GrogHeads Forum

I have literally no idea where to even try reporting this, but I just made an important discovery in the history of astronomy.

Or a re-discovery. Hard to say how to categorize it.

:o

So, I was reading a rare book of lectures originally given by the Baptist Evangelist Elhanan Winchester in London in 1789, and printed in 1790. On page 298 of Vol 3 (out of 4) of those Lectures, he added as a footnote for the printed edition of the Lectures, a remark about the discovery of what we now call Uranus, although at the time in Britain the name proposed by its original discoverer, Herschell, was Georgium Sidum, for King George. (The planet can actually be seen under certain circumstances by the naked eye, and had been noted by Greek astronomers occasionally as a star; Herschell had originally thought it to be a comet; other eminent astronomers calculated its orbit over a period of years and ascertained it must be reckoned as a planet, to which in 1789 Herschell had agreed.)

One of the curiosities of this report, is that by the astronomic science of the day, Venus' mass was reckoned at 1.17 times Earth's; Mercury and Mars were less; Jupiter was calculated at 11.79 Earthmasses, and Saturn at 9.79. We now know of course that they are vastly much more massive than that (Jupiter is 318x massive), although Uranus turns out to be about on par with what they were calculating for Jupiter, about 14.5. At the time, however, astronomers reckoned GS's mass as being ludicrously much higher, no less than 90,688 Earthmasses! I would dearly love to figure out their rationale for making these estimates, but haven't been able to find out yet. (Note that this was not Herschell's calculation; as previously noted, he thought he had found a new comet.)


Anyway, to the point. In the middle of his aside on the grandness of the solar system, Winchester casually mentions along the way:

Quote from: Winchester, 1789 Lectures, Vol 3, Lecture 29, quoting from an unknown astronomy text of the timeBack of [Mars] is Jupiter with his four moons and belt: an amazing great world! -- greater than ours as 94000 are greater than 7970. Back of him is Saturn with his five moons and ring, which ring resembles the brim of a hat round the crown, but not touching the crown...[and then on to Saturn's relative mass]

(Sorry, had to save and post for some 'work' work before continuing.)

Okay, on further thought, the "belt" was probably not the ring an earlier version of the ring (although currently there's a wide estimate on how long it would take the rings of Jupiter to dissipate -- from 100 to over 1000 years, so 100 years ago they could have been a lot thicker). It was probably one of the cloudy striations famous to the planet.

That would explain more obviously why no one in the 19th century up to the 80s ever saw the ring (though in 1979 the ring was detected by magnetic flux), and not even saw it from Earth until 1999 (iirc).

So, never mind.  ::) :P When I saw "belt" in close context to Saturn's rings, I associated it with what we know about Jupiter's ring today, which being much thicker at the time would have seemed to anyone who saw it more like a "belt" than like Saturn's disconnected "hat brim".