Re: [Phys-l] Tutoring Please

[Jack Uretsky <jlu@hep.anl.gov>]

Hi Jim-
	Your question seems to be, broadly speaking, what is the nature of 
knowledge?
	Thales, Anaximenes, and Anaximander (all at Miletus) tried to 
postulate a minimum of universal substances from which all matter was 
composed.  The first two respectively named water and air as the 
primordial substance, Anaximander said that the primordial substance was 
unnameable (all this as reported by Aristotle).  Fire was added by 
Heracleitus.  Empedocles added earth, but he was already asking a broader 
question: what is the universal force that combines these elements into 
the matter that we experience daily?  Empedocles named his universal 
forces "love" and "conflict" and described their function in a poem.
(See Sambursky, <The Physical World of the Greeks> (Princeton U. Press 
1056)).
	What happened to make this description of matter insufficient? 
That is the underlying question, what set of facts is your theory 
attempting to explain?  You seem to decry the long wait between Empedocles
insightful construct and the adoption of the "truth" after 1660.  But 
there was no need for a more accurate description of matter until 
quantitative chemistry came along.  What was lacking before (somewhere 
around) the 17th century was access to the technology that gave rise to 
precision measuring instruments.  These were the outgrowth of a 
complicated mix of commercial needs (standardized weights and measures) 
and manufacturing technology (why didn't the Alexandrians, after Hero,
start manufacturing steam locomotives?).  Then, as we teach in courses on 
atomic physics, the discovery of the periodic table and the law of 
definite proportions made the formulation of an atomic theory of matter 
inevitable.
	So the answer to your question about "Why did it take so long?"
seems to be that there was no need for anything better.  The atomic theory 
of Leucippus and his pupil Democritus was, "just a theory" and was 
strongly disapproved by Aristotle.  'Nuff said?
					Regards,
						Jack


On Sun, 16 Apr 2006, JMGreen wrote:

> Consider the following:
>
> c 600 BCE Greek "scientists" (eg Thales) started to wonder about the
> nature of matter.
>
> c 450 BCE Empedocles postulated that matter was composed of
> "elements."  He proposed the elements earth air fire and water --
> Aristotle thought in terms of dry, cold, hot, wet
>
> c 440 BCE first Leucippus and then
>
> c 420 BCE his colleague Democrius proposed that there were many
> elements and called them atoms (molecules???)
>
> Admirable progress in 30 years!
>
> BUT
>
> c 100 AD Hero of Alexandria was trying to explain that the four
> elements consist of atoms and
>
> c 800 AD Jabir ibn Hayyan, later known as Geber, was trying to teach
> that only two elements were needed: sulpher (which is hot and dry)
> and mercury (which is cold and wet) -- so all _four_ elements are
> present.  And as late as
>
> c 1660 "... they were STARTING to believe that matter is made of
> atoms instead of the old alchemical essences -- earth, air, fire, and water."
>
> TWO MILLENNIA after the fact!
>
> Q1: When did the idea of "earth, air, fire and water" finally go
> away?  Who last refers to this philosophy in serious scientific discourse?
>
> Q2: Why did it take so long, >2000 yrs,  to shake the four-element philosophy?
>
> Q3: What other concepts in physics persist to this day even tough we
> know they are wrongish?
>
> JMGreen
>
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