Answer: The span of each generation is defined by its mission.
In the Torah, one can see how the definitions of “generation” have changed according to times and places. Adam and Eve’s generation lasted 930 years. The ten generations from Adam to Noah lasted over a thousand years. The period from Noah to Abraham is estimated to be about 892 years. 430 years passed from the time G-d informed Abraham about the exile his descendants would endure in Egypt and the Exodus from that exile.
The Moses’ generation (those who received the Torah and wandered in the desert) is known to have lasted 40 years. The next generation that was led by Moses’ closest disciple, Joshua, to conquer the Land of Israel lasted about 30 years.
Our generation is known as, “the seventh generation” – the term brought by the Rebbe in his famous maamar “Bati Le-Gani”.
מתוך התוכנית הלימודית “ג’ תמוז. מי יעצור את השמש”.
Indeed, the dissemination of Chassidic teachings began in the time of the Alter Rebbe, who was born in 5505 (1745). His direct descendant, the Rebbe, Rabbi Menachem Mendel Schneersohn describes our generation as the “seventh” – and transitional – generation, counting from the Alter Rebbe:
“We are the last generation of Exile and the first generation of the ultimate redemption. We are the generation to complete the work of all the generations before us, to finally bring heaven down to earth”.
It can therefore be concluded that the term ‘generation’ is not just a technical or biological concept. It is meant to describe the special role of every era in history.
Without this change of perception, there is no meaning to the progression of generations.
The special role assigned to each generation is best recognized by observing its leadership. As Rashi, the classic commentator on the Torah writes, “The leader of the generation is like the entire generation because the leader is equivalent to all” (Bemidbar 21:21).
Every generation has its leader – a leader like Moses, who encourages and helps the entire Jewish people fulfil their special role and mission in the world. Kabbalah and Chassidut explain that this is because the soul of the leader of the generation includes and reflects all the souls of the generation.