Origin of the Moon - Round World Version - Morgoth's Ring Session 2

[AbelardsJunk]

During the brief discussion of "Melkor's Lunar Base" it is a shame there was not more time to discuss real world scientific theories. I cannot recall when I saw some nerdy documentary explaining the "Theia" origin theory of a collision. So, that got me wondering, what was the most prevalent theory when Tolkien wrote this? When did Theia theory originate?

I started here: https://en.wikipedia.org/wiki/Theia_(planet) .


From the beginning of modern astronomy, there have been at least four hypotheses for the origin of the Moon:

1. A single body split into Earth and Moon
2. The Moon was captured by Earth's gravity (as most of the outer planets' smaller moons were captured)
3. The Earth and Moon formed at the same time when the protoplanetary disk accreted
4. The Theia-impact scenario described above.

The lunar rock samples retrieved by Apollo astronauts were found to be very similar in composition to Earth's crust, and so were likely removed from Earth in some violent event.[9][12][13]

By 2012, Matija Ćuk and Sarah Stewart theorized that Theia could explain why Earth's core is larger than expected for a body its size; Theia's core and mantle could have fused with those of Earth.[14]

Evidence published in 2019 suggests that Theia might have formed in the outer Solar System, and that much of Earth's water originated on Theia.[15]


Melkor spitefully hurling another planet at Arda is at least as epic as ripping a chunk out of it. More, I say. Lose the hokey lunar base (the arctic is way better anyway), while keeping the Eucatastrophe of the beauty of the Moon and...

Is that Ulmo riding that planet?! Ulmo was doing his thing further from the Sun as the universe cooled. Swimming around on pre-frozen Europa. Comet surfing. And just as he's starting to really starting like this planet he's working on, Melkor shows up and chucks it across the system. Thus was born the eternal enmity of Ulmo and Melkor. And Melkor in his pride and folly saw not the harm he brought on himself introducing Ulmo to the other Valar. And ever after was Ulmo a dissenting voice among the Powers, for he came from his solitude in the outer worlds and sought ever the solitude of the Deeps for his meditations.

Meanwhile, it was mostly Aule quieting the tumults of Lava Arda while Manwe holding the atmosphere in place. "Manwe, dearest," interrupted Varda. "Casteth thy far-seeing eyes at yon celestial body descending upon us from the Void!" And so he did. Thus he spake, "Oh sh" --

What did Melkor do when he left Arda over "creative differences?"

THIS

Then gathered Melkor the hardest metals from the cores of both worlds, took it to the Sun and there forged Grond: Hammer of the Underworld.

 

[MithLuin]

So, that got me wondering, what was the most prevalent theory when Tolkien wrote this? When did Theia theory originate?

So, the support for the Theia theory mostly happened in the 1970's and 1980's, as a result of studying the moon rocks brought back during the Apollo missions (1969-1972). J.R.R. Tolkien lived until 1973. So, there is some overlap there, but it certainly wasn't well established during his lifetime.

How did the Moon form? | Natural History Museum

Professor Sara Russell explains the origins of Earth’s closest companion.

www.nhm.ac.uk

Here's some background on when the various theories were proposed, and when they were accepted or discounted.

The origin of the Moon: how it formed and how we found out

This is the story of how we uncovered the Moon's explosive origins

www.sciencefocus.com

1. Fission Theory - A single body split into Earth and Moon
   • Proposed by George Darwin in 1879
   • The idea was that a tidal bulge of molten earth broke off to form the moon, leaving the Pacific Ocean basin behind
   • 1930 - Evidence against this idea in the form of fluid dynamics. Geophysicist Harold Jeffreys showed that if a bulge were to form, it would slow earth's spin, not allowing it to become rapid enough to fling off matter
   • variations persisted until the 1960's
2. Capture Theory - The Moon was captured by Earth's gravity (as most of the outer planets' smaller moons were captured)
   • Proposed by Thomas Jefferson Jackson See in 1909
   • In 1952, supported by chemist Harold Urey and astronomer Horst Gerstenkorn as a gradual event, rather than a rapid one
3. Accretion Theory - The Earth and Moon formed at the same time when the protoplanetary disk accreted
   • Proposed by French mathematician Pierre-Simon Laplace in 1796
   • Based on Immanuel Swedenborg's nebular hypothesis (1735)
   • Not widely accepted
   • Astronomer Gerard Kuiper revived the theory in the 1950's, accounting for the large size of the moon relative to the earth
   • In the 1970's, Soviet astronomer Victor Safronov introduced the idea of planetesimal bodies, that could collide to form planets
4. The Giant Impact Theory - Theia-impact scenario
   • Proposed by Canadian geologist Reginald Aldworth Daly in 1946
   • Meant to account for the size of the moon and propose a new mechanism for the earlier fission theory
   • Largely ignored until 1975 - after the Apollo missions
   • In 1984, the scientific community reached consensus that this theory best explained the data from the Apollo mission moon rocks

So, to map this on to Tolkien's life and work:
When Tolkien was a child, the prevailing explanation of 'where did the moon come from?' would have likely been Darwin's Fission Theory.
In 1930, that theory was more or less disproven.
During the 1950's and 60's, the debate was between Urey's version of Capture Theory and Kuiper's version of Accretion Theory. This maps to the time that Tolkien was working on the Morgoth's Ring material (post LotR)
We landed on the moon in July 1969. Post Apollo missions, it turned out that...no one was right.
But Tolkien died in 1973, before William K Hartmann and Donald R Davis published their 1975 paper on the giant impact hypothesis.