Transcript Integrative Studies 410 Our Place in the Universe

A Short History of Atomic Ideas
• Earliest formulation due to the Greeks
– “atom” = a-tom, Greek for “not divisible”
– Pre-scientific, no scientific reason for believing it!
• In Rome: Lucretius (1st century B.C.)
• Out of favor (along with much other learning and scholarship) for
almost 2000 years
• 18th century: Re-introduced by Daniel Bernoulli, Roger
Boscovitch
• Dalton discovers Laws of Definite and Multiple Proportions
• Kinetic Theory (Clausius, Maxwell, Boltzmann; 19th century)
• Brownian Motion (Brown, Einstein; early 20th century)
Democritus (~460–380 B.C.)
• Lived in northern Greece
• Thought experiment: Subdivide a piece of gold
– Each part is still gold after every division
– Can you subdivide for ever?
– Claimed there must be some limit; matter is made of particles that
cannot be further divided
• These “atoms” move endlessly in all directions in “the
void”
• Also: smelling bread from a distance
– Particles from the bread must break off and travel to our noses
• Determinism?
– A relief from capricious and cruel gods
Lucretius (~95–55 B.C.)
• Roman philosopher and poet; student of Epicurus
• Manuscript De Rerum Natura (On the Nature of Things)
re-discovered in late 14th century
• Contemporary of Julius Caesar; beginning of Rome’s
decline
• Allegedly driven mad by a “love potion” given to him by
his wife, and committed suicide
• Atheistic and deterministic
Lucretius
…clothes hang above a surf swept shore
grow damp; spread them in the sun they dry again.
Yet it is not apparent to us how
the moisture clings to the cloth, or flees the heat.
Water, then, is dispersed in particles,
atoms too small to be observable.
…
For surely the atoms did not hold council, assigning
order to each, flexing their keen minds
with questions of place and motion and who goes where.
But shuffled and jumbled in many ways, in the course
of endless time they are buffeted, driven along,
chancing upon all motions, combinations.
At last they fall into such an arrangement
as would create this universe…
–Lucretius, De Rerum Natura
Early Objections
• Some quasi-religious or philosophical, of course, but some
“scientific” ones as well
• How can atoms continue moving for all time without
stopping?
– According to Aristotle, moving objects come to a halt unless
something intervenes to keep them moving
• The “void” in which atoms supposedly move cannot exist,
according to some philosophers:
– For anything to exist it must have a name, which refers to
something rather than nothing
– Since “nothing” cannot have such a name, it therefore cannot exist
The Western World
after the Fall of Rome
• Medieval
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Dominant church
~ 1000 years of relative stagnation in the west
Experimental research greatly reduced
To answer a question: “Study the Bible or Aristotle!”
• Renaissance
– Invention of the printing press (1450) by Gutenberg
• Books become widely available!
– End of the Church’s domination in the Middle Ages
– Back to the roots (renaissance means “rebirth”)
– Intellectual movement
The Western World
after the Fall of Rome
• Baroque
– Counter-reformation in the 1600s; church much stricter
– G. BRUNO (Italian; 1548) proposes that the Sun is just one of an
infinite number of stars; burned at the stake for heresy (1600)
– 30 Years War (1618-1648) between religions
– Many new inventions: telescope, air pump, etc.
• Enlightenment (1700s)
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Rationalism, secularism, tolerance, freedom
Emergence of science
Political reform and revolution
Optimism and self-confidence
Modern Terminology
• Most substances can be chemically decomposed into other
substances
– E.g. water can be decomposed into hydrogen and oxygen
• Substances that cannot be decomposed are called elements
• An “atom” is the smallest indivisible unit of an element
• A “molecule” is a group of atoms stuck together
– The smallest unit of a compound
• In some cases where it doesn’t matter, we may speak of a
particle, which might actually be an atom or molecule
What is Heat?
• A central part of the mystery
• Majority view around 1800: heat is a fluid, called caloric
• It flows from hotter bodies to colder ones
– E.g. we drop a hot horseshoe in water; caloric flows from the shoe
into the water, cooling the shoe and heating the water
• Mysterious, undetectable (?)
• In the atomic theory, heat has to do with the (random)
motion of the particles
– Faster speeds on average means higher temperature
• Rudolf Clausius: The Kind of Motion We Call Heat (1857)
• A consequence: There is a lowest temperature! (Davy)
Kinetic Theory
• A description of matter in terms of
randomly moving particles
(atoms)
– Response to Aristotle (how can atoms
stay moving forever?) given by
Newton
• For a gas, for example
– Pressure is due to the particles
colliding with the container walls
– Temperature (warmth) is a measure
of the average speed of the particles
Ludwig Boltzmann (1844–1906)
• Professor in Vienna
– Also Graz, Munich, Heidelberg, Berlin,
Leipzig
• Brings kinetic theory onto a firm
foundation: “statistical mechanics”
– Independently: J. W. Gibbs
• Ongoing battles with Ernst Mach and
others over atomic and kinetic theory
• Moody, depressed, highly sensitive to
criticism
• Suicide (perhaps) due to despair at lack of
acceptance of his ideas
The Conflict With Mach
• Mach’s view: “Positivism” (a particularly strong version!)
• Science should be based only on observable facts
– The pressure exerted by a gas on the walls of its container is an
acceptable fact
– “Explaining” that pressure in terms of invisible particles is
unacceptable, since the particles cannot be seen
– Heat is also a primary phenomenon
– Explaining it in terms of the motion of unseen particles is
unacceptable
• For Mach, science is more description than understanding
– Just study the relation between T and P, e.g. how does P change as
T is increased? Then make a catalog of results…
Boltzmann’s View
• Truth in science need not be seen directly, but is what can be
consistently inferred from observations
– Even though we cannot see atoms directly, the atomic hypothesis makes
predictions, e.g. about how P changes if T is increased
– If those predictions are confirmed by experiment, it provides support to
the atomic hypothesis
– If many predictions that follow from the atomic hypothesis are
confirmed, we may believe in the existence of atoms
• Assuming no predictions are found to be wrong!
– In effect, we “see” atoms by their effects
– Not really so different from “seeing” anything!
• This is the modern attitude
• Plus, today we can “see” atoms directly!
Electron Microscope Images
•
Xenon on Nickel
Iron on Copper
Boltzmann and Philosophy
• After Mach retired, Boltzmann returned to Vienna and was
given Mach’s philosophy course to teach
• These lectures became famous, in part for their attacks on
various philosophies and philosophers
• Proposed title of a talk for the VPS:
– “Proof that Schopenhauer is a stupid, ignorant philophaster,
scribbling nonsense and dispensing hollow verbiage that
fundamentally and forever rots people’s brains”
(These were actually Schopenhauer’s own words regarding
Hegel!)
Brownian Motion
• Discovered in 1828 by Robert Brown, a botanist
• He observed that microscopic pollen grains suspended in a
liquid move around erratically, even though the liquid itself
has no observable motion
• Possible explanation: the grains are being jostled and
buffeted by unseen atoms
• In 1905, Albert Einstein calculated the details of this
process and made several predictions
– E.g. how fast a collection of pollen grains should spread out
• Quickly confirmed by experiments
• This convinced the remaining atom skeptics!
Einstein’s “Miraculous Year”
• In addition to the paper on brownian
motion, AE published two other papers
in 1905, on
– The theory of relativity (including E = mc2)
• A revolutionary new view of space and time
– The “photoelectric effect”
• This paper won him the 1921 Nobel Prize
• Any one of these would have made his
reputation as a great scientist; together
they were astounding
A Chemical Timeline
Mendeleyev
Avogadro
Dalton
Lavoisier
Priestley
Cavendish
Stahl
periodic table
molecular weight
atomic theory
conservation of mass
oxygen
hydrogen
phlogiston theory
Newton
Galileo
Paracelsus
1400 1450 1500 1550 1600 1650 1700 1750 1800 1850 1900 1950
year
Early Elemental Ideas
• Aristotle’s four elements
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air
earth
fire
water
What happens when
you boil water?
Water is transformed
into air and earth
• Paracelsus’ three “principles”
– philosophical “salt”
– “sulfur” (not what we call sulfur)
– “mercury” (not what we call mercury)
Paracelsus (1493 - 1541) - famous alchemist,
physician, astrologer, and general occultist.
Born Theophrastus Bombastus von Hohenheim
The Alchemists
• Not scientists per se, but intimately associated with
chemical transformations
• The alchemists had three main goals
– transmuation: the conversion of “base metals” into gold
– panecea: the cure for all ills, the fountain of youth (a.k.a. the
philosopher’s stone or “sorcerer’s stone” for Harry Potter fans)
– creation of human life
• The word alchemy
– probably comes from the Arabic al-kimiya or al-khimiya
– al + khumeia (Greek for cast together or weld)
– also possibly “Al Kemi” or the Egyptian Art
The Phlogiston Theory
• A theory championed by Becher and Stahl to explain the process of
combustion and oxidation of metals
• All combustible materials contain “phlogiston” – the principle of
inflammibility
– Phlogiston is colorless, odorless and is liberated from materials when they
burn
– Reaction: metal + air + heat = “calx” of metal + phlogiston
• The gases produced in combustion are “phlogisticated air”
• Oxygen was originally described as de-phlogisticated air
• Problem
– some materials lose weight when they burn (paper, wax, etc.)
– other materials gain weight when they burn (metals)
– these can’t be explained without phlogiston sometime having negative
mass
– This was not seen as a problem by Becher and others because chemistry
was not seen as a quantitative science
Joseph Priestley
• One of the greatest chemists of the 18th century
• His house was next to a brewery and he began to experiment
with the gas (CO2) given off by fermenting beer.
– he called the gas “fixed air”
– found that it was heavier than air and did not support combustion
– also invented carbonated water
• Discovered oxygen
– oxygen liberated by heating HgO with sun rays focused with a lens
– “… the flame of the candle, besides being larger, burned with more
splendor and heat than in that species of nitrous air; and a piece of
red-hot wood sparkled in it, exactly like paper dipped in a solution of
nitre, and it consumed very fast…”
Antoine-Laurent de Lavoisier
• Considered to be the father of modern
chemistry (along with his wife!)
• Brought precise measurements (especially
weights) to chemistry
• Recognized and named oxygen and hydrogen
• Definitively disproved the phlogiston theory
(which Priestley never rejected)
– heated lead in air in a sealed container
– no mass was gained or lost
– slight vacuum was created (O2 was consumed)
• First to state the Law of Conservation of
Matter
• Pioneer in the naming of chemicals
John Dalton
• British chemist and physicist
• The foremost proponent of the atomic theory
– all elements are composed of indestructible atoms
– all compounds are simple combinations of atoms
• Richard Feynman (physicist) said that if the human race
was wiped out and we could pass on just one sentence of
scientific knowledge, it should begin with “all things are
made of atoms…”
• Began to build a table of atomic weights
– hydrogen (the lightest element) assigned a weight of 1
– water is composed of oxygen and water in an 8:1 ratio
– therefore oxygen was assigned an atomic weight of 8
(he didn’t know that water contained two hydrogen atoms)
Discovery of the Elements
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Mendeleyev's Periodic Table
Dmitri Ivanovich Mendeleyev
• One of several scientists to see the patterns in
the properties of the elements when they were
arranged in order of increasing atomic weight
• Earlier patterns
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Döbereiner – “law of triads” in 1829
De Chancourtois – telluric screw in 1862
John Newlands – “law of octaves” in 1864
Medeleyev (and Meyer) – periodic table in 1869
• Some initially dismissed his table because he
assumed there were errors in the determination
of some of the atomic weights
• Predicted the existence (and properties) of
several as yet unknown elements!
Case Study:
“Cold Fusion”
• An unusually chaotic example of scientific practice
• Many useful lessons about how not to do it!
• But, illustrates the real-word functioning of science very
well
• Ultimately a success story!
Background
• “Fusion” refers to a process in which the nuclei of light
atoms combine (fuse) to form a heavier nucleus, with a
large energy release
• The physics mechanism behind the sun’s burning, as well
as thermonuclear weapons (the “H bomb”)
• The “holy grail” of energy sources
– Cheap fuel (hydrogen!)
– Lots of energy
– No harmful by-products, unlike current fission reactors
Basic Reactions
Why is it so hard?
• The nuclei don’t want to be close together
– Like charges (protons) repel each other
• To overcome this repulsion, you need very high
temperature and pressure
Nuclear Fission
• Problems: limited fuel supply, dangerous byproducts,
expensive technology, limited lifetime of power plant due
to radiation
March 23, 1989
• Stanley Pons and Martin Fleischmann, chemists
from the University of Utah announce at a press
conference that they have achieved nuclear
fusion at room temperature with inexpensive
equipment on a tabletop
– Called “cold” fusion to distinguish it from the
conventional “hot” fusion
– If true, the world’s energy problems are over!
• But only a general outline is given of what they
did, with no details of their work for others to
check
• A media/scientific frenzy ensues…
“Sociological” Factors
• Nuclear fusion is a province of physics; chemists had
apparently scooped the physicists in their own field
• “Small science” versus “big science”
– Small scale; P&F used their own money
• “Ordinary” versus “elite” institutions
– Utah, not Princeton or Caltech or MIT
What happened next…
• Others tried to figure out what P&F had actually done, so
they could test it
• P&F refused to release a paper pending patent applications
• Researchers were reduced to using news footage to figure
out what P&F were doing!
• Right away, it seemed very hard to understand based on
known nuclear physics
– An old, very well-established area of physics
Pro and Con
• The evidence described by P&F for their claim that fusion
had actually occurred was
– A lot of heat was released, too much to have been just due to
chemical reactions
– Some neutrons, a byproduct of the fusion reaction, were detected
• On the other hand
– If enough fusion had occurred to release the measured heat, many
more neutrons should actually have been seen; indeed P&F should
have been dead!
– Neutrons are notoriously hard to detect; P&F did not have any
expertise in this
What happened next…
• Some very early experiments announced that they saw
fusion too
• However, many others, including ones at “elite”
institutions like MIT, failed to reproduce the effect
• There was a great deal of confusion about whether “tricks”
or special knowledge was necessary to get it to work, but
P&F were not forthcoming
• P&F eventually released a preprint; experts noted several
flaws and likely errors
• Occasional “positive” results still reported, but most were
negative, including all from “elite” institutions
• A number of retractions appear
The Endgame
• At the Baltimore meeting of the APS in May, 1989, a series
of talks are given which demolish cold fusion for the
majority of scientists
– Steve Koonin (Caltech): “…the incompetence and delusion of
Pons and Fleischmann.”
• P&F’s careers are essentially ended
The Aftermath
• Some privately funded CF research continues, despite the
lack of reproducible evidence
• Some “positive” results are periodically reported
– Not published in the normal peer-reviewed journals
– Not reproducible
• Mainstream scientists regard it as a dead issue
• Some proponents subscribe to conspiracy theories
• Must science keep an open mind?
Reality must take precedence over public
relations, for nature cannot be fooled.
–Richard Feynman
Seven Warning Signs
of “Bogus Science” (Bob Park)
1. The discoverer pitches the claim directly to the media.
2. The discoverer says that a powerful establishment is
trying to suppress his or her work.
3. The scientific effect involved is always at the very limit of
detection.
4. Evidence for a discovery is anecdotal.
5. The discoverer says a belief is credible because it has
endured for centuries.
6. The discoverer has worked in isolation.
7. The discoverer must propose new laws of nature to
explain an observation.
Magdeburg Hemispheres
Discussion Questions (Bronowski)
1.
2.
3.
4.
Difference between inductive and deductive reasoning?
What is meant by “unity in hidden likeness”? Examples?
How does science impact the world on a philosophical, creative level?
Why is order not obviously seen in nature for scientists? Are scientists
not in tune to noticing these types of things?
5. Other examples of how science is creative and philosophical?
6. Isn’t it true that science is, in part, a collection of facts? Why would
the Royal Society refuse to open the notebooks in Popper’s fable?
7. Details of Yukawa’s story?
8. Is the likeness that scientists discover an approximation?
9. Is objectivity a realistic goal (or should it be) of science?
10. Does there have to be a single thread that ties everything together?
11. How is the past regarded in terms of scientific progress? The present?
The future?
12. Relation between the arts and sciences, and mutual influences?
Discussion Questions (Bronowski)
1. How does science impact the world on a philosophical or
creative level?
2. Other examples of how science is creative and
philosophical?
3. Isn’t it true that science is, in part, a collection of facts?
4. Why would the Royal Society refuse to open the
notebooks in Popper’s fable?
5. Does there have to be a single thread that ties everything
together?
6. Relation between the arts and sciences, and mutual
influences?
“Pathological Science” (I. Langmuir)
1. The maximum effect that is observed is produced by a
causative agent of barely detectable intensity, and the
magnitude of the effect is substantially independent of the
intensity of the cause.
2. The effect is of a magnitude that remains close to the limit
of detectability, or many measurements are necessary
because of the very low statistical significance of the
results.
3. Theories outside the field's paradigm are suggested.
4. Criticisms are met by ad hoc excuses thought up on the
spur of the moment.
5. The ratio of supporters to critics rises and then falls
gradually to oblivion.