Fun fact about the "Book" of Enoch.
It's not one book.
What we tend to call "The Book of Enoch" or "1 Enoch" is, in fact, several books written at different times.
Scholars recognize different works. The Book of the Watchers is one of the more fabulous and sensational of the works which make up 1 Enoch, comprising chapters 1-36. It is probably the earliest, written early-ish in the 2nd Temple Period, sometime probably between the 4th and 3rd centuries BC at the earliest. The Book of the Watchers is an attempt by the unknown author to elaborate on small and obscure set of statements made in the book of Genesis, found in chapter 6 of that book:
"When man began to multiply on the face of the land and daughters were born to them, the sons of God saw that the daughters of man were attractive. And they took as their wives any they chose. Then the Lord said, 'My Spirit shall not abide in man forever, for he is flesh: his days shall be 120 years.' The Nephilim were on the earth in those days, and also afterward, when the sons of God came in to the daughters of man and they bore children to them. These were the mighty men who were of old, the men of renown." - Genesis 6:1-4 (translation: ESV)
So little is written, and yet it invites the reader to wonder just what is meant here. And there's no answers to be found to such questions.
Another Genesis mystery is the very brief statement made earlier about a man named Enoch,
"Enoch walked with God, and he was not, for God took him." - Genesis 5:24
This statement shows up suddenly in a list of genealogy, Jared had a son named Enoch, then Enoch had a son named Methuselah--standard genealogical stuff for the Bible. But this statement about Enoch walking with God and "was not, for God took him" is sudden and happens without any other context.
This made Enoch a fascinating character. And over time an elaborate set of legends, myths, and ideas evolved surrounding the figure of Enoch.
Our first glimpse of this Enoch literature is the Book of the Watchers, comprising the first section of the composite work known as 1 Enoch. An expansion on the brief and vague statements made in Genesis 6:1-4 that interprets those statements as involving a group of angels known as the Watchers who end up falling from grace because they were seduced by the beauty of human women. Which ends up producing a race of demi-celestial creatures, the "nephilim" of Genesis 6:1-4).
In the Septuagint the word nephlim is translated into Greek as gigantes, "giants", possibly because Goliath of Gath is, later in the Hebrew Bible, connected with the nephilim as well as the inhabitants of Ai in Canaan. The Hebrew Bible certainly does speak of Goliath and the inhabitants of Ai as of large stature, though "giant" here is relative. In the Septuagint (and early Hebrew versions of the Hebrew Bible) Goliath's height is nearly 7 feet tall. Tall, and really tall compared to ancient people living in that part of the world, but not fantastically tall. Later Hebrew manuscripts, such as the Masoretic Text of the late medieval period records Goliath's height as much more fantastical, at nearly 10 feet. The older sources present us with a much more realistic height. Though I am only conjecturing as to why the translators of the Septuagint rendered nephilim as "giants" in Greek.
Back to Enoch, the Book of Enoch (1 Enoch) as mentioned is divided into several sections, written at different times during the 2nd Temple and post-Temple period. The Book of the Parables may date to sometime between the mid 2nd to 3rd centuries AD.
By late Antiquity the figure of Enoch and Jewish mystical and legendary ideas surrounding Enoch had become much more elaborate. In the 5th-6th century AD/CE work, known as 3 Enoch, a mystical-apocalyptic Jewish work, the visionary is the historical Rabbi Ishmael ben Elisha Nachmani--though written centuries after he lived, thus this is a pseudopigraphical work--experiences mystical things in the heavens. One of the more fantastical of these visions is an encounter with a quasi-deified Enoch, who after being taken up into heaven by God was transformed into the archangel Metatron and given the position of being second only to God. Apparently this was a bit too fantastic, as it appears that there was a later interpolation into the text, which inserts a heretical rabbi as, upon seeing this, declares "There are indeed two powers in heaven!" and is rebuked, and then God walks back Enoch/Metatron's gloriousness--it's an odd sequence in the text.
So Enoch emerged in the 2nd Temple Period as an apocalyptic figure, and stories about Enoch continued to evolve into being more mystical and elaborate--eventually, at peak Enoch fanfiction, Enoch is actually turned into a kind of second-god (though at this point, it seems things had gone too far with Enoch, and so that gets heavily criticized).
What all of these things have in common, of course, is that absolutely none of it has anything meaningful to say in regard to the study of science.
-CryptoLutheran