Before scientists understood thermonuclear fusion , converting hydrogen to helium plus energy, what was the leading theory of the nature of the sun’s power and composition?
One big-ass lump of burning coal?
Let’s ask Wikipedia.
To sum up, the best anyone was able to offer was heating by gravitational collapse, but it was recognized that this led to contradictions with other science.
What would be the contradictions? Seems like a straight forward result of Boyle’s law, friction, and (the sun, born in the same cloud as the Earth and it’s radioactively heated core) nuclear decay.
God’s might?
Why, yes, this is pretty much exactly what 5th-Century BCE philosopher Anaxagoras of Clazomenae taught. He said the sun was a giant flaming stone, and not the chariot of Apollo. For this he was imprisoned as a heretic.
Of course he was a heretic. Everyone knows Helios is the Sun God.
The maximum age of the Sun under the gravitational collapse model was less than the age of the Earth as known from geology, etc.
Well yeah, but there’s also that fusion thing, when it gets hot enough.
fucking magnets.
The OP was asking what the state-of-the-art understanding was before scientists figured out that nuclear fusion was possible. At that point, nobody knew of a mechanism to keep the Sun hot for the entire age of the Earth (which by the end of the 19th century was thought to be at least 300 million years.)
Oh! Egg on my face. Suddenly the posts in this thread make a lot more sense.
The ancient Greeks theorized a 5th element called Aether to explain the sky, and things in it.
Bzzzzt! WRONG! Everyone (and by that I mean everyone except for certain heretics who shall remain unnamed here) knows that RA is the sun god. He is a fun god. Ra! Ra! Ra!
(Hey, can we escalate this to a flame war?)
No?
Danggit. Now I don’t have any excuse not to mow the property.
Killjoys, I tell you! Killjoys, the lot of you!
Oh, and by the way, this coming Monday night is the Celtic festival honoring the return of Belenus, the sun god. His name is of the proposed origins for the word ‘Beltane’.
That’s right.
BTW, everyone knows that the sun was first discovered by Og the Caveman.
However, it was a woman who first correctly theorized the composition of the sun:
“In her 1925 dissertation Cecilia Payne showed that stars are “all essentially of the same composition,” according to astronomer Owen Gingerich. At the time, however, she distrusted her discovery that stars are made almost entirely of hydrogen and helium. Princeton astronomer Henry Norris Russell wrote to her that “it is clearly impossible that hydrogen should be a million times more abundant than the metals,” but he later discovered that she was right — and took credit for explaining the phenomenon.”
How do those werk?!
No, he wasn’t.
While perhaps not known as much for her beauty than her brawn, Og was a cavewoman.
She did have a lovely eyebrow, though.
As an aside, the gravitational contraction theory of the sun’s energy led to the conclusion that the inner planets were younger than the outer planets. This led to the science fiction idea that Mars’s thin dry atmosphere was due to it being an old planet, Earth was middle-aged, and Venus was a hot wet swamp world like the Permian era on Earth was envisioned. So you get Mars= ancient dying world, Venus= dinosaurs.
Lord Kelvin claimed that the fact that the sun could only be maybe 100 million years old at most refuted Darwin, since that was clearly not enough time for evolution to take place. He was right, that was not enough time, but how did he know how long evolution took?
Is this a serious question? The age of the Earth was a major issue for Darwin and he certainly believed that it was a lot older than that, and that it needed to be older in order for evolution to have reached the stage (the diversity of species and the complexity of some of them) that it has now. In fact, Darwin did not even begin to consider the possibility of evolution until he had become convinced (by Charles Lyell’s work in geology) that the Earth was many millions of years old. Kelvin knew that evolution required more than 100 million years because that is what the biologists (and geologists) of his time were saying.
Anyway, by Kelvin’s time, as AndyL has already pointed out, the geological evidence for an Earth much older than this was well established. The physicists knew that the gravitational collapse model of solar heat was not sufficient, it was just that they did not have any better ideas at the time. The Sun problem (and a related problem about the cooling of the interior of the Earth) was not generally considered a refutation of evolution (or even of natural selection as the main motor of evolution, although that idea was under pressure at the time for other, good and scientific reasons), it was a problem for physics.
By the late 19th century there was little serious doubt that evolution had happened. However, for a number of good scientific reasons (not religious ones) there was some doubt (shared even by Darwin in his later years) whether natural (and sexual) selection was sufficient to account for it. By the early 20th century, however, discoveries in both physics and genetics had removed the bases for these doubts.
Incidentally, the gravitational collapse theory of solar heat, although not sufficient to account for the age of the Sun, is not entirely wrong. When stars form, it is gravitational collapse that initially gets them up to a temperature hot enough for fusion to start.