One dot is enough

The idea

A model is a simplified way of looking at a real system that focuses only on what is most important for a given question.

A drive to Mysuru

A car sets off from Bengaluru. You only want to know when it will reach Mysuru.

Which details of the car do you need?

• Its colour
• Where it is and how fast it goes
• How many seats it has

Draw just enough

A question appears. Choose the simplest picture of the car that can still answer it. Too simple and you cannot answer. Too detailed and you are doing extra work.

A model answers a question

A model is a simplified way of looking at a real system. It focuses only on what is most important for a given question.

Same car, three models. The question decides which details matter. In physics a moving car may be a single point. In chemistry atoms are drawn as spheres and bonds. In biology a cell is a diagram of its key parts. In earth science the Earth may be a smooth sphere in layers.

• Question | Model keeps | Model ignores
• Where will the car be after 2 hours? | position, speed (a dot) | size, colour, seats
• Will it pass between the pillars? | width (a box) | colour, speed
• Which car is Meera’s? | colour, roof rack | engine, speed

Notes

A model is a simplified way of looking at a real system. It focuses only on what is most important for a given question.

Check yourself

A physicist treats a moving car as a single point. What can this model help find?

A chemist draws atoms as small balls joined by sticks. Why is that a good model?

Which statement about models is true?

In earth science the Earth may be treated as a smooth sphere. Which detail is being ignored?

• How far the car travels in a given time — correct. Yes. For distance and time only its position matters.
• The colour of its paint. A point has no colour. This model cannot say anything about it.
• How many people are inside. A point has no inside. This model cannot say anything about it.
• Atoms really look like coloured balls. No. The colours are only for drawing. It is a model, not a photograph.
• It shows which atoms are joined, without every tiny detail — correct. Yes. It keeps what matters for the question: which atoms are joined.
• It shows everything about an atom. No. A model leaves out details on purpose.
• A model must show every detail of the real system. No. Then it would be as complex as the real thing.
• A model leaves out details on purpose, to answer one question — correct. Yes. Leaving details out is the whole idea.
• One model is right for every question. No. Change the question, and the right model changes.
• The Earth’s shape. The sphere keeps the shape. It is the mountains and valleys that are left out.
• Mountains and valleys — correct. Yes. They are tiny compared with the whole Earth, so a smooth sphere is enough for many questions.
• The fact that Earth is round. The model keeps this.