- Scientific theory vs. scientific law
- Scientific laws and mathematics
- Do laws change?
- Examples of scientific laws
- Additional resources
In general, a scientific law is the description of an observed phenomenon. It doesn't explain why the phenomenon exists or what causes it. The explanation for a phenomenon is called a scientific theory. It is a misconception that theories turn into laws with enough research.
"In science, laws are a starting place," said Peter Coppinger, an associate professor of biology and biomedical engineering at the Rose-Hulman Institute of Technology in India. "From there, scientists can then ask the questions, 'Why and how?'"
Difference between a scientific theory and a scientific law
Many people think that if scientists find evidence that supports a hypothesis, the hypothesis is upgraded to a theory, and if the theory is found to be correct, it is upgraded to a law. That is not how it works, though. Facts, theories and laws — as well as hypotheses — are separate elements of the scientific method. Though they may evolve, they aren't upgraded to something else.
"Hypotheses, theories and laws are rather like apples, oranges and kumquats: One cannot grow into another, no matter how much fertilizer and water are offered," according to the University of California, Berkeley (opens in new tab). A hypothesis is a potential explanation of a narrow phenomenon; a scientific theory is an in-depth explanation that applies to a wide range of phenomena. A law is a statement about an observed phenomenon or a unifying concept, according to Kennesaw State University (opens in new tab).
"There are four major concepts in science: facts, hypotheses, laws and theories," Coppinger told Live Science.
Though scientific laws and theories are supported by a large body of empirical evidence that is accepted by the majority of scientists within that area of scientific study, and help to unify that body of data, they are not the same thing.
"Laws are descriptions — often mathematical descriptions — of natural phenomena for example, Newton's Law of Gravity or Mendel's Law of Independent Assortment. These laws simply describe the observation. Not how or why they work," Coppinger said.
Coppinger pointed out that the law of gravity was discovered by Isaac Newton in the 17th century. This law mathematically describes how two different bodies in the universe interact with each other. However, Newton's law doesn't explain what gravity is or how it works. It wasn't until three centuries later, when Albert Einstein developed the theory of Relativity, that scientists began to understand what gravity is and how it works.
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"Newton's law is useful to scientists in that astrophysicists can use this centuries-old law to land robots on Mars. But it doesn't explain how gravity works, or what it is. Similarly, Mendel's Law of Independent Assortment describes how different traits are passed from parent to offspring, not how or why it happens," Coppinger said. Gregor Mendel discovered that two different genetic traits would appear independently of each other in different offspring. "Yet, Mendel knew nothing of DNA or chromosomes. It wasn't until a century later that scientists discovered DNA and chromosomes — the biochemical explanation of Mendel's laws. It was only then that scientists, such as T.H. Morgan, working with fruit flies, explained the Law of Independent Assortment using the theory of chromosomal inheritance. Still today, this is the universally accepted explanation (theory) for Mendel's Law," Coppinger said.
The difference between scientific laws and scientific facts is a bit harder to define, though the definition is important. Facts are simple, one-off observations that have been shown to be true. Laws are generalized observations about a relationship between two or more things in the natural world based on a variety of facts and empirical evidence, often framed as a mathematical statement, according to NASA.
For example, "Apples fall down from this apple tree" is considered a fact because it is a simple statement that can be proven. "The strength of gravity between any two objects (like an apple and the Earth) depends on the masses of the objects and the distance between them" is a law because it describes the behavior of two objects in a certain circumstance. If the circumstance changes, then the implications of the law would change. For example, if the apple and the Earth shrank to a subatomic size, they would behave differently.
Scientific laws and mathematics
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Many scientific laws can be boiled down to a mathematical equation. For example, Newton's Law of Universal Gravitation states:
Fg = G (m1 ∙ m2) / d2
Fg is the force of gravity; G is the universal gravitational constant, which can be measured; m1 and m2 are the masses of the two objects, and d is the distance between them, according to The Ohio State University (opens in new tab).
Scientific laws are also often governed by the mathematics of probability. "With large numbers, probability always works. The house always wins," said Sylvia Wassertheil-Smoller, a professor at Albert Einstein College of Medicine in New York. "We can calculate the probability of an event and we can determine how certain we are of our estimate, but there is always a trade-off between precision and certainty. This is known as the confidence interval. For example, we can be 95% certain that what we are trying to estimate lies within a certain range or we can be more certain, say 99% certain, that it lies within a wider range. Just like in life in general, we must accept that there is a trade-off."
Do laws change?
Just because an idea becomes a law doesn't mean that it can't be changed through scientific research in the future. The use of the word "law" by laymen and scientists differs. When most people talk about a law, they mean something that is absolute. A scientific law is much more flexible. It can have exceptions, be proven wrong or evolve over time, according to the University of California, Berkeley.
"A good scientist is one who always asks the question, 'How can I show myself wrong?'" Coppinger said. "In regards to the Law of Gravity or the Law of Independent Assortment, continual testing and observations have 'tweaked' these laws. Exceptions have been found. For example, Newton's Law of Gravity breaks down when looking at the quantum (subatomic) level. Mendel's Law of Independent Assortment breaks down when traits are "linked" on the same chromosome."
Examples of scientific laws
- The law of conservation of energy, which says that the total energy in an isolated system remains constant. In other words, energy cannot be created or destroyed, according to Britannica (opens in new tab).
- The laws of thermodynamics, which deal with the relationships between heat and other forms of energy
- Newton's universal law of gravitation, which says that any two objects exert a gravitational force upon each other, according to the University of Winnipeg (opens in new tab)
- Hubble's law of cosmic expansion, which defines a relationship between a galaxy's distance and how fast it's moving away from us, according to astrophysicist Neta A. Bahcall
- The Archimedes Principle, which states that the buoyant force on an object submerged in a fluid is equal to the weight of the fluid displaced by that object.
- This resource from the New South Wales Education Standards Authority (opens in new tab) has an in-depth explanation of scientific theories and laws.
- Find out why a theory can’t evolve into a law in this article from Indiana Public Media (opens in new tab).
- Watch a video about the difference between a scientific law and a scientific theory from TEDEd. (opens in new tab)
University of California, Berkeley, "Misconceptions about science." https://undsci.berkeley.edu/teaching/misconceptions.php
NASA IMAGE Education Center, "Teacher's Guide: Theories, Hypothesis, Laws, Facts & Beliefs." https://www.nasa.gov/pdf/371711main_SMII_Problem23.pdf
The Ohio State University, "Lecture 18: The Apple and the Moon: Newtonian Gravity." https://www.astronomy.ohio-state.edu/pogge.1/Ast161/Unit4/gravity.html
Encyclopedia Britannica, "Conservation of energy." November 16, 2021. https://www.britannica.com/science/conservation-of-energy
University of Winnipeg, "Newton's Law of Gravitation." 1997. https://theory.uwinnipeg.ca/physics/circ/node7.html
Neta A. Bahcall, "Hubble's Law and the expanding universe," Proceedings of the National Academy of Sciences, Volume 112, March 2015, https://doi.org/10.1073/pnas.1424299112
Live Science Contributor
Alina Bradford is a contributing writer for Live Science. Over the past 16 years, Alina has covered everything from Ebola to androids while writing health, science and tech articles for major publications. She has multiple health, safety and lifesaving certifications from Oklahoma State University. Alina's goal in life is to try as many experiences as possible. To date, she has been a volunteer firefighter, a dispatcher, substitute teacher, artist, janitor, children's book author, pizza maker, event coordinator and much more.
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A law in science is a generalized rule to explain a body of observations in the form of a verbal or mathematical statement. Scientific laws (also known as natural laws) imply a cause and effect between the observed elements and must always apply under the same conditions.What is a law simple definition? ›
: a binding custom or practice of a community : a rule of conduct or action prescribed (see prescribe sense 1a) or formally recognized as binding or enforced by a controlling authority.What is law simple words? ›
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The meaning and principles of natural law according to Aquinas included: (1) humans must do good deeds and avoid evil deeds or sin, (2) survival and procreation are core human values, and (3) any natural laws that are set by human governments are positive laws.What is law in one word answer? ›
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on 1 May, 1996. Sale of Goods Act , 1930 defines the expression "goods" thus "goods' means every kind of movable property other than .actionable ... sale." This definition too includes all kinds of movable property within the definition of goods -while excluding certain specified items.Why there is a law? ›
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The 12 Laws of the Universe are the Law of Divine Oneness, the Law of Vibration, the Law of Correspondence, the Law of Attraction, the Law of Inspired Action, the Law of Perpetual Transmutation of Energy, the Law of Cause and Effect, the Law of Compensation, the Law of Relativity, the Law of Polarity, the Law of Rhythm ...What is a law vs theory? ›
In simplest terms, a law predicts what happens while a theory proposes why. A theory will never grow up into a law, though the development of one often triggers progress on the other.Can a law change in science? ›
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Fact” means and includes— (1) any thing, state of things, or relation of things, capable of being perceived by the senses; (2) any mental condition of which any person is conscious.
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The First Law of Nature is Self-Preservation!
Self-Preservation is defined as preservation of oneself from harm or destruction.
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In the first law, an object will not change its motion unless a force acts on it. In the second law, the force on an object is equal to its mass times its acceleration. In the third law, when two objects interact, they apply forces to each other of equal magnitude and opposite direction.
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By nature, laws of Physics are stated facts which have been deduced and derived based on empirical observations. Simply put, the world around us works in a certain way, and physical laws are a way of classifying that “working.”How a theory becomes a law? ›
When the scientists investigate the hypothesis, they follow a line of reasoning and eventually formulate a theory. Once a theory has been tested thoroughly and is accepted, it becomes a scientific law.