IPB

Welcome Guest ( Log In | Register )

 
Reply to this topicStart new topic
A look back at a look forward, 1960
JRehling
post Jun 13 2020, 06:53 PM
Post #1


Senior Member
****

Group: Members
Posts: 2483
Joined: 20-April 05
Member No.: 321



When I was a kid in the late 70s, a reality of the world around me was that books had a long shelf life. For my family's budget, used books were more affordable. My school and my library had the same situation. And in many cases, it made no difference. Shakespeare and trigonometry were the same in 1978 as they were in 1958 or 1878. In this context, one of the books I first learned about the solar system from was Alan E. Nourse's "Nine Planets." It was first written in 1960, before Mariner 2, and I probably first read it around the time of Viking and Voyager, although I can't put a pinpoint on the date.

I recently bought another copy of it from eBay and I'm fascinated by the look back in time. I still own original copies of other books from the early 70s, so the issues are similar, but Nourse's book is a bit more detailed than the others. Nourse was writing for adults. He was not a scientist, but a well-read amateur. I'd say the level of scholarship in his book is a notch below Scientific American, but not far below. He might be spinning the interpretations of things he reports, but he is not inventing much, if anything, from whole cloth.

I won't try to itemize all of the things i'm finding but I may turn that into some blog posts. What I find particularly interesting is when an incorrect "fact" is presented and seeing where the error slipped in. Of course, a lack of information is excusable. No one in 1960 had access to many facts about the solar system that we have now, and that's nobody's fault. What is interesting to me is when something flatly incorrect is presented as certain. And here is a partial list:

• Mercury's rotation is synchronous.
• Mercury has an atmosphere.
• Venus's rotation is relatively fast. (He doesn't try to pin it down but asserts a range much faster than the reality.)
• Venus has a lot of water.
• Carbon dioxide is not the main component of Venus' atmosphere.
• Mars really has the linear "canals" reported by Schiaparelli and Lowell.
• Mars has winter caps made of water ice.
• If Mars ever had life, then it almost certainly had intelligent life.
• Jupiter has a solid surface.

And, an assertion of another kind:

• Humans will certainly visit the planets relatively soon after the time Nourse is writing.

This is all a mixture of things believed by scientists at the time with Nourse playing referee in some cases to favor, vigorously, one side of a debate. And one may say, who cares what this one man, a non-scientist, thought? And I find myself caring because he, in turn, was the voice of this subject for so many readers. And this may say something about how science is communicated to us now.

I think, by and large, this particular field of science has learned from getting burned a few times and scientists are simply much more cautious now in ascribing uncertainty to their conjectures. Measurements are subject to calibration.

But it's interesting to track all of these things down as a detective story. For example, a mid-60s published paper on the rotation of Venus noted, based on radar, that the speed of Venus' rotation (the method in question could not detect direction) was in the range of 250 days, with large error bars. This is correct. Then the author noted that the significance was "obvious" as the range included the rotation speed that would mean that Venus rotated synchronously. The measurement was not incorrect, but the implication was! Yes, by coincidence (?) the rotation and revolution periods of Venus are within 10%, but they are decidedly unequal and since they are in opposite directions, Venus is most certainly not tidally locked.

What I find most interesting here is the use of these as a cautionary tale – how our incomplete knowledge should best be handled. We are about as ignorant now of, say, nearby exoplanets, as the world of 1960 was of the solar system. Or, to take things to a more critical example, of a new pandemic. What are the (understandable) missteps, like presuming that Venus's clouds must be water, or that a rotational period of about the same as a planet's orbital period is likely equal to that number, rather than a near miss?

I have a bit of non-astronomical interest in this, as well, as I have in my professional life worked with assembling question-answer pairs for students. And this puts us back in the shoes of philosophers who have long wondered, how can we know a thing?
Go to the top of the page
 
+Quote Post
Phil Stooke
post Jun 14 2020, 02:55 AM
Post #2


Solar System Cartographer
****

Group: Members
Posts: 9078
Joined: 5-April 05
From: Canada
Member No.: 227



Very interesting! I used to read Nourse's science fiction.

A comment about Mercury. It's not at all easy to see markings on Mercury with the eye but they can be seen, and people had made maps. Antoniadi's was probably the best known. It was based on the notion of synchronous rotation. But if you think rotation is synchronous you could predict which markings would be visible as Mercury goes from a gibbous phase to a crescent, and they don't show up as you would expect. An area that should be dark is not visible, or a bright spot shows up where it shouldn't be. That could be viewed as evidence the rotation was not synchronous, but instead it was widely interpreted as proof of clouds (probably dust clouds) in an atmosphere. Clouds hid the areas you expected to see or cleared occasionally to reveal a feature not seen before. Librations could also confuse the issue and some people tried to accommodate libration zones in the maps. The details of the planet's rotation, putting the same features in the same place regularly, didn't help people make sense of the observations.

Phil


--------------------
... because the Solar System ain't gonna map itself.
Go to the top of the page
 
+Quote Post
JRehling
post Jun 14 2020, 07:02 AM
Post #3


Senior Member
****

Group: Members
Posts: 2483
Joined: 20-April 05
Member No.: 321



Mercury's rotation is a fascinating case (all of these are!). Those are all good points. Moreover, Mercury has the killer combination of:
1) As you say, it's not very high contrast in the first place.
2) The elliptical orbit means that it will always be furthest from the Sun at the same point in its orbit.
3) The rotational resonance so that it will show the same face to us on exactly half the occasions when it is present at that point in its orbit.
4) Slow enough rotation that it is not seen to rotate significantly during any particular occasion when near an elongation.

I've looked at Mercury in a daytime sky with great seeing and a 235mm aperture and it is easy to see Mercury on those occasions, but it certainly is far more blank than the Moon, much less Mars, and while I have certainly photographed surface details, I'm not sure that I ever felt like I was seeing any with my eye.
Go to the top of the page
 
+Quote Post
angel1801
post Jun 14 2020, 09:37 AM
Post #4


Member
***

Group: Members
Posts: 159
Joined: 4-March 06
Member No.: 694



I rarely post here. But in June 2019 I found a brought a book about space called "The Big Book: Space & Exploration" that I read and borrowed from public libraries back in the late 1970's and early 1980's. It was product of the Christensen Press.

Ii has four books in one. They are:

1. The Challenge Of Space
2. Mission Outer Space
3. The Intrepid Explorers
4. The Race For The Moon

All came out between 1978 and 1985.


--------------------
I call heaven and earth to witness against you this day, that I have set before thee life and death, the blessing and the curse; therefore choose life, that thou mayest live, thou and thy seed.

- Opening line from episode 13 of "Cosmos"
Go to the top of the page
 
+Quote Post
JRehling
post Jun 14 2020, 06:35 PM
Post #5


Senior Member
****

Group: Members
Posts: 2483
Joined: 20-April 05
Member No.: 321



Phil, your comments on Mercury got me to dive into this a little bit. Luckily, we have all the information now that the astronomers in the past did not.

I found at least four sketches of Mercury performed by Antoniadi in the 1920s. These were all from western elongations and thereby all covered the same quarter of Mercury. I discovered that he and others of his time made their observations during the daytime, which I have also done. It is very hard to see Mercury well in a dark sky because of its low altitude, but it can get to fabulously high altitudes during the daytime (more so where I live in California than in Europe) and it is actually a very nice level of brightness for viewing in those circumstances – it easily outshines the blue sky on a day of low transparency, but isn't glaring bright the way Venus can be.

Antoniadi fell into several traps, as we mentioned earlier – because he looked at occasions of greatest elongation, he was always seeing Mercury in one of two orientations as its spin-orbit resonance toggles it between two states, more or less. Two of his four sketches showed one approximate orientation (±10°) and the other two showed another orientation (±5°).

The next trap: Each of those orientations shows a dark patch in the same apparent location at about 40°S latitude. One is the dark lightly-cratered plains south-southwest of the bright rayed crater Debussy, and the other is a larger area of intercrater plains far to the south of the Caloris Basin. Because these two dark areas, between them, appeared to be one consistent patch in the same location of all his sketches, he presumed it to be one thing, which he dubbed "Atlantis." (In neither case does it appear so much a geological unit as the coincidental variation in albedo surrounded by other features. If he wondered what Atlantis was, it really isn't anything, in the sense that Mare Imbrium on the Moon or Syrtis Major on Mars represent geological units.) I am reminded of the discovery, in antiquity (repeated somehow or other by multiple civilizations and individuals), that the evening star and the morning star were both Venus. But this time, the "same" inference was wrong. The two toggling Venus's are the same object, but the two toggling "Atlantis"es are two objects.

Now, as you say, he was hooked on the idea that Mercury's rotation was synchronous and this dual-identity "Atlantis" gave him some misleading confirmation of this. However, this was not original to Antoniadi, and everything we see in his sketches appeared in the sketches of others before. His maps were a bit more detailed, but the mental missteps preceded him and were presumably for the same reasons.

And, since the rest of Mercury in his views does not correspond very well from one "toggle" to the other, he presumed that a mercurian atmosphere was playing tricks. He therefore presumed that the more detailed of the two toggles was the real surface, and the other was cloud. The more detailed one corresponds to the pale Caloris Basin and its dark, circular framing areas. This ~quarter of his map is real, and shows the vicinity of Caloris reasonably faithfully. In fact, he drew the dark arc enclosing Caloris to the south as coming to a sharp point. In modern photos from Messenger, one may see the broad, fuzzy dark arc coming to a sharp point consisting of the dark crater named Atget. Now, as a real fun quirk of the history, Atget was a photographer who died in Paris in August 1927. Two of Antoniadi's sketches were made from Paris in June and October of that year. The two men may have passed in the street linked in a way neither of them would ever know. In fact, I may be the first to notice this today.

One more thing probably contributing to the notion of clouds: More than one – perhaps all – of his sketches mention veils near the limb, which he inferred to be bright clouds. These optical features are real, and I've photographed them, and they are perhaps more easily seen than any albedo feature on the planet; they are not, of course, clouds. They are due to a specular component of the mercurian regolith, more pronounced than the same quality on the Moon. Terrain nearer the sub solar point appears brighter than the same terrain will appear at other times. This coincidentally resembles a bright "rind" seen near the limb of Mars, but in the case of Mars it really is due to atmosphere and clouds! Antoniadi was an avid observer and mapper of Mars (I imagine all observers of Mercury are also well familiar with Mars!) and it would be natural to consider that the "same" thing seen on both planets had the same explanation. And once again, something natural to consider was accepted as fact – incorrectly.
Go to the top of the page
 
+Quote Post
JRehling
post Jun 14 2020, 06:39 PM
Post #6


Senior Member
****

Group: Members
Posts: 2483
Joined: 20-April 05
Member No.: 321



Thanks for that, angel1801. I have several "old" astronomy books and publications on my shelves marking the various years from 1960 to 1981 and, obviously, the years of planetary exploration (and radar, which began just a bit earlier) mark a sharp change. The sophistication of the conversations increased dramatically in those 14 years from Mariner 2 to Viking.
Go to the top of the page
 
+Quote Post
nprev
post Jun 14 2020, 10:58 PM
Post #7


Merciless Robot
****

Group: Admin
Posts: 8640
Joined: 8-December 05
From: Los Angeles
Member No.: 602



One thing I've always found ironic is how the Galilean moons of Jupiter were widely assumed to be nothing more than iceballs, barely worth a mention in pre-Voyager books.

The main lesson we've learned from exploration of the Solar System is that very few of our pre-spaceflight assumptions were correct about...well, pretty much everywhere. Nature is both more subtle and more inventive than our imaginations. We don't really know anything till we go look. wink.gif


--------------------
A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
Go to the top of the page
 
+Quote Post
JRehling
post Jun 14 2020, 11:30 PM
Post #8


Senior Member
****

Group: Members
Posts: 2483
Joined: 20-April 05
Member No.: 321



Yes, there was a pre-Apollo National Geographic map of the Moon that included a little graphic comparing the solar system's natural satellites by size – about the only thing known about them – and each was represented by a whitish circle. It was that paradigm, unspoken, that shattered when I first saw a magazine cover with Voyager images of each Galilean. No blank, white circles among the four!

Nourse, however, does say, after a bit of discussion, "So we must come to the conclusion that… there are some major differences in composition and surface properties…" of the Galileans. Nobody could have guessed the extent of those differences, but he did at least emphasize that there was a hint of that already.
Go to the top of the page
 
+Quote Post
Phil Stooke
post Jun 15 2020, 03:21 AM
Post #9


Solar System Cartographer
****

Group: Members
Posts: 9078
Joined: 5-April 05
From: Canada
Member No.: 227



nprev: "We don't really know anything till we go look."

Very true. I will even confess to thinking Pluto might be boring until we got there. Now I think what amazing sights those other large KBOs must have in store for us.

Phil


--------------------
... because the Solar System ain't gonna map itself.
Go to the top of the page
 
+Quote Post
SulliedGoon
post Mar 2 2021, 07:55 PM
Post #10


Newbie
*

Group: Members
Posts: 11
Joined: 24-July 11
From: Cumberland Plateau
Member No.: 6084



I recall reading a book during childhood.
It was probably a 60's era book about the Moon.
It was full of Moon pictures wherein the author
used arrows to point to anomalous "structures" -
vehicle tracks, pyramids, tunnels etc.

Completely absurd and usually I could not see
whatever the author claimed he could see. It
was like a "Where's Waldo" book that is missing
"Waldo".

But, I still have fond memories of that book.
It is a time machine that takes one back to
a naive time when anything seemed possible.
Go to the top of the page
 
+Quote Post

Reply to this topicStart new topic

 



RSS Lo-Fi Version Time is now: 18th October 2021 - 07:10 AM
RULES AND GUIDELINES
Please read the Forum Rules and Guidelines before posting.

IMAGE COPYRIGHT
Images posted on UnmannedSpaceflight.com may be copyrighted. Do not reproduce without permission. Read here for further information on space images and copyright.

OPINIONS AND MODERATION
Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators.
SUPPORT THE FORUM
Unmannedspaceflight.com is funded by the Planetary Society. Please consider supporting our work and many other projects by donating to the Society or becoming a member.