Exploration: Entering the World of Secondary Science
Laws, theories and predictions
See how laws and theories differ, and how science tests its ideas.
Science has three words that people often mix up: law, theory and principle.
| Word | What it does | Example |
|---|---|---|
| Law | Describes what happens, a regular pattern | Newton's laws: the jerk you feel when a bus stops suddenly |
| Theory | Explains why it happens, using evidence | Atomic theory explains how molecules form |
| Principle | A broad idea you can use in many situations | Conservation of energy, when you climb stairs |
"Isn't a theory just a guess?" In daily life, "it's only a theory" means a guess. In science it means the opposite: an explanation built on careful testing and evidence. It can still be improved when new evidence comes.
Science also predicts: how far a kicked football will go, how much carbon dioxide a reaction will make, how your breathing changes when you run. A prediction is a reasoned expectation, not a guess. Your phone's weather alert is a prediction, and it is why people bring in the washing before the rain.
Making a prediction testable. Varsha tells her friend Meghna, "It will rain this afternoon because the clouds look dark." Meghna can turn that into science by asking for measurements and past patterns:
- What did the sky look like the last time it rained?
- What is the humidity today? Was it above 80 per cent last time?
- What are today's wind speed and direction?
- Is the temperature dropping, as it did before the recent rains?
"Why is tomorrow's forecast more certain than next week's?" Small changes in the air add up over time, so the further ahead you look, the less certain the prediction becomes.
When a prediction fails, scientists don't hide it. They go back and check their assumptions, their model and their measurements. An idea is dropped only because of evidence, never because of someone's opinion. No theory is ever final, and that is science's strength.
Check a claim like a scientist. A viral message says food becomes harmful during an eclipse. Ask what physically happens: the Moon's shadow falls on us and there is less sunlight for a while. The temperature barely changes, and food does not go bad in a shadow. There is no physical, chemical or biological reason for the claim, so science rejects it.
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