For Friday Night

"When G-d gave the Torah," our Sages write, "He opened the seven firmaments for the Jewish people. Just as He tore open the upper realms, so He tore the lower realms. They saw that G-d is the ultimate reality." What does this mean? Obviously, some kind of spiritual revelation. But what was it that they saw? what are the "upper realms" and the "lower realms" which g-d "tore open" for us?

"And you who cleave to G-d, are all alive today" (Deuteronomy 4:4). To "cleave" means to join together, to be one. How can this word apply to the relationship of a tiny human being and boundless, eternal G-d?

What does it mean to "lengthen" the echad ("one") of the Shema?