scientific law vs theory vs hypothesis

The Difference Between a Scientific Hypothesis, Theory, and Law

Let’s address some common misconceptions about the basic concepts of science..

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Nobody is exempt from misunderstanding scientific concepts and/or applying them incorrectly. Statistics from the National Science Board show that Americans scored an average of 5.6 over 9 true-or-false and multiple-choice science-related questions in 2016. Because of the low number of questions, the study is better at differentiating low and medium levels of knowledge than those with higher levels of knowledge. However, the r esults weren’t much different in previous studies, suggesting that Americans generally have had the same basic levels of science literacy since the beginning of the century.

In this context, we’d like to clear up and emphasize the distinctions between scientific hypothesis, theory, and law, and why you shouldn’t use these terms interchangeably. 

Hypothesis: the core of the scientific method

The scientific method is an empirical procedure that consists of systematic observation, measurement, and experiment, and the formulation, testing, and modification of hypotheses.  It’s a process that’s meant to ensure that the collection of evidence, results, and conclusions are not biased by subjective views and can be repeated consistently by others.

Although there might be variations due to the requirements of each branch of science, the steps of the scientific method are more or less the same.

The scientific method often starts with an observation or asking a question, such as the observation of certain natural phenomena or asking why a particular phenomenon exists or why it occurs in a particular way.

Observation motivates a question and the question motivates an initial hypothesis. The initial hypothesis is a conjecture that works as a temporary answer to the question, formulated via induction on the basis of what’s been observed. 

To better understand this, let’s take the case of physician Ignaz Semmelweis. In mid-19th Century, he worked at the First Obstetrical Clinic of Vienna General Hospital, where 10% of women in labor died due to puerperal fever. Meanwhile, the Second Obstetrical Clinic had an average maternal mortality rate of 4%. Semmelweis asked himself why there was a discrepancy in mortality rates between the two clinics. 

  Through observation, he determined and eliminated a number of differences between the two clinics. Because the techniques, climate, etc., were pretty much the same in both places, he ended up concluding that it had something to do with the health workers who helped women in labor. In the Second Clinic, births were attended only by midwives, while in the First Clinic, births were often attended by medical students who also performed autopsies. Semmelweis came up with the hypothesis that medical students spread “cadaveric contamination” in the First Clinic and this was causing the puerperal fever. 

He ordered all medical students to wash their hands with chlorinated lime after performing autopsies, and the mortality rate in the First Clinic decreased by 90%. 

Semmelweis is considered one of the early pioneers of antiseptic procedures .

This story doesn’t only demonstrate the importance of the initial hypothesis, but also the importance of testing it through experiments, field studies, observational studies, or other experimental work. In fact, this is the next step in the scientific method, and it’s essential to draw conclusions. 

Theory: the Why and How of natural phenomena

A scientific theory can be defined as a series of repeatedly tested and verified hypotheses and concepts. Scientific theories are based on hypotheses that are constructed and tested using the scientific method, and which may bring together a number of facts and hypotheses.

A theory synthesizes the discovered facts about phenomena in a way that allows scientists to formulate predictions and develop new hypotheses. For example, we can hypothesize the reasons why an animal looks or acts in a certain way based on Darwin’s theory of evolution. Or we can predict that antiseptics will prevent diseases if we take into account the germ theory . The confirmation of these hypotheses and predictions reinforces the theories they’re based on.

For a theory to be valid, it must be testable, hold true for general tendencies and not only to specific cases, and it must not contradict verified pre-existing theories and laws. 

Law: the patterns of nature

In general, a scientific law is  the description of an observed phenomenon. It doesn’t explain why the phenomenon exists or what causes it. Laws can be thought of as the starting place, the point from where questions like “why” and “how” are asked.

For example, we can throw a ball under certain conditions and predict its movement by taking into account Newton’s laws of motion . These laws do not only involve several statements but also equations and formulas.  However, while Newton’s laws might mathematically describe how two bodies interact with each other, they don’t explain what gravity is, or how it works. 

Contrary to popular belief, scientific laws are not immutable. They must be universal and absolute to qualify as laws, but they can be corrected or extended to make them more accurate. For example, Euler’s laws of motion amplify Newton’s laws of motion to rigid bodies ,  and how gravity works was only understood in more detail when Albert Einstein developed the Theory of Relativity.

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Common misconceptions about scientific laws, theories, and hypotheses.

• There is a hierarchy between laws, theories, and hypotheses: Some people think that hypotheses “evolve” into theories and theories “evolve” into laws. While a number of verified hypotheses can be included in a theory, it’s never only one. And theories do not turn into scientific laws because they’re simply different concepts. As stated above, theories explain phenomena and laws reflect patterns. 

You don’t have to be a scientist to understand scientific terms. In the information era, scientific concepts surround us, but even if access to knowledge is easier than ever nowadays, there are still a lot of misconceptions around. It’s always better to be on the safe side and getting your facts straight. 

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Maia Mulko Maia is a bilingual freelance writer and copywriter with a degree in Communication Studies. Although she has written for several different niches and publications, she spent most of her career writing for Descentralizar, a Spanish publication that investigates stories at the intersection of technology and society. She has also written scripts for a wide variety of science-related YouTube channels. Maia is particularly interested in space, AI, mobility, gaming, robotics, and assistive technologies. 

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Hypothesis, Model, Theory, and Law

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In common usage, the words hypothesis, model, theory, and law have different interpretations and are at times used without precision, but in science they have very exact meanings.

Perhaps the most difficult and intriguing step is the development of a specific, testable hypothesis. A useful hypothesis enables predictions by applying deductive reasoning, often in the form of mathematical analysis. It is a limited statement regarding the cause and effect in a specific situation, which can be tested by experimentation and observation or by statistical analysis of the probabilities from the data obtained. The outcome of the test hypothesis should be currently unknown, so that the results can provide useful data regarding the validity of the hypothesis.

Sometimes a hypothesis is developed that must wait for new knowledge or technology to be testable. The concept of atoms was proposed by the ancient Greeks , who had no means of testing it. Centuries later, when more knowledge became available, the hypothesis gained support and was eventually accepted by the scientific community, though it has had to be amended many times over the year. Atoms are not indivisible, as the Greeks supposed.

A model is used for situations when it is known that the hypothesis has a limitation on its validity. The Bohr model of the atom , for example, depicts electrons circling the atomic nucleus in a fashion similar to planets in the solar system. This model is useful in determining the energies of the quantum states of the electron in the simple hydrogen atom, but it is by no means represents the true nature of the atom. Scientists (and science students) often use such idealized models  to get an initial grasp on analyzing complex situations.

Theory and Law

A scientific theory or law represents a hypothesis (or group of related hypotheses) which has been confirmed through repeated testing, almost always conducted over a span of many years. Generally, a theory is an explanation for a set of related phenomena, like the theory of evolution or the big bang theory . 

The word "law" is often invoked in reference to a specific mathematical equation that relates the different elements within a theory. Pascal's Law refers an equation that describes differences in pressure based on height. In the overall theory of universal gravitation developed by Sir Isaac Newton , the key equation that describes the gravitational attraction between two objects is called the law of gravity .

These days, physicists rarely apply the word "law" to their ideas. In part, this is because so many of the previous "laws of nature" were found to be not so much laws as guidelines, that work well within certain parameters but not within others.

Scientific Paradigms

Once a scientific theory is established, it is very hard to get the scientific community to discard it. In physics, the concept of ether as a medium for light wave transmission ran into serious opposition in the late 1800s, but it was not disregarded until the early 1900s, when Albert Einstein proposed alternate explanations for the wave nature of light that did not rely upon a medium for transmission.

The science philosopher Thomas Kuhn developed the term scientific paradigm to explain the working set of theories under which science operates. He did extensive work on the scientific revolutions that take place when one paradigm is overturned in favor of a new set of theories. His work suggests that the very nature of science changes when these paradigms are significantly different. The nature of physics prior to relativity and quantum mechanics is fundamentally different from that after their discovery, just as biology prior to Darwin’s Theory of Evolution is fundamentally different from the biology that followed it. The very nature of the inquiry changes.

One consequence of the scientific method is to try to maintain consistency in the inquiry when these revolutions occur and to avoid attempts to overthrow existing paradigms on ideological grounds.

Occam’s Razor

One principle of note in regards to the scientific method is Occam’s Razor (alternately spelled Ockham's Razor), which is named after the 14th century English logician and Franciscan friar William of Ockham. Occam did not create the concept—the work of Thomas Aquinas and even Aristotle referred to some form of it. The name was first attributed to him (to our knowledge) in the 1800s, indicating that he must have espoused the philosophy enough that his name became associated with it.

The Razor is often stated in Latin as:

entia non sunt multiplicanda praeter necessitatem

or, translated to English:

entities should not be multiplied beyond necessity

Occam's Razor indicates that the most simple explanation that fits the available data is the one which is preferable. Assuming that two hypotheses presented have equal predictive power, the one which makes the fewest assumptions and hypothetical entities takes precedence. This appeal to simplicity has been adopted by most of science, and is invoked in this popular quote by Albert Einstein:

Everything should be made as simple as possible, but not simpler.

It is significant to note that Occam's Razor does not prove that the simpler hypothesis is, indeed, the true explanation of how nature behaves. Scientific principles should be as simple as possible, but that's no proof that nature itself is simple.

However, it is generally the case that when a more complex system is at work there is some element of the evidence which doesn't fit the simpler hypothesis, so Occam's Razor is rarely wrong as it deals only with hypotheses of purely equal predictive power. The predictive power is more important than the simplicity.

Edited by Anne Marie Helmenstine, Ph.D.

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Scientific Law vs. Theory: How Are They Different?

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When reviewing scientific research or information about the world around you, it's important to know how to separate scientific law from theory . These closely related terms are similar yet not the same. Discover that both are equally important components of the scientific method as you explore scientific law vs. theory.

Scientific Law vs. Theory: What Is the Difference?

The most basic difference between scientific law and scientific theory is as simple as the difference between "what" and "why."

What Is Scientific Law?

A scientific law focuses solely on describing what . A scientific law provides a description of a directly observable phenomenon. It describes what will or is expected to happen in a certain set of circumstances.

What Is Scientific Theory?

What is a scientific theory explores why . A theory is about underlying causes, seeking to explain the reason the phenomenon occurs. The focus of a theory is to provide a logical explanation for things that occur in nature. There can be more than one theory about the same phenomenon.

Can a Theory Become a Law?

The idea that a scientific theory could become a law once proven to be a fact is a common misconception. In science, laws and theories are two different types of scientific facts. A scientific theory cannot become a scientific fact, just as no explanation (theory) could ever become a description (law). Additional data could be discovered that could cause a law or theory to change or be disproven, but one will never become the other.

Quick Tip: Remembering Law vs. Theory

To easily tell the difference, remember that laws describe "what" and theories explain "why." Consider using a mnemonic device such as " l ook d own t owards E arth" to help you remember the difference.

• l aws - l ook
• d escribe - d own
• t heories - t owards
• e xplain - E arth

Scientific Law Examples

Scientific laws are formed through repeated observations or experiments. They begin with a scientific hypothesis and are developed via scientific study that provides empirical information and data analysis. There are many examples of scientific laws.

• law of conservation of energy - The law of conservation of energy states that energy can't be created or destroyed. It can only be changed into a different form or transferred to another object.
• law of cosmic expansion - Edwin Powell Hubble is behind the law of cosmic expansion. Often referred to simply as Hubble's Law , it states that galaxies move in a direction away from one another. This motion occurs at a fixed velocity in proportion to distance.
• Newton's first law of motion indicates that an object will stay in its current state (rest or motion) unless affected by a force.
• The second law of motion says that when a force acts on an object, its change in velocity depends on its mass.
• The third law of motion states that every action produces a reaction that is equivalent and opposite.
• law of orbits - Johannes Kepler's law of orbits indicates that planets move around the sun in an elliptical manner. This means that the planets follow a set, oval-shaped pattern around the sun.
• law of universal gravitation - Newton's law of universal gravitation indicates that everything in the universe that has mass is attracted toward the center of the Earth. This attraction is called gravity.

Notice that each of the above laws describes a phenomenon, but does not seek to provide a reason that the phenomenon occurs. Providing an explanation of why is the job of theory, not law.

Scientific Theory Examples

Scientific theories are formed via the scientific method . As with laws, every theory begins with a scientific hypothesis , which must be carefully researched. If there is sufficient evidence to support that the hypothesis provides a valid explanation for a phenomenon, the hypothesis can become a theory.

• atomic theory - Atomic theory indicates that all matter is made up of atoms, which are microscopic particles that cannot be divided, created or destroyed. It explains why substances composed of one element (such as pure gold) are different from items that consist of multiple elements (such as a metal alloy).
• big bang theory - The big bang theory suggests that the universe began many billions of years in the past as a result of an expansion event of great magnitude. This universal expansion is continuing on an ongoing basis.
• germ theory of disease - The germ theory of disease posits that many diseases are caused by germs. These pathogens are tiny microorganisms that find their way into the body.
• plate tectonic theory - The theory of plate tectonics indicates that the Earth's outer layer is divided into a few dozen plates rather than being a solid surface. These plates make up the solid crust of the planet. They move relative to one another, above the Earth's mantle, which lies between its crust and the core.
• theory of evolution - The theory of evolution suggests that all species are related to each other and change (evolve) over time. This notion was first posited by Charles Darwin in the mid 19th century. His early theory focused on the role of natural selection in evolution.

Notice that each of the above theories provide an explanation for a phenomenon that has been observed. Some are universally accepted, while others are under debate. They are not, however, just guesses or thoughts about possible causes for events. Instead, they have been thoroughly studied using the scientific method.

Build a Strong Vocabulary of Science Terms

Now that you know the difference between a theory vs. scientific law, you are on your way to developing a strong vocabulary of science-related terminology. Continue exploring key scientific words by reviewing this collection of science terms made simple . Everything you learn will help you be better able to understand and discuss scientific concepts.

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Scientific Theory Definition and Examples

A scientific theory is a well-established explanation of some aspect of the natural world. Theories come from scientific data and multiple experiments. While it is not possible to prove a theory, a single contrary result using the scientific method can disprove it. In other words, a theory is testable and falsifiable.

Examples of Scientific Theories

There are many scientific theory in different disciplines:

• Astronomy : theory of stellar nucleosynthesis , theory of stellar evolution
• Biology : cell theory, theory of evolution, germ theory, dual inheritance theory
• Chemistry : atomic theory, Bronsted Lowry acid-base theory , kinetic molecular theory of gases , Lewis acid-base theory , molecular theory, valence bond theory
• Geology : climate change theory, plate tectonics theory
• Physics : Big Bang theory, perturbation theory, theory of relativity, quantum field theory

Criteria for a Theory

In order for an explanation of the natural world to be a theory, it meets certain criteria:

• A theory is falsifiable. At some point, a theory withstands testing and experimentation using the scientific method.
• A theory is supported by lots of independent evidence.
• A theory explains existing experimental results and predicts outcomes of new experiments at least as well as other theories.

Difference Between a Scientific Theory and Theory

Usually, a scientific theory is just called a theory. However, a theory in science means something different from the way most people use the word. For example, if frogs rain down from the sky, a person might observe the frogs and say, “I have a theory about why that happened.” While that theory might be an explanation, it is not based on multiple observations and experiments. It might not be testable and falsifiable. It’s not a scientific theory (although it could eventually become one).

Value of Disproven Theories

Even though some theories are incorrect, they often retain value.

For example, Arrhenius acid-base theory does not explain the behavior of chemicals lacking hydrogen that behave as acids. The Bronsted Lowry and Lewis theories do a better job of explaining this behavior. Yet, the Arrhenius theory predicts the behavior of most acids and is easier for people to understand.

Another example is the theory of Newtonian mechanics. The theory of relativity is much more inclusive than Newtonian mechanics, which breaks down in certain frames of reference or at speeds close to the speed of light . But, Newtonian mechanics is much simpler to understand and its equations apply to everyday behavior.

Difference Between a Scientific Theory and a Scientific Law

The scientific method leads to the formulation of both scientific theories and laws . Both theories and laws are falsifiable. Both theories and laws help with making predictions about the natural world. However, there is a key difference.

A theory explains why or how something works, while a law describes what happens without explaining it. Often, you see laws written in the form of equations or formulas.

Theories and laws are related, but theories never become laws or vice versa.

Theory vs Hypothesis

A hypothesis is a proposition that is tested via an experiment. A theory results from many, many tested hypotheses.

Theory vs Fact

Theories depend on facts, but the two words mean different things. A fact is an irrefutable piece of evidence or data. Facts never change. A theory, on the other hand, may be modified or disproven.

Difference Between a Theory and a Model

Both theories and models allow a scientist to form a hypothesis and make predictions about future outcomes. However, a theory both describes and explains, while a model only describes. For example, a model of the solar system shows the arrangement of planets and asteroids in a plane around the Sun, but it does not explain how or why they got into their positions.

• Frigg, Roman (2006). “ Scientific Representation and the Semantic View of Theories .”  Theoria . 55 (2): 183–206. 
• Halvorson, Hans (2012). “What Scientific Theories Could Not Be.”  Philosophy of Science . 79 (2): 183–206. doi: 10.1086/664745
• McComas, William F. (December 30, 2013).  The Language of Science Education: An Expanded Glossary of Key Terms and Concepts in Science Teaching and Learning . Springer Science & Business Media. ISBN 978-94-6209-497-0.
• National Academy of Sciences (US) (1999). Science and Creationism: A View from the National Academy of Sciences (2nd ed.). National Academies Press. doi: 10.17226/6024  ISBN 978-0-309-06406-4. 
• Suppe, Frederick (1998). “Understanding Scientific Theories: An Assessment of Developments, 1969–1998.”  Philosophy of Science . 67: S102–S115. doi: 10.1086/392812

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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.

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Facts, Hypotheses, Theories, and Laws: What’s the Difference?

Perhaps no topic in science garners more confusion among the general public than the distinction between a theory and a hypothesis. This confusion is highly regrettable, because the distinction is one of the most fundamental concepts in science, and a lack of understanding about these definitions leads to a great deal of confusion. Therefore, I will attempt to alleviate the maelstrom of nonsense and bewilderment surrounding these terms and endow my readers with a proper understanding of their meanings.

Let’s begin with the definition of “fact.” This is actually the hardest of these terms to define. Basically, it’s just something that has been observed and tested and shown to be true. Importantly, facts generally don’t offer explanations, they are just how things are. If we want an explanation of why things are the way that they are, we have to turn to hypotheses and theories.

This is where most people mess up. In the common vernacular, a theory is “an educated guess,” but in science, an educated guess is a hypothesis, not a theory. Further, when I ask my students to define a theory, I often get answers like, “something that we think is true, but haven’t tested,” or even worse, “an idea that can’t be tested.” Television further reinforces these misconceptions, by constantly misusing “theory.” In virtually every episode of shows like “House M.D.” and “Bones” someone says, “my theory is that…” The reality is that in science, a theory is much, much more than just an educated guess. In fact, theories are the highest form of scientific certainty. They have been rigorously test over and over again and they have been shown to have a very high predictive power. In other words, they consistently and accurately predict the outcomes of experiments.

For example, suppose that I am currently holding a pen in the air. What will happen if I release my hand? Hopefully, you all thought, “the pen will drop,” but why did you make that prediction? In fact, you were simply applying the theory of universal gravity. This is the theory that all bodies produce gravity and are acted upon by the gravity of other bodies. Also note that by dropping the pen, I would demonstrate the fact of gravity. In other words, it is a fact that gravity took hold of the pen and caused it to fall. To explain that fact, we apply the theory of universal gravity which tells us that the earth produces a field of gravity which attracted the pen (in reality of course the theory also tells us the exact rate of acceleration of the pen). So you see, we use theories to explain facts. As such, they actually supersede facts in their certainty and importance.

So if a theory is an explanatory framework with a high predictive power, what then is a hypothesis? A hypothesis is basically an educated guess. It’s a possible explanation that hasn’t yet achieved the certainty of a theory. There may be experimental support behind it, but not on the level that a theory has. It is, however, entirely possible for a hypothesis to become a theory once enough evidence has been accumulated.

At this point, you all are probably wondering what a law is, because my explanation of a theory probably sounds a lot like what you expected for the definition of a law, and there is a very good reason for that. Namely, the terms “theory” and “law” are essentially synonymous. “Law” is an older term that we don’t use as much anymore, but it has the same level of certainty as a theory. For example, the law of universal gravity and the theory of universal gravity are synonyms. They mean the exact same thing and either one is equally correct.

So why does this matter? Other than scientists, who really cares if people say “theory” when they mean “hypothesis?” The reality is that this confusion leads to a great many misunderstandings and faulty arguments. The most prominent example is the argument that, “evolution shouldn’t be being taught as a fact because it’s just a theory.” As we’ve just seen, theories are actually our highest form of scientific certainty, and they actually supersede facts because they explain the facts. So saying, “evolution is just a theory” is no different from saying, “gravity is just a law.” Theories make up the cornerstones of every branch of science. For example, the germ theory of disease states that viruses, bacteria, etc. make us sick, cell theory states that all living things are made of cells, atomic theory states that all matter is made of atoms, etc. Obviously, there aren’t any outcries about people teaching the notion that matter is made of elements as a fact, even though its “just a theory.” Further, all theories contain a factual component because they explain the facts (I illustrated this previously with my gravity example). So, when it comes to evolution, the idea that life on this planet has slowly changed over millions of years is considered scientific fact. We have ample evidence for it from fossils, genetics, etc. The theory is the “theory of evolution by natural selection” which states that natural selection has been the primary driver of evolution. So the core thing that most creationists oppose (i.e., the idea that life has evolved) is not a theory, it is a fact. The theory of natural selection simply explains what caused those changes to take place.

In summary, a fact is a tested and confirmed observation or measurement. A hypothesis is basically an educated guess, and the terms theory and law synonymously describe a thoroughly tested explanatory framework which has a high predictive power and explains facts.

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Spoiler Alert: A Scientific Hypothesis, Theory, and Law Are Not the Same Thing

You need to understand this to understand science..

Defining Science

When reading scientific articles (and many other articles on Futurism ), you'll likely to come across the terms "hypothesis," "theory," " and "law." In the scientific community, these words have very specific definitions; however, once you get outside the scientific community, these definitions can be unclear, as the same terms are used differently in a colloquial context.

This is a bit of a problem.

People frequently try to discredit Charles Darwin's greatest work by saying that "evolution is just a hypothesis." — No, it's not.

People frequently try to elevate the (totally absurd and non-scientific) simulation hypothesis by calling it "simulation theory."  — Saying that reality might actually just be a giant computer simulation is definitely  not  a scientific theory.

So, what does it mean when you call something a hypothesis, a theory, or a law?

A hypothesis is a reasonable guess based on something that you observe in the natural world. And while hypotheses are proven and disproven all of the time, the fact that they are disproven shouldn't be read as a statement against them. In truth, hypotheses are the foundation of the scientific method.

As a refresher, here's how the scientific method works: After making an observation and formulating a question, a scientist must create a hypothesis — a potential answer to the question. They then make a testable prediction, test this prediction (over and over and over), and analyze the data. Once this is done, they can then state whether or not their hypothesis was correct.

Even then, a hypothesis needs to be tested and retested many times by many different experts before it is generally accepted in the scientific community as being true.

Example: You observe that, upon waking up each morning, your trash is overturned and junk is spread around the yard. You form a hypothesis that raccoons are responsible. Through testing — maybe you stay up all night to watch for raccoons — the results will either support or refute your hypothesis.

The above example illustrates why the simulation hypothesis is  not  science (and definitely not a scientific theory) .  There's nothing to observe. There's nothing to test. Like the idea of God or an immortal soul, it is beyond the natural world and, so, beyond the realm of science.

A scientific theory consists of one or more hypotheses that have been supported by repeated testing. Theories are one of the pinnacles of science and are widely accepted in the scientific community as being true. A theory must never be shown to be wrong; if it is, the theory is disproven. Theories can also evolve . This doesn't mean the old theory was wrong. It's just that new information was discovered.

The evolution from  Newtonian physics to general relativity  is a good way to explain how new information can cause a theory to evolve into a more complete theory:

When Sir Isaac Newton discovered the theory of gravity and wrote laws that explained the motions of objects, he was not wrong about how the world worked, but he wasn’t fully right either. Albert Einstein later discovered the theories of special and general relativity — that the force of gravity exists due to the bending of spacetime, which is caused by massive objects. This created a more complete theory of gravity. In fact, when you stay far below the speed of light, many of the equations in general and special relativity give you Newton’s results, so Newton wasn't incorrect. He just had a partial answer.

So, what happens when you have two theories that contradict each other, such as the Steady State and Big Bang theories (the former says the universe's density doesn’t change over time and has no beginning or end, while the latter claims the universe is becoming increasingly less dense and started at some point in time).

In this case, scientists made observations, hypotheses, and testable predictions to figure out which theory was right. For example, one scientist might observe that the universe is expanding, hypothesize that it had a beginning, and test their hypothesis by doing the math. Eventually, either one theory is overturned completely (in this case, the Big Bang theory turned out to be correct), or the correct aspects of each theory are combined to form a new theory — one singular theory.

In many cases, one theory forms the foundation upon which other theories are built. An example is Einstein's theories of  general  and  special relativity. These theories lay the foundation for many, many other theories and equations (such as Hubble’s law and the Schwarzschild radius).

Scientific laws are short, sweet, and always true. They're often expressed in a single statement and generally rely on a concise mathematical equation.

Laws are accepted as being universal and are the cornerstones of science. They must never be wrong (that is why there are many theories and few laws). If a law were ever to be shown false, any science built on that law would also be wrong.

Examples of scientific laws (also called "laws of nature") include the laws of thermodynamics, Boyle’s law of gasses, the laws of gravitation.

A law isn't better than a theory, or vice versa. They're just different, and in the end, all that matters is that they're used correctly.

A law is used to describe an action under certain circumstances. For example, evolution is a law — the law tells us that it happens but doesn't describe how or why.

A theory describes how and why something happens. For example, evolution by natural selection is a theory. It provides a host of descriptions for various mechanisms and describes the method by which evolution works.

Another example is Einstein’s famous equation E=mc^2. The equation is a law that describes the action of energy being converted to mass. The theories of special and general relativity, on the other hand, show how and why something with mass is unable to travel at the speed of light.

Hopefully, this has helped expand your understanding of what it means when scientists call something a hypothesis, a theory, or a law. And if you see someone in Internet Land using the terms inappropriately, please, shoot them this article.

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Teaching the Difference Between Theories and Laws in Science

Hey science teachers! One of the most common questions we get in the science classroom is about the difference between theories and laws. These terms are fundamental to understanding science, yet they’re often confused by students (and sometimes adults, too!). Let’s break them down and explore how to effectively teach these concepts in the high school classroom.

👉 Psst! There is a free downloadable poster for teaching the difference between theories and laws at the end of this blog post just for you!

Theory vs. Law Reading Comprehension and Worksheets

In this hypothesis vs. theory vs. law reading comprehension and worksheets package, students will learn key characteristics and the differences between theories, laws, and hypotheses. This includes an informative, article, text-dependent questions, and answer key.

🤔 Scientific Theories

A scientific theory is a well-substantiated explanation of an aspect of the natural world that is based on a body of evidence and has stood the test of time through multiple lines of inquiry and experimentation.

Key Features of Theories:

• Evidence-Based: Theories are supported by a large body of evidence gathered from multiple experiments and observations.
• Explanatory Power: They explain how and why certain phenomena occur.
• Predictive Power: Theories can be used to make predictions about future observations.
• Revisable: They can be modified or refined as new evidence becomes available.

Example: The Theory of Evolution explains the diversity of life on Earth and is supported by evidence from fields such as genetics, paleontology, and comparative anatomy.

Tips for Teaching Scientific Theories:

• Use Analogies: Compare a scientific theory to a comprehensive book that explains everything we know about a topic, but with room for new chapters as we learn more.
• Highlight Examples: Discuss well-known theories like the Theory of Relativity or the Germ Theory of Disease, emphasizing their broad acceptance and predictive power.
• Engage with Evidence: Have students look at the evidence supporting these theories, perhaps through research projects or interactive timelines showing key discoveries.

Theory vs. Law Amoeba Sisters Video Handout

In this handout, students will learn about what scientific theories and laws are and discover why scientific theories will never become scientific laws.

👩🏻‍⚖️Teaching SCIENTIFIC LAWS

A scientific law is a statement that describes a consistently observed phenomenon or a relationship in nature. Laws are typically expressed mathematically and describe what happens under certain conditions.

Key Features OF LAWS:

• Descriptive Nature: Laws describe what happens but don’t explain why it happens.
• Universal Acceptance: They are universally accepted as true and apply consistently across different situations.
• Predictability: Laws allow scientists to predict the outcomes of certain conditions reliably.

Example: Newton’s Law of Universal Gravitation describes the gravitational attraction between two masses but does not explain the mechanism of gravity.

Teaching Tips FOR SCIENTIFIC LAWS:

• Mathematical Formulas: Use equations and formulas to illustrate how laws can predict outcomes (e.g., using Newton’s Laws to predict the motion of objects).
• Consistent Patterns: Show how laws apply universally, using examples from everyday life (e.g., the law of conservation of mass in chemical reactions).
• Hands-On Activities: Conduct experiments that demonstrate these laws in action, helping students see their consistent and predictable nature.

✏️ Key Differences Between Theories and Laws

When you are teaching the difference between theories and laws, consider the following key points:

• Theories explain why phenomena occur; laws describe what happens.
• Theories are broader and provide deeper explanations; laws are specific and often mathematical.
• Theories can evolve with new evidence, while laws tend to remain consistent as long as the conditions are met.
• Both laws and theories are based on hypotheses. They can be used to make predictions, and both can be revised if necessary. 

🫀 MY FAVORITE THEORIES VS. LAWS ACtivities

Here’s a list of my favorite resources for teaching the difference between theories and laws.

🎥 TED ED Lesson: What’s the difference between a scientific law and theory?

In this fun free lesson , students watch a fun TED ED video and answer questions as they learn why science needs both laws and theories to understand the whole picture. Bonus – this activity is customizable!

Hypothesis Vs. Theory Vs. LAW Reading Comprehension and Worksheets

This 2-page reading comprehension for teaching the difference between theories and laws! It includes clear explanations and examples of hypotheses, theories, and laws. It also comes with worksheets that include questions and graphic organizers!

🚀 NASA Activity: Theories, Hypothesis, Laws, Facts & Beliefs

In this free PDF from NASA , students learn about the differences theories, laws, facts, hypotheses, and beliefs, and read 35 statements to discern what they are.

SCientific use of Theory And Law Video Handout

The Amoeba Sisters are amazing! This is a great video handout for students to use before, during, and after they watch this engaging and fun video on theories and laws.

🖥️ Scientific Theories vs. Scientific Laws CPALMS TutoriaL

In this fun interactive tutorial on the CPALMS website, students will click, learn, and practice information on inferences, hypotheses, variables, and the difference between theories and laws.

⭐ Here’s that freebie as promised!

Theory vs. law posters.

This set of free posters make a wonderful reminder to your students about the difference between theories and laws. They include definitions, characteristics, examples, and an analogy of each. Two sizes are included: full poster size and 8.5×11 for notebooks. They will look amazing in your classroom!

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Law vs. Hypothesis vs. Theory

Run-in with the law.

The Hypothesis: It's More Than An Educated Guess

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Hypothesis vs. Theory

A hypothesis is either a suggested explanation for an observable phenomenon, or a reasoned prediction of a possible causal correlation among multiple phenomena. In science , a theory is a tested, well-substantiated, unifying explanation for a set of verified, proven factors. A theory is always backed by evidence; a hypothesis is only a suggested possible outcome, and is testable and falsifiable.

Comparison chart

Examples of Theory and Hypothesis

Theory: Einstein's theory of relativity is a theory because it has been tested and verified innumerable times, with results consistently verifying Einstein's conclusion. However, simply because Einstein's conclusion has become a theory does not mean testing of this theory has stopped; all science is ongoing. See also the Big Bang theory , germ theory , and climate change .

Hypothesis: One might think that a prisoner who learns a work skill while in prison will be less likely to commit a crime when released. This is a hypothesis, an "educated guess." The scientific method can be used to test this hypothesis, to either prove it is false or prove that it warrants further study. (Note: Simply because a hypothesis is not found to be false does not mean it is true all or even most of the time. If it is consistently true after considerable time and research, it may be on its way to becoming a theory.)

This video further explains the difference between a theory and a hypothesis:

Common Misconception

People often tend to say "theory" when what they're actually talking about is a hypothesis. For instance, "Migraines are caused by drinking coffee after 2 p.m. — well, it's just a theory, not a rule."

This is actually a logically reasoned proposal based on an observation — say 2 instances of drinking coffee after 2 p.m. caused a migraine — but even if this were true, the migraine could have actually been caused by some other factors.

Because this observation is merely a reasoned possibility, it is testable and can be falsified — which makes it a hypothesis, not a theory.

• What is a Scientific Hypothesis? - LiveScience
• Wikipedia:Scientific theory

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Comments: Hypothesis vs Theory

Anonymous comments (2).

October 11, 2013, 1:11pm "In science, a theory is a well-substantiated, unifying explanation for a set of verified, proven hypotheses." But there's no such thing as "proven hypotheses". Hypotheses can be tested/falsified, they can't be "proven". That's just not how science works. Logical deductions based on axioms can be proven, but not scientific hypotheses. On top of that I find it somewhat strange to claim that a theory doesn't have to be testable, if it's built up from hypotheses, which DO have to be testable... — 80.✗.✗.139

May 6, 2014, 11:45pm "Evolution is a theory, not a fact, regarding the origin of living things." this statement is poorly formed because it implies that a thing is a theory until it gets proven and then it is somehow promoted to fact. this is just a misunderstanding of what the words mean, and of how science progresses generally. to say that a theory is inherently dubious because "it isn't a fact" is pretty much a meaningless statement. no expression which qualified as a mere fact could do a very good job of explaining the complicated process by which species have arisen on Earth over the last billion years. in fact, if you claimed that you could come up with such a single fact, now THAT would be dubious! everything we observe in nature supports the theory of evolution, and nothing we observe contradicts it. when you can say this about a theory, it's a pretty fair bet that the theory is correct. — 71.✗.✗.151

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What’s the difference between a scientific law and theory - matt anticole.

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Chat with a friend about an established scientific theory, and she might reply, “Well, that’s just a theory.” But a conversation about an established scientific law rarely ends with “Well, that’s just a law.” Why is that? What is the difference between a theory and a law... and is one “better”? Matt Anticole shows why science needs both laws and theories to understand the whole picture.

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The Difference Between a Fact, Hypothesis, Theory, and Law In Science

Words like “fact,” “theory,” and “law,” get thrown around a lot. When it comes to science, however, they mean something very specific; and knowing the difference between them can help you better understand the world of science as a whole.

In this fantastic video from the It’s Okay To Be Smart YouTube channel , host Joe Hanson clears up some of the confusion surrounding four very important scientific terms: fact, hypothesis, theory, and law. Knowing the difference between these words is the key to understanding news, studies, and any other information that comes from the scientific community. Here are the main takeaways:

Fact: Observations about the world around us. Example: “It’s bright outside.”

Hypothesis: A proposed explanation for a phenomenon made as a starting point for further investigation. Example: “It’s bright outside because the sun is probably out.”

Theory: A well-substantiated explanation acquired through the scientific method and repeatedly tested and confirmed through observation and experimentation. Example: “When the sun is out, it tends to make it bright outside.”

Law: A statement based on repeated experimental observations that describes some phenomenon of nature. Proof that something happens and how it happens, but not why it happens. Example: Newton’s Law of Universal Gravitation .

Essentially, this is how all science works. You probably knew some of this, or remember bits and pieces of it from grade school, but this video does a great job of explaining the entire process. When you know how something actually works, it makes it a lot easier to understand and scrutinize .

Theory vs. Hypothesis vs. Law... Explained! | YouTube

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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