University of San Francisco

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University of San Francisco Modern Physics for
Frommies II The Universe of Schrödingers
Cat Lecture 1
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Agenda

• Administrative matters
• Physics and the Scientific Method
• Notation and Units
• Mass vs. Weight
• Some History

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Administrative Matters

• Lecture Location and Time Fromm Hall Wednesdays
  1 PM 240 PM Prompt start.
• Lecturer Terrence A. Mulera HR 102
• Office Hours TBA and by appointment
• Contact Information
• e-mail mulera_at_mail.usfca.edu
• Phone [phone]

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Administrative Matters 2

• Class Wikis
• http//modphysfromm2.wiki.usfca.edu/ or link from
  Fromm web site.
• .pdf notes, 4/page posted hopefully night before
  class. These may change by time of lecture.
• Hard copies. How many do we need?
• Power Point slides posted immediately following
  lecture. Will include any changes to .pdf notes
• Material from preceding class (Albert Einsteins
  Universe) still available at http//modernphysicsf
  rommies.wiki.usfca.edu/

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Administrative Matters 3

• USF Physics and Astronomy Colloquia
• Open to the public
• Wednesday afternoons 4 -5 PM in HR 127
• Light refreshments at 330 PM
• First colloquium will be sometime after start of
  regular USF spring semester.
• Schedule of colloquia will be provided as soon as
  it is available. Will also be posted in Fromm
  Hall.

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Please turn off or silence cell phones and pagers.
Thanks for the cartoon to Mooses, 1652 Stockton
St., San Francisco, CA
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Physics and the Scientific Method

• Physics is a science

-Limited to that which is testable

• Concerned with how rather than why

• Best defined in terms of the Scientific Method
• Formulated in the 17th century

• Other concerns reserved to Philosophy,
• Metaphysics and Theology.

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Example Newtonian Gravitation
Observations Things fall, planets orbit in
ellipses etc.
Empirical Law There is an attractive force
between objects which have mass.
Theory Newtons Law of Gravitation
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Testing Good agreement with experiment and
observation. Measurement of falling
objects Celestial mechanics pre-1900
Refinement of Theory and Further Testing
1905 1920 Einsteins theory of general
relativity Eddingtons observation of bending
light Precession of Mercurys orbit
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Future Refinement and Testing Quantum gravity?
CAVEAT A scientific theory can never be proved,
it can only be shown to be not incorrect to the
limit of our ability to test it.
Alternatively, if you cannot devise an experiment
which will disprove your conjecture, your
conjecture is not science. - Karl Popper
(1902-1994)
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Helen Quinn, What is Science, Physics Today (July
2009)
Posted on Wiki http//modphysfromm2.wiki.usfca.edu
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Scientific Notation
Very large and very small numbers with many zeros
before or after the decimal point are
inconvenient in calculations.
For convenience we write them as
.
.
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Results usually presented as 1 digit to left of
decimal with exponent adjusted accordingly, i.e.

Multiplication
Division
Exponents add and/or subtract
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Units
Mostly rationalized mks units, i.e. distance in
meters, mass in kilograms, time in seconds.
Occasional use of cgs units, i.e. centimeters,
grams, seconds and of English units, i.e. ft.,
slugs, seconds
Special units. e.g. light years, parsecs, fermis,
barns introduced as needed
Mass vs. Weight
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Mass vs. Weight
Mass (if non zero) is a measure of the quantity
of matter present.
e.g. 1 kg of say air corresponds to n molecules
of air 2 kg corresponds to 2n molecules
Mass is independent of the gravitational
environment of the matter. 1 kg on Earth 1 kg
on Mars 1 kg in interstellar space etc.
Alternatively, mass is a measure of an objects
resistance to acceleration.
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Weight is a force on an object due to gravity.
Units kg m/sec2 ? Newton (N)
Weight is dependent on the gravitational
environment of the object. Weight on Earth ? 3 x
weight on Mars ? 6 x weight on moon.
Common usage Weights quoted in kg with
environment understood to be surface of Earth.
Further confusion lbs. are units of weight,
mass units are slugs. 1 slug x (32 ft/sec2) 1
lb
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A Brief History of Views of the Universe
Arbitrary definition of Modern Physics Post
1900 CE Two major foundations Relativity Qua
ntum Mechanics
Where were we? Where are we?
Maybe we can ask Where are we going?
Its difficult to make predictions, especially
about the future. - Yogi Berra
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The Ancients (mostly Greeks) Physics from the
Greek physika meaning natural things or the
study of nature.
All of the ancient civilizations tried to
understand their worlds in terms of
myths. Anthromorphizication of natural
forces e.g. Egyptian sun god, Ra
Greek mythology Zeus, Athena, Aphrodite, Aeres
etc.
Ca. 600 BC the Pre-Socratics began to apply
reason to the comprehension of nature
What is the underlying order that is hidden in
nature?
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What is the most basic substance in the
universe? Is the structure of nature based on
mathematics, processes or substances?
Some of the Players
Thales (600 BC) H2O is the primary and simplest
element Anaximander World composed of
interacting, aggressive opposites Anaximenes
Like Thales only air rather than H2O Empedocles
Earth, air, fire and water Paramendes
Processes. Matter is conserved. Pythagoras
Defined the world in terms of mathematics. Coined
the term philosopher. Leucippus and Democritus
Elementary particles. Coined the term atom.
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Socrates ? Plato ? Aristotle
Earth and its place in the universe
geocentric Complex system of interlocking spheres
with names like prime mover, cycles and
epicycles.
Aside A heliocentric theory was proposed as
early as the 6th century BC by non other than
Pythagoras.
.
Physical phenomena 4 elements. Properties and
motions of objects could be described in terms of
the chemical reaction properties of these
elements.
Motion 4 basic types Alteration Chemical
reaction Natural local motion Weight falling,
smoke rising Horizontal or violent motion
Pushing, pulling, throwing Celestial motion
Involves the interlocking spheres mentioned
above. Ptolemaic model.
.
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Archimedes of Syracuse (287 212 BC)
Archimedes Thoughtful by Fetti (1620)
Killed by a Roman soldier at the siege of
Syracuse (2nd Punic war)
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Discoveries and Inventions Credited to Archimedes
Hydrostatics Archimedes principle
Principle of levers Give me a place to stand
on, and I will move the Earth. Block and tackle
systems Archimedes screw
Military weapons Archimedes claw Death ray
(mirrors focusing the Sun on enemy ships)
Possibly apocryphal but principle verified by MIT
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Mathematics
Infinitesimals. Calculus? Value of p Area under
the arc of a parabola Attempted to calculate the
number of sand grains which the universe could
contain. Lead to his devising a system of dealing
with extremely large numbers using powers of
myriads (10,000 in Greek).
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Interregnum Aristotle - Renaissance
Not much happening in physics but lots going on
in history Rome dominates the classical
world Rome falls ca. 450 AD Dark ages in Europe
ca. 450 750 AD
Light of classical civilization preserved in
Islamic countries. Returned to the West in the
Middle ages, 750 1350 AD.
Concept of the zero Algebra Anatomy Star
charts Pre-Copernican heliocentric theories
Black Death strikes Europe, 1347 AD, third of
population dies
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Renaissance Ca. 1400- 1600 AD The Copernican
Revolution
Observation ? Tables of planetary motion
Geocentric (Ptolemaic) model noticeably
inaccurate and difficult to calculate.
If I had been present at the creation, I would
have recommended a simpler design for the
universe - Alphonso X (1221 1284)
King of Spain
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Nicholas Copernicus (1473-1543)
Tried a heliocentric model much like that
proposed by Aristarchus 1700 years earlier.
Model was successful but not overly so. Assumed
orbits were perfect circles, required
reintroduction of complexity Few converts over 50
years
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Tycho Brahe (1546 1601)
Greatest of the early observational
astronomers. Naked eye, telescope was invented
shortly after his death.
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Observed a new star or nova. Observed the 1563
alignment of Jupiter and Saturn. Noted that it
occurred two days later than predicted by the
Copernicus model
Spent the next 30 years compiling stellar and
planetary measurements.
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Convinced planets orbit Sun
No stellar parallax ? Earth stationary.
Sun orbits Earth
Few took this model seriously
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Johanes Kepler (1571 1630)
Tychos assistant. Inherited data base upon
Tychos death.
Elliptical orbits
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T
Speculated that some force (like magnetism)
originating from the Sun was responsible for
planetary motion.
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Galileo Galilei (1564 -1642)
1608 1st working refracting telescopes Hans
Lippershey, Zacharias Janssen, Jacob Metius in
the Netherlands Galileo greatly improved design
in 1609
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Three objections to Keplers heliocentric
theories
(1) The Earth cannot move because birds, falling
stones etc, would be left behind.
Inertia later Newtons 1st law. Galilean
relativity
(2) Non circular orbits are contradictory to the
non changing perfection of the heavens.
Novae, supernovae, comets already
observed Telescopes allowed observation of
sunspots, mountains on Moon
(3) No stellar parallax observed.
Telescope ? stars are much farther away than
Tycho thought
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Final nails in the coffin
The moons of Jupiter, a miniature Solar System
CLEA exercise See wiki
Observation of the phases of Venus can only be
explained in terms of a heliocentric model.
Observation of the transit of Mercury across the
face of the Sun
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Sir Isaac Newton (1642-1726)
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Newtonian Mechanics (translational)

• Three laws of motion
• A body at rest or in constant rectilinear motion
  remains at rest or in motion unless acted upon by
  an outside force.

2)
3) Momentum is conserved
Action - Reaction
There are rotational extensions to these laws
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Angular momentum,
This must also be conserved. Careful, its a
vector so direction as well as magnitude is
conserved
Newtons Law of Gravitation
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Joseph Louis Lagrange a.k.a. Giusseppe Lodovico
Lagrangia (1736-1813)
Jean Le Rond dAlembert (1717-1783)
Leonhard Euler (1736-1783)
William Rowan Hamilton (1805-1865)
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Triumphs Celestial mechanics, planetary orbits
Navigation Mechanical Engineering and the
Industrial Revolution
The above Classical Mechanics was accompanied by
the 2nd great triumph of pre-20th century
physics, Classical Electromagnetic Theory, a.k.a.
Classical Electricity and Magnetism, a.k.a.
Classical Electrodynamics.
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Electrical charge
Ancient Greece, ca. 600 B. C.
Rub a rod of amber or hard rubber with a
cloth. After rubbing, rod is able to attract
small bits of paper or other light material.
No real advance in understanding until ca. 1600
A. D. William Gilbert (court physician to
Elizabeth I) studied materials that act like
amber.
electric (elektron is Greek for amber)
Electric modern term is insulator Non-electric
conductor
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About 100 years later Charles Du Fay showed that
there are 2 forms of electrification.

attraction If you rub various insulators ?

repulsion
Postulate There are 2 types of electrical
charges like charges
repel unlike charges
attract
Benjamin Franklin Assign () charge to one type
and (-) charge to the other.
Which is is arbtrary. Consistent use of a sign
convention allows a very concise mathematical
formulation of experimental facts.
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Franklins arbitrary choice rubbing glass rod
w/silk ? ()
rubbing amber or hard rubber ? (-)
Hindsight Picking signs opposite to Franklins
choice ? more sensible conceptual picture.
Hindsight is always 20-20 - .Anonymous
J. J. Thomson ca. 1900 Discovered the electron.
Its charge under the Franklin convention is (-)
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Coulombs Law
William Gilbert (1544-1603)
Charles du Fay (1698-1739)
Charles de Coulomb (1736-1806)
Benjamin Franklin (1706-1790)
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Magnetism
The nation that controls magnetism controls the
universe.
-Diet Smith in Chester Goulds Dick Tracy, New
York Daily News Syndicate (1962)
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Magnetism
Historical Interactions between ferromagnetic
materials (Fe, Ni, Co) Forces of attraction and
repulsion Resemble but are quite distinct from
electrostatic Use of permanent magnet in Earths
magnetic field as compass for navigation. In
1819 Ørsted showed connection between electric
current and magnetism. Faraday and others,
culminating in Maxwells equations.
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James Clerk Maxwell (1831-1879)
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Maxwells Equations (differential form)

• E. M. wave equation

where
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Triumphs Electrical Engineering, Electric power
and communication
Wireless communication Radar Modern optics First
electronic computers
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The Deterministic Universe
Determinism ? The future is completely determined
by the past. ? The future can be
predicted if enough is known
of the past.
What is enough?
Consider a universe whose component objects are
labeled with the index i. Each object has mass mi.
If we know the initial position, xiI, and
velocity, viI of each particle plus the resultant
or sum of all the forces acting on it as a
function of time, Fi(t), then we can, in
principle, calculate the final position, xiF, and
velocity, viF. ,
xiI
xiF
viI
Fi(t)
viF
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Kelvin, Lord William Thomson (1824-1907)
There is nothing new to be discovered in physics
now. All that remains is more and more precise
measurement. -1900
Heavier than air flying machines are
impossible. -1895
X-rays will prove to be a hoax. -1896
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Lord Kelvin
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Wilhelm Röntgen 1845 - 1923
Mrs. Röntgen né Anna Ludwig 1872 - 1919
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Orville Wright 1871 - 1948
Wilbur Wright 1867 - 1912