Quote:
Originally Posted by darryl
...I note your comments about Jupiter's core, and had a very cursory look at the state of the science when the story was written. I found nothing definitive, though what I did find suggests that real information about the composition of Jupiter only surfaced after close encounters with our probes. I'm not so sure that the science of the time invalidated Simak's speculation on this point and if so whether he should have known of it...
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I don't know the exact timelines (apart from the determination that it was not a solid body) but I suspect they are much like the following:
- Part 1; That Jupiter was not solid but gaseous (what is now called a Gas Giant); 17th Century using known diameter and Kepler's orbital law, so deriving mass and average density (this is trivial to calculate).
- Part 2; Helium was discovered mid 19th Century, it was discovered in the sun (from its spectrum) as it was unknown at that time on earth. Hydrogen was discovered in the 18th Century (on earth) so I assume it was identified in the sun (from its spectrum) before helium.
- Part 3; Discovery that hydrogen (mostly) and helium comprise most of the mass in the universe (before the concept of dark matter came along
). I am unsure when that was identified but I would assume early 20th Century, if not before, because the visible mass of the universe is predominantly stars and our own sun was then known to be hydrogen and helium. It would then be a reasonable assumption that gas giants comprised mostly of hydrogen (mostly) and helium as there are not enough other gases, in comparison, floating around to form giant gaseous planets. Hydrogen predominates in the universe as helium is just the fusion product of hydrogen (so from stars and the theoretical big bang). Confirmation of the gases of Jupiter from earth by spectroscopy are compromised by Jupiter's cloud cover, its outer layer turbulence and, I assume, the low level of reflected light from the sun - when and if hydrogen and helium had been confirmed as predominant in Jupiter by spectroscopy before the first space probes I do not know.
- Part 4; Following the discovery of Jupiter's gaseous composition it would have been known that the density of the gas increases the deeper into the planet one went (due to gravitational compression) and this could be calculated for a known gas. Following the discovery that Jupiter's composition was likely hydrogen (mostly) and helium I would have thought that by early 20th Century that it would have been known (or at least possible to know) that due to pressure hydrogen at depths would be liquid hydrogen and then solid hydrogen deeper still as is proposed now. Liquid hydrogen and solid hydrogen were prepared on earth in the last quarter of the 19th Century.
- Part 5; From fly by spacecraft it is known that the surface is predominately hydrogen (90% by volume, 75% by mass) and almost all the rest helium. The spacecraft Galileo released a probe into Jupiter which survived to around 95 miles before being crushed by gaseous pressure, but confirmed hydrogen and helium likely all the way down. So it is currently believed that as the interior pressure increases hydrogen becomes liquid and then solid, and within that a possible small rocky core (rock being that which is not gas, liquid or a phase of those). It needs to be kept in mind that the liquid and solid phases of hydrogen are very light, being only approx. 7% and 8% that of water respectively, and so cannot be compared with our usual experience of liquid and solid.
So, I think that Simak perhaps did not know anything of Parts 1 to 4 above, any of which would have alerted him to a possible problem with his story, and thought no one else knew any more than he did. Or he did not research it (not researching the facts in case they were to come up with information contrary to the agenda is a journalistic device
). If he did research it and knew that there was a likely problem with his story he ignored what he found (avoiding information that compromises the agenda is another journalistic device
).
In the end, as I have said, I quite liked the book. In the end, the more I think of it, it is improved for me by just considering the collection of stories as being someone's dream; so they are in a frame in which facts and the past, present and future have no meaning.
PS: am not trying to be a smartass here
. I studied the History of Modern Physics at university and enjoyed it, and that led me to developing a general interest in the history of science.