 ## MODELLING THE SPEED OF LIGHT

Not only can we scale the size of the sun and the planets, and the distance between them, but we can also scale the speed of light.

The speed of light (a universal constant denoted by “c”) is 299,792 kilometres per second. (299,792,458 metres per second to be exact).

We can use the calculations on scale that we’ve already worked out to determine what the speed of light would be in our model.

From earlier, we know that 1 kilometre is represented by 0.00647 millimetres.

The speed of light is therefore represented in our model by taking the speed of light (in kilometres) and multiplying it by this number, giving the answer in millimetres.

This gives our scaled down speed of light to be 1,940 millimetres per second.

That’s just a shade under 2 metres per second. The average adult walking pace is about 5 kilometres per hour. That’s 1.4 metres per second. So for an adult a brisk walking pace might represent the speed of light in our model. For a child, it would be a jogging pace, but certainly not a full running pace. So now that we know the distance from the Sun to the Earth in our model is 968 metres, you can start at the "Big Ball" and walk at a brisk pace (for an adult) or jog if a child, and you will get to the “Earth” in 8 minutes and 19 seconds simulating the speed of light travelling from the Sun to the Earth.

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