunei Zohar further states that every tzaddik (righteous person) will rule over a star, and therefore have a world unto himself. The 18,000 worlds mentioned above would therefore be that number of stars, presided over by the 18,000 tzaddikim that are alluded to in the verse (Ezekiel 48:35), "Around Him are 18,000." However, these may only refer to those worlds visited daily by the divine presence, but there may be innumerable worlds for the lesser tzaddikim.
We therefore have a most fascinating reason why the stars were created, and why they contain intelligent life. Since an overcrowded Earth will not give the tzaddikim the breadth they require, each one will be given his own planet, with its entire population to enhance his spiritual growth.
Once we know that the stars and their planets were created as an abode for the tzaddikim, we might naturally wonder how they will be transported to them. However, the Talmud even provides an answer to this question. Discussing the passage (Isaiah 40:31), "They shall mount up with wings as eagles," the Talmud states that in the future world, God will grant the tzaddikim wings to escape the earth. The Zohar goes a step further and states that "God will give them wings to fly through the entire universe."
In a way, this teaching predicts the advent of space travel. But more than that, it provides us with at least one of the reasons why space flight would be inevitable as part of the prelude to the messianic age. This, of course, could bring us to us general discussion of the role of modern technology in Torah perspective, a lengthy subject in its own right.