As the author Douglas Adams wrote in The Hitchhikers’ Guide to the Galaxy:
A long time ago, people thought that the Earth was at the center of everything, that the Sun, planets and stars orbited the Earth, but in the mid 16th century, a German philosopher by the name of Nicolaus Copernicus published a book: De revolutionibus orbium coelestium—in those days everything was written in Latin—in which he set out a new theory. He said that the current theory was wrong; that the sun was at the center, and everything else revolved around it.
Space is really big. You just won’t believe how vastly, hugely, mindbogglingly big it is. I mean, you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space.
Today we know the Sun to be the centre of our solar system, just as other stars form the centre of many other solar systems. The Earth and the other planets in our solar system revolve about the Sun. But our sun is on the outskirts of a galaxy called the Milky Way, and the Milky Way is not the only galaxy.
The universe is thought to contain something like 100 billion galaxies, and each galaxy might contain something like 100 billion stars.
Outer space is the void beyond any celestial body, such as planets and stars. There are only a few particles scattered here and there in space, whereas a cubic metre of the air we breathe on Earth contains millions of molecules.
As the astronomer, Carl Sagan said:
As long as there have been humans, we have searched for our place in the cosmos. Where are we? Who are we? We find that we live on an insignificant planet of a humdrum star, lost in a galaxy, tucked away in some forgotten corner of a universe in which there are far more galaxies than people.
In this zone we’ll meet scientists building models of the universe using computers, and studying rocks from Mars and grains from comets to try to understand how the early universe was formed. There’s a scientists using telescopes to search for distant planets and stars, and another scientist looking for supernovae.