Scientific Principle — Definition & Examples

The terms scientists use to describe what they study can seem arbitrary. It may seem as though the words they use are only words with nothing else to them. But studying the terms scientists use to describe various phenomena lets you better understand the meaning behind them.

Newton’s law of universal gravitation demonstrates the universalizable, common nature of laws that describe nature and the universe.

Scientific Principle — Definition & Examples
Scientific Principle — Definition & Examples

Examples of Scientific Principles in Everyday Life

Principles can also be general ideas that govern disciplines such as cell theory, gene theory, evolution, homeostasis, and laws of thermodynamics being a scientific principle definition in biology They’re involved in a variety of phenomena in biology and, instead of providing a definite, universal feature of the universe, they’re meant to further theories and research in biology.

There are other examples of scientific principles in everyday life. It’s impossible to distinguish between a gravitational force and the inertial force, the force to accelerate an object, known as the principle of equivalence. It tells you that if you’re in an elevator in free fall, you wouldn’t be able to measure the gravitational force because you couldn’t distinguish between it and the force that pulls you in the direction opposite to gravity.

Newton’s Three laws of Motion

Newton’s first law, that an object in motion will remain in motion until acted upon by an external force, means objects that have no net force (the sum of all forces on an object) will not experience acceleration. It will either remain at rest or move with a constant velocity, direction, and speed of an object. It’s very central and common to many phenomena in how it connects the motion of an object with the forces that act upon it no matter whether it’s a celestial body or a ball resting on the ground.

Newton’s second law, F = ma, lets you determine the acceleration or mass from this net force for these objects. You can calculate the net force due to the gravity of a falling ball or a car making a turn. This fundamental feature of physical phenomena makes it a universalized law.

Newton’s third law illustrates these features as well. Newton’s third law states that for every action, there is an equal and opposite reaction. The statement means that in every interaction, there is a pair of forces acting on the two interacting objects. When the sun pulls the planets towards it as they orbit, the planets pull back in response, These laws of physics describe these features of nature as inherent within the universe.

Principles of Physics

Heisenberg’s Uncertainty Principle can be described as “nothing has a definite position, a definite trajectory, or a definite momentum,” but it also requires a further explanation for clarity. When physicist Werner Heisenberg tried studying subatomic particles with increased precision, he found it impossible to exactly determine a particle’s momentum and position simultaneously.

Heisenberg used the German word “Ungenauigkeit,” meaning “imprecision” not “uncertainty” to describe this phenomenon that we would call the Uncertainty Principle. The momentum, the product of an object’s velocity and mass, and position are always at a tradeoff between one another.

The original German word describes the phenomena more accurately than the word “uncertainty” does. The Uncertainty Principle adds uncertainty to observations based on the imprecision of a physicist’s scientific measurements. Because these principles depend highly on the context and conditions of the principle, they are more like guiding theories used to make predictions about the universe phenomena than laws are.

If a physicist studied the motion of an electron in a large box, she could get a fairly accurate idea of how it would travel throughout the box. But if the box were made smaller and smaller such that the electron couldn’t move, we would know more about where the electron is, but know much less about how fast it was traveling. For objects in our everyday life, such as a moving car, you can determine the momentum and position, but there would still be a very small amount of uncertainty with these measurements because the uncertainties are much more significant for particles than everyday objects.

Principle vs. Law

A law describes an event, but it does not explain why the event happens. Laws describe relationships, specific situations, and conditions. This is different from a principle, which tells us why and how things happen.


Principles are ideas based on scientific rules and laws that are generally accepted by scientists. They are fundamental truths that are the foundation for other studies. Principles are qualitative.

They aren’t really rules that can be written down with mathematical symbols. They are more like guiding ideas that scientists use to make predictions and develop new laws.

Principle of Relativity: Physical laws take the same form in all systems of reference. (Albert Einstein)

Principle of Special Relativity: The speed of light is the same for all observers. (Albert Einstein)

Pauli Exclusion Principle: No two particles with the same quantum numbers can be at the same position in space and time. (Wolfgang Pauli)


Newton’s law of gravitational attraction describes how objects are influenced by gravity. If you drop an apple, it will fall. If you throw an apple in the air, it will follow a specific path while falling down. Newton’s laws don’t tell us why the apple falls or what causes it to fall, just that it does fall.

Similarly, the law of conservation of mass says that mass can’t be created or destroyed. It doesn’t say why this is true, neither does it say how it is true. It just says what happens—mass is always conserved.

Scientific laws can be written as mathematical equations, so they are called quantitative. However, there aren’t very many laws in biology. They are more common in physics and chemistry. I listed a few of these equations below.

Newton’s 2nd Law: F = ma

Hooke’s Law: F = kx

Gauss’ Law: ∇E=ρ

Sometimes, people use the terms “principle” and “law” interchangeably. This is because both result in reliable predictions of natural phenomena.

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