This week’s parasha is Vayelech, which begins with Moses’ statement that “Today I am one hundred and twenty years old” (Deut. 31:2). It was the 7th of Adar, Moses’ birthday, and also his day of passing. Moses goes on to conclude his final speech to the people, then sings a deeply prophetic farewell song in next week’s portion Ha’azinu, followed by his blessings to the people in the last parasha of the Torah, V’Zot HaBracha.
Moses was the greatest of all prophets, the humblest man to walk the earth, and the central founding figure of Judaism. He was blessed with living a full and healthy life spanning exactly 120 years. It has become common today for people to wish each other 120 years of life. Why is this the specific figure? Can humans not live longer? Don’t we see in Genesis that Adam lived 930 years, Noah lived 950 years, and Methuselah (Metushelach) lived a record 969 years? What happened?
The Flood Generation
Ten generations from Adam, the world had descended into endless sin and immorality. God decreed that man’s days “will be numbered at one hundred and twenty” (Genesis 6:3). Many believe this to mean that God decreed humans will no longer be able to live past 120 years. Indeed, when looking at modern records of longevity, the vast majority of the world’s oldest people die close to 120 years. There has only been one official case of anyone exceeding 120, a Frenchwoman named Jeanne Calment who lived 122 years.
However, the traditional Jewish interpretation is that the Genesis verse above does not mean man is unable to live past 120. After all, our forefathers Abraham, Isaac, and Jacob lived long after this decree, and they lived 175, 180, and 147 years, respectively. Rather, the Jewish Sages state that God decreed the arrival of the Great Flood 120 years hence. God gave mankind 120 years to repent, and possibly avert the Flood. Noah was commissioned to go around and inspire people to mend their ways, and he had 120 years to do it.
Unfortunately, Noah failed in this endeavour, unable to bring even a single person to righteousness (as the Ark only carried his own family at the end). This is one reason for why the Flood is known in Hebrew as mabul Noach, literally “Noah’s Flood” (or mei Noach, “Noah’s waters”), as if he was partially responsible for not doing enough to inspire people to change. Because of this, many (including Rashi) have commented on the verse “Noah was a righteous and pure man in his generation” (Genesis 6:9) to mean that Noah was only righteous in his faulty generation. Had he lived in another generation, such as that of Abraham, he would not have been deemed so righteous!
We see from the Biblical chronology that after the Flood, people’s life spans steadily shorten. Moses’ older siblings Aaron and Miriam lived 123 and 126 years. Moses died at 120, and this appears to have become the new limit. After Moses, there are only a few people noted to have lived longer, one of which is Yehoyada the High Priest, who lived 130 years (II Chronicles 24:16).
What accounts for this steady degeneration in longevity?
The Talmud (Shabbat 112b) states: “If the earlier [scholars] were sons of angels, we are sons of men; and if the earlier [scholars] were sons of men, we are like asses…” This is one of many passages that attests to the well-known concept of yeridat hadorot, “the descent of the generations”. It is said that each passing generation falls lower and lower in its wisdom and spiritual greatness. This concept can solve the puzzle of longevity.
The body is a finite lump of matter. It is only animated and vitalized by the infinite soul within it. Thus, the greater the soul, the longer the body can live. As the spiritual potential in each generation falls, so too does the lifespan.
Moreover, it is taught that Adam contained essentially all of the souls of humanity within him (Sha’ar HaGilgulim, ch. 11). As more and more people were born over the centuries, this single universal soul broke down further and further into smaller and smaller fragments. With the exception of a number of “new souls”, the vast majority of the world’s 7 billion people are all parts of the soul of Adam. It is therefore not surprising that today’s spiritual capabilities (and with that, the lifespans) are severely limited.
At the Speed of Light
Science may offer another intriguing possibility. According to modern physics, time as we know it doesn’t really exist. The universe is one interwoven fabric of both time and space. The faster one moves through space, the slower the effects of time for that person. There is actually a formula to measure the impact of this time dilation, known as the Lorentz transformation. It is given by the equation ΔT = t√1-v2/c2, where v is one’s speed and c is the speed of light.
Theoretically, the speed of light is the absolute maximum in our universe. At light speed (just under 3.00 x 108 m/s, or 300,000 km/s), time will totally stop for the traveller (if plugging it into the formula, one gets a value of zero). This seems impossible. However, if we plug in a value very close to light speed, such as 2.99 x 108 m/s, we get a very interesting result.* A person who has perceived living 80 years will have actually lived 980 earthly years! That makes Adam’s 930 years a more palatable 76, and Methuselah’s record 969 as 79. This fits in well with the verse in Psalms that a normal lifespan is 70 to 80 years (Psalms 90:10). But how could Adam and Methuselah have lived at near-light speed?
Beautifully, the Sages teach us that Adam was not a human like us. In many texts (such as Bereshit Rabbah 20:12), Adam is described not simply as a being of flesh, but rather as a being of light. Though most will interpret this metaphorically, there are those sages, such as the Arizal (for example, in Sefer HaLikutim, Bereshit, ch. 3) that interpret this quite literally. It remains to be seen what this means exactly, and if it has anything at all to do with physics, but perhaps there is much more to the idea of Adam being a man of light than we can imagine.
*To be fair, choosing a value such as 2.99 x 108 m/s may be deemed quite arbitrary. One can also plug in finer values even closer to the speed of light, such as 2.997 or 2.9972, and so on, each of which would give a more refined result. The point of this exercise is simply to illustrate the relativity of time, and what might explain the difference in perceived years between our generations and those of the first people, through a scientific perspective.