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How to Explain the Difference Between Theory, Law, and a Fact

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This article was co-authored by Bess Ruff, MA . Bess Ruff is a Geography PhD student at Florida State University. She received her MA in Environmental Science and Management from the University of California, Santa Barbara in 2016. She has conducted survey work for marine spatial planning projects in the Caribbean and provided research support as a graduate fellow for the Sustainable Fisheries Group. This article has been viewed 154,601 times.

Within scientific communities, “theory,” “law,” and “fact” are technical terms which have distinct and complex meanings. Many people who do not have a scientific background—including students in introductory science classes in high school and colleges—do not have a firm understanding of the differences between these 3 terms. Many adults are also unaware of the distinctions between these 3 terms, and can benefit from a polite, conversational explanation. This article will help you understand and explain the differences between proper scientific uses for each of the three terms.

Explaining the Difference between Scientific Theory and Law

• Laws have never been refuted (hence their relatively small number) and are not explanations; they are descriptions and are often stated through relatively simple mathematical equations.
• Scientific laws, despite their formality, can change or have exceptions as scientific understandings of phenomena evolve. [2] X Research source

• As an example, the Law of Gravity has been known in the scientific community since the late 17th century. The law describes the natural phenomenon of gravity, but does not provide an explanation as to how and why gravity functions.

• A theory builds from initial hypotheses (educated guesses) and can be revised in accordance with the development of a scientific understanding of a phenomena’s cause.
• A theory is confirmed by all available evidence such that it can be used to predict new, as yet unobserved phenomena.

• For example, the scientific Theory of Natural Selection corresponds with the Law of Evolution. [5] X Research source While the law states an observed natural phenomena (life forms develop new characteristics based on external circumstances), the theory describes how and why this happens.

Explaining the Difference between Scientific Law and Fact

• While facts can be scientifically refuted or may not be consistent across time and place, they are held as true until they have been proven wrong.

• When explaining a scientific fact, start with a point of general observation.
• For example, begin your explanation by saying something like, “it is always bright outside at noon.” This is a fact in that it describes a state of nature—however, this statement may not be true in Antarctica or Greenland, where darkness lasts throughout the day in certain seasons.
• Explain how this will lead to a revision of the scientific fact: “within certain degrees of latitude, it is always bright outside at noon.”

• Facts are less formal than laws, and are not seen as an “official” definition of a phenomenon that occurs or of the reason that something happens.
• Facts are more localized and generalize less than laws. Explain that, if the Law of Evolution describes the way that species throughout the world evolve over time, a scientific fact related to evolution (and natural selection) could be: “giraffes with long necks can reach more leaves than giraffes with short necks.”

• For example, scientific theories do not develop into scientific laws. To explain the difference, focus on this distinction: laws describe phenomena, theories explain phenomena, and facts describe observations.

Explaining Scientific Theories, Laws, and Facts in the Classroom

• A theory is worth very little if it doesn't correctly predict all known evidence.
• Theories are subject to changes as new evidence becomes available. (Most theories that you will discuss in a high school science class are well-confirmed and are unlikely to be revised in any significant sense.)

• The theory of relativity: that the laws of physics are the same for all observers
• The theory of evolution by natural selection: that the observed changes in species occur due to selection of well adapted specimens over less well adapted specimens.
• Big Bang theory: that the universe began as an infinitely small point that underwent expansion to form the universe as we know it today.

• For example, we know that the germ theory of illness is a fact because we can take bacteria from someone suffering from an illness, look at that bacteria under a microscope, and then inject that bacteria into another individual, who will then get that same illness.
• We know that the Earth is round because we can travel due west and eventually end up where we started from.

• Ancient peoples noticed peculiar points of light that “wandered” among their background. (We now know these to be the planets.)
• The planets moved through the sky because they, like the Earth, were orbiting around the sun, each at different speeds, different distances from the Sun.
• Nicolaus Copernicus is generally considered to be the first to propose this theory, and supported his theory with hard evidence, but ancient cultures stumbled upon this through speculation.
• We now consider this a fact because we have sent many craft to these planets and can predict their motions to a very high precision. Of course, our predictions come from the theory (and the laws underlying that theory).

• Newton's Law of heating and cooling: the change in temperature of two bodies in thermal contact is proportional to their difference in temperature.
• Newton's Laws of motion: statements about how large objects made of atoms behave when moving at low speeds relative to each other.
• The Laws of Thermodynamics: statements about entropy, temperature, and thermal equilibrium.
• Ohm's Law: the voltage across a purely resistive element is equal to the current through the element times its resistance.

• For example, one must infer that the derived laws actually predict the facts. Accumulating all of the previous forms of knowledge, a scientist makes a general statement to explain all the evidence.
• Other scientists reaffirm the facts and use the theory to make predictions and obtain new facts.

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• ↑ http://lifehacker.com/the-difference-between-a-fact-hypothesis-theory-and-1732904200
• ↑ http://www.livescience.com/21457-what-is-a-law-in-science-definition-of-scientific-law.html
• ↑ https://ncse.com/library-resource/definitions-fact-theory-law-scientific-work
• ↑ http://futurism.com/hypothesis-theory-or-law/
• ↑ https://pseudoastro.wordpress.com/2008/12/21/terminology-what-scientists-mean-by-fact-hypothesis-theory-and-law/

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Scientific Hypothesis, Model, Theory, and Law

Understanding the Difference Between Basic Scientific Terms

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Words have precise meanings in science. For example, "theory," "law," and "hypothesis" don't all mean the same thing. Outside of science, you might say something is "just a theory," meaning it's a supposition that may or may not be true. In science, however, a theory is an explanation that generally is accepted to be true. Here's a closer look at these important, commonly misused terms.

A hypothesis is an educated guess, based on observation. It's a prediction of cause and effect. Usually, a hypothesis can be supported or refuted through experimentation or more observation. A hypothesis can be disproven but not proven to be true.

Example: If you see no difference in the cleaning ability of various laundry detergents, you might hypothesize that cleaning effectiveness is not affected by which detergent you use. This hypothesis can be disproven if you observe a stain is removed by one detergent and not another. On the other hand, you cannot prove the hypothesis. Even if you never see a difference in the cleanliness of your clothes after trying 1,000 detergents, there might be one more you haven't tried that could be different.

Scientists often construct models to help explain complex concepts. These can be physical models like a model volcano or atom  or conceptual models like predictive weather algorithms. A model doesn't contain all the details of the real deal, but it should include observations known to be valid.

Example: The  Bohr model shows electrons orbiting the atomic nucleus, much the same way as the way planets revolve around the sun. In reality, the movement of electrons is complicated but the model makes it clear that protons and neutrons form a nucleus and electrons tend to move around outside the nucleus.

A scientific theory summarizes a hypothesis or group of hypotheses that have been supported with repeated testing. A theory is valid as long as there is no evidence to dispute it. Therefore, theories can be disproven. Basically, if evidence accumulates to support a hypothesis, then the hypothesis can become accepted as a good explanation of a phenomenon. One definition of a theory is to say that it's an accepted hypothesis.

Example: It is known that on June 30, 1908, in Tunguska, Siberia, there was an explosion equivalent to the detonation of about 15 million tons of TNT. Many hypotheses have been proposed for what caused the explosion. It was theorized that the explosion was caused by a natural extraterrestrial phenomenon , and was not caused by man. Is this theory a fact? No. The event is a recorded fact. Is this theory, generally accepted to be true, based on evidence to-date? Yes. Can this theory be shown to be false and be discarded? Yes.

A scientific law generalizes a body of observations. At the time it's made, no exceptions have been found to a law. Scientific laws explain things but they do not describe them. One way to tell a law and a theory apart is to ask if the description gives you the means to explain "why." The word "law" is used less and less in science, as many laws are only true under limited circumstances.

Example: Consider Newton's Law of Gravity . Newton could use this law to predict the behavior of a dropped object but he couldn't explain why it happened.

As you can see, there is no "proof" or absolute "truth" in science. The closest we get are facts, which are indisputable observations. Note, however, if you define proof as arriving at a logical conclusion, based on the evidence, then there is "proof" in science. Some work under the definition that to prove something implies it can never be wrong, which is different. If you're asked to define the terms hypothesis, theory, and law, keep in mind the definitions of proof and of these words can vary slightly depending on the scientific discipline. What's important is to realize they don't all mean the same thing and cannot be used interchangeably.

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The Scientific Hypothesis

The Key to Understanding How Science Works

Hypotheses, Theories, Laws (and Models)… What’s the difference?

Untold hours have been spent trying to sort out the differences between these ideas. should we bother.

Ask what the differences between these concepts are and you’re likely to encounter a raft of distinctions; typically with charts and ladders of generality leading from hypotheses to theories and, ultimately, to laws.   Countless students have been exposed to and forced to learn how the schemes are set up.  Theories are said to be well-tested hypotheses, or maybe whole collections of linked hypotheses, and laws, well, laws are at the top of the heap, the apex of science having enormous reach, quantitative predictive power, and validity.  It all seems so clear.

Yet there are many problems with the general scheme.  For one thing, it is never quite explained how a hypothesis turns into a theory or law and, consequently, the boundaries are blurry, and definitions tend vary with the speaker.  And there is no consistency in usage across fields, I’ll give some examples in a minute.  There are branches of science that have few if any theories and no laws – neuroscience comes to mind – though no one doubts that neuroscience is a bona fide science that has discovered great quantities of reliable and useful information and wide-ranging generalizations.  At the other extreme, there are sciences that spin out theories at a dizzying pace – psychology, for instance – although the permanence and indeed the veracity of psychological theories are rarely on par with those of physics or chemistry.

Some people will tell you that theories and laws are “more quantitative” than hypotheses, but the most famous theory in biology, the Theory of Evolution, which is based on concepts such as heritability, genetic variability, natural selection, etc. is not as neatly expressible in quantitative terms as is Newton’s Theory of Gravity, for example.   And what do we make of the fact that Newton’s “Law of Gravity” was superceded by Einstein’s “General Theory (not Law) of Relativity?”

What about the idea that a hypothesis is a low-level explanation that somehow transmogrifies into a theory when conditions are right?  Even this simple rule is not adhered to.  Take geology (or “geoscience” nowadays):  We have the Alvarez Hypothesis about how an asteroid slamming into the earth caused the extinction of dinosaurs and other life-forms ~66 million years ago.  The Alvarez Hypothesis explains, often in quantitative detail, many important phenomena and makes far-reaching predictions, most remarkably of a crater, which was eventually found in the Yucatan peninsula, that has the right age and size to be the site of an extinction-causing asteroid impact.  The Alvarez Hypothesis has been rigorously tested many times since it was proposed, without having been promoted to a theory. 

But perhaps the Alvarez Hypothesis is still thought to be a tentative explanation, not yet worthy of a more exalted status? It seems that the same can’t be said about the idea that the earth’s crust consists of 12 or so rigid “plates” of solid material that drift around very slowly and create geological phenomena, such as mountain ranges and earth-quakes, when they crash into each other.  This is called either the “Plate Tectonics Hypothesis” or “Plate Tectonics Theory” by different authors.  Same data, same interpretations, same significance, different names. 

And for anyone trying to make sense of the hypothesis-theory-law progression, it must be highly confusing to learn that the crowning achievement of modern physics – itself the “queen of the sciences” – is a complex, extraordinarily precise, quantitative structure is known as the Standard Model of Particle Physics, not the Standard Theory, or the Standard Law!  The Standard Model incorporates three of the four major forces of nature, describes many subatomic particles, and has successfully predicted numerous subtle properties of subatomic particles.  Does this mean that “model” now implies a large, well-worked out and self-consistent body of scientific knowledge?  Not at all; in fact, “model” and “hypothesis” are used interchangeably at the simplest levels of experimental investigation in biology, neuroscience, etc., so definition-wise, we’re back to the beginning.

The reason that the Standard Model is a model and not a theory seems basically to be the same as the reason that the Alvarez Hypothesis is a hypothesis and not a theory or that Evolution is a theory and not a law:  essentially it is a matter of convention, tradition, or convenience.  The designations, we can infer, are primarily names that lack exact substantive, generally agreed-on definitions.

So, rather than worrying about any profound distinctions between hypotheses, theories, laws (and models) it might be more helpful to look at the properties that they have in common:

1. They are all “conjectural” which, for the moment, means that they are inventions of the human mind.

2. They make specific predictions that are empirically testable, in principle.

3. They are falsifiable – if their predictions are false, they are false – though not provable, by experiment or observation. 

4.  As a consequence of point 3., hypotheses, theories, and laws are all provisional; they may be replaced as further information becomes available. 

“Hypothesis,” it seems to me, is the fundamental unit, the building block, of scientific thinking. It is the term that is most consistently used by all sciences; it is more basic than any theory; it carries the least baggage, is the least susceptible to multiple interpretations and, accordingly, is the most likely to communicate effectively.  These advantages are relative of course; as I’ll get into elsewhere, even “hypothesis” is the subject of misinterpretation. In any case, its simplicity and clarity are why this website is devoted to the Scientific Hypothesis and not the others.

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Theory vs. Hypothesis vs. Law… Explained!

Some people try to attack things like evolution by natural selection and man-made climate change by saying “Oh, that’s just a THEORY!”

Yes, they are both theories. Stop saying it like it’s a bad thing! It’s time to learn the difference between a fact, a theory, a hypothesis, and a scientific law.

Special thanks to Joe Hanson, Ph.D., for allowing us to publish his terrific videos.

It’s Okay To Be Smart is written and hosted by Joe Hanson, Ph.D. @jtotheizzoe Facebook: http://www.facebook.com/itsokaytobesmart For more awesome science, check out: http://www.itsokaytobesmart.com Produced by PBS Digital Studios: http://www.youtube.com/user/pbsdigita…

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This is the Difference Between a Hypothesis and a Theory

What to Know A hypothesis is an assumption made before any research has been done. It is formed so that it can be tested to see if it might be true. A theory is a principle formed to explain the things already shown in data. Because of the rigors of experiment and control, it is much more likely that a theory will be true than a hypothesis.

As anyone who has worked in a laboratory or out in the field can tell you, science is about process: that of observing, making inferences about those observations, and then performing tests to see if the truth value of those inferences holds up. The scientific method is designed to be a rigorous procedure for acquiring knowledge about the world around us.

In scientific reasoning, a hypothesis is constructed before any applicable research has been done. A theory, on the other hand, is supported by evidence: it's a principle formed as an attempt to explain things that have already been substantiated by data.

Toward that end, science employs a particular vocabulary for describing how ideas are proposed, tested, and supported or disproven. And that's where we see the difference between a hypothesis and a theory .

A hypothesis is an assumption, something proposed for the sake of argument so that it can be tested to see if it might be true.

In the scientific method, the hypothesis is constructed before any applicable research has been done, apart from a basic background review. You ask a question, read up on what has been studied before, and then form a hypothesis.

What is a Hypothesis?

A hypothesis is usually tentative, an assumption or suggestion made strictly for the objective of being tested.

When a character which has been lost in a breed, reappears after a great number of generations, the most probable hypothesis is, not that the offspring suddenly takes after an ancestor some hundred generations distant, but that in each successive generation there has been a tendency to reproduce the character in question, which at last, under unknown favourable conditions, gains an ascendancy. Charles Darwin, On the Origin of Species , 1859 According to one widely reported hypothesis , cell-phone transmissions were disrupting the bees' navigational abilities. (Few experts took the cell-phone conjecture seriously; as one scientist said to me, "If that were the case, Dave Hackenberg's hives would have been dead a long time ago.") Elizabeth Kolbert, The New Yorker , 6 Aug. 2007

What is a Theory?

A theory , in contrast, is a principle that has been formed as an attempt to explain things that have already been substantiated by data. It is used in the names of a number of principles accepted in the scientific community, such as the Big Bang Theory . Because of the rigors of experimentation and control, its likelihood as truth is much higher than that of a hypothesis.

It is evident, on our theory , that coasts merely fringed by reefs cannot have subsided to any perceptible amount; and therefore they must, since the growth of their corals, either have remained stationary or have been upheaved. Now, it is remarkable how generally it can be shown, by the presence of upraised organic remains, that the fringed islands have been elevated: and so far, this is indirect evidence in favour of our theory . Charles Darwin, The Voyage of the Beagle , 1839 An example of a fundamental principle in physics, first proposed by Galileo in 1632 and extended by Einstein in 1905, is the following: All observers traveling at constant velocity relative to one another, should witness identical laws of nature. From this principle, Einstein derived his theory of special relativity. Alan Lightman, Harper's , December 2011

Non-Scientific Use

In non-scientific use, however, hypothesis and theory are often used interchangeably to mean simply an idea, speculation, or hunch (though theory is more common in this regard):

The theory of the teacher with all these immigrant kids was that if you spoke English loudly enough they would eventually understand. E. L. Doctorow, Loon Lake , 1979 Chicago is famous for asking questions for which there can be no boilerplate answers. Example: given the probability that the federal tax code, nondairy creamer, Dennis Rodman and the art of mime all came from outer space, name something else that has extraterrestrial origins and defend your hypothesis . John McCormick, Newsweek , 5 Apr. 1999 In his mind's eye, Miller saw his case suddenly taking form: Richard Bailey had Helen Brach killed because she was threatening to sue him over the horses she had purchased. It was, he realized, only a theory , but it was one he felt certain he could, in time, prove. Full of urgency, a man with a mission now that he had a hypothesis to guide him, he issued new orders to his troops: Find out everything you can about Richard Bailey and his crowd. Howard Blum, Vanity Fair , January 1995

And sometimes one term is used as a genus, or a means for defining the other:

Laplace's popular version of his astronomy, the Système du monde , was famous for introducing what came to be known as the nebular hypothesis , the theory that the solar system was formed by the condensation, through gradual cooling, of the gaseous atmosphere (the nebulae) surrounding the sun. Louis Menand, The Metaphysical Club , 2001 Researchers use this information to support the gateway drug theory — the hypothesis that using one intoxicating substance leads to future use of another. Jordy Byrd, The Pacific Northwest Inlander , 6 May 2015 Fox, the business and economics columnist for Time magazine, tells the story of the professors who enabled those abuses under the banner of the financial theory known as the efficient market hypothesis . Paul Krugman, The New York Times Book Review , 9 Aug. 2009

Incorrect Interpretations of "Theory"

Since this casual use does away with the distinctions upheld by the scientific community, hypothesis and theory are prone to being wrongly interpreted even when they are encountered in scientific contexts—or at least, contexts that allude to scientific study without making the critical distinction that scientists employ when weighing hypotheses and theories.

The most common occurrence is when theory is interpreted—and sometimes even gleefully seized upon—to mean something having less truth value than other scientific principles. (The word law applies to principles so firmly established that they are almost never questioned, such as the law of gravity.)

This mistake is one of projection: since we use theory in general use to mean something lightly speculated, then it's implied that scientists must be talking about the same level of uncertainty when they use theory to refer to their well-tested and reasoned principles.

The distinction has come to the forefront particularly on occasions when the content of science curricula in schools has been challenged—notably, when a school board in Georgia put stickers on textbooks stating that evolution was "a theory, not a fact, regarding the origin of living things." As Kenneth R. Miller, a cell biologist at Brown University, has said , a theory "doesn’t mean a hunch or a guess. A theory is a system of explanations that ties together a whole bunch of facts. It not only explains those facts, but predicts what you ought to find from other observations and experiments.”

While theories are never completely infallible, they form the basis of scientific reasoning because, as Miller said "to the best of our ability, we’ve tested them, and they’ve held up."

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  Learning Objectives

• Describe the difference between hypothesis and theory as scientific terms.
• Describe the difference between a theory and scientific law.

Although many have taken science classes throughout the course of their studies, people often have incorrect or misleading ideas about some of the most important and basic principles in science. Most students have heard of hypotheses, theories, and laws, but what do these terms really mean? Prior to reading this section, consider what you have learned about these terms before. What do these terms mean to you? What do you read that contradicts or supports what you thought?

What is a Fact?

A fact is a basic statement established by experiment or observation. All facts are true under the specific conditions of the observation.

What is a Hypothesis?

One of the most common terms used in science classes is a "hypothesis". The word can have many different definitions, depending on the context in which it is being used:

• An educated guess: a scientific hypothesis provides a suggested solution based on evidence.
• Prediction: if you have ever carried out a science experiment, you probably made this type of hypothesis when you predicted the outcome of your experiment.
• Tentative or proposed explanation: hypotheses can be suggestions about why something is observed. In order for it to be scientific, however, a scientist must be able to test the explanation to see if it works and if it is able to correctly predict what will happen in a situation. For example, "if my hypothesis is correct, we should see ___ result when we perform ___ test."

A hypothesis is very tentative; it can be easily changed.

What is a Theory?

The United States National Academy of Sciences describes what a theory is as follows:

"Some scientific explanations are so well established that no new evidence is likely to alter them. The explanation becomes a scientific theory. In everyday language a theory means a hunch or speculation. Not so in science. In science, the word theory refers to a comprehensive explanation of an important feature of nature supported by facts gathered over time. Theories also allow scientists to make predictions about as yet unobserved phenomena."

"A scientific theory is a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experimentation. Such fact-supported theories are not "guesses" but reliable accounts of the real world. The theory of biological evolution is more than "just a theory." It is as factual an explanation of the universe as the atomic theory of matter (stating that everything is made of atoms) or the germ theory of disease (which states that many diseases are caused by germs). Our understanding of gravity is still a work in progress. But the phenomenon of gravity, like evolution, is an accepted fact.

Note some key features of theories that are important to understand from this description:

• Theories are explanations of natural phenomena. They aren't predictions (although we may use theories to make predictions). They are explanations as to why we observe something.
• Theories aren't likely to change. They have a large amount of support and are able to satisfactorily explain numerous observations. Theories can, indeed, be facts. Theories can change, but it is a long and difficult process. In order for a theory to change, there must be many observations or pieces of evidence that the theory cannot explain.
• Theories are not guesses. The phrase "just a theory" has no room in science. To be a scientific theory carries a lot of weight; it is not just one person's idea about something

Theories aren't likely to change.

What is a Law?

Scientific laws are similar to scientific theories in that they are principles that can be used to predict the behavior of the natural world. Both scientific laws and scientific theories are typically well-supported by observations and/or experimental evidence. Usually scientific laws refer to rules for how nature will behave under certain conditions, frequently written as an equation. Scientific theories are more overarching explanations of how nature works and why it exhibits certain characteristics. As a comparison, theories explain why we observe what we do and laws describe what happens.

For example, around the year 1800, Jacques Charles and other scientists were working with gases to, among other reasons, improve the design of the hot air balloon. These scientists found, after many, many tests, that certain patterns existed in the observations on gas behavior. If the temperature of the gas is increased, the volume of the gas increased. This is known as a natural law. A law is a relationship that exists between variables in a group of data. Laws describe the patterns we see in large amounts of data, but do not describe why the patterns exist.

What is a Belief?

A belief is a statement that is not scientifically provable. Beliefs may or may not be incorrect; they just are outside the realm of science to explore.

Laws vs. Theories

A common misconception is that scientific theories are rudimentary ideas that will eventually graduate into scientific laws when enough data and evidence has accumulated. A theory does not change into a scientific law with the accumulation of new or better evidence. Remember, theories are explanations and laws are patterns we see in large amounts of data, frequently written as an equation. A theory will always remain a theory; a law will always remain a law.

Video \(\PageIndex{1}\): What’s the difference between a scientific law and theory?

• A hypothesis is a tentative explanation that can be tested by further investigation.
• A theory is a well-supported explanation of observations.
• A scientific law is a statement that summarizes the relationship between variables.
• An experiment is a controlled method of testing a hypothesis.

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Marisa Alviar-Agnew  ( Sacramento City College )

Henry Agnew (UC Davis)

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When Does a Theory Become a Fact?

If you want the short answer… You’re asking the wrong question: theories never become facts! Instead, scientific theories are created from large collections of facts. Theories such as gravity, natural selection, evolution, and global warming aren’t random guesses or personal opinions. They’re time-tested explanations for why we observe the things we do.

Building a House

Much like some houses are made of many bricks, theories are made from many facts. Theories are very strong scientific ideas, as they are based on so much information and so many different observations. Image by mattinbgn.

Setting another brick into the wall, you wipe sweat off your forehead. As a master bricklayer, you've been building houses since you were young, but this will be your finest work yet. In fact, the home owner is visiting the construction site to see how your work is going.

She looks disappointed with her hands on her hips. "Is this it?" she says complaining. "When is it going to become a brick?"

You start to become slightly annoyed: the house, though not yet finished, is already beautiful. "What do you mean?" you ask. "The house is obviously being made from brick." You show her the brick in your hand.

"No, no! When will my house finally transform into a single, solid brick?" she yells, stomping her foot. "People said that if anyone could build my house perfectly, it would be you. Now that the building is almost done, why isn't my home one big brick yet?!"

What? You sit back, confused. That isn't how bricklaying works, that's not how building a home works either! Good houses are made of bricks, they don't become a brick.

When Do Theories Become Facts?

The same thing is true of scientific theories: theories are made from facts, theories never become facts. Facts are the small, detailed observations that we make about the world. For example, “when I let go of this apple, it falls to the ground” would be a fact. Only when scientists start gathering many of these facts together can theories be built.

What is a Theory?

When this apple detaches from the tree, do you expect it to go up into the sky? Or to fall to the ground? The scientific theory of gravity lets us expect that it will fall to the ground. Image by Michael Palmer via photorasa.com.

Theories are our best explanations for why all these observations (the facts) are happening. Why does water run downhill? Why do expensive vases fall off tables? Why does the moon revolve around the Earth? The theory of gravity explains all these different events. It’s such a powerful theory!

Updating Scientific Theories

However, houses built on bad foundations often need to be taken down and rebuilt. Scientific theories also sometimes need to be updated or changed. For example, biologists used to think that plants and animals couldn’t change over time. But people began to discover fossils, and ancient dinosaurs don’t look like anything alive today. This new fact wouldn’t fit into the old theory, so people began searching for a better theory that could explain all the facts.

Our current theory, called the theory of natural selection, now can explain SO many facts: everything from how bacteria become immune to antibiotics and why some animals are so beautifully colorful to why bat wings resemble human arms and chickens look like tiny velociraptors. No wonder it’s considered one of the greatest theories in biology.

Theories like gravity and natural selection have been rebuilt several times since they were first created. But that doesn’t mean we shouldn’t trust them. Theories are the best explanations we have at the moment, they aren’t just hunches or opinions. They are based on a ton of data and observation. If you uncover new facts or devise a theory that explains more facts than the old one, share it! That’s how science works.

Additional images via Wikimedia Commons.

Have a different answer or more to add to this one? Send it to us .

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Bibliographic details:.

• Article: When Does a Theory Become a Fact?
• Author(s): Dr. Biology
• Publisher: Arizona State University School of Life Sciences Ask A Biologist
• Site name: ASU - Ask A Biologist
• Date published: February 13, 2018
• Date accessed: May 8, 2024
• Link: https://askabiologist.asu.edu/questions/theory-versus-fact

Dr. Biology. (2018, February 13). When Does a Theory Become a Fact?. ASU - Ask A Biologist. Retrieved May 8, 2024 from https://askabiologist.asu.edu/questions/theory-versus-fact

Chicago Manual of Style

Dr. Biology. "When Does a Theory Become a Fact?". ASU - Ask A Biologist. 13 February, 2018. https://askabiologist.asu.edu/questions/theory-versus-fact

MLA 2017 Style

Dr. Biology. "When Does a Theory Become a Fact?". ASU - Ask A Biologist. 13 Feb 2018. ASU - Ask A Biologist, Web. 8 May 2024. https://askabiologist.asu.edu/questions/theory-versus-fact

Gravity is such a strong scientific theory, it explains many of our observations, from dropped apples falling from trees, to the moon affecting our ocean tides.

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Fact vs. Theory Vs. Hypothesis Vs. Law

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Space math ii – problem 23, theories, hypothesis, laws, facts & beliefs.

Grade Levels

Grades 5-8, Grades 9-12

Space Science

Lesson Plans / Activities

In this lesson, students will distinguish the difference between the terms theory, hypothesis, fact, law and belief. Student and teacher pages are included. Problem 23, Theories, Hypothesis, Laws, Facts & Beliefs  [136KB PDF file] This activity is part of Space Math II .