Explaining how we see at night
A scientific explanation answers a question in three parts. The claim answers the question. The evidence is what we saw, measured or read. The reasoning explains how the evidence supports the claim, using science ideas. Our question is: why can a cat see better than a person in dim light? A good claim: a cat sees better in dim light because its eyes catch more of the little light there is. Evidence: a cat has large eyes and wide pupils, and a shiny layer behind the eye makes its eyes glow in headlights, while a person’s eyes do not. Reasoning: a large eye and a wide pupil let in more light, and the shiny layer bounces light back for a second chance to be sensed, so a cat gets more light than a person. A weak answer such as “because it is a cat” has no evidence and no reasoning. Remember also the other points of this concept: light travels in straight lines, we see when light enters the eye, and the pupil lets light in.
| Part | Cat in dim light |
|---|---|
| Claim | A cat sees better than a person in dim light. |
| Evidence | Large eyes, wide pupils, shiny layer that makes eyes glow. |
| Reasoning | More light enters and the shiny layer gives light a second chance to be sensed. |
Explanation card. Write your own claim, evidence and reasoning to answer: “How does an owl see in the dark?” Use three boxes on a folded card. Then read it to someone at home: can they find the evidence? Can they find the reasoning? Check that each part says something different.