As explained in the preface, I have used high-school mathematics to present some of the material in this book. If you want to know what that means, if you want to learn whether you have the background necessary to do the mathematics, then scan through this introductory material. But remember, it is not necessary to follow all the derivations, particularly the ones in the boxes, if you just want to learn what the main ideas in modern gravity and astronomy are. So if you find your mathematics too old or rusty, then see how you get along without it.

High-school mathematics

The mathematics used is basic numeracy, algebra, and a tiny bit of trigonometry (which you can skip).

It is essential to understand scientific notation for numbers, that is how to write numbers in the form 3.2 × 106 and know what the factor 106 means. Scientists use this notation all the time, because otherwise they would be writing out long confusing strings of zeros. The number 3.2 × 106 means 3 200 000, obtained by moving the decimal point in 3.2 six places to the right. Similarly, the number 5.9 × 10−3 is 0.0059, obtained by moving the decimal point three places to the left.