Physical law facts for kids

A physical law (also called a scientific law or law of nature) is a rule that scientists have found to be true over and over again. It's like a universal truth about how the world works. These laws are based on many observations and experiments. Scientists aim to discover and describe these laws to understand nature better.

Physical laws are different from human laws (like traffic laws) or religious rules. They also cover more than just physics; they can be found in biology and other sciences too.

How are Physical Laws Discovered?

Scientists discover physical laws through careful experiments and observations. They repeat experiments many times to make sure their findings are consistent. If something always happens the same way under the same conditions, it can become a scientific law.

Some laws are so basic they are almost like definitions. For example, Newton's second law of motion, often written as F = dp/dt, helps us understand force. Before Newton, people knew about force, but he gave it a clear mathematical definition. This law explains how force, mass, and acceleration are connected.

Newton's first law of motion is another example. It says that an object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction, unless an outside force acts on it. This law describes how objects behave naturally without any interference.

What is the Difference Between a Law and a Theory?

It's important to know that a scientific law is different from a scientific theory.

• A scientific law describes what happens. It tells us that a certain event will always occur under specific conditions. For example, the law of gravity describes that objects with mass attract each other.
• A scientific theory explains why something happens. It provides a detailed explanation for a set of observations and laws. For example, the theory of evolution explains why living things change over time.

Both laws and theories are very important in science. Laws tell us the rules of nature, and theories help us understand the reasons behind those rules.

Images for kids

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  Scientific theories explain why something happens, whereas scientific law describes what happens.

See also

• Scientific method
• Barrow, John (1991). Theories of Everything: The Quest for Ultimate Explanations.
• Davies, Paul (1992). The Mind of God
• Feynman, Richard (1965). The Character of Physical Law
• Hans Wehrli: Metaphysik - Chiralität als Grundprinzip der Physik, 2006
• Baaquie, Belal E., "Laws of Physics : A Primer". Core Curriculum, National University of Singapore.
• Carroll, John W. Stanford Encyclopedia of Philosophy entry
• Francis, Erik Max, "The laws list". Physics. Alcyone Systems
• Pazameta, Zoran, "The laws of nature". Committee for the scientific investigation of Claims of the Paranormal CSICOP.

In Spanish: Ley de la física para niños