David Sedley
Rabbi, teacher, author, husband, father

Parshat Nitzavim: On the impossibility of space travel

How NASA proved the Rambam wrong
Illustrative: An astronaut with Earth in the background. (Public domain/pxhere)
Illustrative: An astronaut with Earth in the background. (Public domain/pxhere)

Aristotle (384–322 BCE) was perhaps the single most influential thinker to shape the Western world. His ideas dominated science, philosophy, and almost every field of human thought for almost two millennia. His “main interests” were “Biology, Zoology, Psychology, Physics, Metaphysics, Logic, Ethics, Rhetoric, Music, Poetry, Economics, Politics, and Government,” according to Wikipedia. That is a lot of fields. It is possible that nobody in history ever knew as much or wrote influentially on as broad a range of topics as Aristotle.

Yet we now know that almost everything he claimed, in matters of science, at least, was completely wrong.

But he dominated Western thought for so long because his ideas were adopted by the Church, and later by some Muslim and Jewish thinkers, becoming almost canonical.

And the main reason Aristotle was popular with monotheistic theologians was that his idea of a prime (or unmoved) mover, fit almost too perfectly with their concept of God. Aristotle wrote:

It is clear… that there is a substance which is eternal and unmovable and separate from sensible things. It has been shown also that this substance cannot have any magnitude, but is without parts and indivisible [with no] finite magnitude… But it has also been shown that it is impassive and unalterable…” (Metaphysics 12:7).

Engraving of Aristotle teaching Alexander the Great by Charles Laplante. (Public Domain/WIkimedia Commons)

If Aristotle’s words seem familiar, it may be because it is extremely similar to the very beginning of Rambam’s monumental work on Jewish law, Mishneh Torah. In fact, Rambam’s reliance on Aristotle was one of the reasons the medieval French rabbis banned his books.

One of the many things that Aristotle was completely wrong about (and perhaps we will touch on others in future essays) was his belief that the earth was made up of four elements, but the heavens were composed of the aether (though he never used that term) — a fifth element (“quintessence”), which was unchanging and unlike anything in the physical world.

Aristotle’s theory placed the earth, where all physical action occurred, firmly at the center of the universe, and the moon, sun, and stars were all outside this realm, moving in perfect, spherical orbits.

Although built on and developed from the teachings of Plato (who developed an earlier idea of Empedocles), Aristotle’s was certainly not the only theory of the earth’s place in the heavens. For example, Aristarchus of Samos (c. 310 – c. 230 BCE) placed the sun at the center of his universe and put the planets in their correct order. Aristarchus’s theory had the advantage of being much closer to what we now know to be the scientific truth.

Justus Sustermans – Portrait of Galileo Galilei, 1636. (Public Doman/ Wikimedia Commons)

But for hundreds of years, up until Copernicus, and even after, the Western world accepted that the earth was the center of the universe, and the heavens were a place of perfection, untouchable by humans or any physical matter. How Galileo Galilei (1564–1642) must have wished that Aristarchus’s theory had trumped Aristotle’s in this matter, as he was forced to recant his heliocentric “heresy,” while apocryphally uttering the phrase, “Eppur si muove” (“And yet it moves”).

In Parshat Nitzavim we read:

It is not in heaven, to say: “Who will go up for us to heaven, and take it for us, that we may hear it and do it?” Nor is it over the sea, to say: “Who will travel over the sea for us, and bring it unto us, and make us hear it, that we may do it?” But this matter is very close to you; in your mouth and in your heart, to perform it. (Deuteronomy 30:12-14).

While there are several explanations in the Talmud, and even more in the commentaries, Rashi, citing Eruvin 55a, gives the plain meaning of these words. “But if it were in heaven, you would have to ascend after it and learn it.”

“Heaven” in this context does not mean some spiritual realm, for the Torah certainly was in that spiritual realm and Moshe did have to go there to bring it down to Mount Sinai. “Heaven” in this context means the realm of the sun and the moon, which is physically distant, and parallels “over the sea,” which is similarly distant (Maharsha states explicitly that the verse refers to “beyond the sphere of the moon”).

For Rashi and most of the classical commentators, traveling beyond the earth to obtain the Torah would have been extremely difficult, just like traveling to a distant land over the sea.

But for the Aristotelian-influenced Rambam, leaving the earth for the heavens would have been physically impossible.

Below the sphere of the moon, God created a [type of] matter which differs from the matter of the spheres. He created four forms for this matter, which differ from the forms of matter of the spheres, (Yesodei Hatorah 3:10).

Rambam maintained that there was no way physical matter could ever pass into the realm of the heavenly spheres, stars, or planets. Those bodies are made of perfect, unchanging matter, possess souls, knowledge, intellect, and constantly praise God (ibid. 9). For Rambam, space travel contradicts the laws of philosophy.

Rambam’s theory of the nature of the universe opens his halakhic magnum opus. And it led Rabbi Yaakov Kamenetsky, one of the great rabbinic leaders of the second half of the 20th century, to remain glued to a television screen on July 16, 1969, as first Neil Armstrong, and then Buzz Aldrin, stepped foot on the moon. Up until that moment, Rabbi Kamenetsky’s faith in Rambam had been far stronger than his trust in NASA. Witnessing that monumental event caused him a crisis of faith.

He wrote in Emet LeYaakov (Bereishit 1:1 p. 15), “When we saw men descending from a spaceship on a ladder onto the surface of the moon. I thought to myself: ‘What would the Rambam, who wrote that the moon has a spiritual form, answer now?’ I thought that, at that point, Kabbalah defeated philosophy… But I could not accept that his words were a mistake. If Rambam could be mistaken in Hilkhot Yesodei HaTorah, why should he not also be mistaken in Hilkhot Shabbat or other places?… “

Rabbi Kamenetsky was forced to concede that the opening of Rambam’s monumental work of Jewish law was not, in fact, part of the Torah.

“We are forced to say that what Rambam taught us in these chapters (Hilkhot Yesodei Hatorah, Chapters 1-4) is neither ma’aseh merkavah (‘the works of the chariot’) nor ma’aseh bereishit (‘the works of creation’). Rather, he wrote those four chapters from his deep mind and from his knowledge of secular wisdom, i.e., not from the wisdom of Torah, but only from philosophy… and Rambam only wrote these as an introduction to the Mishneh Torah while the main part of the book begins with Chapter Five.”

(Shortly after the Apollo mission, Rabbi Menachem Kasher wrote a Hebrew pamphlet entitled “Man on the Moon” in which he deals with halakhot related to the moon landing, and he too rejects Rambam’s Aristotleanism)

So history proved that in this regard Rashi was correct — space travel is extremely difficult. But Rambam’s reliance on Aristotle led him to begin his Mishneh Torah with bad science.

About the Author
David Sedley lives in Jerusalem with his wife and children. He has been at various times a teacher, translator, author, community rabbi, journalist and video producer. He currently teaches online at WebYeshiva. Born and bred in New Zealand, he is usually a Grinch, except when the All Blacks win. And he also plays a loud razzberry-colored electric guitar.
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