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Article by NRICH team# The Moving Planets

### Eclipse of the Sun

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### Eclipses of the Sun

### Shaping the Universe I - Planet Earth

### Shaping the Universe II - the Solar System

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Age 7 to 14

Published 2011 Revised 2022

Since people first looked up and wondered what the lights in the sky were, we have tried to solve the mysteries of the stars and planets. Mathematics has always been a powerful tool for studying, measuring and calculating the movements of the planets. So mathematics was used to both discover, then prove the first basic `rule' of our planets - that they travel around the sun, not around Earth. In
the 1500's and 1600's, now famous men such as Nicolaus Koppernik ( Copernicus ), Isaac Newton and Galileo Galilei worked hard to convince the authorities of this truth.

Between 1609 and 1618 Johannes Kepler announced his laws of planetary motion. Using the careful observations recorded by Tycho Brahe , he showed that the shape of a planet's path around the sun (orbit) was an ellipse (almost a circle). He calculated the
speed that each planet travelled. He also worked out the relation between size of the orbit and the time it takes for the planet to go once around the sun (revolution).

Later, Isaac Newton used some different mathematics to develop the theory of planetary motion in terms the effects of gravity. However, the planets Uranus, Neptune and Pluto had not yet been discovered.

Perhaps you have heard about total eclipses of the sun? People in different parts of the world will see different amounts of the sun blocked as the moon passes between the Earth and the sun. Long ago, people were terrified by eclipses because they didn't know when they would happen or what caused them. Scientists are able to predict all of this through the use of mathematics. To find out
more about eclipses and the sun visit The Dynamic Sun .

Mathematics has allowed us now to measure lots of things about eclipses and so calculate exactly when they will happen, where they can be seen from, and what they will look like.

This article explores ths history of theories about the shape of our planet. It is the first in a series of articles looking at the significance of geometric shapes in the history of astronomy.

The second in a series of articles on visualising and modelling shapes in the history of astronomy.