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"Nature's great book is written in mathematics" -Galileo
"Can you measure it? Can you express it in figures? Can you make a model of it? If not, then your theory is apt to be based more on imagination than knowledge." William Thompson, Lord Kelvin. (Quoted by Herbert N. Casson in "Kelvin: His Amazing Life and Worldwide Influence." in The Efficiency Magazine of Circa 1927. Reference taken from Hal Hellman's Great Feuds in Science.)
Thomas Dolby "Science!" music video
What Is Science?
Science concerns "experiental" knowledge, which is knowledge of the things that exist in the world and the laws that govern their interactions, and hence knowledge of things that affect human experience. (Experiental knowldege is also sometimes call "a posteriori" knowledge, because it is knowledge gained after experience. The other great branch of knowledge, "deductive" or "a priori" knowledge, is knowledge of things that can be deduced purely from concepts, and thus is knowable before expereince.) Science is humanity's most reliable and prolific form of experiental knowledge production. (Indeed, it's possble that science is humanity's only reliable form of producing knowledge of things that exist.) For the purposes of this text, "science" will be defined as the set of human activities that jointly contribute to expanding and refining human knowledge of the universe, and of the laws, processes, and events that have shaped that universe. In my view, science can usefully be seen as having an organized body of knowledge, a method, a process, a set of standards and an ethos. In the terms or this course, science is fundamentally based on explanation arguments, which I would like to discuss a little bit before I get into specifically scientific reasoning.
Types of Explanation
Whodunnit explanations refer to some being with free will that chooses to accomplish some particular act. The prosecution in a criminal trial attempts to prove that the only way to reasonably explain the available evidence is to assume that the defendant did the crime. The defense tries to show that there is at least one reasonable explanation for the evidence that doesn't require us to assume that the defendant did the crime. This doesn't just apply to crimes, but to any event that might have been caused as a result of a choice made by some free-willed entity. Since whodunnit explanations depend on assuming that somebody chose to do something, they can't be tested in the same way as natural law. (We can't put the defendant into the same situation to see if he'll commit the same crime.) Instead, whodunnit explanation arguments focus on means, motive and opportunity. Did he have the kind of equipment necessary to do the act in question? Did he have what he would have considered a good reason to do the act? And, is it possible for him to have been in the right place at the right time to do the act? (Not surprisingly, no theory of Intelligent Criminality, in which God is considered to have arranged the evidence so that it just happens to be consistent with the defendant having committed the crime, is ever accepted by any court of law.)
What happened explanations cover unexpected events where willed intervention is ruled out. When a bridge falls, a building collapses, and especially when an airplane crashes, people tend to want to know precisely what chain of events led to the event. Typically, as much physical evidence as possible is gathered in an effort to reconstruct that chain of events. Inconsistencies can be important here. If a piece of metal is bent in a way different from what might be expected from the event as it is presently known, that can tell us something. For instance, the bulged and burst shapes that result from explosions are different from the twisted and compressed shapes that result from impacts. (Of course, air crash investigators have no truck with any kind of Intelligent Breakage theory.)
The boundry between what happened and whodunnit explanations is not always clear. "Pilot error," meaning that the pilot made a mistake, is sometimes blamed for airplane crashes. Such a plane crash may be the pilot making a mistake, which is a failure of bahavior under his control. Or it might be caused by the pilot suffering a coronary, a stroke or a sudden attack of "happy feet." The crash is thus caused by his behavior, but that behavior was beyond his control.
Natural law explanations are the kind found in science, when science is done right. Before Ptolemy, Copernicus, Kepler and Newton, a common explanation for why planets move was "angels did it." The answer to the question of "why did they move the planets where they did?" would be "I dunno." The answer to the question of "where will they move the planets to tomorrow?" would also be "I dunno." Starting with Ptolemy, scientists started developing mathematical models of how the planets move, and which could give successively better answers to both of those questions. Eventually, Isaac Newton proved that if you assumed that all masses attracted each other according to a certain mathematical law, you could account for all obseverd past motions and predict all future motions with a very high degree of accuracy. Newton's argument was an explanation argument. He showed that his "law of universal gravitation" explained all the facts far better than any competing theory. (Compared to Newton's theory, for instance, "angels do it" doesn't explain anything at all.)
There is a distressing, and illogical tendency in some people to see gaps in natural law explanations as opportunities to insert supernatural non-explanations for the observed anomalies. These people say things like "natural law cannot explain this particular event" or "see, natural law predicts something slightly different from what we actually see here," and then imagine that it is scientific to then assert that their favorite supernatural being fills the gap or is responsible for the difference. This is false. Science is always full of gaps and anomalies, and the work of science to develop adequate explanations for those gaps and anomalies. Imagine the effect on science if that method had been applied to observed anomaies in the orbit of Uranus. Newton's theory, when it was first tested, wasn't 100% successful in predicting the path of the Planet Uranus. Now suppose a "theory of "Intelligent Piloting," which "explained" the anomalies by saying "here God intervened to pilot Uranus on a slightly different path" was accepted by the scientific community of the time. The anomalies would have been seen as explained, and thus would not have resulted in the discovery of the planet Neptune. If Intelligent Piloting had been universally taken as science, astronomy would have basically stopped at that point. Astronomy didn't stop, because mathematicians and astronomers dared to assume that Newton was still right, and that these anomalies must be the result of presently unknown factors, such as a couple of planets no-one had noticed before.
Ockham's Razor (spell it any way you like) is the fundamental principle of knowledge production. We cannot generate knowledge about the universe without it. There is no piece of actual knowledge of anything that exists or doesn't exist that isn't based on Ockham's razor.
Occam's Razor is a rule. It is a set of instructions of how to figure out which explanation you should select. For instance, say we are trying to explain the fact that, when you place a very hot object near to, but not touching a very cold object, the hot object will slowly become colder, and the cold object will slowly become warmer, until the two objects are the same temperature, even if the two objects are inside a vacuum.
Let us say that there are several theories on offer for this phenomenon.
Theory number one, the "Just Does" theory, holds that heat just does jump from the hotter object to to the colder object.
Theory number two, the "Intelligent Warmer" theory, holds that an undetectable supernatural being invisibly intervenes to move heat from the hot object to the colder object.
Theory number three, the "Kinetic" theory, holds that heat is nothing more than the vibrational movement of of the molecules and atoms that make up the objects.
Theory number four, the "Caloric" theory, holds that heat is a fluid that can be put into an object, and which will leak out of the object in all directions just so long as there is less caloric in the surroundings than in the object itself.
Theory number five, the "Heat Fairies" theory, holds that heat is a fluid that can be carried from one object to another by tiny beings with pretty insect wings that dip tiny little buckets into hot objects to get the heat out so they can carry it over to colder objects, where they pour the heat in.
There are two stages to Ockham's Razor. The first stage is to discard all the theories that are clearly inadequate. What this means is that, under Occam's razor, we only consider theories that actually provide some kind of more or less reasonable explanation for the phenomena.
Theory number one, the "Just Does" theory, is obviously inadequate. Basically, it's not even an explanation at all. In fact, it's more like a refusal to provide an explanation than anything else. Technically speaking, it shouldn't even be called a theory, because it's logically equivalent to saying, "the heat moves, and I don't know why."
Theory number two, the "Intelligent Warmer" theory, is equally inadequate. Again, it's not even an explanation at all. Imagine that you were to ask a holder of this theory how the Intelligent Warmer moves heat from one object to another. The answer would probably be something like "he just does." Now that's hardly adequate, is it? Basically, theory number two is just theory number one with the profoundly unhelpful addition of the completely useless "Intelligent Warmer."
Theory number three, the "Kinetic" theory, clearly fails to explain how heat gets from a hotter object to a colder object inside a vacuum. In order for the movement of one particle to affect the movement of another, those particles have to come in contact. Molecular movement cannot be transmitted across a vacuum, because there are no molecules in a vacuum to carry the movement across. I want you to notice how the failure of the Kinetic theory is different from the failures of the Just Does and the Intelligent Warmer theories. With the Kinetic theory, there is a mechanism that can be compared to the phenomena, and we can think about whether or not that mechanism could possibly make the phenomenon happen. With the other two theories, there is no mechanism, and there is nothing to think about. This is why they are not even explanations at all, and should not even really be called "theories." The only difference between them is that the Just Does theory basically refuses to give an explanation, and the Intelligent Warmer theory pretends to give an explanation, but really doesn't.
Theory number four, the "Caloric" theory, actually has a reasonably adequate explanation for how heat gets from one object to another. If heat is a fluid, an actual stuff that can flow into and out of objects, it could flow across the vacuum. Hotter objects would spit out more caloric than colder objects, and so hotter objects would tend to get colder, and colder objects would tend to get warmer, as caloric moved back and forth between them.
Theory number five, the "Heat Fairies" theory is just as adequate, in that it gives us a mechanism by which heat can move from one object to another through a vacuum.
So, after applying the first stage of Occam's razor, we are left with two reasonably adequate theories. There is the caloric theory, in which heat is a fluid that moves between objects of its own accord, and the heat fairies theory, in which heat is a fluid that is carried from object to object by fairies. None of the other theories is even remotely close to adequate, because none of them explain how heat gets across a vacuum.
The second stage of Occam's razor says that we should choose the theory that requires us to accept the existence of the fewest new entities. If a theory requires us to believe in something that we don't see anywhere else in the universe, then we should not believe in that thing unless we have absolutely no other choice. Both the caloric theory and the heat fairies theory require us to believe that heat is a fluid. We don't see this kind of fluid anywhere else, so Occam's razor says we should not accept its existence if we have any choice. But, at this point in our deliberations, we don't have any other choice. Our only two adequate theories both require that heat be a fluid. On the other hand, the heat fairies theory requires us to believe in fairies, which we also do not see anywhere else in the universe. These fairies come with a lot of unanswered questions. Where do they come from? How do they live? Why can't we see them? Where do they get the little buckets? The heat fairy theory is therefore much more complicated in terms of existence of new objects than the caloric theory. (I like to refer to this as being more "ontologically complicated.") Occam's razor can be formulated as telling us to accept only the least ontologically complicated adequate theory. Since the caloric theory is less ontologically complicated than the only other adequate theory, Occam's razor says we should accept the caloric theory, at least as far as this example is concerned.
I like this example because it allows me to make a very important additional point about how science makes progress. We can imagine that a scientist follows the above reasoning and accepts the caloric theory, at least tentatively. In real life however, there were other situations involving heat where the caloric theory turned out not to be an adequate explanation. In real life, the caloric theory was accepted for a number of years until certain other considerations made it clear that, overall, the kinetic theory actually turned out to be a much better explanation of heat. Crucial to this was the discovery of radiation, and the idea that rapidly moving molecules can generate infrared radiation as they bang into each other in a hot object. This allowed the kinetic theory of heat to explain how heat got across a vacuum. Prior to the discovery of radiation, some physicists accepted the caloric theory, and others accepted the kinetic theory. This was entirely appropriate, because neither theory fully passed the test of Occam's razor. The caloric theory explained more things, but was more ontologically complicated. The kinetic theory was ontologically simpler, but it did not explain as much. Once radiation was discovered, the ontologically simpler theory was also shown to be equally adequate, and so it became the accepted theory.
I would also like to note that, if no one had invented the caloric theory, it would still have been utterly bizarre for someone to offer the intelligent warmer theory as a serious competitor to the kinetic theory of heat. Suppose physicists only know about the kinetic theory, do not know about radiation, and therefore do not yet generally accept the kinetic theory of heat. If someone came along and said "I can bridge the gap between molecular movement and transmission of heat across a vacuum by theorizing that an Intelligent Warmer moves the heat across the vacuum" he would quite rightly be laughed out of physics. Even if the kinetic theory of heat is not then adequate to explain the movement of heat across a vacuum, the intelligent warming theory is not only equally inadequate, because it does not explain how the Warmer moves the heat, it is also so ontologically complicated as to be ludicrous. How did the Intelligent Warmer come into existence? How does it live? What does it eat? Where does it get the energy to move the heat?
Finally, if radiation is discovered, and the kinetic theory becomes adequate, the intelligent warmer theory becomes a sort of mental disease. Imagine if a defender of the intelligent warming theory were to begin by saying, "the other theories cannot provide an explanation for how heat gets across a vacuum, and so the Intelligent Warmer must exist," and when confronted with the concept of radiation, to reply "I don't accept that explanation." What would you think about the mental capacity or intellectual honesty of someone who argued in that fashion? You might find yourself thinking that nobody would ever offer this kind of "argument," but unfortunately, at least one defender of Intelligent Design has offered just exactly that kind of reasoning, and indeed this style of reasoning seems to be the closest thing that Intelligent Design has to an argument.
Imagine that you have never seen an astronomy book. Imagine that no one has ever told you anything about astronomy. Imagine that you don't even know that there is such a thing as astronomy. Now imagine that you go out into the open on a very clear night and look up at the sky, and that what you see with your unaided eyes is everything you know about the night sky. What would you think, and how would you try to explain all those little lights?
Ancient astronomers had no telescopes. All they had were their eyes, and their starting point was the night sky as you can see it today in any place without light pollution. Their first method of study was simply to make note of the positions of the brightest stars relative to the positions of other bright stars. This careful observation paid immediate dividends, because they noticed right away that some bright stars did not stay in the same places relative to other bright stars, but changed relative position over time. The Greek word for wanderer was "planet," and that's what they called these wandering stars.
Now, I want you to put yourself in the place of an ancient astronomer. You know nothing about physics. You know nothing about vacuum. You know nothing whatsoever about these little lights in the sky except what you can see with your unaided eyes. What would you think is the best explanation for what you see up there? At the time, the simplest and most obvious explanation: first offered by Anaximander, was that the Earth hung at the center of an enormous hollow sphere made of some "crystal" (transparent material) in which the stars were embedded. Pythagoras later pointed out that some of the stars moved around relative to the others. Later thinkers, such as Eudoxus, accounted for the movements of the wandering stars by assuming that each of them was carried in the wall of its own smoothly moving crystal sphere that fit neatly inside the larger sphere. Since several planets, including the Moon in particular, had complicated motions, it was assumed that they fit inside smoothly moving spheres that fit inside other smoothly moving spheres and so on until all movements were accounted for. At the end of the process, they had an elaborate model of the universe as a set of many hollow crystal spheres, each one moving in its own stately circle, and all nested together, one inside the other, around a central, unmoving Earth.
Based on the information available at the time, this was an absolutely brilliant model of the universe. As far as anybody could tell, it explained everything. And it passed the test of Occam's razor because there was no ontologically simpler model that also explained the same facts at that time. I want to emphasize this, because it is sometimes thought that the ancients held "primitive" or irrational views of the universe before the enlightened moderns came along and corrected them. Nothing can be further from the truth. Modern people are no smarter than ancient people. The difference between modern people and ancient people is that modern people have the advantage of coming in after the ancients had already done an enormous amount of hard cognitive work which enabled the steady incremental process which led to our modern understanding of the world.
Once Eudoxus' model was developed it could be checked against more and more careful observations. Later thinkers such as Callippus, added more intermediate spheres to make the model better fit the observations. After a while, people started to think that the model was getting a bit too complicated. A fellow called Hipparchus decided things would be simpler if, instead of all the crystal spheres fitting one inside the other around a common center, some of them were much smaller, and fitted inside the walls of other spheres. If a star was embedded in the wall of a small sphere that rotated inside the wall of a much larger sphere that also rotated, the star would follow a path that would look like a series of small loops arranged in a circle. Hipparchus called the larger circle the "deferent," and the smaller loops "epicycles." He also introduced the idea that the rest of the universe did not revolve around the center of the Earth, but around an imaginary pointhe called the "eccentric" lay near the center of the Earth. Hipparchus' system required far fewer spheres than was thought necessary for Eudoxus' model and, as far as anyone can tell, it produced more accurate results. It's true that "spheres embedded in the walls of other spheres" is a little more complicated than "spheres inside spheres inside spheres," but it isn't much more complicated, and it was certainly just as easy to visualize. Hipparchus's model was a major advance in astronomy and, although his works are now lost to us, his system was elaborated by Ptolemy, and is now known as the Ptolemaic system.
Modern thinkers often suffer from the delusion that Copernicus was the first person to think that the sun might be the center of the universe instead of the Earth, but this is not so. A fellow called Philolaus had that idea two thousand years earlier. It was further developed by a man called Aristarchus, whom Copernicus is known to have read. (The manuscript of Copernicus's book contains reference to Aristarchus, but that reference is missing from the published edition.) Why did ancient thinkers prefer the "geocentric" (earth centered) model of Anaximander to the "heliocentric" model of Heraclides? Well, one possible answer is that they thought that the geocentric model was less ontologically complicated than the heliocentric. The heliocentric model requires people to believe that the earth moves and the sun doesn't. This idea radically contradicts every observation that could be made at the time, and so it is the kind of thing that should not be believed if there is any less radical alternative. I won't go so far as to say that the ancients were right to reject Aristarchus' model, (his arguments were pretty damn good) but that rejection was not unreasonable given both Occam's razor, and the state of knowledge at the time.
What Copernicus did was work out a thorough mathematical treatment of the heliocentric model, and show that it easily explained certain things, such as the fact that the planets Mars, Jupiter and Saturn periodically appeared to move some distance backwards in their orbits, much more easily than the Ptolemaic model could. It's not that the Ptolemaic model could not explain these things, it's that the Ptolemaic explanation was very, very complicated, and the Copernican explanation was very simple. Unfortunately, if you just assumed that the planets moved at constant speed in circular orbits around the center of the sun, the Copernican model would not match observations very well at all. So Copernicus, like Hipparchus, included some eccentrics and epicycles in his system. For this reason, the Copernican system was not a clear winner over Ptolemy. You could make the system simple, but only at the expense of accuracy, or you could make the system accurate, but only at the expense of simplicity.
The theories of Ptolemy and Copernicus existed side-by-side inside science for over a hundred years. It was not until Johannes Kepler had the idea that the planets might move in elliptical orbits that the Copernican system finally fit the observations well enough to be considered the clear winner over Ptolemy. Replacing circles with elipses did not increase the overall complexity of the Copernican system because, although the ellipse is a more complicated figure than the circle, using ellipses allowed astronomers to dispense with the eccentrics and epicycles that Copernicus had been forced to include in his system. Indeed, adding the notion of the elliptical orbit to the Copernican system created a model of the solar system that was both elegantly simple, and which fit observations to a very high degree of accuracy. Before Kepler, Occam's razor did not clearly support the heliocentric model because no version of the heliocentric model could satisfy both conditions of being both ontologically simpler and clearly accurate. It was only after the addition of Kepler's ellipses that the heliocentric model could meet the criteria of being the ontologically simplest theory that adequately explained the observations.
Check out this orrery! (Solar System Model) When you's seen the Copernican version, click on "Tychonian" at the lower right of the screen.
The thing that most distinguishes science from non-science is that people who do science use the scientific method, and people who don't use the scientific method are not doing science. Thus the fundamental way to tell whether someone is or is not a scientist is to look at her methods, and not just whether she has a degree or wears a white lab coat.
As far as anyone can tell, the scientific method was first developed by the philosopher Thales, who lived a god-awful time ago. Sir Isaac Newton is credited with developing a more precise formulation of the method, but it wasn't really called the "scientific method" until after the scientist, logician and philosopher Charles Sanders Peirce called it the "method of science." It is important to note that people made an awful lot of scientific progress before anyone started thinking about the scientific method. Heck, people did an awful lot of science before it was even called "science." But just because they didn't know what the scientific method was, doesn't mean that they were not using it. Our understanding of what the scientific method is comes from looking at what successful scientists did that produce the best results. The "scientific method," is just our present term for "whatever method it was that produced all that lovely reliable knowledge." Thus, in my view, the scientific method as we understand it formally is an abstraction from everyday scientific practice. It may be that nobody follows the scientific method exactly, but it is true that scientists can only be successful to the extent that they follow the scientific method. As I understand it, the scientific method can be seen as having four phases, which I will call observation, hypothesis, deduction, and testing. In the observation phase, people collect together all of the most reliable and possibly relevant data about some pattern of experiences. Say that a particular kind of cancer appears to become significantly more common in a certain population. People wishing to understand this phenomenon would, in the observation phase, gather the most reliable information the code about the past and present incidence of cancer in that population, as well as information about anything else that may have become more of less common in that population, such as an increase in illegal drug use, a chemical spill, a decline in smoking, or an increase in recent personal appearances by C-list celebrities. In the hypothesis phase, people would basically make guesses about what they thought the underlying explanation was that for all that observed pattern of experiences. In the cancer case, one person might hypothesize that the unexpected cancers were being caused by the decline in smoking, and another might think that the cancers were caused by increased exposure to C-list celebrities. In the deduction phase, people develop conditional predictions, based on logically deducing what would happen in different circumstances, if a given hypothesis was true. For instance, the first person mentioned above could deduce that the abolition of the tax on cigarettes in that area would lead to a decline in those cancers, if his hypothesis was true. And the second person could deduce that if the production of Hollywood Squares was moved into the area, the incidence of cancers would increase, if his hypothesis was true. Finally, in the testing phase, experiments are conducted and the results analyzed. This is rarely a simple matter, because of the number of variables that have to be taken into account. For instance, if the cancer rate fails to increase after Hollywood Squares start shooting in the area, this could be because the hypothesis is false, or it could be because the presence of Hollywood squares Squares has discouraged other celebrities from making personal appearances. And, if the incidence of cancer went down after C-list celebrities were banned from the area, the experimenter would have to make sure that his experiment did not have some other effect that accounted for the difference.
The scientific method is basically based on carefully doing two different things: creating hypotheses to attempt to explain observations, and making observations to attempt to confirm or disconfirm theories by seeing if the real world turns out to be the way the theory predicts it will be. How this works in practice can get pretty complicated, but that's the basis of it. Thus, in theory, the scientific method consists of observation, hypothesis, deduction and experiment, but in practice it consists of that plus a whole lot of other work to make sure that the observations and experiments were done and interpreted correctly.
An "anomaly" is an unexpected or unexplained observation. The word "anomaly" actually means "not according to law", so a scientific anomaly is something that doesn't fit with the laws of nature as we presently understand them, if we have any laws at all. The earliest anomaly that I know about was the ancient observation that while every other river known to the ancient Greeks flooded in the winter, the Nile flooded in summer instead. An ancient philosopher calle Thales of Miletus set out to explain this, and in this attempt managed to get the scientific method started. At the dawn of astronomy, just about everything was an anomaly. People observed that the night sky contained several thousand little points of light, that the vast majority of these lights stayed put relative to each other ("fixed stars") but some moved around in fairly regular ways ("planets"), and that every so often new lights appeared ("novae") and sometimes even stranger things happened ("meteors", "comets"). At first, no-one could satisfactorally explain any of this, so all the observations were basically anomalies. Later, when we began to understand lots of things, the things we didn't yet understand, the things that didn't quite fit our best theories, those things were our anomalies. These anomalies can be phrased as questions: Why do planets orbit at the particular distances they do? Why do they orbit at the particular velocities they do? Why did the planet Uranus not orbit exactly the way that Newton's theory said it would? For that matter, why didn't Mercury orbit exactly the way Newton said it would? What is that thing that William Herschel has discovered out there beyond the orbit of Saturn? And, how exactly does matter get to have mass?
A "hypothesis" is an idea that is offered in an attempt to explain a particular observation or set of observations. This hypothesis can concern a physical law, as in Johannes Kepler's early hypothesis that the orbits of the planets were determined by a complicated formula involving spheres enclosing and being enclosed by geometrical solids, or his later hypothesis that a planet's velocity was mathematically related to its distance from the Sun. Or a hypothesis might concern the existance of a physical object, as in Alexis Bouvard's hypothesis that there was another planet out there affecting the orbit of Uranus. Or a hypothesis might concern the nature of an observed object, as when William Herschel hypothesized that the moving object observed by himself and several other astronomers was a comet. Or a hypothesis to explain mass might concern a hideously complicated subatomic interaction, called the "Higgs Mechanism". It's important to recognize that a hypothesis is not merely something we can say to feel like we understand. Saying "Goddess Venus makes people fall in love" is not a hypothesis because there's no mechanism described, no mathematical rule, and no way to make predictions. Most fundamentally, the idea is not falsifiable. Ask a believer in this idea to come up with hypothetical circumstances that would prove his belief false, and you get a blank look followed by a quick change of subject. (This is one of the main differences between science people and nonscience people. People who understand science only accept falsifiable ideas as hypotheses. Nonscience people want their ideas to be accepted as true, and don't care whether they can be tested or not. Regretably, some nonscience people want to use state power to help them tell people that their nonscientific ideas are in fact science. These people are ignorant at best. At worst, they are profoundly dishonest.)
"Deduction" means thinking about what it would mean if a particular hypothesis was true rather than false. If Kepler's early hypothesis was true, we would be able to create a nested arrangement of touching geometric spheres and solids such that every planet's orbit lay in the surface of some hollow sphere, and the spheres were spaced so as to allow exactly enough space for a some hollow geometric solid between each two spheres. If it wasn't, we wouldn't. If Kepler's later hypothesis were true, mathematicians would be able to predict the future motions of the planets by applying his formula to what we know about their past motions. If it wasn't, they wouldn't. If Bouvard's hypothesis were true, mathematicians would be able to predict future positions of this new planet with enough accuracy that astronomers would be able to find it in their telescopes. If it wasn't, there'd never be a planet there when they looked. If Herschel's hypothesis were correct, his object would have a highly non-circular orbit, and would develop a tail, (or two) as it got closer to the sun. If it wasn't, the object would behave differently. If the Higgs Mechanism exists (and certain other things are true) a new particle called the "Higgs Boson" will be detectible at collision energies above . . . when you smash very tiny things together very, very, very fast. If it doesn't . . . a lot of physicists are going to be very embarrassed. It's important to remember that we are only concerned with things that will only be true if the hypothesis is true, and will be false if it's false. Things predicted by the hypothesis that would be true even if the hypothesis is false are not at all interesting here. Again, falsifiability is important. Unfalsifiable hypotheses do not allow deductions. Nothing can be deduced from the idea that Goddess Venus causes love, because the theory does not allow the making of predictions that would only be true if the idea is true, and which would only be false if the idea is false.
Once we have made a few deductions from our hypothesis, we try to figure out a way to check if those deductions are actually true. Kepler put in quite a bit of time figuring out different ways spheres and solids could fit inside each other, looking for a way in which the known orbital distances of the planets would naturally fall out of the system. When he came up with the later hypothesis, he checked its predictions against the known orbital motions of the planets. Bouvard couldn't test his own hypothesis fo himself, but Urban le Verrier made the appropriate calculations and Johann Galle turned his telescope in the right direction at the right time. People kept watching Herschel's object to see if it got nearer the Sun, or developed a tail. As for the Higgs Mechanism, they've built this great big accelerator called the Large Hadron Collider over in Europe, and they're busy shooting tiny things into other tiny things in an effort to find Higgs bosons, among other things. At this point, the Goddess Venus "explanation" for love begins to look very silly. What machinery could we build, what study could we design, to test the idea that Goddess Venus is responsible for the presence and absence of love in human beings?
In the simplest terms, theories can be "confirmed" or "disconfirmed" by observations. "Disconfirmation" is actually the easiest concept to explain, so I'll start there. Basically, if we make an observation to test a prediction implied by a hypothesis, and things are not as predicted, then the hypothesis is disconfirmed, which gives us a reason to discard it. Kepler's idea about spheres and geometric solids never did work out, so it was disconfirmed, and he eventually discarded it. And Herschel's idea that the body in question was a comet was disconfirmed by the observation that it had a very nearly circular orbit. "Confirmed", on the other hand, means something like "tested, and not proved wrong yet" rather than simply "proved right". It's in the nature of science to always be at least a little tiny bit uncertain, so a "confirmed" hypothesis is always one that's proven right so far, rather than proven right for good and all. Basically, if we make an observation to test a prediction implied by a hypothesis, and things are as predicted, then the hypothesis is confirmed, which gives us good reason to keep it around. Kepler's later theory allowed astronomers to make several predictions, all of which came true. (For instance, Kepler's theory allowed astronomers to predict transits across the sun of both Venus and Mercury.) Bouvard's prediction of a new planet was confirmed when astronomers pointed their telescopes as Le Verrier instructed and, lo and behold, found that new planet just where he said it would be then.
"Success", for a hypothesis, means getting sufficiently spectacular or sufficiently many confirmations that smart scientists begin to think that they can do things with this theory. Newton's model of universal gravitation gave a mathematical way to predict the future motions of the planets. These predictions came exactly true (as far as we could tell) for the orbits of Venus, Mars, Jupiter and Saturn, so some astronomers decided that Newton's hypothesis was confirmed, even though the predictions didn't come exactly true for the orbits of Mercury and Uranus. Sometimes doing waaaaaaay better than every other available hypothesis is enough to get a hypothesis adopted. Successful hypotheses are called "theories". (In science, the word "theory" means pretty much what non-scientists mean by the word "fact". Calling a hypothesis a "theory" is very close to saying that you think it's true.) When a hypothesis is well-confirmed and proving to be useful, it is "adopted" by leading thinkers in the relevant field, who then attempt to apply it to new problems. This is a bit more complicated than it sounds. When a theory is new, and it isn't clear whether it works or not, it also isn't necessarily clear who the leading thinkers are. Sometimes, the most famous people in the field fall upon the new theory with glad cries and carry it forth to adulation and new triumphs. Sometimes, the most famous people in the field shun the promising new theory with expressions of horror and disgust. What seems to be important here is that the theory be adopted by clever scientists who are also in a position to exploit the new theory. (Who are the clever people? I couldn't possibly tell you. If I was that smart, I'd be one of them. History can tell us who some of the clever scientists were simply by picking out the people who early adopted theories that turned out - eventually - to be right. As for who the clever people are right now, well, they're probably among the scientists who are well respected by everyone else in their field, and they're definitely people with imagination and good thinking habits, but more than that, I can't tell you.) Once a hypothesis has been adopted by scientists capable of seeing its interesting implications, they start calling it a "theory", and keep on deriving and testing those implications. After a while, it gets taken for granted.
Once a hypothesis gets called a "theory" and is taken for granted, it becomes part of science's background knowledge. Scientists start to act on the assumption that the theory is true. Usually this is pretty safe. Theories that have survived a lot of testing and criticism strongly tend to survive further testing and criticism. (For instance, the theory of evolution through natural selection has survived, with flying colors, an enormous amount of testing and criticism.) But sometimes theories, even well established theories, sometimes make predictions that don't quite come exactly true. For instance, Newton's theory of universal gravitation predicted certain orbital motions for Uranus and Mercury. When people checked these predictions by looking at those little lights in the sky we call "planets", the found that they weren't quite exactly moving the way Newton's theory said they would. When this happens, it constitutes an unexpected or unexplained observation, or "anomaly", and we're sort-of back at step one, only with a bit more knowledge behind us this time. Anomalies don't necessarily threaten theories. When Bouvard noticed the anomalies in the orbit of Uranus, he didn't think it meant Newton was wrong. He thought that the physical universe might be different, and hypothesized a new planet out there. In this case, the observation led to a new hypothesis turned out to be true in a way that didn't threaten the original theory. When they tried to explain the anomalies in mercury's orbit however, things didn't go so well. They looked for a new planet, but no new planet was found. They thought the Sun mightly be oddly shaped, but observations kept showing that the Sun wasn't any of the shapes that worked. So then they had a real anomaly. Newton's theory was solving so many problems in so many areas that nobody wanted to give it up, so they put the Mercury problem on the back-burner in the expectation that eventually, somehow, it would be explained.
The essence of the scientific method is finding hypothesis that work. This means more than having something that feels good to say about anomalies. It means finding hypotheses that actually explain things, that can be expressed mathematically, which generate testable predictions, which generate at least some predictions that surprisingly come true and which generate interesting anomalies that lead us to new hypotheses, and so on.
Body of Knowledge
Introductory science textbooks tend to produce a somewhat simplified view of scientific knowledge. Usually, the reader is presented with two groups of claims. There are the scientifically established claims, which are all treated as equally true, and there are the scientifically discredited claims, which are all treated as false. This is perfectly fine, just so long as you can trust the book. (Which you can, ......... usually.) There is no practical problem with regarding well-established scientific claims as true, and scientifically discredited claims as false. (In fact, I think this attitude amounts to just about the best way to define "true" and "false" for all practical purposes.) However, for the theoretical purpose of understanding science, this language is somewhat inadequate, mainly because some people tend to see the word "true" as denoting claims that could not possibly turn out to be false, and "false" as donating claims that could possibly not turn out to be true. (I, of course, think that this is the wrong way to look at truth and falsity.) So, instead of science dividing claims into two piles, one unequivocably labeled "true" and the other unequivocably labeled "false," there are in fact many piles, blending into each other, and running the gamut from extremely well established claims at one end to utterly discredited claims at the other end. (Notice that I do not talk about this in terms of "degrees of truth." That would be stupid.) A more accurate description would be in terms of strength of evidence. The most well-established claims are the ones for which we have the strongest evidence, and the most discredited claims are the ones against which we have the strongest evidence. I think this is an excellent way of looking at scientific knowledge, and will serve for almost all theoretical purposes, but there's one more element that should be discussed. A claim, or theory, can be utterly discredited even if there is no specific evidence against it. This is because a claim can turn out to be useless. A person who accepts this kind of claim as true is in exactly the same position as someone who rejects it as false. Such claims can be true or false without making any difference in present or future observations whatsoever. For this reason, science is not interested in claims that cannot generate testable predictions. These claims cannot lead to new knowledge, and they do not constitute knowledge in themselves.
Scientific progress is the gradual and haphazard accumulation, refinement and correction of experiental knowledge over time. It's what I call a "historical" process, because it is subject to all the all the weird complications of human life that make history so complicated. Political, social and even psychological factors can play an enormous part in determining what scientists believe and what they find important. Science doesn't progress majestically through time, piling up triumph after triumph. Science stumbles drunkenly through history from triumph to disaster to bizarre twist and turn to eventually getting back on track for a while. Still and all, progress is made, but only by applying logic to evidence. To give a very simplified example, there was a long and winding, but very scientific road from the prehistorical myth of a flat earth to modern ideas of the universe. Actually, the "flat earth" ideas was discarded pretty early. The Ancient Greeks quickly decided the Earth was a sphere based on observations of objects near the horizon. My simplified story starts with Empedocles (490-430 BCE) who, for various reasons, hypothesized that all matter was composed of four "elements"; earth, air, fire and water. This was not a bad idea. It worked better than previous theories, and it guided physical thinking for the next two thousand years or so. Next came a guy called Philolaus (470-385 BCE), who decided that "up" and "down" were concepts that applied only to the Earth, not the universe as a whole, and that the center of the universe was not the Earth, but a "central fire", around which revolved everything else, from the sky at the bottom, through the planets, the Earth and Counter-Earth, the Sun and Moon, Olympus and finally another big fire outside everything. "Counter-Earth" was something he came up with to fix an apparant anomaly in his system. Scientists then believed that the Earth was mostly made up of the heavy elements earth and water, while the heavenly bodies were made of the lighter elements air and fire. In an eerie forshadowing of Newtonian physics, heavy bodies were presumed to have a stronger influence on lighter bodies than light bodies did on heavy bodies. If the heavy Earth was somehow magically revolving around the light central fire, heavy Earth would be pull the fire out of position. The obvious solution was to hypothesize that there was another heavy body on the other side of the central fire (call it "Counter-Earth) that pulled the other way, counteracting the influence of the Earth, and keeping the fire in the center. When you remember that this was pretty much the first scientific cosmology, it's pretty darn good. Weird by modern standards, but those standards didn't exist then, and in fact would not exist if it were not for people like Philolaus who came up with theories that worked pretty darn well at the time. After Philolaus came Aristarchos of Samos (310-230 BCE) who, perhaps following the principle later known as Occam's Razor, radically simplified Philolaus' model. He decided that the central fire was in fact the Sun, set the Earth and the planets revolving around that Sun, and did away with Counter-Earth, Olympus and the outer fire. Thus was inaugurated the heliocentric theory of the cosmos, about 1800 years before Copernicus! However, most other ancient astronomers, for reasons that seemed good at the time, disagreed with Aristarchus. They noticed that loose objects tend to fall to Earth, and that everything still looked like it revolved around the Earth, so they decided that Earth had to be the center of everything after all. This idea reached it's fullest flower in Aristotle's theory that the Earth was surrounded by 56 transparent spheres, made of "aether", that together held and accounted for the movements of the Moon, the Sun, the five planets and the fixed stars. Aesthetically, this was a very satisfying theory, and it explained most of everything people saw when they looked up into the sky, so people liked it and accepted it.
I was going to write out a whole section about how anomalies with Aristotle led to Ptolemy, who fixed Aristotle but led to problems that Copernicus fixed, and so on to Gallileo, Brahe, Kepler, Newton, Herschel, Bouvard, Le Verrier, Galle . . . blah blah blah, but, you know what? I'm tired, and I think you've got the picture.
In practice, scientific progress is rarely, if ever, accomplished by a single experiment. Even the simplest hypothesis usually takes a large number of experiments to establish as supported or unsupported. Generally what happens is that a hypothesis is tested multiple times in multiple ways. Even if an experiment goes as predicted, it does not necessarily follow that the hypothesis is confirmed or disconfirmed. Rather, it might be true that the result could be explained in a number of ways, and further experiments must be designed and carried out in order to determine which explanation is correct. The scientific process is thus a continuous series of iterations of the scientific method applied to successions of progressively more refined hypotheses. Generally, the most effort is applied in the most promising direction, but that does not mean that no effort is spared for hypotheses that are less likely to be true. Rather, all reasonable hypotheses tend to be pursued, each according to how likely to be true it appears to some particular scientist at that time.
An important part of the scientific process is carried out by the established scientific journals. Scientists who think that they have something interesting to say will write papers and send them to journals. The editors of these journals will send these papers out to other scientists that they think are competent to judge the quality and integrity of the work presented. There then follows a messy process of criticism, comment and revision as the authors of the papers attempt to meet the standards set by the reviewers, but eventually some of these papers make it into the pages of the journals. Publication by a refereed scientific journal does not guarantee that the conclusions expressed in the paper off well-founded. Rather, what the journals are supposed to guarantee is that the authors have given a clear and complete description of their experimental procedures, have correctly interpreted their purported results, and have properly cited the relevant previously published work. This process, when it works right, makes sure that the journals only publish papers that have a reasonable chance of being right, and which give enough information for other scientists to critique the experimental method, or repeat the experiment. (Nowadays the role of the journal is being supplemented, and perhaps slowly replaced, by the online preprint archive arXiv.org, which functions in a similar way.)
The Scientific Community
Scientists have a phrase, "standing on the shoulders of giants," which they use to indicate that individuals typically only make great discoveries after others have laid a great deal of groundwork. Sir Isaac Newton, for instance, used this phrase to indicate his debt to previous scientists and astronomers. (Some of whom should more properly be called astrologers than astronomers.) The scientific method is often a group effort, with one person providing the observations, another the hypotheses, a third the deduction and perhaps even a fourth designing the experiments. This means that scientists tend to have a lot to do with other scientists, and deal with other scientists in ways that they do not deal with non-scientists. We can thus define a pattern of "scientific interaction" as the set of interactions and behaviors that scientists typically direct towards fellow scientists, and not to other people. Obviously, this will include reading each others' relevant papers, corresponding on points of mutual interest, organizing and attending conferences, and arguing with each other both in person and via the pages of scientific journals. In general, or at least ideally, these interactions will all be characterized by one overriding theme. That theme is an effort to make sure that the scientific method is applied as thoroughly as possible to whatever questions are currently of interest to science. In sociological terms, members of the scientific community generally engage in a political process, both between themselves, and in regards to others, to ensure that the scientific process is protected and promoted as much as reasonably possible.
Scientific Standards
In the world outside of science, the word "certainty" generally means that an emotional conviction that some claim is correct, or even a determined unwillingness to accept the claim could be false. Many of the beliefs that are held by nonscientists to be "certain" are in fact not even particularly likely to be true, and in many cases are in fact very unlikely to be true. Unlike most nonscientists, scientists recognize that no conclusion about the state of the universe or the laws of nature can ever be held with absolute certainty. Thus even the best established theories of science, which are far better supported than any nonscientific claim, are still held by scientists to be tentative conclusions about the universe that could possibly be wrong. Thus when a theory is accepted by the scientific community, that does not mean that anyone thinks that it is absolutely certain to be true. Rather it means that scientists think it is very likely be true, that it has no unrefuted competitors, and that scientists think that accepting it as true is likely to lead to productive work in the future. When a piece of scientific work is accepted by other scientists, it does not mean that there are absolutely no holes in its arguments, or that absolutely every step in its explanations has been nailed down tight. What it means it is that scientists think that its arguments are good enough, that its explanations are detailed enough, for it to rank with all the other work that has been generally accepted. It is always possible to raise trivial objections to any scientific paper, but if scientists were required to specifically spell out absolutely every step in a process, no scientific work would ever be completed. Scientific work is judged by a very high standard, but it is never required to be perfect. This means that there are two ways to abuse scientific standards. First, of course, scientific standards can be abused by accepting or promoting work that does not rise to the standards generally imposed. But second, scientific standards can be abused by dismissing work that meets those standards merely because it is not absolutely perfect.
Terminology
Scientists have their own way of talking about things, but I'm really not going to talk about that. Instead, I'm going to develop a vocabulary for talking about science, which may not be the same as the vocabulary that scientists use to talk about their work, but will hopefully enable me to be more precise in how I talk about what I think science is.
Ad Hockery. An "ad hoc" assumption is an assumption made purely to explain some diversion from predicted or hoped-for results, or (some contradiction of well-established theory.) If an experiment does not go the way the scientist wanted it to go, he is perfectly free to try to save his theory by coming up with a plausible explanation that allows his theory to still be true, even though the results of the experiment appear to disconfirm that theory. If this explanation appears plausible to other scientists, they may continue work on this theory. And sometimes these ad hoc assumptions even turn out to be true. However, when a theory's multiple failures are covered only by a series of ad hoc assumptions, it is a strong sign that the theory is in serious trouble.
Consistency. An experimental or observational result is "consistent" with a theory if it does not contradict the theory. Take the theory that the "fixed" stars are all embedded in a giant crystal sphere that has the Earth at its exact center. The observation that the stars appear to rotate around an axis running through the North Star is consistent with this theory, but it is also consistent with the theory that the stars are distributed theough an immense volume of outer space, and their apparant rotation is merely the result of the Earth turning on an axis running through the North Star. Thus the same observation can be consistent with a large number of different, mutually contradictory theories. (We can also imagine that, contrary to what we actually see, the fixed stars don't appear to rotate. This imaginary, but logically possible, observation would be consistent with the "crystal sphere" theory, but it would not be consistent with any theory that required the Earth to rotate.)
Confirmation. An observation or experiment "confirms" a theory if the result of the observation or experiment is logically deducible from that particular theory and from no other competing theories. An experimental result confirms the theory if both the following things are true. 1. This theory predicted that particular result. 2. All other competing theories predicted different results from that experiment, or made no predictions about that situation. A confirmation does not necessarily prove a theory, but it does contribute to such proof. Please note that confirmation is much stronger than consistency. All confirming results are consistent, but not all consistent results are confirmations. Suppose, in the example above, we had somehow eliminated the "crystal sphere" theory and were attempting to decide between two theories attempting to expain the Sun's apparant motion around the Earth. The first "Sun Moves" theory is that this motion is real, and that the Sun really does whiz around a fixed Earth. The second, "Earth Rotates" theory asserts that the Sun is basically fixed, and that the Earth rotates on its axis to produce the appearance of motion. The mere observation that the Sun appears to circle the Earth is no help here because it is consistent with both theories. But the observation that the fixed stars also appear to rotate about the Earth on a 24-hour cycle confirms the "Earth Rotates" theory because is is both consistent with that theory, and inconsistent with its competitor.
Disconfirmation. An observation or experiment "disconfirms" a theory if it produces a result that is different from what the theory predicts would happen in those circumstances. Disconfirmation does not necessarily falsify a theory, but it does cast doubt on the disconfirmed theory, and definitely indicates that more work needs to be done.
Discredited. I shall refer to a claim as "discredited," when I think that it has been scientifically established that there is no point to entertaining that claim as a hypothesis any longer. The easiest way, in theory, to discredit a claim, is to show that it is inconsistent with our best observations. However, proponents of such a claim can often make excuses for why our observations turn out different, and some of these excuses can be valid. Therefore, a claim is really only completely discredited when all of the possible excuses have been ruled out, or it comes with so many excuses that trying to get anything useful out of the claim is so complicated as to be not worth the trouble. (Logically self-contradictory claims are, of course, automatically discredited.)
Fact. I shall use the word "fact" or "scientific fact" to denote any claim that is so well established that there really is no present practical point to doubting it. A scientific fact is a claim that is rightfully considered reliable by scientists in that they find that they can treat it as true under all circumstances. One way to know whether some claim is a scientific fact is to ask whether or not anyone is currently raising any credible arguments against that claim. If there are no logically credible arguments against the claim, then I'm just going to call it a fact. If there is even one even remotely reasonable argument against some claim, then I will hesitate to call it a fact, even if I personally think it is true.
Falsification. A theory is falsified if it has been disconfirmed so thoroughly that there is no reasonable explanation for all these disconfirmations other than to say that the theory is false. Please note that being falsified is very different from being falsifiable. Seriously, these two concepts are very different.
Falsifiability. A theory is falsifiable if it is logically possible for some experiment or observation to turn out in some way as to prove the theory false. (Notice that being falsifiable is very different from being falsified.) It is important to note that this is a logical possibility, not necessarily a practical one. It may be practically impossible to prove a certain theory false, merely because the proponents of the theory are very creative in coming up with excuses for their pet theory. This does not mean that the theory is not falsifiable. A theory will fail to be falsifiable if it comes with built-in excuses. The theory that disease is caused by demons is not falsifiable because there is no hypothetical observation that could prove the demons do not exist. The theory that disease is caused by bad-smelling air is falsifiable, because we can conceive of observing disease without bad-smelling air, observing bad-smelling air without disease, and finding that there is no significant correlation between the appearance of bad-smelling air and the appearance of disease. Both of these theories are discredited. The bad-smelling air theory is discredited because it has been abundantly disconfirmed. The demon theory is discredited because it is unfalsifiable, and thus cannot contribute to scientific progress. In contrast, the germ theory of disease is not discredited because, although lots of things could have happened to prove it wrong, none of those things has ever happened.
Law. The term "law" has two main usages in science. First, it is used in names for particular ideas, as in "The Laws of Thermodynamics." Used in this way, it does not mean anything. If something is called a "law," that does not mean it is any more respectable than something that is not called a law. In fact, things that are called laws can be disconfirmed or discredited. The "laws" of thermodynamics are not scientific laws at all, but have in fact been shown to be special cases of Statistical Mechanics. Secondly, it is used more precisely to refer to what are believed to be universal regularities of nature. Einstein's theories of general and special relativity and Darwin's theory of evolution through natural selection are scientific "laws" in that sense.
Meaning. A statement is meaningful if there is some practically possible observation that can be made to determine whether or not is true or false. If the term "demon-infested" is defined in such a way that there is no practical way to tell a demon-infested object from a non-demon-infested object, then the term "demon-infested" is meaningless. This also applies to terms whose "meaning" is defined obliquely. If someone claims that your stereo must be infested with demons because it is not working correctly, and neither you nor he can figure out why, the term "infested with demons" is still meaningless because there is no way to tell the difference between a stereo that is infested with demons and one that merely has a malfunction of unknown origin. (In such a case, the term "infested with demons" just means ""not working.")
Proof. A theory is proved, in my view, if it is so well confirmed, and its competitors are so well disconfirmed that there is no further real point in testing the theory. Individual scientists make different individual judgments on whether or not particular theories are proved. And your judgment of whether or not a particular theory is proved can be different from mine. Since no theory is ever proved absolutely, there really isn't much point in trying to work out an objective definition of the word "proof."
Replicability. (Or reproducibility.) Results in science are supposed to be replicable, which is to say that other scientists who perform the same experiment in the same way will get the same result. If a scientist claims to have gotten a certain result with a certain experiment, but competent other scientists prove to be unable to get that result from that experiment, then it isn't replicable. When a result turns out to be unreplicable (or irreproducible), the most obvious explanation is that the original scientist made some kind of mistake, and so unreplicable results are generally ignored by science.
Reputation. Certain scientists, labs and areas of study have good reputations, and attract a lot of attention and resources from the scientific community. Certain other scientists, labs and areas of study have bad reputations, and attract little or no attention or resources from the scientific community. Ideally, scientists and labs get good reputations by producing useful theories, replicable results and other reliable information. Areas of study get good reputations by being areas where productive work can be done. Scientists and labs get bad reputations by producing irreproducible results, or otherwise doing shoddy scientific work. An air of study gets a bad reputation by constantly failing to be an area where replicable results can be gained, or otherwise useful work can be done. A field of study in which researchers consistently promise that they have or soon will have compelling results, and yet which produces no working devices, and no clear reproducible experiments, will have a very bad reputation. A scientist who has earned a bad reputation will not be taken seriously by other scientists. A lab that has earned a bad reputation will not be taken seriously by scientists. And a field of study that has gotten itself a bad reputation, will also not be taken seriously.
Result. A result is simply whatever is observed when an observation is made or an experiment is performed. Ideally, results rule science because results are direct parts of our experience, and sciences primary job is to explain our experience. A theory that contradicts well-established results should be abandoned. However, a mere claim that someone has achieved a particular result is never by itself enough to overturn a theory. When a theory-contradicting result comes from a lab without a proven track record, the fact that result contradicts an established theory actually gives very good reason to think that somebody at the lab has made a mistake. Thus results that contradict well-established theories tend to be very tightly scrutinized, and are only taken seriously if they are presented together with evidence that the relevant experiments were performed with a very high standard of care.
Theory. Most philosophers of science offer very precise definitions of the word "theory." In my view, this does not fully reflect the way scientists use this word. Scientists use the word "theory" in three main ways. First, they use it as part of names for particular ideas, as in the "Theory of Relativity." Used in this way, it does not mean anything. Secondly, scientists use the word in the same way that nonscientists use it, to mean any kind of hypothesis from a wild speculation to some idea that is actually been pretty well established. Finally, they also occasionally use the word in a very precise way to denote a theory that meets the rigorous standards demanded of the kind of theories that are worth investing the resources necessary to properly test them. A scientist might claim that some idea isn't really a theory as a way of saying that he thinks it's too vague to be tested, or that there's not enough experimental evidence to justify taking it seriously, or that it is already contradicted by existing, well-established results. Thus a scientist might refer to some idea as a "non-theory" as a way of emphasizing his opinion that it is not the kind of idea that ought to be taken seriously by the scientific community.
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Copyright © 2011 by Martin C. Young