IS 240: Discovering the Atom
Dr. Dean Johnston
Department of Chemistry and Biochemistry
Dr. David Robertson
Department of Physics and Astronomy
Course Overview
• Science as a “way of knowing”
• Focus on the atomic structure of matter
– How do we know about it?
– What does it tell us?
– Is there anything inside them?
• A multi-disciplinary perspective – chemistry and
physics
• Includes laboratory exercises
• Builds a foundation for later IS science courses
Course Structure
• Periodically split into two groups (A and B) for
lab work in parallel tracks lasting two weeks
• Each split session involves one chemistry and one
physics lab
• Each group spends one week at each, swapping in
between
• “Joint” sessions glue things together
Course Materials
• Text: The Last Sorcerers: The Path From Alchemy to
the Periodic Table, by Richard Morris
• Other readings provided as handouts or on line
• Course web page:
http://www.otterbein.edu/home/fac/dvdgrbrt/is240/
– Notices, lecture notes, the syllabus, online resources, grades,
and more…
• On reserve at the library:
– The Blair Handbook
– The Everyday Writer
Modes of Inquiry
• “Ways of knowing” – ways to ask (and answer)
questions
–
–
–
–
–
–
Are there regularities in the natural world? If so, what are they?
What are the basic things that exist in the world?
Was there a creator?
What is the nature of good and evil?
Is there such a thing as beauty?
How can human societies best be organized?
• Different modes may be more or less appropriate
for different questions
• Most people use all of them
Philosophical
• Study of the ultimate reality, causes, and principles
underlying being and thinking
• Esthetics, ethics, politics, metaphysics, logic,
epistemology (nature and origin of knowledge)
• A search for wisdom based on logic and principle
• May be based in part on observation, though often
speculative
Philosophy is a hypothetical interpretation of
the unknown, or of the inexactly known. It is
the front trench in the siege of truth, while
science is the captured territory.
–Will Durant
Theological
• Knowledge is revealed, through
– Scriptures
– Personal revelations, prayer
– Contemplation and interpretation of mystics
• Modern religious interpretations focus mainly on
ethical questions
– How should you live your life?
– What are right and wrong?
• Historically, theology has not always considered
science to be a valid way of knowing
Scientific
• Conclusions based on systematic observation and
manipulation of the natural world
• Only deals with the natural world!
– Excludes the “supernatural” by definition
• Systematized by Bacon,
Descartes and Galileo
in the 17th century
• Aims to give conclusions
that are independent of the
individual
The task of science is both to
extend the range of our
experience and to reduce it to
order.
–Niels Bohr
The Scientific “Method”
The whole of science is
nothing more than a
refinement of everyday
thinking.
–Albert Einstein
A Classical Example
• Aristotle observes that during lunar eclipses the Earth’s
shadow on the moon is curved
A Lunar Eclipse
A Classical Example, cont.
• He assumes it will be curved for all eclipses
• A hypothesis that explains this: the earth is round
• A prediction of this hypothesis is that the location of the
stars in the sky should be different for observers at
different latitudes
• This is confirmed by additional observations
– E.g. Canopus is visible in Egypt but not further north
Polaris
Local Sky
• Depending on your
location you see
completely different stars!
North Pole
N
South Pole
Solar Eclipse
• Umbra – region of total shadow
• Penumbra – region of partial shadow
Observations
• Scientific Fact (AAAS): An observation that has been
repeatedly confirmed
• Examples:
– The sky is blue
– Humans have 46 chromosomes in somatic cells under normal
conditions
– The sun rises in the east and sets in the west
• Always subject to reconsideration (in principle) but in
practice assumed to be true
• Some are better established than others
– At the “cutting edge” the facts may not be so clear (yet)
Experimental vs. Historical
Observations
• Experimental
– Tests/observations can be repeated with different conditions
– Hypotheses can be refined after further testing
– Physics, chemistry, molecular biology, etc.
• Historical
– Evidence that something happened in the past
– Reconstruction of the past
– Forensic science, geology, paleontology, cosmology, much of
biology, etc.
• Different sciences rely to different degrees on the two
kinds of observations
Scientific Theories
• The word “theory” connotes “uncertainty” to nonscientists, but this is incorrect in the scientific context
• AAAS Definition: “A well substantiated explanation of
some aspect of the physical world”
• The highest rank of scientific explanation!
– Not “just” a theory
• Substitute “body of knowledge known as...” for “theory
of...” (e.g., “body of knowledge known as relativity” rather
than “theory of relativity”)
• Use “hypothesis” for an untested idea
What is the aim of
(experimental) science?
• A search for order or patterns in nature
– The “scientific method” sets out the rules for the search
• In physics and chemistry these patterns are generally
expressed mathematically
– E.g. for falling bodies, d is proportional to t2
– Water is composed of hydrogen and oxygen in a mass ratio of 1:8
• (At least) two amazing facts:
– That such patterns exist at all!
– That so much can be explained by so few basic ideas (patterns)
• Much of the history of science has involved the search for
ever more general, all-encompassing patterns in nature
Johannes Kepler (1571–1630)
• Key question: How are things
happening?
• Major Works:
–
–
–
–
Harmonices Mundi (1619)
Rudolphian Tables (1612)
Astronomia Nova
Dioptrice
Kepler’s
Beginnings
• Astrologer and mystic
• Tried to find “music in
the heavens”
• Attempted to explain
distances to the five
known planets by
nested spheres resting
on the five “Platonic”
solids
• Pre-scientific
Johannes Kepler
Manuscript: trying to disentangle
The mystery of Mars’ orbit 
Kepler’s First Law
The orbits of the planets are ellipses, with the Sun at one
“focus”
Kepler’s Second Law
An imaginary line connecting the Sun to any planet sweeps
out equal areas of the ellipse in equal times
Kepler’s Third Law
The square of a planet’s orbital period is (in appropriate
units) equal to the cube of its orbital semi-major axis: P2 = a3
Planet
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
Orbital Semi-Major Axis
Orbital Period
(au)
(Earth years)
0.387
0.241
0.723
0.615
1.001
1.000
1.000
1.524
1.881
5.203
11.86
9.539
29.46
19.19
84.01
30.06
164.8
39.53
248.6
P2/a3
1.002
1.000
1.000
0.999
1.000
0.999
1.000
1.001
Isaac Newton (1642–1727)
• Key question: Why are things happening?
• Invented calculus and physics while on
“vacation” from college
• His three Laws of Motion, together with
the Law of Universal Gravitation, explain
the motion of planets and of objects on
Earth (and more!)
• Later in life he was Master of the Mint,
dabbled in alchemy, and spent a great deal
of effort trying to make his personal
enemies miserable
Newton’s Laws of Motion
A general framework for describing any motion
1. Every body continues in a state of rest or in a state of
uniform motion in a straight line unless it is compelled
to change that state by forces acting on it (Law of
Inertia)
2. The change of motion (acceleration) is proportional to
the force applied (F = ma where m is the mass of the
object)
3. For every action (force), there is an equal and opposite
reaction
Law of Universal Gravitation
R
MEarth
Mman
GM Earth M Man
F
2
R
Orbital Motion
Cannon “Thought Experiment”
The Unity of Nature
• Newton showed that the orbital motion of planets reflects
the same pattern in nature as does motion on Earth (balls
rolling down planes, cannonballs, falling apples, etc.)
• Also explained the ocean tides
– Due to gravitational attraction of the moon
• Many apparently different phenomena are thus related!
• Later, Einstein showed that Newton’s Laws are an
approximation to an even deeper, more subtle pattern
• That new pattern incorporates everything Newton does,
plus more – including the structure of the universe itself!
Scientific Theories
• Must be falsifiable (Karl Popper)
– There must be some way the theory could fail
– Appeals to, e.g., supernatural influences are not allowed!
• Should make predictions
– The more, the better!
• Theories that are very well tested and have the widest
applicability are often known as “laws of nature”
• Always subject to revision or modification, though
• Occam’s Razor: simpler is usually better!
Experiments
• Experiments must be repeatable
– Others must be able to duplicate your results!
• Possible outcomes of an experiment:
– The experiment may support the theory
• We then continue to make predictions and test them
– The experiment may falsify the theory
• We need a new theory that describes both the original data and the
results of the new experiment
• Since we cannot do every possible experiment, a theory
can never be proven true; it can only be proven false
The aim of science is not to open the door to everlasting
wisdom, but to set a limit on everlasting error.
–Bertolt Brecht, in The Life of Galileo
Other Characteristics
• Science is cumulative and progressive
– The new absorbs the old
– Successful theories are never “merely” wrong, even when
overthrown
• They are usually seen to be approximations of the new, deeper
principle
• Science is self-correcting
– Scientific work is open – scientists make their work available to
others so that they may test it
– Outright fraud is rare, and (usually) quickly detected
– Mistakes are uncovered by independent checks
Summary
“Science is the systematic enterprise of gathering
knowledge about the world and organizing and
condensing that knowledge into testable laws and
theories.
[American Association of Physics Teachers, Am. J. Phys.
67 (8), p. 659 (1999)]
“The success and credibility of science is anchored in
the willingness of scientists to:
1. expose their ideas and results to independent
testing and replication by other scientists; this
requires the complete and open exchange of data,
procedures and materials;
2. abandon or modify accepted conclusions when
confronted with more complete or reliable
experimental evidence.
Adherence to these principles provides a mechanism
for self-correction that is the foundation of the
credibility of science.”
The Domain of Science
• Science deals with natural phenomena, and only allows
natural explanations
– Remember, theories must be falsifiable!
• Some questions are not answerable in this way
–
–
–
–
–
–
Is there life after death?
Do we have souls?
Is abortion wrong?
Should capital punishment be allowed?
What is the best form of government?
…
• However, science may provide input for these questions,
e.g. by predicting consequences
Science and Religion
• Often seen as being in conflict
– Copernicus vs Ptolemey; Galileo
– Evolution
• Whether or not there is a conflict, and if so what it entails,
is a philosophical judgment that each person must make
– Many scientists are religious
– Many churches accept scientific findings
– The converses are true also!
“Same World” Model
• Science and Religion deal in principle with the same
subjects
• Conflicts are hard to resolve since science cannot accept
evidence on faith and religion need not accept scientific
explanations
– Example: What is the age of the Earth?
• Usually results in a claim that one is right and the other
wrong
– Fundamentalists
– Some scientists who see religion as unnecessary and regressive
“Separate World” Model
• Science and Religion deal in principle with different
subjects
• Therefore no overlap or conflict; can co-exist peacefully
– Science deals with the natural world
– Religion deals with the spiritual world, ethics
– There may be conflict in a few areas, which vary from person to
person
• The position of many churches and scientists
Measurements: The Metric System
• Units of length:
– The meter (m)  3 ft. 4 in.
– The kilometer (km) = 1000 m or about 0.6 mi.
• Units of mass:
– The kilogram (kg). 1 kg weighs about 2.2 lbs. (The lb. is a unit of
weight)
• Units of time:
– The second, same as in the English system
Scientific Notation
• 108 means multiply by 10 eight times
– 108 is 1 followed by 8 zeroes
– Example: 1.5  108 km = 1.5  100,000,000 = 150,000,000 km
– 100 is a 1 followed by no zeroes, i.e. just 1
• A negative exponent means divide instead of multiply:
– 10–6 means divide by 10 six times
– Example: 2  10–6 m = 2/1,000,000 = 0.000002 m
• To multiply numbers, add exponents:
– Example: 104  1023 = 104 + 23 = 1027
• To divide, subtract exponents:
– Example: 104 / 1023 = 104 – 23 = 10–19
– Note: 1 / 104 = 100 / 104 = 10–4
Exercises
• Evaluate the following:
1.
2.
3.
4.
102  1017 = 1019
100  10–4 = 10–4
102/108 = 10–6
(1.5  103)  (2  1023) = 3  1026
“Fermi Problems”
• (Very!) rough estimation
• Looking basically for the right power of 10 in the answer
– Is the answer more like 10 or 100 or 1000…?
– Round off, drop fractions, estimate needed information to the
nearest power of 10
• No single “right” answer; only more or less reasonable
ones
• The Classic: How many piano tuners are there in Chicago?
Example
• How long would it take a person to run from New York to
LA? (A week? A year? Several years?)
– Assume good runner: maybe 6 mph for 5 hours a day
– Hence about 30 miles per day
• Probably too optimistic, but in the right ballpark
– Distance from NY to LA about 3000 miles, so
T = (3000 mi)/(30 mi/day)
or about 100 days
• If another person arrived at 123.45 days, that’s fine – it has
the same “order of magnitude” (power of 10)
• Need to know some basic quantitative facts about the world
Problems
1. About how many pizzas are consumed in the US each
day?
• Say 300 million people in the US (3  108)
• Maybe 2/3 of these eat pizza regularly (2  108)
• Say these people eat half a pizza every three weeks
– Likely more for students , less for some others
•
•
So every three weeks about 1  108 pizzas are eaten
About 1  108 /20 = 1  108  5  10–2 = 5  106 per day
Problems
1. Estimate the total amount of human blood in the world. If
Lake Erie were emptied of water and filled with this
blood, about how deep would it be?
• Say 6 billion people in the world (6  109)
• Say each has about 5 pints of blood on average (30  109
pints total)
• A pint is half a quart, or about 30 cubic inches
• Assume Lake Erie a rectangle about 200 mi by 80 mi
– Surface area about 6  1013 square inches
•
Depth = (volume of blood)/(area) would be about
(30  109  30)/ 6  1013 = 30  5  10–4 = 1.5  10–2 inches
The probability that a woman of age 40 has breast
cancer is about 1%. If she has breast cancer, the
probability that she tests positive on a screening
mammogram is 90%. If she does not have breast
cancer, the probability that she nevertheless tests
positive is 9%. What are the chances that a woman
who tests positive actually has breast cancer?
Powers of Ten
– From Man to Universe –
100 meters
=1 meter
The Human
Scale
Powers of Ten
– From Man to Universe –
101 meters
=10 meters
Pond with
lilly pads
Powers of Ten
– From Man to Universe –
102 meters
=100 meters
Japanese Tea
Garden
Powers of Ten
– From Man to Universe –
103 meters
= 1000 m
= 1 km
Golden Gate
Park
Powers of Ten
– From Man to Universe –
104 meters
=10 km
San Francisco
Powers of Ten
– From Man to Universe –
105 meters
=100 km
SF Bay area
Powers of Ten
– From Man to Universe –
106 meters
=1000 km
California
Powers of Ten
– From Man to Universe –
107 meters
=10,000 km
North and
Central America
Powers of Ten
– From Man to Universe –
108 meters
=100,000 km
Earth in
Space
Powers of Ten
– From Man to Universe –
109 meters
=1,000,000 km
Earth and
Moon
Powers of Ten
– From Man to Universe –
1010 meters
Part of Earth’s
Orbit around
the Sun
Powers of Ten
– From Man to Universe –
1011 meters
 1 A.U.
(an “Astronomical Unit”)
Venus, Earth
and Mars
Powers of Ten
– From Man to Universe –
1012 meters
Orbit of
Jupiter
Powers of Ten
– From Man to Universe –
1013 meters
The Solar
System
Powers of Ten
– From Man to Universe –
1014 meters
Solar System
in Space
Powers of Ten
– From Man to Universe –
1015 meters
The Sun “a bright star”
Powers of Ten
– From Man to Universe –
1016 meters
 1 lyr
(light year)
The Sun “just another star”
Powers of Ten
– From Man to Universe –
1017 m
 10 lyr
The Nearest
Stars
Powers of Ten
– From Man to Universe –
1018 m =
100 lyr
Stars within
50 lyr
Powers of Ten
– From Man to Universe –
1019 m =
1,000 lyr
A cloud of Stars
- making up constellations
Powers of Ten
– From Man to Universe –
1020 m
 10,000 lyr
Spiral Arm of
the Milky Way
Powers of Ten
– From Man to Universe –
1021 m
 100,000 lyr
The Milky Way
– Our Galaxy
Powers of Ten
– From Man to Universe –
1022 m
 1,000,000 lyr
The Local
Group
Powers of Ten
– From Man to Universe –
1023 m
 10 x 106 lyr
The Virgo
Cluster
Powers of Ten
– From Man to Universe –
1024 m
= 108 lyr
Clusters
of Galaxies
Powers of Ten
– From Man to Universe –
1025 m
 109 lyr
The Observable
Universe:
Many clusters of
galaxies – and even
more empty space
Powers of Ten
– From Man to Universe –
100 meters
=1 meter
The Human
Scale
Powers of Ten
– From Man to Universe –
10–1 m
= 0.1 m
Lilly and bee
Powers of Ten
– From Man to Universe –
10–2 m
= 0.01 m
Bee’s head
Powers of Ten
– From Man to Universe –
10–3 m
=1 mm
=1 millimeter
A bee’s eye
Powers of Ten
– From Man to Universe –
10–4 m
= 0.0001 m
=100 micrometers
Pollen grain
Powers of Ten
– From Man to Universe –
10–5 m
= 0.00001 m
= 10 m
Bacteria
Powers of Ten
– From Man to Universe –
10–6 m
= 1 m
Virus on a
Bacterium
Powers of Ten
– From Man to Universe –
10–7 m
= 0.1 m
= 100 nanometers
= 100 nm
A virus
Powers of Ten
– From Man to Universe –
10–8 m
= 10 nm
DNA in a virus
Powers of Ten
– From Man to Universe –
10–9 m
= 1 nm
Molecules of
DNA
Powers of Ten
– From Man to Universe –
10–10 m
= 1 Angstrom
=1Å
Carbon’s outer
electron shell
Powers of Ten
– From Man to Universe –
10–11 m
= 10 picometers
= 10 pm
The inner
electron cloud
Powers of Ten
– From Man to Universe –
10–12 m
= 1 picometer
= 1 pm
Within the
electron cloud
Powers of Ten
– From Man to Universe –
10–13 m
=100 femtometers
=100 fm
The nucleus
Powers of Ten
– From Man to Universe –
10–14 m
= 10 fm
Carbon nucleus
Powers of Ten
– From Man to Universe –
10–15 m
= 1 fm
Inside the
proton
Powers of Ten
– From Man to Universe –
10–16 m
= 100 attometers
= 100 am
Quarks and gluons
A Short History of Atomic Ideas
• Earliest formulation of the idea due to the Greeks
– “atom” = a-tom, Greek for “not divisible”
– Pre-scientific, i.e. no scientific reason for believing it!
• In Rome: Epicurus and Lucretius (95 to 55 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
– Rules for combining elements to make compounds
• Kinetic Theory (Clausius, Maxwell, Boltzmann; 19th century)
– Description of matter in terms of randomly moving particles (atoms)
• 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 Medieval Setting
•
•
•
•
Dominant church
~ 1000 years of relative stagnation in the west
Experimental research greatly reduced
To answer a question:
“Study the Bible or Aristotle!”
The Renaissance Setting
• 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 Baroque Setting
• 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.
Dalton
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 on 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
Case Study: “Cold Fusion”
• A (fairly) recent example of scientific practice