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#What is a Scientific Law? Definition, Examples - Quiz - Video - Lesson Transcript

Instructor: Nadine James

Nadine has taught nursing for 12 years and has a PhD in Nursing research

In this lesson, you will learn about scientific laws. The topic will be defined for you and several types of scientific laws will be described. Finally, examples of scientific laws and theories will be provided to assist you with learning the difference between the two terms.

Definition of a Scientific Law

A scientific law is a statement that describes an observable occurrence in nature that appears to always be true. It is a term used in all of the natural sciences (astronomy, biology, chemistry and physics, to name a few). But what is an observable occurrence? Well, it's something that can be seen by anyone and happens with no intervention by man.

In science, sometimes a law is called a 'principle.' The law or principle may describe only the occurrence, or it may describe the occurrence and predict it as well. However, a law does not make explanations about the natural occurrence.

Background of Scientific Laws

Some terms related to scientific law are 'hypothesis' and 'theory.' However, a scientific law is different from a hypothesis, or a theory. The main difference is that a scientific law has been tested more than the other two - it's called being empirically tested. But another important difference is that a hypothesis is an explanation of an observation found in nature, while a law is based on observation only. In other words, the hypothesis is the why, while the law is the what.

The scientific method's process begins with the formulation of a hypothesis - which is an educated guess based on observations. Then the hypothesis is tested through research. After repeated testing and verification, the hypothesis may be moved up to a theory.

It's important to remember that a hypothesis and a theory cannot be proven, but they can be supported or rejected. So, can a scientific law be proven? Well, let's do a little more explanation before we get into that question.

Characteristics of Scientific Laws

Basically, scientific laws come from physics. Most laws can be represented as an equation (which is a mathematical formula). The formula can be used to predict an outcome. Specifically, once applied, the formula predicts that a new observation will conform to the law.

Now let's be clear: a scientific law does not have absolute certainty - nothing in science does. It could be overturned by future observations. For instance, Newton's Law of Gravitational Force was later found to only apply in weak gravitational fields. But does that mean that Newton's law is not important? Not at all! So, have we answered our question from above - can a law be proven? Yes, but it's always open to change.

Examples of Scientific Laws

Let's look at a few examples.

Example One

Newton's Law of Gravitational Force is written as g = GM / r^2. This law describes gravitational force. The gravitational force (g) is comparative to the gravitational force (G) times the mass of the earth (M) divided by the radius of the earth squared (r^2).

For instance, you have a ball in your hand and you drop it. What happens? It falls to the ground. How fast it falls to the ground depends on the gravitational constant (G) times the mass of the ball (M) divided by the distance between the ball and the floor (r^2). This is an example of a law that can predict. If you have the mass of the ball, you can calculate the amount of time it will take for the ball to fall to the ground. However, the law does not explain why the gravitational force exists in nature.

Example Two

Newton's Second Law of Motion is written as F net = (mass) * (acceleration). This law describes how an object moves. It means that an object will move according to the total amount of force applied. The amount of force applied is measured in newtons (N). The net force takes into account all the forces applied to an object.

Think of a basket of softballs. The basket has an applied force of 30 Ns to the left (this is you pulling the basket). What other forces are acting on the basket? Gravity, friction and the support of the floor are the three other forces acting on the basket. So, in what direction will the basket move according to Newton?