Chabot College ISLS - Six Easy Pieces - Richard Feynman - Structured Analysis

Chapter 2 - Basic Physics

Scott Hildreth - Spring 2006


   "For a successful technology, reality must take precedence over
public relations, for nature cannot be fooled."
Richard Feynman, Appendix to the Rogers Commission Report on the Space Shuttle Challenger Accident.
 

Page 23- A small number of things acting in an infinite variety of combinations.

Quotes

"Any other spot in nature has a similar variety of things and influences. It is always as complicated as that, no matter where it is. Curiosity demands that we ask questions, that we try to put things together and try to understand this multitude of aspects as perhaps resulting from the action of a relatively small number of elemental things and forces acting in an infinite variety of combinations."

 

"If we understood rocks, would we also understand the sand and the moon?"

Questions:

Look at the clouds above you - what questions could you ask based on what you see similar to how Feynman asks questions of the seashore?

How about people? Can you categorize behavior, emotions, people's actions by a small number of elemental things?

Key terms:
  Page 24 - The scientific method

 

"Observation, reason, and experiment make up what we call the scientific method. "

"The rules of the game are what we mean by fundamental physics. Even if we knew every rule, however, we might not be able to understand why a particular move is made in the game, merely because it is too complicated and our minds are limited."

 

Questions:

What other parts to the scientific method did Feynman not mention here? Why?

Key terms:

 

Castling - in chess, moving a rook and king simultaneously in a specific pattern; the only time more than one piece may be moved during a single turn, and allowed only if neither piece has yet moved.

 

Page 25- How can we tell whether the rules we guess are right?

 

"There are, roughly speaking, three ways. First, there may be situations nature has arranged...to be simple and to have so few parts that we can predict exactly what will happen.

 

"A second good way to check rules is in terms of less specific rules derived from them....From the point of view of basic physics, the most interesting phenomena are of course in the new places...where the rules do not work."

 

"The third way to tell whether our ideas are right is relatively crude but probably the most powerful of them all. That is, by rough approximation."

 

"In the same way, we can often understand nature, more or less, without being able to see what every little piece is doing, in terms of our understanding of the game.

 

Questions:

Can you think of situations where things are so simple as to easily predict *exact* results?

How about a derived rule, or a rule arising because of an exception to a prior rule?

 

Why would Feynman consider the third rule even more powerful?

 

Consider clouds?

 

 

 

1) Simple Situation, with "exact" results:

Keys falling to the ground.

2) New rule, derived from this because of an observed exception:

Light bending around a star.

 

3) Rough approximation: Light bending around an even more massive object might allow "gravitational lensing" to occur.

More about Alexander Alekhine

 

Pages 26 - The aim is to see complete nature as different aspects of one set of phenomena

 

"That is the problem in basic theoretical physics, today - to find the laws behind experiment; to amalgamate these classes."

 

- Thermodynamics (unifying heat and mechanics)

- Electromagnetic Field Theory (unifying electricity, magnetism, and light)

- Quantum Mechanics of Chemistry (unifying chemical phenomena, properties of substances, and behavior of atomic particles.)

"...[I]s it going to be possible to amalgamate everything, and merely discover that this world represents different aspects of one thing?

Questions:

Is amalgamation a process that other sciences also undertake? Are there examples from Galileo and Darwin and Freud that come to mind?

 

 

meson = a particle that carries the force binding protons and neutrons in the nucleus; composed of two quarks.

See more: Quantum Physics from Georgia State University.

 

Page 27 - Physics before 1920

 

Before 1920:

"The 'stage' on which the universe goes is the three-dimensional space of geometry...and things change in a medium called time. "

The elements on the stage are particles, which have some properties:

- inertia

- forces

a) an "enormously complicated interaction force" of short range

b) smooth long-range gravitational force.

 

 

 

Questions:

Why does he use 1920 as the dividing line for this section of the chapter?

 

Could we today find a similar "decade" of division, prior to which our understanding was quite different?

 

 

Key terms:

Inertia = the tendency for matter to remain in its current state of motion; if at rest, to stay at rest and resist moving; if in motion, to stay in motion at a constant speed and resist acceleration.

Forces = Interactions between two objects, either directly (touching) or indirectly (by "fields"), that results in an accelerating the objects.

 

 

Pages 28 & 29 - What are the short range forces?

 

"In gravity, everything attracts everything else, but now imagine that there are two kinds of 'things.'"

 

"The ultimate basis of an interaction between the atoms is electrical."

 

"...in the nucleus itself there were found two kinds of particles, protons and neutrons, almost of the same weight and very heavy."

 

Questions:

What is Feynman's writing style?

Is it effective for nonscientists?

 

How can we "see" this electrical interaction, and test whether there are plus and minus charges?

 

 

 

Pages 30-32 - The Electromagnetic Field and Light

 

"The natural interpretation of electrical interaction is that two objects simply attract each other: plus against minus. However, this was discovered to be an inadequate idea to represent it."

"This potentiality for producing a force is called an electric field."

"We then have two rules: (a) charges make a field, and (b) charge in fields have forces on them and move."

Questions:

Are there other force fields?

Do "fields" really exist, or are they mathematical?

Are there other ways to picture forces without using fields?

 

Key terms:

Electromagnetic Waves = all forms of light, including the visible light our eyes are sensitive to collecting, as well as more energetic:

- Gamma Rays

- X-rays

- Ultraviolet Light

and less energetic

- Infrared

- Microwaves

- Radio Waves

How does EM radiation move?

 

 

Page 33 - - Quantum Physics

 

Quotes:

"At higher frequencies they [waves] behave much more like particles! It is quantum mechanics, discovered just after 1920, which explains this strange behavior."

"[T]he picture of space as a 3D space, and of time as a separate thing, was changed... into a curved space-time to represent gravitation."

"It is difficult, and takes a lot of imagination."

Questions:

What were the discoveries that led to the idea that waves behaved more like particles? Do particles behave like waves?

Why was "time" pulled into the idea of "space"?

 

 

 

Page 34 - The Uncertainty Principle

 

"The uncertainty of the momentum and the uncertainty of the position are complementary, and the product of the two is constant."

 

"Why are atoms so big?"

 

Questions:

What does the Uncertainty Principle mean?

 

How big IS a nucleus?

If the nucleus of an atom was 1 inch wide, the electrons would be at least 2 miles away...

Key terms:

momentum = the product of mass x velocity; you have more momentum if you have more mass, and if you move faster.

h/2p = the "reduced" Planck's constant, encountered throughout subatomic physics and quantum mechanics.

 

 

Page 35 - Quantum Doubt!

 

Quotes:

"[I]t is not possible to predict exactly what will happen in any circumstance."

 

"Nature, as we understand it today, behaves in such a way that it is fundamentally impossible to make a precise prediction of exactly what will happen in a given experiment."

"It is not necessary that science do that [return identical results]; it may be a fact of experience, but it is not necessary."

Questions:

If everything is uncertain, how can we know anything at all?

 

Why Isn't repeatability really necessary in science experiments for them to be considered valid?

Key terms:

Photon = a convenient way to picture light, as a "package" of energy of finite (and calculable) amount. Streams of photons can be thought of as waves, with equal success in macroscopic physics.

 

 

Page 36-37- Quantum Electrodynamics

 

"One of the consequences is that things which we used to consider as waves also behave like particles, and particles behave like waves; in fact everything behaves the same way.... So quantum mechanics unifies the idea of the field and its waves, and the particles, all into one."

 

"[Quantum Electrodynamics] is our greatest success so far in physics. In this one theory we have the basic rules for all ordinary phenomena except for gravitation and nuclear processes."

 

 

Questions:

Is this still true today? Is QED still the greatest success thus far in physics?

 

Key terms:

Positron = a positively charged particle with the same mass and properties of the electron (including spin and behavior). Effectively, "antimatter electronics"

 

 

 

 

Pages 38-39 - Nuclear Physics

Quotes:

"What are nuclei made of, and how are they held together?"

"So we are stuck with a theory, and we do not know whether it is right or wrong, but we don know that it is a little wrong, or at least incomplete." (Recall this is 1961)

 

 

Notes:

We know now that the complete theory, called the "Standard Model" includes all of the known particles and accounts for all of the nuclear behavior observed in experiments.

 

Key terms:

The Standard Model:

Particle Adventure

SLAC

 

Pages 40 -43- Particles

 

Quotes:

"Thus we are confronted with a large number of particles, which together seem to be the fundamental constituents of matter. Fortunately, these particles are not all different in their interactions with one another. In fact, there seem to be just four kinds of interactions between particles:

- the nuclear force (Strong)

- the electromagnetic force

- the beta-decay (neutron decay) interaction (Weak)

- gravity

"The photon is coupled to all charged particles... Gravity is coupled to all energy."

 

Questions:

 

What does "coupling" mean here?

What is the purpose of the charts and relationships that Feynman tries to build?

What similarities do you see between Feynman and Darwin?

 

 

Key terms:

MeV = Mega-electron Volt; a unit of energy, that, when used with Einstein's mass-energy equivalence E=mc^2 may also be thought of as mass.

 

Pages 44-45- Summary

 

Quotes:

"We do not know how the universe got started, and we have never made experiments which check our ideas of space and time accurately, below some tiny distance, so we only know that our ideas work above that distance."

"We seem gradually to be groping toward an understanding of the world of sub-atomic particles, but we really do not know how far we have yet to go in this task."

 

Questions:

Is the standard model right?

 

 

 

 

Check out Physics News from January, 2004

 

For more information on modern physics, check out Physics 2000


Last Modified - 3/13/06 - SH

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