Is the solar system in the Lord of the Rings based on our real solar system?

Question

There is an interesting article where an astronomer has matched the planets of our solar system to names referenced in the Lord of the Rings novels. It includes a very nice artist's depiction with the planets and their Tolkienesque names and such.

But is the realistic scientific view of our solar system a part of the Lord of the Rings universe? If I understand it correctly, though there has been a flat earth and a round earth, the Earth has always been the centre of the universe, with a much smaller sun and earth moving through the sky, like an actual geocentric model of the universe. Is this correct?

Answer 1

Tolkien does write that Middle Earth is essentially our earth, in a fictional past:

I have, I suppose, constructed an imaginary time, but kept my feet on my own mother-earth for place. I prefer that to the contemporary mode of seeking my own remote globes in 'space'. However curious, they are alien, and not lovable with the love of blood-kin. [...] Many reviewers seem to assume that Middle-earth is another planet!

(Letters of J.R.R. Tolkien, letter No. 211 (a very good letter))

Many of the ME stars are also references to real stars. Of course, Arda changes radically after the first age. Before that, Aman and Middle Earth were two continents on a flat(!) Arda, encircled by the Sun (Anar) and the Moon (Rana). Then, Illúvatar curved down the corners of the Earth (or something), and made Arda round. And after the fall of Númenor, Illúvatar removed Aman from Arda, and changed continents and oceans.

So, to answer your question: third age (and later) Arda is practically identical to Earth (astronomically), and first age somehow seems to be flat and different. (Yes, I know, it's weird)

As a reference: This answer of mine includes a map of Arda 'after the war of the Gods' (first age)

EDIT: here is the 'changing of the world' bit from Akallabêth:

Then Manwe upon the Mountain called upon Illúvatar, and for that time the Valar laid down their government of Arda. But Illúvatar showed forth his power, and he changed the fashion of the world; and a great chasm opened in the sea between Númenor and the Deathless Lands, and the waters flowed down into it, and the noise and smoke of the cataracts went up to heaven, and the world was shaken. [...]
But the land of Aman and Eressea of the Eldar were taken away and removed beyond the reach of Men for ever. [...]
For Illúvatar cast back the Great Seas west of Middle-earth, and the Empty Lands east of it, and new lands and new seas were made; and the world was diminished, for Valinor and Eressea were taken from it into the realm of hidden things.

And here is a bit from 'Of the Sun and the Moon and the Hiding of Valinor' (Silmarillion):

But the Flower and the Fruit [of the now dead Two Trees] Yavanna gave to Aule, and Manwe hallowed them, and Aule and his people made vessels to hold them and preserve their radiance: as is said in the Narsilion, the Song of the Sun and the Moon. These vessels the Valar gave to Varda, that they might become lamps of heaven, outshining the ancient stars, being nearer to Arda; and she gave them power to traverse the lower regions of Ilmen, and set them to voyage upon appointed courses above the girdle of the Earth from the West unto the East and to return.

And to show that the night sky was indeed the same as ours: In 'Of the Coming of the Elves and the Captivity of Melkor', Varda makes the stars (and planets, all are described as stars here):

[...] and therewith she made new stars and brighter against the coming of the First-born; wherefore she whose name out of the deeps of time and the labours of Eä was Tintalle, the Kindler, was called after by the Elves Elentári, Queen of the Stars. Carnil and Luinil [lit. red and blue (stars?)], Nenar and Lumbar, Alcarinque and Elemmire she wrought in that time

Those were the planets

and many other of the ancient stars she gathered together and set as signs in the heavens of Arda: Wilwarin, Telumendil, Soronúme, and Arríma; and Menelmacar with his shining belt, that forebodes the Last Battle that shall be at the end of days. And high in the north as a challenge to Melkor she set the crown of seven mighty stars to swing, Valacirca, the Sickle of the Valar and sign of doom.

(This sickle is also found in LotR, chapter 'Strider'):

The Sickle* was swinging bright above the shoulders of Bree-hill.

and the footnote:

*The Hobbits' name for the Plough or Great Bear

More on the planets:

There are some notes on Star-names at the end of "Morgoth's Ring":

In the second, all but final, draft my father is seen in the act of devising the names of the constellations, with various experimental forms before those that appear in the final text were reached; but he set down the names of the stars without hesitation, thus: *Karnil, Luinil, Nénarm Lumbar, Alkarinque, Elemmire. Above Karnil he wrote 'M', above Lumbar 'S', above Alkarinque 'Jup', and above Elemmire again 'M'. No letter stands above Luinil, but above Nénar there is an 'N' which was struck out.
Now if Alkarinque is Jupiter, then a great red star named Karnil and marked with an 'M' must be Mars - which in turn leads to the identification of Lumbar ('S') with Saturn, and Ellemire ('M') with Mercury. [...]

He is unsure about the the identities of Luinil and Nénar. They seemed to be Neptune and Uranus, but that doesn't fit in with the text 'new stars and brighter against the coming of the First-born'

So we know:

• Carnil is Mars
• Luinil is not definite, 'luin' is blue, so people guess it might be Neptune, or even Orion (a constellation)
• Nénar is also not definite, maybe Uranus
• Lumbar is probably Saturn
• Alcarinque is Jupiter
• Elemmire is Mercury

Answer 2

"But is the realistic scientific view of our solar system a part of the Lord of the Rings universe?"

Yes. Tolkien was actually very concerned about having his created world match what was known by science. There are examples in his Letters e.g relating to association of the Witch-king's Fell Beast with prehistoric creatures, but specific to this question I'm going to refer you to Myths Transformed Essay 1 (published in Morgoth's Ring) where he states:

At that point I was inclined to adhere to the Flat Earth and the astronomically absurd business of the making of the Sun and Moon. But you can make up stories of that kind when you live among people who have the same general background of imagination, when the Sun 'really' rises in the East and goes down in the West, etc. When however it is the general belief that we live upon a 'spherical' island in 'Space' you cannot do this any more.

Note in particular that he says "you cannot do this any more" - Tolkien is quite prepared to let scientific knowledge guide the structure of his world.

"If I understand it correctly, though there has been a flat earth and a round earth"

This is true of the published Silmarillion, but in actual fact Tolkien had begun to abandon the old "Flat Earth" versions of the story, and had even gone so far as to write a "Round Earth" version of the Ainulindale, given as version "C*" in Morgoth's Ring.

What he had not done was incorporate the "Round Earth" changes into his other Tales, so the Tales of the Trees, the Sun and the Moon and the Fall of Numenor were never updated to reflect this new thinking. As a result Christopher Tolkien reverted to the "Flat Earth" versions for the published Silmarillion (CT also freely admits that there may have been an element of personal preference - one gets the sense that he just liked those versions).

"the Earth has always been the centre of the universe, with a much smaller sun and earth moving through the sky, like an actual geocentric model of the universe. Is this correct?"

Not really, no. Tolkien doesn't actually state much that gives any indication of relative size and positions, at least outside of the older cosmology of the Ambarkanta (published in the Shaping of Middle-earth).

It's important however to realise that this is intended to be a mythical cosmology, and not a physically accurate description of the world. Tolkien says as much - and quite directly - earlier in the same Myths Transformed essay I previously cited:

The High Eldar living and being tutored by the demiurgic beings must have known ... the 'truth' (according to their measure of understanding). What we have in the Silmarillion etc. are traditions handed on by Men in Numenor and later in Middle-earth (Arnor and Gondor); but already far back ... blended and confused with their own Mannish myths and cosmic ideas.

That Arda is the Solar System is beyond doubt; Tolkien said so in the Athrabeth Finrod ah Andreth (also Morgoth's Ring) as well as elsewhere:

Physically Arda was what we should call the Solar System. Presumably the Eldar could have had as much and as accurate information concerning this, its structure, origin, and its relation to the rest of Ea (the Universe) as they could comprehend.

So if the Eldar have accurate information (or at least access to accurate information) about the physical nature of the world, then it becomes obvious that any statements in the books that contradict that nature are part of the Myth.