Teaching physics is a triple challenge. Students and pupils are a
challenge; being a teacher is a challenge; and physics is a challenge as
well. Part of the challenge is mentioned on the
page on physics teaching. What follows is a collection on personal
musings on the matter. To download the free physics text, click here.
See my other blog page
Teaching about fundamental physics has evolved to doing research.
See my other blog.
On physics in 9 lines
Physics is a fascinating adventure. Numerous physicists finish
university without knowing that physics can be summarized in 9 lines. The 9 lines are found here. They agree with all
experiments. The 9 lines also imply all known equations of motion: those
of general relativity and those of the standard model of elementary
particle physics.
The 9 lines show that the knowledge about nature is finite.
Also, they are very different from each other. Thus they show that physics
still lacks unity.
On "why" questions, again
The question "Why?" can ask either for a cause or for an aim. In the
sciences, we like to search for causes. We do not search for aims.
Searching for aims is something that every person has to do inside himself
or herself.
Searching for causes is fascinating. We are all curious. We are made
this way. Understanding causes helps us understanding the world.
Understanding causes helps us improving the world. That is why we teach.
On lies and physics
Educators have to strengthen pupils. In contrast, lies are
uttered by weak people to weaken others. Lies do a lot of harm. Some lies
kill. Some lies about illnesses have killed hundred of thousands of
people. An important aim of an educator is to teach his pupils to
distinguish lies from truths. Physics is perfect for this.
On "why" questions
One regularly hears that "why" questions are not answered in physics or
even in science. This is wrong. People who tell you this have an
agenda (usually to keep you stupid, or to prevent you to ask further, or
to discourage you in general) that is opposite to that of a teacher.
Above all, these people are lying.
Physics, the science of motion, of course answers "why" questions about
motion in nature. More precisely, physics answers with explanations. An
explanation is an argument showing that a particular observation is
a special case of a general property of nature. It might well be that the
answer leads to more "why" questions. But physics is fascinating precisely
because it does answer "why" questions. In the third millennium, we are
especially lucky: fundamental physics answers all "why" questions
except for a few dozen; applied physics has many more open "why"
questions. And all these open questions are fascinating.
On the quantum of action
Numerous physicists finish university without knowing that
action is quantized. And without knowing that there is a smallest action
value in nature, the elementary quantum of action. References are found here.
There is a historical reason. When everbody was convinced that Planck's
quantum of action h was the minimal action, spin 1/2 was discovered (more
precisely, spin h/2). This led people to stop telling that h is the
smallest action. But despite spin 1/2, the value h remains the smallest
action that is transferred, observed or measured.
On teaching quantum physics
Quantum physics is the exploration of
ℏ, the quantum of action.
Unfortunately, in the 21st century, many teachers have forgotten this.
Some scholars state that the essence of quantum theory is
non-commutativity. Some scholars state that the essence of quantum
theory is a Hilbert space. Some scholars state that the essence of
quantum theory is quantization. This is all misleading or wrong.
Some scholars state that the essence of quantum theory is the
indeterminacy relation. That is better, because this relation is
indeed due to ℏ.
The essence of quantum theory is and remains the non-vanishing value of
ℏ. Even the new SI system
underlines this.
On teaching physics and motion
A wonderful physics teacher, Friedrich Herrmann, wrote
wonderful books. His teaching method is exceptionally clear and his
comprehension of motion is outstanding. Nevertheless, he was abused by
many professional physicists and by the German Physical Society, in the
21st century. Not all professionals are always right. How did the master
react? He continued on the right way. His texts remain free for download.
Links are provided on this site.
On teaching physics and motion - 2
Physics is not easy even for teachers. My physics teacher friend Mark
was criticized, in 2019, because he tried to (correctly) add, on the German
Wikipedia, that light moves. He was told that this was wrong by
all Wikipedia physics editors. The explained to him that they were
physics teachers and that light does not move; so they took Mark's
statement out of the text again. Not all teachers are always right.
Lying or relying?
Physics is the science of motion. Science is just another word for
knowledge. Knowledge is a collection of facts. Facts are observations,
including measurements. In short: physics is observing everything about
motion.
For some people, it is necessary to stress that facts are the opposite of
lies, and that truth is agreement with observations or measurements. There is
no room for lies in knowledge, in physics or in any other science.
On facts and knowledge you can rely. On lies you cannot.
Be curious
In this world full of wonders, ask questions. Frequently. Enjoy searching for
answers. Search, search and search again. Understand. Enjoy the
understanding. This is what teachers did and do, and what they tell their
pupils to do.
A problem with physics
Around 2010, a German university changed the name of a degree course from
"physical technology" to "technology management". The number of student
applications
doubled. Before the name change, an investigation had
shown that the term "physical" in the name of the course turned many students
away.
On physics, wikipedia and books
Unfortunately, in 2016 - and still in 2019 - the physics articles in
wikipedia are still of insufficient quality. The concepts are badly explained,
the examples are not complete, the introductions lack clarity,
the structure is confusing, the figures are poor, and
contributor fights abound. Given that wikipedia is not improving much
any more, there is little hope that this will change
in the future. In physics, there is a need for good books! Consider
writing one, or consider helping in other ways.
On being a honest teacher
Be a guide to your students. Give them clear and truthful advice. Do not
lie. Never tell your students not to read books. Every given reason is a
lie. Never tell your students to read only your own books (or papers).
Never tell your students that lectures are better for learning than reading
books. It is a lie. Never tell your students that computer programs or
videos are better for learning than reading books or lectures. It is a
lie. Do not prefer adulation by your students over telling them the truth.
With every advice you give your students, ask yourself: does it give them
strength or does it take away strength from them?
What teachers can learn from business leaders
A successful business leader summed up his approach in the following way:
"Simplify, execute, grow." A famous teacher summed up his aim thus: "To
fortify people, to clarify things." Business leaders ensure that ideas and
decisions are clear and that people have a future. So do teachers. Below are
a few examples on what this means for the teaching of physics.
On infinite quantities
Numerous physicists finish their university studies without knowing that
whenever a reasoning or a calculation yields a result of infinite size,
then the reasoning and calculation is wrong. There are no exceptions.
Nothing is ever infinite in nature. How could it be? The statement that
something can be infinite cannot be verified; and it always easily
falsified. Every single experiment falsifies it. In other words,
'infinite' is a false belief, an ideology, and never a fact. Some are so
stubborn that the point is best made like this: 'infinity' is always a
lie. If you falsely believe that infinity exists in nature, find the error
in your assumptions - especially if you give lectures.
On force
Numerous physicists finish their university studies with a bizarre concept
of force. In physics, force is the change of momentum with time, and
momentum is a conserved quantity. Conservation means that a change in a
volume of space can only happen through flow out of that volume. In other
words, physics students need to learn that any force is due to the flow of
momentum out of a closed surface. Momentum is like electric charge: it is
a quantity that is conserved, can accumulate, and can be exchanged. The
change of electric charge is called current; the change of momentum is
called force. The difference between charge and momentum is that charge is
a scalar, and momentum a vector. But both current and force always imply a
surface through which they are flowing. By far the clearest explanation of
this point is the secondary school physics course by Friedrich Herrmann,
found at
http://www.physikdidaktik.uni-karlsruhe.de/ where it can be
downloaded for free in several languages. To make this point especially
clear, Herrmann introduces the unit "1 huygens=1 kg m/s" for momentum, and
defines 1 newton as 1 huygens/second. If you do not believe that force
implies a flow through a surface, look at the equation for continuity in
its integral form. The percentage of physicists who get this wrong is
surprisingly large. Check yourself - especially if you work on general
relativity and falsely believe that force does not exist as a concept.
On the wave function
Numerous physicists finish their university studies with a bizarre concept
of wave function. In physics, the wave function describes the state of a
quantum particle. In non-relativistic quantum mechanics, a wave function
is, as Feynman explains, a little arrow at each point in space.
Equivalently, the wave function is a cloud of rotating arrows. Students
need to learn this. If you do not have a intuition for non-relativistic
wave functions, take some time to explore the website by Bernd Thaller, on
visual quantum mechanics, at http://vqm.uni-graz.at/ and read his two books
on the topic. And read Feynman's book "QED - the strange theory of light
and matter". Check yourself - especially if you falsely believe in "many
worlds" and similar nonsense.
On Feynman and simplification
Numerous physicists finish their university studies without learning
anything from the career of Richard Feynman. When he was young, he was a
calculator, i.e., a physicist who believed that calculation was the essence
of physics. With age, he changed completely, and stressed clear concepts
and foundations over detailed calculations. Only then did he became the
famous teacher and popularizer of physics that he is remembered for. The
older Feynman, like Einstein, had as motto: "simplify, simplify - without
sacrificing truth". The same motto is helpful in all other sciences, in
business, and in life in general. Students need to learn this. If you do
not believe the importance of simplification, read Feynman's book "QED -
the strange theory of light and matter". The number of established
physicists who follow the opposite path - obfuscation by calculation - is
large. Check yourself - especially if you spent some time on string theory
and falsely believed that you could advance the topic without anybody ever
clarifying its basic foundations.
On action as measure of change
Numerous physicists finish their university studies without a clear idea
what action measures. Action measures the amount of
change
occurring in a system. The more changes, the larger the action. In fact,
action should be renamed change. If you have no intuitive idea for the
concept of action, explore the issue and convince yourself - especially if
you give lectures.
On action as an observable
Numerous physicists finish their university studies without knowing that
action is a physical observable. Students need to learn this. Action is
the integral of the Lagrangian over time. It is a physical observable:
action measures how much is happening in a system over a lapse of time. If
you falsely believe that action is not an observable, explore the issue and
convince yourself - especially if you give lectures. (For literature on the
topic,
see this page.)
On relativistic invariants
Numerous physicists finish their university studies without knowing that
the Planck constant h, the Boltzmann constant k, and the gravitational
constant G are - like the speed of light c - observer invariant. Students
need to learn this. If you falsely believe that these constants are not
relativistic invariants, explore the issue and convince yourself -
especially if you give lectures.
On maximum force and the difference between fact and belief
Numerous physicists finish their university studies without knowing that
there is a maximum force c^4/4G and a maximum power c^5/4G in nature.
Students need to learn this. First of all, students need to know what a
force is; this issue is treated above. The maximum values are only
realized with help of horizons. In simple words, horizons appear when mass
is compressed to its Schwarzschild radius. Observing or realizing higher
force or power values would imply reaching beyond a horizon. These maximum
values, discovered independently by various people over the years, provide
a test of logical reasoning for every physicist. Some people do not
believe in such a maximum value, but fail or even refuse to present a way
to exceed it. They exchanged reality for a dream world. Another class of
people claim to have found a way to produce or measure a force value larger
than c^4/4G without creating a horizon. Just check. They either
overlooked a horizon or they do not reach the maximum value. For example,
some people claim to be able to exceed the force limit c^4/4G with the help
of boosts; well, in relativity, no boost can increase a force value to more
than the force value seen by a comoving observer. Just check any book on
special relativity. Another example are people who think that forces
simply add up. Well, this is true, as long as all forces start at the same
point. Nothing prevents adding up forces from many systems so as to exceed
the force limit. But at one point, c^4/4G is the upper limit. At that
value, a horizon appears. Test it by yourself. In summary, if you falsely
believe that maximum force and power do not exist, explore the issue and
convince yourself - especially if you give lectures.
On Planck's natural units - 1: the foundations of physics
Numerous physicists finish their university studies without knowing that
all observables are based on Planck's natural units. Students need to
learn this. Planck discovered in 1899 that all results of measurements -
all units, all numbers, all quantities - can be constructed from the
invariants c, G and hbar. This is the essence of our observation of
nature. The business of modern physics is to find out where these
multiples come from - and not much more! Concretely, modern physics has to
find out where the coupling constants, the masses of elementary particles
and their mixing angles come from. They are all multiples of Planck's
natural units. (Note: these are the only multiples that are not understood
so far; all others, and thus all other measurements, are understood.) If
you falsely believe that Planck units are unimportant, explore the issue
and convince yourself - especially if you give lectures.
On Planck's natural units - 2: the impossibility to vary them
Numerous physicists finish their university studies without knowing that
all observables are based on Planck's natural units. Students need to
learn this. All standards of measurement and all results of measurements
are constructed from the invariants c, G and hbar. "Changing" the value of
one of these quantities, has
no effect on our description of nature,
because it also changes the measurement standards. There is no way to
detect variations in G, hbar or c - neither variations over time nor
dependences on location - because these changes would be compensated by the
changes of the relevant measurement units and standards. If you falsely
believe that variations of c, G or hbar can be measured, explore the issue
and convince yourself - especially if you give theory lectures.
On Planck's natural units - 3: the impossibility to exceed them
Numerous physicists finish their university studies without knowing that
Planck's natural units are limits. Students need to learn this. No single
experiment yields local energy speeds larger than c, action values smaller
than hbar, or forces larger than c^4/G; the same is valid for other
combinations of them. This is the most hidden aspect of 20th century
physics. For example, elementary particles cannot have energies larger
than the Planck energy. If you falsely believe that c, G, hbar or their
combinations can be exceeded, explore the issue and convince yourself -
especially if you give lectures.
On pupils
A teacher should like his pupils. Pupils that are difficult are pupils
that suffered a lot. If you have trouble with your pupils, recall their
suffering; then imagine them when they will be 50 years old. After that,
do what is the most appropriate for them.
