Okay, I got this stuck in my head, so: what if we converted the Finwean births into the new aging system?
From AAm, plus the statement in VII that Feanor was begotten 9 VY before he was born, we have this timeline:
- 1160 - Begetting of Feanor
- 1169 - Feanor born
- 1170 - Death of Miriel
- 1181 - Begetting of Fingolfin
- 1190 - Fingolfin born
- 1221 - Begetting of Finarfin
- 1230 - Finarfin born
- 1251 - Begetting of Fingon
- 1260 - Fingon born
- 1280 - Finarfin m. Earwen
- 1291 - Begetting of Finrod & Turgon
- 1300 - Turgon & Finrod born
- 1353 - Begetting of Aredhel
- 1362 - Aredhel born
What aging system was Tolkien using? VII comes shortly after V in the NoME chronology. V states that Eldar gestated for 9 SY (and the slightly earlier X implies this was 10 times longer in Aman), then grew at a rate of 12:1 (compared to mortals) until 24 (male) / 18-21 (female), and then at a rate of 144:1 thereafter. Under this system, Finarfin is 25.5 (equivalent) at his marriage, and nearly 27 at the birth of Finrod. (Interestingly, whatever system we use, Fingon and Finrod were born at the exact same point in their fathers' lives.)
Under the aging system used in the Final Timeline, from XVIII, gestation took 3 SY, a growth year = 3 SY, and a life-year (after 24 GY) = 144 SY. Finarfin now takes only 396 SY to reach the "age" he was at Finrod's begetting, compared to 610 SY in the AAm. We could apply that same compression to all the dates, assuming (eg) Fingon should be the "same age" when his brother Turgon is begotten, and end up with a significantly compressed Finwean timeline that would definitely pull Aredhel back before the making of the Silmarils.
But... the XVIII aging scheme specifically states 'in Middle-earth', and elsewhere says something like 'whatever aging system is assumed for Aman'. That's great for Galadriel, since it means that her "20 growth-years" can be more than 60 SY, but it doesn't pin down how long they should be
instead. I've looked over the texts immediately before XVIII, and it doesn't look like Tolkien ever really pinned that down.
I actually suspect that's because of this exact problem: if he specified how fast the Eldar aged in Aman, he would have to edit the Annals/Tale of Years. That was a big task, and I get the feeling he just didn't want to touch it.
EDIT: I went through and calculated it out how the Final Timeline would look with faster aging, and to my amazement it actually... fits together?
Crucially, the two methods of calculating Finrod & Turgon's birth give the same value. Only one event moves around, and I don't see "Finarfin was married only after Fingon was born" as a crucial point in Tolkien's mind.
The ages given by the AAm timeline / aging system look very deliberate: both Finarfin and Turgon were begotten almost exactly when their older siblings reached full growth (meaning that blisteringly short gap between Feanor and Fingolfin hits even harder). I would actually quite like to use this.
But... is it too much? Am I mind-reading Tolkien too far? Is this
really justified as "simple calculations" when I'm moving entire blocks of the timeline around?
hS