Here is a fascinating back and forth discussion on whether humans can ascend to God's heavenly realm AND whether God can descend to ours -- the answer seems to be that there must always be a ten tefachim (ten handbreadth) separation of the two realms.
Let's listen to what the Sages say:
[4b] The Holy Ark was nine tefachim tall and the thickness of the Ark-cover was one tefach; we have here ten. And it is written: It is there that I will set My meetings with you, and I shall speak with you from atop the Cover.
[5a] And it was taught in a Baraisa: R’ YOSE SAYS: THE DIVINE PRESENCE HAS NEVER DESCENDED BELOW into the human domain., AND MOSES AND ELIJAH NEVER ASCENDED TO THE HEAVENS, AS IT IS STATED: AS FOR THE HEAVENS, THE HEAVENS ARE GOD’S; BUT THE EARTH HE HAS GIVEN TO MANKIND [Psalms 115:16]
And the Shechinah never descended below? But it is written: God descended upon Mount Sinai! [Exodus 19:20]
The Gemara answers: The Shechinah remained above ten tefachim from the mountaintop.
The Gemara persists: But it is written: On that day His feet will stand on the Mount of Olives! [Zechariah 14:4]
And Moses and Elijah never ascended to the Heavens?! But it is written: And Moses ascended to God! [Exodus 19:3]
The Gemara answers: Moses remained below ten tefachim from the Heavens.
Commentary: That is, the purely human domain is the airspace up to ten tefachim from the ground, while the purely Godly domain extends down to the ten tefachim below the lower limit of the Heavens. The intervening area is sometimes called Earth and sometimes called Heaven, and may accommodate either the Shechinah or man. (Chasam Sofer [Machon Chasam Sofer ed.]; Menachem Meishiv Nefesh, quoting Yad David; see also HaKoseiv in Ein Yaakov).
The Gemara persists: But it is written: And Elijah ascended to Heaven in the whirlwind.
The Gemara answers: Elijah remained below ten tefachim.
The Gemara again asks: But it is written: He allows him to grasp the face of the Throne; He spreads upon him His cloud.[Job 26:9] And R’ Tanchum said regarding this verse: It teaches that the Almighty spread some of the radiances of His Presence and His cloud upon [Moses].
The Gemara here, too, answers: Moses remained below ten tefachim.
The Gemara persists: Nevertheless, it is written: He allows him to grasp the face of the Throne.
The Gemara answers: The Throne was lowered for [Moses] until it reached ten tefachim, and [Moses] grasped it there. Hence, Moses did not leave the earthly domain.
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[5a2] THE TZITZ WAS A SORT OF GOLD PLATE, TWO FINGERBREADTHS WIDE AND ENCIRCLING the Kohen Gadol’s forehead FROM EAR TO EAR. AND INSCRIBED ON IT, on TWO separate LINES, were the words “HASHEM” (i.e. the Tetragrammaton) ON THE UPPER line AND “HOLY TO” ON THE LOWER. AND R’ ELIEZER THE SON OF R’ YOSE SAID: I SAW [THE TZITZ] IN THE CITY OF ROME, AND “HOLY TO HASHEM” WERE all INSCRIBED ON ONE LINE.
Commentary: [the Tetragrammaton] – the full four-letter Name of God [yud, kei, vav, kei] (Rashi to Shabbos 63b). The Baraisa, however, mentions only the first two letters to avoid spelling out the entire Name. And although these first two letters themselves form a Name [yud, kei], which also should not be spelled out, here it is permitted because the Baraisa mentions the two letters only as an allusion to the full four-letter Name.
Chasom Sofer [Machon Chasam Sofer ed.] derives from Tosafos that the prohibition against pronouncing the four-letter Name includes even stating its individual letters in order; this Tosafos, then, is the source of the custom of saying, yud, kei, vav, kei, wherein the two kei letters are replaced.
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[It is interesting to note that even though R’ Eliezer gave an eyewitness account that contradicted the Sages’ opinion, the Sages still relied on their tradition. This is because the Sages concede that a tzitz is valid “after the fact” if both words are inscribed on one line. The Sages felt that the tzitz observed by R’ Eliezer was just such a case, and therefore did not disprove their insistence that “in the first instance” the words appear on two lines.]
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[5b1] And what is the meaning of the word k’ruv [cherub]? R’ Abahu said: “like a child,” for indeed in Babylonia they call a child “ravya.”
Abaye said to [R’ Ababu]: But then, how do you explain that which is written: the one face, the face of the Cherub; the second face, the face of a man. [Ezekiel 10:14]. Now, if the word “cherub” (k’ruv) means “like a child,” then the face of the Cherub is the same as the face of a man! Since, however, the verse separates “cherub” and “man” into two categories, it would seem that the word “cherub” does not refer to a child.
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Rather, according to R’ Yehudah, [the Sages] learned an oral tradition that a succah requires walls ten tefachim tall. For Rav Chiya bar Ashi said in the name of Rav: Measures, interpretations and partitions are oral laws given to Moses at Sinai that have no Scriptural basis. Hence, according to R’ Yehudah, the minimum height requirement of a legal wall including a succah wall, is a Halachah LeMoshe MiSinai.