One idea, many records
A ball tossed up comes down. Every time.
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- Science has three words for big ideas.
- A law describes a pattern.
- A theory explains why the pattern happens.
- A principle is a broad idea.
The idea
Scientists repeat observations and improve their measurements. They test ideas with experiments. Then they organise what they learn.
A law describes a regular pattern seen in nature. It can be in words or in maths. Newton's law of gravitation describes the pull between any two masses. It covers the tossed ball.
A theory does more. It explains why a pattern happens. It is based on evidence gathered over time. The particle theory of matter explains why a gas fills a room.
A principle is a broad idea. It helps us understand many situations. Archimedes' principle says a liquid pushes up on anything put in it. It helps us see why a boat floats.
The three words overlap a little. Some ideas got their name long ago. The name was kept.
In science, a theory is not a guess. It is an explanation built on careful testing. New evidence can change a theory. Being ready to change is one reason people trust science.