Bits about “Science” and “Physics”

Ken Cheney




Probably the most important thing to take away from this course is some knowledge of what “science” is and what it is not.  The problem is that science is not a thing but a philosophy.

You may have heard of or been taught about “The Scientific Method” (hypothesis, prediction, experiment, failure, back to a new hypothesis; success changes hypothesis to law).  This “Method” is not exactly wrong but misses most of reality.

A Warning About Names:

“Hypothesis, theory, model, fact” How something is labeled probably reflects history more than anything concrete.  Don’t take these names or definitions of them seriously!

For example “Newton’s Laws” are wonderful but the “Theory of Relativity” gives better answers when the Laws and Theory differ enough to measure.

What scientists do everyday is to grapple with their problems any way they can with no respect for formal methods and, often at the best of times, only with a small nod to logical rigor.  This is no different from what any creative person does.

What seems to be the defining characteristic of science is what happens after the flash of inspiration.  An artist will stand back and look at her creation, a musician (aside from Mozart who evidently got it right the first time!) will play the new riff to see how it sounds, a lawyer will check the existing law, . . . 

What defines what a scientist does?  Read on for some hints.

Gleick about Feynman and how he DID science

In J Gleick, Genius: The Life and Science of Richard Feynman (New York, 1992).  described Feynman's approach to science:-

So many of his witnesses observed the utter freedom of his flights of thought, yet when Feynman talked about his own methods not freedom but constraint ... For Feynman the essence of scientific imagination was a powerful and almost painful rule. What scientists create must match reality. It must match what is already known. Scientific creativity, he said, is imagination in a straitjacket ... The rules of harmonic progression made for Mozart a cage as unyielding as the sonnet did for Shakespeare. As unyielding and as liberating - for later critics found the creator's genius in the counterpoint of structure and freedom, rigour and inventiveness.


Thoughts from Cheney

Here are some thoughts I had; this is from the introduction to a lab on Hook’s Law.  This “Law” states that the force it takes to deform an object is linear with the deformation.  Of course no one takes this “Law” to be absolutely true (things break if you pull too hard) but is a VERY useful approximation.


To prove a theorem in math is true is, in principle, quite possible even if it proves very difficult at times.

To prove that a theory in Physics is true is quite impossible. It is easy to prove a theory is false, just find one counter example. For example anyone can disprove the law of conservation of energy by finding a machine that puts out more work then it consumes.

If we can’t prove a theory what is the next best thing? Apparently the best we can do is to show that the theory has not been found wrong for a very wide variety of conditions. As more and more conditions are tested we feel more and more comfortable acting as if the theory was "true".

A practical engineer might feel that even if the theory eventually turns out to be false the chances of the exception turning up in any particular bridge or dam are very small.

Mathematicians of course aren’t granted this casual attitude.

Notice that anyone who thinks that they have proved a theory doesn’t understand the thoughts above. Anyone who claims to have proved a theory in Physics is either a fool or a liar, or perhaps, both.

In science you expect to make more and more precise checks of a theory but to never completely prove it.


To make the most convincing check of this theory (Hook’s Law) you should choose as wide as possible selection of objects. To remain within the limitations of the approximations the stresses applied must be small.


Feynman on what is not science

Mr. Feynman asked a similar question after teaching a semester of science in Brazil and realized that the students did not learn any real science, they just memorized facts to pass the test.  Therefore, when he was invited by the students to give a review of his experiences of teaching in Brazil, he asked if he could speak candidly, without any limits, and they agreed.

As the lecture hall was full, he started out by defining science as an understanding of the behavior of nature.   Then he asked, “What is a good reason for teaching science?, allowing of course, that no country can consider itself civilized unless…

Then he stated that, “The main purpose of my talk is to demonstrate to you that NO science is being taught in Brazil!”

He went on to point out that he was very excited upon arriving in Brazil, that he noticed so many young elementary school students were buying books on physics, as they do not teach physics to young children in the United States.  However, the reason he found that amazing was that you do not find many physicists in Brazil…and he was wondering…Why is that? So many kids are working so hard and nothing comes of it.

Then he held up the elementary physics textbook they were using.  “There are no experimental results mentioned anywhere in this book, except in one place where there is a ball, rolling down an inclined plane, in which it says how far the ball got after one second, two seconds, three seconds, and so on.  The numbers have ‘errors’ in them--- that is if you look at them, you think you’re looking at experimental results, because the numbers are a little above, or a little below, the theoretical values.  The book even talks about having to correct the experimental errors---very fine.  The trouble is, when you calculate the value of the acceleration constant from these values, you get the right answer.  But a ball rolling down an inclined plane, if it is actually done, has an inertia to get it to turn, and will if you do the experiment, produce five-sevenths of the right answer, because of the extra energy needed to go into the rotation of the ball.  Therefore, this single example of experimental ‘results’ is obtained from a fake experiment.  Nobody had rolled such a ball, or they would never have gotten those results.

“I have discovered something else,” he continued.  “By flipping the pages at random, and putting my finger in and reading the sentences on that page, I can show you what’s the matter---how it’s not science, but memorizing, in every circumstance.”

…another example…he stuck his finger in and began to read: “Triboluminescence.  Triboluminescence is the light emitted when crystals are crushed…” … ”and there, have you got science? NO! You have only told what a word means in terms of other words. You haven’t told anything about nature---what crystals produce light when you crush them, why they produce light.  Did you see any student go home and try it?  He can’t.

“But if, instead, you were to write, ‘When you take a lump of sugar and crush it with a pair of pliers in the dark, you can see a bluish flash.  Some other crystals do that too.  Nobody knows why.  The phenomenon is called “triboluminescence.”  Then someone will go home and try it.  Then there’s an experience of nature.”



Many different people use the term “science” in many different ways.  Since this is a Physics course I will define “science” as Physicists use it.  To distinguish this usage I will refer to it as SCIENCE.

SCIENCE evidently consists of the interaction of two things: OBSERVATIONS and a SCIENTIFIC THEORY.

The interaction is that OBSERVATIONS must be connected by Scientific Theories, and Scientific Theories must make predictions that can be (at least in principle) checked by OBSERVATIONS.  It is not considered SCIENCE until this interaction has been demonstrated.

Either OBSERVATIONS or A SCIENTIFIC THEORY alone, no matter how good, are not SCIENCE as done by a Physicist.

A SCIENTIFIC THEORY here does not mean a guess or two but an organized system of assumptions and the predictions that have been shown to follow from these assumptions. 

This is NOT the same meaning of theory as is used in everyday life or in mathematics.


Euclidian geometry was the first example of this.  Thirteen books followed from five axioms.

Newtonians Mechanics:  Everything from the fall of apples to the motion of galaxies followed from three laws of motion and one law of gravity.

 Relativity:  A revolution in our view of the world – time, space simultaneity, . . .- follow from two assumptions.

Darwin’s Evolution:  Perhaps the most important of all “Scientific Theories” follows from perhaps two observations.  Over a billion years of life make sense only when viewed through the lens of Darwin’s theory.

If a discipline has about as many assumptions as predictions it is not a Scientific Theory in this sense.


  When a science is being formed there will be efforts to check out guesses but to be taken seriously a science must have a few assumptions that lead to many predictions.

Many civilizations have had marvelous collections of observations that allowed them to construct things ranging for the pyramids to clipper ships.  But these observations were not connected by theories that would predict new observations; therefore they are not SCIENCE.

On the other hand some civilizations have developed wonderful theories concerning everything from perfect societies to triangles to God.  These theories typically have not been checked by OBSERVATIONS; therefore they are not SCIENCE.

Recall Churchill said, “Democracy is, of course, the worst possible form of government, except for those that have been tried.”  Actually a flavor of SCIENCE here!

Theorems about triangles can’t be proven by observations because we cannot make perfect observations.  We can make very good observations, but not perfect observations!

Perhaps I’d better not go into the problems involved in making observations about God!


You should appreciate that physicists come in two and a half flavors!

There are experimentalists who make OBSERVATIONS, theorists who make up theories predicting or explaining OBSERVATIONS, and (the half) computational physicists who write computer simulations of physics to find out what should result from theories that are impossible to check by math alone.


1.      Authority counts for nothing! “OBSERVATIONS Rule”!

“Nothing is so sad as a beautiful theory destroyed by an ugly fact!”

            Author unknown.

2.      OBSERVATIONS can be done by anyone “skilled in the art”.  Unlike sainthood, anyone who studies and practices enough can make the observations.

3.      OBSERVATIONS are not taken too seriously until they have been made by independent observers, preferably using different methods.

Notice that this makes fraud (lying about your observations) very unlikely to succeed since in the normal course of events other will try to replicate your results.

4.      Theories are not taken seriously until they succeed in predicting or explaining;

5.       Few assumptions, many predictions.

It is perhaps most convincing for a theory to predict (correctly) something previously unknown.

However it is also convincing if a THEORY can “explain” OBSERVATIONS that earlier theories could not explain.

Explain in this sense means that the observation is one that follows naturally from the theory.

Antimatter was predicted quite unexpectedly by Dirac’s theory of the electron.

On the other hand Bohr’s theory of the atom correctly “predicted” the previously known but otherwise inexplicable spectra of Hydrogen.  (Later it turned out there was a better way but Bohr blazed the trail to Quantum mechanics.)

6.      Theories can never be “proved”.  This follows from our necessarily imperfect observations.


7.      Theories can be disproved.  One observation contrary to the prediction of the theory is all that is needed to disprove the theory. 

Experimentalists continually look for ways to “disprove” the most popular theories.  As of 2006 experimentalists are very frustrated in that they have not found any chinks in the most popular theory of fundamental particles (after forty years of trying!).

The Pythagorean theorem would be disproved if we observed just one triangle where the square of the hypothesis differed from the sum of the squares of the other sides by more than the necessary errors in the measurements.  Actually I don’t think much time is devoted to trying to disprove this theorem.

8.      It is fair, in fact expected, for the theoretician to defend her theory as far as possible:  Criticize the observations, criticize the calculations comparing theory and experiment, criticize the statistics, show how a minor change in the theory can accommodate the new observations, . . .

9.      It is not expected that the theoretician will resort to violence or politics to defend her theory!


10.  It is expected that, if all else fails, the theoretician will admit that her theory is wrong.

Of course in fields where observation is difficult (e.g. Sociology, and education) theories may only die when their inventor dies

11.  It is expected in a similar fashion that an experimentalist will (after exhaustive checks) defend her observations against charges that the observations don’t match theory or other observations.

An extreme, successful, example of this defense was Davis’s experiment searching for solar neutrinos.  For about forty years his results seemed impossible.  Eventually, better theories and other observations showed that Davis’s results were correct.

Sound innocent don’t they!  But, arguably, these may be human’s greatest invention.



At first glance you would say that Physics is the science that treats mechanics, heat, waves, electricity, …, atoms, nuclei, and fundamental particles.

This is true, but is not the whole story (after all chemists deal with atoms, civil engineers deal with mechanics, electrical engineers deal with electricity, etc.), but in any case this is not how a physicist views physics.  A Physicist would probably tell you that she might study almost anything from the stock market to the creation of the universe.  What makes her a physicist is not the subject but the method and attitude.

Consider first some other disciplines.

Engineers in the end build things, preferably economically in time, money, and material.  But most important, things that work!  Engineers must do this in the face of many uncertainties (weather, construction flaws, stray airplanes, . . .) and overwhelming complexity.

Chemists “build” atoms, again preferably economically and in an ecologically sound fashion.  The theory of how atoms combine into molecules has been known since the mid nineteen twenties.  However the equations are too complicated to solve!  So, like engineers, chemists must succeed without a detailed theory.

What a physicist is trained to do when they are presented with a problem is to determine the fundamental principles that apply to this particular problem and to deduce what can happen by starting from those principles and calculating what results are implied by those principles.

Since this complete analysis is usually impossible what does a physicist do? 

The physicist plan of attack is to simplify the problem until it can be solved.  Then, if possible, complications are added and solved one at a time.

This plan leads to jokes about finding solutions for spherical chickens in a vacuum!

What are the good and bad features of the physicist’s plan of attack?


The most important feature is the attitude that problems must be solved completely, half-baked solutions WILL NOT DO!  So problems that can be solved get solved.  Happily this has included lots of problems:  Atoms, simple molecules, mechanics (from molecules to galaxies), heat, electricity, . . ..

Even more!  If a device can be shown to fail even under ideal conditions then there is no point in building it to fail under real world conditions.  So physicists are very useful in sorting out devices that might work from devices that can’t work!  Since almost all conceivable devices can’t work this ability to select saves amazing amounts of time and money.

Right out of school (26 years old) I was hired by an aerospace company well staffed by bright aeronautical and rocket engineers.  I didn’t know much about anything but was about the only physicist around.  So, when anyone had a wild idea I was the one who got to play with it to see if it could possibly work, or at least if it was clearly impossible.  This was not what I was hired for but it certainly was fun to do along with my “real” job.

Since physicists aren’t burdened with all the detailed knowledge necessary for engineers, chemists, and biologists they tend to be generalists with the background to learn almost anything (if properly motivated: usually by curiosity but if necessary by money).  Being generalists physicists are often able to come up with novel solutions to problems in many fields (some of these solutions might even work).


The downside of a physicists training and attitude is that they don’t know much about any particular subject (except perhaps too much about the subject of their thesis).  If you hire a civil engineer you expect the engineer will know about current practices, building codes, and all sorts of useful things.  If you hire a physicist for the same job the physicist will have a lot of studying to do to get up to speed!

Another problem is that many problems really are complicated (the opposite sex for example) and don’t lend themselves to simplified solutions (or perhaps any solutions?).  In this case you really need someone with lots of practical experience!

Possibly your physicist will simply not be interested in a problem that depends on lots of arbitrary details and is too messy to yield to an elegant attack.

Practically, if you are a physicist, people who work in the personal departments of prospective employers haven’t a clue about what you can do.  Since they don’t know what a physicist does these personal people are pretty hopeless about putting you in contact with the people in the company who need your help!