In "Account of a conversation between Newton and Conduitt", the aged Newton reveals some of his speculations about the true system of the world to his inlaw https://en.wikipedia.org/wiki/John_Conduitt
had laid out celestial motion, but it didn't explain how old the Solar System was or how God kept it stable, how long the Sun would burn until its fire went out, what is the fate of humanity, or the role of comets.
He explains his hints to Conduitt: celestial bodies grow by accretion due to gravity, and as they grow bigger, pass from moons to planets to even larger (!) comets. Comets, in looping past the Sun, slowly become 'cooked'. The Sun would go out due to its constant conflagration, but fortunately, it is constantly renewed and powered by the fresh fuel provided it by comets passing nearby. 'Intelligent beings' (angels?) oversee this whole process of regular fueling of the sun, but unfortunately the https://en.wikipedia.org/wiki/Great_Comet_of_1680
passed so close to the Sun that it seems likely that it will soon fall directly into the sun, rather than feeding it a small measure of fuel. With an enormous quantity of fuel abruptly dumped into the Sun, it will flare up like a bonfire and quite likely roast the Earth (like a red supergiant might, incidentally), naturally killing everything on it. This possibly happens regularly, since humanity seems to have been created only recently, as evidenced by how recently such major innovations like printing or needles had been made (contradicting any supposition humanity had existed for more than a few thousand years). After this, possibly God would renew creation by repopulating instead the moons of Saturn or Jupiter.
This is a remarkable cosmology and has a lot of sense to it (how does
the Sun burn more than a long time without a magical process like fusion or regular resupply?), but is still very alien. Angels in charge of comets! Things really were different then.
It would make for an excellent retro SF or steampunk novel, if nothing else. (Naturally, the heroes would be recruited by the angels to help deal with the crisis of the return of Newton's comet... Perhaps Ted Chiang would like to write a followup to "Exhalation" http://www.lightspeedmagazine.com/fiction/exhalation/
or "Seventy Two Letters" https://web.archive.org/web/20010802144026/http://www.tor.com/72ltrs.html
It's also interesting for why it's wrong: Newton needs comets to be at least planet-sized, because comets are too rare to be plausibly fuel sources for the Sun if they're small (they wouldn't dump enough fuel in to keep combustion going for another few years/decades/centuries until the next big comet), but of course they're very small; if they were planet-sized, you'd think they'd severely disturb planetary orbital calculations, so was the existing astronomical data insufficiently precise to prove the absence of such orbital disturbances or was there some other issue?
The argument for the short duration of the human race is also wrong, since we know anatomically modern humans have been around for at least 50,000 years at this point. What's particularly interesting about his argument is that if he had made it at a randomly chosen point in human history, then he would have correctly concluded the opposite
, that the human race was ancient, due to the lack of discernible progress: in fact, he could only have made this argument in a tiny window between the start of the Scientific/Industrial Revolution and the archaeological/geological/evolutionary proof of mankind's antiquity starting around the 1800s, so maybe 400 years or 0.4 millennia; he had to have the bad luck to be born into that exact 0.8% historical window for the argument from progress to be wrong! Kinda remarkable.
(Linked in http://www.thenewatlantis.com/publications/the-unknown-newton-a-symposium
) #newton #astronomy #anthropics #sf