The Universe Made Simple/Introduction

You're reading this book because you want to know more about the universe that you live in. But what is the universe?

What is the universe?
The universe is everything that there is. Some people like to think of the universe as a vast container, in which everything that exists resides. However, no one knows whether or not this container is infinite in size, or if it has an "outer limit." No one knows for sure, as this question of "Is the universe finite or infinite?", has been asked for ages. Many scientists speculate that it expands outward as a balloon and has no end, continuing forever in all directions without any meaning at all. Still, some believe there is a limit and that all the galaxies and stellar objects are contained within a limited universe. This moves out of the realm of science and into the realm of metaphysics and philosophy, because there is no empirical data to suggest any conclusion as of yet.

When you look at the night sky, and see the stars, you are looking out into a very close part of the universe. The stars you see are such an incredible distance away that it makes you stand awestruck by it all. The blackness you see is the empty space of the universe; the parts that are not filled with light. However, there may be objects moving in the blackness that have no light shining on them, and we can only wonder what else is moving through space.

How did people discover all this?
We're constantly hearing about research, and how some scientist here has discovered some new thing. But how is it actually all done? The answer is that in many cases it is extremely complicated, and that the method changes depending upon what you want to find out, and what you're looking at. Sometimes scientists build huge, special devices just to help them inspect something.

We discover things about the universe, however, by simply looking at it. We use huge telescopes that can see millions and millions of miles away. We have sent special robots called probes out into space to go and take pictures of distant things, and transmit the pictures back to Earth. We've even sent people in space-ships out into space. But space-travel is extremely expensive, difficult and dangerous. Most of the time, scientists work by taking observations, looking at how things move, and then using mathematics to work out what they must be like if they're moving like that or looking like that.

What will this book teach you?
This book aims to be simple but informative. It will try not to miss out any important information, but it will also not confuse you with intricate details or physics.

The book will be like a journey. We will begin on Earth, then set off into the Solar System, out into the Galaxy, beyond it into the further Universe, and then even further. At each stage we hope to give you an appreciation of scale, and how everything fits together.