Things to consider before you rewrite classical physics.
Every so often I get email from people who are convinced they can improve physics all by themselves, by armchair theorizing. They propose "new physics", often trying to rework physics from the ground up. They usually don't want advice, but confirmation.
Now I readily admit that physics evolves, and our understanding of it today may be modified in the future. The history of the subject gives many examples of this. That fact gives encouragement to those who think "If I just modify this equation, throw out some laws I don't like, or postulate some new principles, I might reach conclusions that will earn me a Nobel prize (or solve our energy crisis, etc. etc.)"
But the folks who write to me are unlikely to gain fame and recognition for their work. It's instructive to examine why.
They are usually talking about the classical physics of macroscopic phenomena, a subject that has been so thoroughly studied and applied successfully to real-world devices and processes that it's almost certainly not wrong in any measurable way. (And if something is not measurable, how can we confirm it by experiment?) And even if our instruments improve so we can measure well enough to require modification of a basic physics law, it will be a mighty small modification.
The folks who propose changing physics sometimes engage in hand-waving about relativity or quantum mechanics, hoping to lend support to their ideas, but this connection is irrelevant at best when their purpose is to justify, say, a perpetual motion machine idea that could be built in macroscopic dimensions to produce useful work (another macroscopic concept).
The laws, principles and equations found in elementary textbooks summarize classical physics very well. Could some of them be wrong? Even wrong by just a little bit? That's very unlikely, or we would have noticed by now. After all, these laws are used every day around the world in physics and engineering applications to industry. Even worse, if one of the basic laws actually were wrong, many others would be also, for they are all interconnected by tight mathematical logic. Surely flaws of this kind would have been noticed. Classical physics is used every day by physicists and engineers in laboratories and factories around the world, and, surprise, it works! 
So when someone tells me that they think that F = ma should really be F = ma + ε where ε is a very small correction term, some skeptical questions should be asked.
Occasionally someone proposes an experiment that he feels would show that conventional textbook physics is wrong. In all cases I've examined, this fails for one or both of the following reasons: (1) The experiment hasn't been done, and all indications are that it wouldn't behave as he expects anyway. (2) He's analyzed the situation incorrectly, applying the physics incorrectly.
On rare occasions the person actually does do an experiment, sometimes with cleverly designed apparatus, then applies shoddy experimental analysis, biased to reach the conclusion desired. This is a form of expectation bias.
Examples.Examples may be found on the internet.
Terrence Witt is a retired businessman who published in 1997 a large book titled Our Undiscovered Universe: Introducing Null Physics, the Science of Uniform and Unconditional Reality. He purchased space for full page ads in magazines like Smithsonian, Scientific American, Discover, and Popular Science. The word "reality" in the title gives away his misguided purpose. Witt criticizes science for ignoring "Why?" questions , then proposes his own answers to them. This is a red flag, for real scientists know that we have no way to answer "Why?" questions, and any such "answers" are no more than unconfirmable speculation. (Science deals only
The true value of this book is indicated by the fact that it can now be bought online for one cent plus $3.99 shipping . It originally sold for $60. An anonymous poster on a web forum claimed to have been Witt's professor in a university physics course, and would have flunked Witt, but he was only allowed to give him a grade no lower than "C". On the evidence of this book, that's believable.
Gary Novak has a degree in biology and claims to be expert in mushroom culture. This apparently qualifies him to criticize established physics. He asserts that energy is misdefined in physics, and should be mv instead of mv2/2 (mv is momentum in standard physics). Gary thinks that a "squared velocity is absurd". I asked him once whether the well-verified equation for a free-falling body, d = gt2/2 is equally absurd, because it has "squared seconds" in it. He didn't answer. Gary also has no grasp of the difference between scalars and vectors. A sample of his eccentric physics should be enough. See Energy Misdefined in Physics.
Here's a sample of Gary's physics.
Kinetic energy is being defined as mass times velocity squared. But in fact, it is mass times velocity nonsquared, which is called momentum. Momentum is kinetic energy. Velocity squared does not represent nature, because nothing moves at velocity squared.Gary now has on his web page this revealing assertion "...energy must be absolute value rather than negative for one direction. Subtracting power for rocket exhaust is absurd. Since every force must have an opposite force, there would be no power or energy to an explosion, if one direction had a negative value." Here Gary is making the freshman-level blunder we in the physics ed-biz often call the horse-cart problem. Gary's web pages are excellent demonstrations of how a few simple misconceptions at the freshman level can escalate to a full-blown conviction that all of physics is wrong. And once this conviction takes root, it cannot be shaken by pointing to the source of the error and explaining how to do it correctly.
Alex Belov is a newcomer contributor to the eccentric physics gallery. He's convinced that he's found a flaw in the way combined rotational and translational motion is treated in textbooks, and has devised several over-complicated and difficult-to-analyze experiments to "prove" it. Others have pointed out his errors in applying physics, and his careless experimental methods, but he doesn't correct his errors. Belov claims a master's degree in electrical engineering, but refuses to name the school, so his credentials might be checked. (On another web forum in 2011 he claims to have a "masters and almost a Ph.D. (a few months left) in applied mathematics and theoretical physics." Alex seems to have a problem finding a web home for his revolutionary ideas. At present [August 2012] his paper Rotational and Translational Motion as a Standalone Natural Phenomenon is still available, but the all-important pictures seem to have been lost.
These folks have websites and have contributed to web forums and discussion groups, so I am free to give their names. One reader said I should not provide these folks more publicity by giving links their web pages. Any knowledgeable person reading these links should immediately recognize they are the work of cranks. I have long maintained that one important part of understanding what science is and what it isn't is to look at the writings of those who misunderstand, misrepresent and abuse science.
These three examples (of many one could cite) illustrate that such "independent thinkers" usually work alone, and do not benefit from interaction with knowledgeable persons in the field, even when they promote and defend their ideas in public forums. They generally do have a small band of "fans" who barely understand the subject at hand, but think the idea "sounds good" and who are happy to see anyone bashing "establishment science".
Often the people who concoct this stuff have had some physics courses, high school or college, but didn't do very well in them. Yet they have unlimited confidence in their own interpretation of physics while continually displaying evidence of their own ignorance of it. So confident are they in their own personal world view that they assume that their own inability to understand conventional physics is sufficient proof that standard physics must be wrong. 
Typical mistakes.A common error one sees in crackpot theories is equation cherry-picking. Physics is more than mere equations to be memorized. Each equation represents a process or situation in nature that must be carefully defined. Many equations in physics have certain conditions or limitations that must be met in order to be correctly applied. These conditions are generally spelled out in textbooks in the text accompanying the equation. Cranks tend to ignore that, applying equations indiscriminately and blindly.
Every symbol in an equation represents a physical quantity, a quantity that must be precisely defined. Some of these are named with words drawn from colloquial language, but are used in science with very different meaning. Words such as force, work, momentum, energy, power, all have meanings that are too easily confused (by novices) with their colloquial usages. Someone once tried to tell me that torque and work were synonyms because they both are the product of force and distance!
Some technical terms describe things we can sense, such as mass, color, temperature, though in all cases our unaided senses are crude approximations to what we can measure with dedicated instruments. Some technical terms represent useful concepts that help us think and talk about physical processes, but are not things we can sense, nor even measure directly. Examples include gravitational, electric and magnetic fields. We measure these only indirectly, by measuring something closely related to them. For example, force isn't measured directly. We measure the effect of a force on a mass, inferring the size and direction of the force from the acceleration it gives to a mass. Even so "fundamental" a concept as energy is not a thing or "stuff" but a handy "bookkeeping" concept for describing how material bodies interact. One may even legitimately raise the philosophical question of whether distance and time are as real as mass, or just a convenient way to describe where and when things with mass are located relative to one another and how they move. Failure to realize these subtle distinctions can lead to errors in thinking about physics, even to absurd conclusions.
But these facts about physics only fuel the independent thinkers, who cannot grasp that "reality" is an elusive philosophical concept. But physicists are not troubled about questioning whether such concepts as force are real, so long as they are precisely defined, measurable and demonstrably useful concepts.
The dimensions of the problem.Physical concepts and quantities are represented mathematically, but they are not merely numbers. Most have dimensions that serve to distinguish types of quantities and to ensure consistency in equations. This term is not to be confused with the colloquial use of the word 'dimension' to indicate a measurement of size. Physical dimensions are indicators of the physical constraints of physical quantities, constraints on how they can relate to one another.
For example, the dimension of length is designated [L] and the dimension of time is designated [T]. Velocity then has the dimensions of length/time, or [LT-1]. But acceleration has dimensions of length/time2 designated [LT-2]. If someone writes an equation for acceleration as a = d/t3 (where d is distance and t is time) we know that this cannot be a correct physical equation. Likewise if someone, for a joke, writes E = mc3 we physicists immediately laugh at such foolishness. But there are some cranks, innocent of any real physics understanding, who might consider it a hypothesis worthy of consideration.
The subject of units and dimensions is often inadequately treated in textbooks. For more about this see Unit Systems, particularly parts III and X. Many students come away with the idea that units and dimensions are synonyms, because they both follow rules of algebra. They might even be surprised to be reminded that some quantities have units but no dimensions (angle), while some different quantities have the same dimensions but different units (work and torque).
Speaking hypothetically.The word "hypothesis" in science means "a guess" or conjecture. It is usually a motivated or "educated" guess based on experimental evidence, or some theoretical difficulty. "Wild" guesses aren't given much weight in science. Hypotheses may be a basis for brainstorming a problem, but aren't taken seriously as science until they (or their consequences) are confirmed by experiment, and it is shown that they are not contradictory to other established science. Even when an experiment seems to confirm a hypothesis, we usually require that other scientists repeat (replicate) the experiment with the same results.
Hypotheses are generally motivated by a new piece of evidence that doesn't seem to fit existing understanding. Sometimes hypotheses are motivated by dissatisfaction with a theory or law that is difficult to apply, or is somehow unsatisfying to deal with conceptually.
Pseudoscientists often take a different approach. They make a guess (hypothesis) in order to use it to derive a very particular desired result. The desired result precedes the hypothesis, and the hypothesis has no other foundation or rationale than a desire to achieve that result. The difference between this and standard scientific practice may seem subtle. Much of the difference lies in motivation. The scientist is motivated by a desire to find out how nature works. The pseudoscientist is motivated by an unfounded conviction about how he wants some aspect of nature to work, and is willing to sacrifice any other part of established science to make that happen.
Often non-scientists imagine that scientists just sit around idly brainstorming and making up hypotheses. Hypotheses are "dime-a-dozen" and of little value until tested and confirmed in the real world of the laboratory. Assertions about science aren't true because just because we want them to be true. Hypotheses don't arise by reading Tarot cards or throwing dice. They are motivated by what one already knows about science, and by the nature of the problem at hand. Scientists also usually have a good intuitive idea of the consequences of any hypothesis they make, but intuition still must be rigorously tested by logic, mathematics and experiment.
In unity is strength.Established science is a structure of statements about nature, expressed usually in mathematical form (with explanatory discussion) and held together by the cement of mathematical logic. So interconnected is this structure of laws, theories and mathematics that Richard Feynman once said that if, through selective amnesia, he forgot half of what he knew about physics, he could reconstruct it from the other half. Pseudoscientists do not realize that if they tinker with this structure of physics, they can't get by with changing an equation or two, for every change affects nearly everything else. So they must have a good understanding of the whole structure of science. If they display ignorance of the wider consequences of their ideas, their ideas will likely be summarily dismissed.
Typically, perpetual motion machine inventors reject the law of conservation of energy, yet insist that their idea violates no other laws of physics. That, of course, is impossible. For if energy conservation is invalid, then so is momentum conservation, Newton's laws, and the laws that describe how forces combine. I think this failure to understand how all these laws are rigourous linked is the fault of physics education at the lower levels (introductory courses). Too often these courses never require students to do mathematical derivations that show how fundamental laws are linked. There are courses at this level in which students never have to construct a mathematical derivation of anything beyond simple substitution algebra.
The person who hopes to create new physics has a tough road to travel. To be taken seriously he must show why his proposed change is necessary. (Where's the problem?) He must show how it affects everything else in physics, and those changes must agree with experimental evidence from all the diverse fields of physics. (What are the consequences?)
Maybe the key lies in things we can't see.We hear a lot about dark matter, dark energy, parallel universes, space wormholes, and other exotic ideas in the popular media. Casual readers may think such things are confirmed and are part of established science. Far from it. One can only call them unconfirmed hypotheses at this point.
No one has extracted and bottled any dark matter or dark energy. Nor is anyone trying to do so, for these concepts are part of a mathematical structure that attempts to describe certain things we observe happening, mostly things happening in the universe at vast distances from us. It appears that dark matter and dark energy are not something we may ever directly observe, not even something we could use in earthly machinery. They are "virtual" concepts useful for describing things happening very far away, or things going on in the realm of very high energy subatomic phenomena.
There are competing cosmological models that do not require hypothetical entities like dark matter and energy. Only time (and experiment) will determine which model will prevail and become accepted science.
But there are pseudoscientists who are eager to latch onto any concept that might serve to support their personal fantasies about nature. They are especially attracted to concepts they don't understand. Some imagine they could make a machine that would be fueled by dark matter or energy, and solve our energy supply problems. But theirs is a house of cards built upon sand, an elaborate idea leading to wonderful conclusions, but built upon shaky hypotheses.
A historical example of this sort of error is the "luminiferous aether" of the late 19th century. It was a hypothetical substance that filled all of space and provided a medium for light and electromagnetic waves. The idea was abandoned for two major reasons. (1) No experiment, even cleverly devised ones, could produce direct evidence of its existence. (2) It was supported only by analogy to other wave phenomena, like sound and water waves, which do require a material medium. Reliance on analogies may be sometimes suggestive, but never conclusive, and can lead to error in science. This particular error lasted some 30 years. Some physicists worry that currently fashionable concepts of dark energy, dark matter and string theory may be the same sort of error. But pseudoscientists still try to use these concepts to support their hope of inventing machines run on "free energy". One book even admits that the aether theory was found to be inadequate, but a new theory with two intermingling aethers can be made to work!
Hard science and soft science.Some who propose "alternative science" theories place their hope in the acknowledged fact that science is never complete or perfect. There is much we have to learn, and some of what we accept as established science may be modified in the future. Therefore, says the hopeful "independent thinker", maybe science is wrong in just the way required for my pet theory to be true. That hope is misplaced, and represents a failure to distinguish the various kinds of "established science".
The sort of physics that evolves frequently and continually is that which describes complex processes, but not the fundamental, basic, established laws of physics. For example, we continue to improve our understanding of weather, climate, our solar system, disease, genetics, the mind, etc. But none of this even touches the validity of Newton's laws of motion, which remain as true as ever. Even the physics revolutions of relativity and quantum mechanics have not affected the truth of classical mechanics laws. They are solidly established, you might say they make up "hard science". Yet it is these fundamental laws that pseudoscientists challenge, the laws and theories that are least likely to have any fault, while they largely ignore those parts of physics where changes are more likely ("softer science").
The spectrum of what we call "accepted physics" covers a wide range of "certainty" from "rock solid" to "very highly reliable". It used to be said that in physics, "If you must use statistics to justify a conclusion, then you should devise a better experiment." There's a strong suspicion of results that are only statistical. Results are suspect if there's no clear mechanism or process to justify them. This caution ensures that results are not isolated from other physics laws and principles. It is still true that the statistical threshold of acceptance in physics is much higher than in other sciences, such as medicine and psychology.
Know the territory before embarking on uncharted paths.
Those who try to reinvent physics are usually ignored because they exhibit serious misunderstandings of conventional physics. If one proposes something that would replace or modify all of standard physics, one had better first know all of standard physics. One person working alone is unlikely to have that breadth and depth of understanding. Some naively believe the romanticized stories of a great idea being hatched by a dream, a vision, or by being hit on the head by an apple. It doesn't work that way, except in fictionalized biographies. There are very few cases of outsiders, without formal education, contributing to science in a notable way. Michael Faraday (1791-1867) is often held up as an example. Another is the Scottish instrument-maker and astronomer James Ferguson (1710-1776) who learned by self-study and personal experimentation, and became a member of the Royal Society. It would be hard to list any others you may have heard of. And I can't think of any who made the kind of major advances that changed physics so greatly that their work could be classed as scientific breakthroughs.
Innovators should examine their motives.It is not merely one's "amateur" status that is the reason some aspriring revolutionaries are dismissed. Usually independent armchair theorizers are up against several barriers.
Rationalizations.Every eccentric scientific theory attracts a small, but vocal, fan base. I hear from those folks, too. They may say, "I know this idea is riddled with mathematical blunders and questionable physical arguments, and is unsupported by experiment, but some of the ideas seem to be right, and therefore the whole theory might be true." Indeed, in any elaborate and novel rewriting of physics one can pick out some details that are correct in a general or superficial sort of way, or at least might be somewhat defensible. It's difficult for anyone to be wrong on all counts. But that fact in no way lends support to the whole theory.
The Greek philosopher Democritus (c. 460 – c. 370 BC) is said to have proposed an atomic theory of matter. Was it a scientific theory of any importance? No. It was purely speculative, not based on solid experimental evidence, and it didn't lead to any useful experimentation or confirmation. It was a philosophical conjecture only. and it has no connection to our modern atomic theory.
There's a special class of "alternative science" that I haven't a good name for. These are "theories of everything" that drastically revise the language and content of physics, but produce no new results, and no modification to known experimental results. Why would anyone undertake such a monumental task? Often it's because they "don't like" the language and concepts of standard physics and want something that fits their intuitive sense of "rightness". They may even hope that a new conceptual language may pave the way for future advances. We know from past history of physics that such alternative conceptual approaches can indeed work at least in a limited subset of physics. Newtonian classical mechanics can be replaced with Lagrangian mechanics. Schroedinger's operator formulation of quantum mechanics can be replaced with Heisenberg's matrix mechanics (and vice versa). It has been rigorously established that the two are mathematically identical and yield the same results, though they "look" dramatically different in execution. In fact, advanced physics students learn both, and freely mix them, using whatever is easier for particular problems.
But most of the independent thinkers who propose alternatives are ignored, and the reason is usually that they haven't succeeded completely. Their reformulation is incomplete or incorrect in serious ways.
The loneliness of the unheralded genius.One feature stands out in the "work" of the lone wannabe genius. It is unfinished. At its heart is an unfounded and unconfirmed hypothesis about nature, perhaps with a few suggestions about how this idea (if it were true) would revolutionize science. But the dirty work of testing that hypothesis and working out the messy details of the math is left to others. These people seem to think that it is enough to have an idea, for which they should receive worldwide acclaim. They think that other scientists should drop whatever they are doing and jump on the bandwagon to do whatever is necessary to realize the wonderful consequences of this idea.
It is said that in science new ideas must justify themselves. Skepticism is the backbone of science, that is, every new idea is treated with caution until it has been thoroughly and successfully tested, and found consistent with the rest of established science. Those who propose new ideas should not expect others to do all this work.
Endnotes. I have long been a critic of textbooks, and have documented errors found in physics textbooks. See Didaktikogenic Physics Misconceptions. These deficiencies of textbooks do get in the way of student understanding, but usually do not affect the underlying core physics. If the textbook errors were corrected or purged completely, this would in no way affect the physics as physicists understand it. So when I speak of "textbook physics" I mean that basic, fundamental physics that textbooks, in their imperfect way, try to get across. Presenting physics at the freshman level is a thankless task, for it is bound to be in many ways superficial and incomplete, even in bloated and expensive textbooks that weigh seven pounds.
 Some clarification is in order on the nature of scientific questions. Of course science does have answers to questions such as "Why is the sky blue?" The questions it cannot answer and does not attempt to answer are those seeking ultimate causes"Why?" questions of philosophical speculation, not science. Valid scientific questions are "How?" questions, seeking only a detailed description of natural processes or laws and a tight unification with other established science. "How is the spectrum of yellowish sunlight modified in passing through the atmosphere to give us blue skies? What processes do this?"
 A common attitude is that physics ought to be understandable by anyone, without formal study. Otherwise, it must be wrong. Or perhaps it is deliberately made complicated and incomprehensible by the "scientific priesthood" to preserve their monopoly on the subject.