| Tuesday,
January 12, 2009
Mike Flynn on the Flat Earth:
Flat Earth
I don't know why this myth persistently arises. No
educated person of the Middle Ages thought the earth was flat. Aristotle was
required reading, and he established the sphericity by proofs in _On the
heavens,_ II, 13-14. John of Sacrobosco, likewise, in his widely used
textbook, _Treatise on the Sphere._ Isidore of Seville wrote of the Earth's
roundness in the _Etymologiae._ In fact, we even find the following comment
_en passant_ in Aquinas' _Summa theologica:_
Sciences are differentiated according to the various
means through which knowledge is obtained. For the astronomer and the
physicist both may prove the same conclusion—that the earth, for instance,
is round: the astronomer by means of mathematics (i.e., abstracting from
matter), but the physicist by means of matter itself.
_Summa theologiae,_ Question 1, First Article, Reply
Obj. 2
Even the common people were evidently familiar with
this. We have a sermon by a popular traveling preacher that refers in
passing to the sphericity of the earth, and in the popular Middle English
work _The Travels of Sir John Mandeville_ (a fictitious character possibly
based on Marco Polo, Orderic of Pordenone, John of Marignolli, et al.) we
read that in Sumatra:
And you must understand that in this land and many
others thereabouts, the star Polus Arcticus [Pol Aris] cannot be seen; it
stands ever in the north and never moves, and by it seamen are guided. It is
not seen in the south.
Why Boorstin thought otherwise, I don't know, unless
he referred to Lactantius (Roman, 3rd cent) or Cosmas Indicopleustes (Greek,
6th cent), neither of whom were medieval nor very influential, or to the
ever-popular tale of Boniface accusing Vergilius before Pope Zachary of
"teaching a doctrine in regard to the rotundity of the earth, which was
contrary to the Scriptures." The doctrine "in regard to" sphericity was
this: The rotundity of the earth implied a tropics. Temperatures increased
toward the tropics. Geographers concluded that the tropics themselves were
too hot for human life. Thus, to assert that there were people on the other
side of the earth (called the anti-podes because they walked upside down wrt
us) meant that there were people who could not be descended from Adam. Then,
as now, the Curch taught the common descent of all people. It turned out the
science was wrong. But the Vergilius-Boniface thingie is often now cited as
flat-earth thinking. (BTW: Boniface, Ver gilius, and Zachary were all
canonized, so it could not have been a very serious thingie.)
Medievalists sometimes complain that historians of
modern history do not know their medieval history very well. Boorstin may be
a case of that. The following web exchange between a couple of history
professors (with Cicero chiming in at the end) is instructive:
Tim This reminds me of a question I frequently
ask my students at the beginning of a course on the history and philosophy
of science from Aristotle to Galileo. Virtually all of them, it turns out,
are convinced that the pancake theory held sway until the voyage of
Columbus. When I then ask them to describe the causal mechanism of a lunar
eclipse, most of them look at me as though I were recommending the study of
hieroglyphics -- What can that possibly have to do with the shape of the
earth? But one or two get the point. If they don't, the readings from
Aristotle's Physics and Ptolemy's Almagest make it for me.
Another day, another blow against chronological
snobbery ...
Lawrence That your students think your
lunar eclipse question so strange shows they have no real knowledge of the
Earth's shape, but merely take it on faith from others, just as they take
their ideas of the ancient world from others.
Ironically, this type of ignorance is the same we
moderns attribute (wrongly) to the ancients.
Tim Just so. The majority of my students also seem to
be convinced that we moderns are much smarter than the greatest minds of
millenia past. The disinformation campaign waged by people like William
Whewell and Washington Irving regarding the vast ignorance and intellectual
servility of the middle ages has been wildly successful, one of the great
propaganda triumphs of all time.
Then I make them work through a few of the proofs from
Ptolemy or from Newton's Principia and their smug self assurance evaporates,
leaving something more mature in its place.
Education, real education, is the process of laying
conceptual sandbags against the rising tide of cultural darkness.
Marcus Tullius Cicero To be ignorant of what occurred
before you were born is to remain always a child.
==
Flat Earth II
Responding to your e-mail....
Noodling on the Web, I found that Boorstin did indeed
refer to the two minor figures, Lactantius (Roman, 3rd cent.) and Cosmas
(Greek, 6th cent.) and from these two data points extrapolated the ignorance
of an entire civilization. (Technically of two civilizations: Cosmas was
Byzantine, although he didn't know it.) These two were cited prominently by
Draper and White in their anti-Catholic screeds, and those who came after
accepted it on faith. They were not prominently cited by much of anyone
during the Middle Ages; although of course one may be an expert on some
matters and stone cold ignorant on others. Boorstin hedged his bet by saying
everyone forgot the Earth was a sphere only until 1300, when he allows that
they started to remember. But among those who mentioned the Earth's
sphericity in the Dark Age and the Early Middle Age were Augustine of Hippo,
Venerable Bede, Isidore of Sevile, John Scotus Eriugena, Roger Bacon, and
many others. As you may recognize these are far more household names than
poor old Lactantius and Cosmas.
I also note that Boorstin cited Augustine(!) as one
who "heartily agreed" that antipodes "could not exist." But the antipodes
referred to the _people_ who supposedly walked there upside down, not to the
_land_ we now call the antipodes. It is entirely possible to believe the
earth is20a sphere and not believe there are people on the other side of it.
The relevant quote:
"As to the fable that there are Antipodes, that is to
say, *men* on the opposite side of the earth, where the sun rises when it
sets on us, men who walk with their feet opposite ours, there is no reason
for believing it. *Those who affirm it do not claim to possess any actual
information;* they merely conjecture that, since the earth is suspended
within the concavity of the heavens, and there is as much room on the one
side of it as on the other, therefore the part which is beneath cannot be
void of human inhabitants. They fail to notice that, even should it be
believed or demonstrated that the world is round or spherical in form, it
does not follow that the part of the earth opposite to us is not completely
covered with water, or that any conjectured dry land there should be
inhabited by men. For Scripture, which confirms the truth of its historical
statements by the accomplishment of its prophecies, teaches not falsehood;
and it is too absurd to say that some men might have set sail from this side
and, traversing the immense expanse of ocean, have propagated there a race
of human beings descended from that one first man." (De Civitate Dei [On the
City of God], xvi, 9)
IOW, it was like the modern debate on
extraterrestrials, with the early-day ET enthusiasts claiming the earth was
so vast that it was unreasonable that there wouldn't be men "out there" on
the other side, somewhere. Augustine is from Missouri. "Show me." Like a
good skeptic, he points out that the other hemisphere might have no land or,
having land, might not be inhabited. He doesn't think it is; but his real
objection is to the thought that there would be people who don't share
common descent with us. (In fact, the Pacific does cover a broad swath of
antipodal area.)
Augustine also refers to the sphericity of the earth
in De Genesi at literam [On the literal meanings of Genesis] when he wonders
how "it was evening and morning" could be literal when the Earth is a sphere
and it is evening and morning somewhere on Earth all the time.
But if I make such a statement, I fear I shall be
laughed at both by those who have scientific knowledge of these matters and
by those who can easily recognize the facts of the case. At the time when
night is with us, the sun is illuminating with its presence those parts of
the world through which it returns from the place of its setting to that of
its rising. Hence it is that for the whole twenty-four hours of the sun’s
circuit there is always day in one place and night in another. ... We cannot
say that in the other region there is no daylight when=2 0the sun is there,
unless our thinking is influenced by the fantasies of poets, so that we
believe the sun dips into the sea and in the morning arises on the other
side out of his bath. .... But such a supposition is preposterous. (De Gen.
ad lit.; I, 10:21)
Although water still covered all the earth, there was
nothing to prevent the massive watery sphere from having day on one side by
the presence of light, and on the other side, night by the absence of light.
Thus, in the evening, darkness would pass to that side from which light
would be turning to the other. (De Gen. ad lit.; I, 12:25)
Now, if even an amateur like me can find these things
with little problem, what excuse has Boorstin beyond the usual fact that
historians of one period are often ill-informed on others. I do not know if
Boorstin is also animated by the usual prejudices. As Thucydides wrote, men
will accept without argument conclusions they find agreeable; but will bring
all the force of logic and reason against those they do not like. Boorstin
may simply have never questioned Draper or White as sources.
Mike Flynn
I have no idea why Boorstin, who is good on
American history and technology, would be animated by the usual
prejudices, but perhaps so. In any event, this should settle the matter
once and for all.
=============
Another view:
Flat Earth
In the appearances of this argument I have run into,
Boorstin's _The Discoverers_ is invariably disparaged. The problem is that
Boorstin cites quite a few specific medieval texts that - at least based on
the parts he refers to - do in fact support the claim that "Flat Earth" was
a common idea. I've never once seen these references discussed or disproved
or countered; there is only ever the assertion that Boorstin is a liar,
without further evidence.
I do think that if the point of the exercise is to
denounce claims unfounded on evidence and present some that are, this is not
the right way to do it.
Rollory
I think Flynn answers that above.
============
From Pravda, of all places.
You'll appreciate this. It is from the
English-language section of Pravda, of all places.
http://english.pravda.ru/science/
earth/106922-earth_ice_age-0
First paragraph: "The earth is now on the brink of
entering another Ice Age, according to a large and compelling body of
evidence from within the field of climate science. Many sources of data
which provide our knowledge base of long-term climate change indicate that
the warm, twelve thousand year-long Holocene period will rather soon be
coming to an end, and then the earth will return to Ice Age conditions for
the next 100,000 years."
And note the assumed education and reading
comprehension level for their readers...
--John R. Strohm
===========
Harry Erwin's Letter From
England=
Tory MP stopped and searched as
a terrorist suspect for taking pictures of a cycle lane: <http://tinyurl.com/94cgu9>
Related story about electronic privacy <http://tinyurl.com/8rxl3l>
The consensus here seems to be
that the Gaza operation is being driven by internal Israeli politics--it
will continue until the current Israeli government feels that it has beaten
back the electoral threat posed by Likud <http://tinyurl.com/a6k48x>
<http://tinyurl.com/8kyhoa>
UK economy at a 28-year low <http://tinyurl.com/9zlf3e>
<http://tinyurl.com/75bnv3
>
Local job losses <http://tinyurl.com/7ldld5>
Fall in standards for UK PhDs <http://tinyurl.com/9t462u>
--
Harry Erwin, PhD, Program Leader,
MSc Information Systems Security, University of Sunderland.
<http://scat-he-g4.sunderland.ac.uk/~harryerw>
Weblog at: <http://scat-he-g4.sunderland.ac.uk/~harryerw/blog/index.php>
============
"It might take a long time to solve this problem."
The hubris is all the more breathtaking for its
foundation in deep- rooted naivety and a fundamental ignorance of human
nature, history, not to mention contemporary culture outside the United
States:
http://www.boston.com/bostonglobe/
ideas/articles/2009/01/11/a_talk_with_
lawrence_lessig/?page=full
-- Roland Dobbins
The gods of the copybook headings, with terror
and slaughter return.
=========
Space weather
If you go to the link <http://www.nap.edu/catalog.php?record_id=12507>
on that Space Weather article, you can download a PDF of the entire report
for free.
Tom Brosz
=============
Skylon SSTO 'Space Plane'
Dear Jerry,
I read this morning about Reaction Engines Limited's
Skylon Project and was curious about your opinion of the system.
http://www.reactionengines.co.uk/
skylon_overview.html
http://www.reactionengines.co.uk/
skylon_vehicle.html
They claim the vehicle will travel from 0 m/s on the
runway to a 300km equatorial orbit with a payload of 12,000 kg.
Using the estimate of 100,000 kg per satellite from
the Japanese Aerospace Exploration Agency's "Study of Space Transportation
for Space Solar Power Systems"
http://tinyurl.com/8pm9hn, the Skylon could put a SSPS on orbit in 10 or
so launches. Am I wrong to be somewhat excited by the prospect of this
vehicle?
In either case, I wish you continued good health and
prosperity in the new year. As always, I remain,
Your Fan,
Preston A. Rickwood,
I answered:
Do you know more than is on their web site? The
mass fraction is not sufficient to make orbit as a SSTO vehicle, meaning
that they have to fly for some considerable time at high mach speeds as an
air breather. The NASP people could not figure out how to do that.
From the DC/X experience I came to the conclusion
that Hydrogen is not the right fuel for operations to begin with, but
perhaps they know something about hydrogen than I do.
They don't provide the precise flight profile, but
given the mass fraction (220 / 261) there is no possibility of reaching
orbital velocity as a rocket; meaning that some 40 tonnes of oxygen must be
scooped from the atmosphere just to achieve the mass ratio needed by the
rocket equation, plus however much more is required to overcome the drag
from flying in the atmosphere. I don't think they can do that, but I sure
wish them luck. I doubt they'll find their $10 billion, but again I wish
them luck.
We may have learned a lot since NASP days. I was
once very much a fan of aircraft/rocket hybrids (as was the late Arthur C.
Clarke) but it is my understanding that the NASP project demonstrated pretty
clearly that we do not -- or did not, in that time period -- possess the
materials to make the input scoops and the leading edges of the wings for
such a craft.
Not being much of an airplane designer I can't
comment on their design or its flightworthiness, but I would think the
engines they describe have yet to be built.
Jerry Pournelle
Apparently the idea is to use air-breathing mode to
reach Mach 5.5 and edge of the atmosphere, then switch to pure rocket mode
to reach orbital velocity.
The engine is apparently being tested in stages, one
of which can be seen in the photo accompanying this interview.
http://spacefellowship.com/News/?p=7890
The Space Fellowship article states, "With regards to
a timetable, [Future Programmes Director] Mark [Hempsell] added that there
is an immediate and funded technology demonstration programme for the next
two years. This will then lead in to a full development programme which will
probably take a further 8 years."
I also found a link on the Reaction Engines site that
provides more information about the engine design.
http://www.reactionengines.co.uk/sabre.html
I guess they're hoping materials science for the
vehicle will catch up to their engine design by the time they are finished
with it. I suppose I hope the same.
Thanks for your kind attention,
Preston
I have made inquiries among rocket scientists and
engineers (some very much in competition with Skylon) and the consensus
is: these are serious people, and they have been doing some serious
development; but no one knows how they will solve the engineering problems
that tanked the NASP project, and if there are new developments since NASP
they aren't generally known to the space development community. In other
words, my view remains: I don't know how they are going to do this, but I
sure wish them luck.
We would have to know how much fuel is needed to
reach the point at which the ship becomes a pure rocket. Mach 5.5 is a
significant velocity, but it will still require a significant mass ratio
approaching to get to orbit starting from Mach 5.5 and 75,000 feet;
whether they can achieve that mass ratio is not known to me.
Most "fly high then switch to rocket power"
designs use two vehicles, both recoverable: one flies to get both craft
above the atmosphere so that the ISP is vacuum rather than sea level, and
there is no atmospheric drag to overcome. This allows two different
engines, and possibly two different fuel systems. A Mach 5.5 velocity of
5.5 is achievable with existing materials, and since these are serious
people I presume they have an operations plan that gets them to Mach 5.5
with sufficient fuel to achieve the required mass fraction to get
53,000 pounds into orbit from that speed and altitude. I leave the
calculations to the reader (look up my SSX paper on this web site for the
basic rocket equation and delta vees required).
I very much wish them well. My opinions on the
operational unsuitability of hydrogen remain; Max Hunter when to his grave
convinced that we would achieve routine Single Stage To Orbit operations,
and that would be done with propane. Many space development engineers now
experiment with methane. Max preferred propane because it is much more
readily available and we know a lot more about handling it, and the
exhaust velocity penalties were, in his judgment, not great enough to
overcome propane's advantages. (Assuming SSTO is achievable, the penalty
would be in payload: more flights required to get a given mass to orbit,
but the cost of the craft and the cost per flight will be lower.)
The more serious people in private space
development the better.
Mr. Heinlein has Delos Harriman say in "The Man
Who Sold the Moon" that "good research always pays off."
=========
Slavery
I take exception to your comment: "Alas, a slave
market shows where unregulated capitalism will go if left to itself."
It is only through the state established institution
of slavery, the enforcement of property rights of one mans over life of
another, that allowed a robust market in slaves to exist. Slavery is a
creation of regulations/governments, not of capitalism.
David Young
I would have thought slavery was illegal in the
United States, but every now and then the police find instances of it.
Make it legal and I think you will find plenty of instances -- and private
slave catchers to enforce it, without any government bureaucracy needed.
It is true that one of the great political issues prior to the Civil War
was the Fugitive Slave Act and its enforcement in the North where slavery
was not legal, but slavery exists in the Middle East to this day even
though it is illegal.
And I predict with confidence that if you make it
legal to sell human flesh in the marketplace, it will not be a decade
before you will be able to buy some.
It is not that all, or most, or even a few
capitalists would engage in such practices; but it only takes a few. Now
would you care to discuss what would happen were there an open market in
transplantable organs? But we all know very well what would happen.
Note that I am not opening a debate on whether or
not there ought to be an open market on transplantable organs. That's a
more complex matter than it appears to be. But then so is one's "right" to
sell oneself into slavery to obtain money to pay debts or support a
family.
==
Yes, she did.
If this were true...
"I
suspect I know more about the views held by Miss Rand than most."
...you would not have written this...
"That she could never reconcile the gap between
knowing what is and knowing what ought to be (and how to prove you know what
ought to be)..."
...in the readily available light of this:
http://www.aynrandlexicon.com/lexicon/isoughtdichotomy.html
Most such dismissals of Rand end up foundering on the
rocks of those of her works that the critic didn't bother to read. Had you
merely written "I suspect I know more about the views held by Miss Rand than
most **of her other critics**", it would be credible.
Whatever you think about her ideas, there is really no
excuse nowadays for any critic to be ignorant of what those ideas are, or of
what she really did say -- and not just because Harry Binswanger put his "Ayn
Rand Lexicon" online. A good place is www.noodlefood.org (check out the
essays by Greg Perkins), and good people are Tara Smith and Onkar Ghate.
We're easy to find :)
Jim May
Those who really dislike the fine art of hair
splitting should skip what follows.
First. let me assert that whatever the truth of
your analysis my first statement is still objectively true: that is, fewer
than half the population have read anything by Miss Rand (and probably
fewer than half ever heard of Objectivism): So had I stated that I know
more about the views held by Miss Rand the probability is very high that I
would be speaking the objective truth; but in fact I didn't say that. I
said I suspected as much, and that's a statement about my subjective
beliefs, and I know very well that I know more about my beliefs than
you do.
That said, I thoroughly understand that there are
those who believe that if only we knew and understood Miss Rand, we would
believe what she taught. Indeed, as I recall Miss Rand was one of that
number. I also understand the argument that if one studies the subject
properly, one will abandon all those subjective feelings about ethics and
morality and accept the objective truths thereby made manifest.
In other words, those smart enough will get it
and understand that Objectivism does in fact reconcile the gap between
knowing what is and knowing what ought to be (and how to prove you know
what ought to be). This implies that objectivists are the most intelligent
people in the society. That hypothesis generates a number of deductions
some objectively testable.
As I said, I am not trying to start a quarrel
with Miss Rand's followers; but I fear I have had as much enlightenment
from her writings as I need, and my excuse must be that I don't have
enough years left to read everything else. Alas, the Objectivists
are not the only people who tell me that if only I read everything
available about their philosophy I would certainly have a better
understanding of the universe.
============
Re: The myth of the medieval flat Earth
Dear Dr. Pournelle,
I believe that, at the very least, the popularity of
the idea that medieval society believed the Earth to be flat can be blamed
on Washington Irving and his “biography” of Columbus. Certainly, it is not
widely thought in Europe that Columbus’s opponents believed the Earth to be
flat. Perhaps his sources were faulty or, more likely, the truth did not fit
his narrative. The dispute between Columbus and the churchmen advising the
Spanish crown was over the size of the Earth, and Columbus was, in fact,
wrong. Had the Americas not been in the way, he could never have
accomplished the voyage he proposed; the distances were simply too great.
Further evidence that medieval Europe believed the
Earth to be spherical can be found in Dante. In the Purgatorio, he
explicitly shows a spherical world, with the mountain of Purgatory antipodal
to Jerusalem. What is more, he understands many of the logical consequences
of a spherical world: not only are there stars which are not visible in the
northern hemisphere, but as the poets travel westward, the sun passes them
on their right (something which Herodotus rejected as patently false, giving
us a terminus post quem for the concept of a round world).
David Levinson
============g
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