Up to the exercises on SI units

A Very Bad Joke
(and a moral)

A group of Civil Engineers were at a conference being held in Central Australia. As part of the conference entertainment, they were taken on a tour of the famous rock, Uluru.

"This rock", announced the guide, "is 50 000 004 years old."

The engineers - always impressed by precision in measurement - were astounded.

"How do you know the age of the rock so precisely?" asked one of the group.

"Easy!", came the reply. "When I first came here, they told me it was 50 million years old. I've been working here for four years now."

Alright, I admit that was pretty horrible, but there is a moral to the story. All the humour in this joke was because the guide considered the number 50 000 000 to be a precise measurement of Uluru's age.

Of course, we realise this is not the case. In fact, the best we can say is that the "50" part is roughly correct and the order of magnitude of the number is correct. That is to say, the number is about the right size, or more simplisticly, we have the "right number of zeros" on the result.

The next pages cover this topic of significant figures more precisely. We begin with some slightly less far-fetched applications than the above and then move on to develop the theory behind significant figures in measurement.

In the process, we will also cover scientific notation and give some examples explaining calculations with significant figures. Finally, there are the ever-present exercises to reinforce the concepts at the end.

Significant figures in practice.
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