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Transcript
What should be the public awareness of Physics?
Is Physics a coherent body of useful
contemporary knowledge? Or…
only a Method of Inquiry unchanged
since the Age of Enlightenment?
Intro. Phys. I – to American Revolution
Intro. Phys. II – to American Civil War
Modern Phys. – to the Great Depression
Relearning the ignorance of the “Enlightenment”
Planetary motion (Copernicus, Galileo, Brahe, Kepler 1500-1600)
Newton’s laws
(Newton 1687)
Electricity
(Coulomb 1777)
Magnetism
(Oersted 1819)
Line spectra
(Kirchhoff 1859)
Kinetic theory
(Maxwell 1860)
Relativity E&M
(Voigt 1887)
Atomic confirmation (Einstein 1905)
‘the concept of force has reached the end of its life cycle …
(suggesting) its disbarment from the inventory of fundamental
concepts in physics.’
Max Jammer, Concepts of Force, 1957
‘In all methods and systems which involve the idea of force there is
a leaven of artificiality… there is no necessity for the introduction of
the word “force” nor the sense-suggested ideas on which it was
originally based.”
Peter G. Tait, Dynamics, 1895
‘If people were to learn to conceive the world in a new way, without
the old notion of “force,” it would alter not only their physical
imagination, but probably also their morals and politics.’
Bertrand Russell, The ABC of Relativity, 1925
Quotes from Force-Trained students:
‘How can a rocket work in outer space where there is nothing
for the force to push on?’
‘The moon doesn’t fall to earth because the centrifugal
force holds it out.’
‘If weight is gravitational force, and orbiting astronauts are
weightless, then they must be outside the range of gravity.’
‘We know that nuclei are small because -projectiles miss
them and go mainly forward. If nuclei were large, -particles
would hit them, feel a force, and bounce backward.’
Are the problems we assign even realistic?
____________________________________
Am. J. Phys. 71, 1152 (2003); dispute / R.K. Adair 73, 184 (2005).
1. Viscous drag nonlinearly couples horizontal & vertical – solve numerically.
2. Aerodynamics of backspin dominates the range achieved.
A lousy approximation!
THE NATURE OF MATTER
_________________________________________________________
All matter consists of little bits of positive and negative electricity:
in perpetual motion;
attract each other at short distances;
repel each other when pressed too close together.
________________________________________________________
The most important discovery ever made.
If all other scientific information we know were lost in some
cataclysmic event, and only this information survived,
all could be ////
rediscovered in a very short time.
- Richard P. Feynman
`
(Ohio State Board of Education –12/10/02)
Iron atoms positioned on a carbon surface
Second Quantization - The Discrete Photon
700 keV Li+ beam (v=4.4 mm/ns) incident on a thin (3 g/cm2) carbon foil.
The blue light is H-like 4f-5g in Li2+ (4500Å, =3 ns, x=1.3 cm).
The green light is He-like 2s 3S-2p 3P in Li+ (5485Å, =44 ns, x=19 cm).
Can we picture
attractive and repulsive interactions
without the force concept?
Quantum Field Theory
is conceptually easy!
ACTION-AT-A-DISTANCE
Exchange of a ‘gauge boson’
Particle exchange can produce both attraction and repulsion.
It is intermittent, like rain on the roof.
The Force concept requires an average over a time interval.
Nature has revealed a beautiful secret!
The behavior of the Universe becomes very simple
if it is described in a way in which space and time
are symmetric.
What makes it seem hard, is the fact the we must live
our lives by standing at a point in space and watching
time pass, but not the reverse.
It’s like our perspective in riding the Earth around the
Sun, which seems as if the Sun were going around us.
However, the heliocentric equations are much simpler.
TIME
“Time is what keeps everything from happening at once.”
- Attributed to John Archibald Wheeler
Quoted by Woody Allen
“Time flies like an arrow; fruit flies like a banana.”
- Groucho Marx
‘Backward turn, turn backward, O time in your flight.
Make me a child again, just for tonight.’
- Elizabeth Akers Allen
Electron-positron pair production
The “photon-dressed” electron
Electron-Positron Pair
Creation and Annihilation
Once created, e+ and e- are stable until annihilated
Are they all really
the same electron?
time
Future
Here-Now
space
Past
Why didn’t Isaac Newton think about the possibility of
getting hit on the head when he sat under the apple tree?
 x

Where does the pendulum spend the most time? The least time?
Time exposure
Dwell time:
High:
many / slow
Low:
Few / fast
Equal time inside
No time outside
Most time at end points
Least time at center
Most time at aphelion
and perihelion
The secret of life, computers, & transitors
Laplacian Determinacy – A Costly Mistake
Pierre Simon Laplace - 1776: “An intelligence that knows all of the
relations of the entities of the universe at one instant could state their
positions, motions, and general effects any instant in the past of future.
Henri Poincare – 1903: “Small differences in the initial conditions
can produce very great ones in the final phenomena – prediction
Then becomes impossible (1st recognition of chaos).
Werner Heisenberg – 1924: There is a fundamental limit on the
accuracy to which position and velocity can be co-determined.
Stephen Hawking –1988: In the cosmology of the Big Bang and
Black Holes, space and time themselves break down.