Every night as the Sun sets beyond the horizon the last rays of sunlight throw the sky into a beautiful display of colours As night approaches these colours give way to a deep dark sky covered in a tapestry of little twinkling stars When you look up at these stars and the darkness in between you are looking at the biggest thing that exists the Universe But where does our Sun go at night What are the stars made of and where did they come from Are we alone in the Universe or could there be another boy or girl somewhere on a distant planet looking up at the sky and wondering these very same ideas Our Universe is very complicated and many scientists spend their entire lives trying to unravel its greatest secrets in fact many of these secrets are yet to be uncovered But don’t worry Professor Astro is here to help and I am just about the cleverest alley cat you’ll ever meet So batten down the hatches and buckle up it’s time to blast off and discover Professor Astro Cat’s Frontiers of Space 3
the universe One thing we know for certain about the Universe is that it is really really big because it holds all the stars in the sky and much much more In fact the Universe is so big we are not even sure if it ever ends Imagine setting off from Earth in a spaceship and travelling forever without hitting anything that’s how big the Universe is But hold on let’s start at the beginning First of all how was the Universe born The Universe exploded into existence 13 8 billion years ago in an event called the Big Bang Everything in the Universe was created in that moment all the stuff that makes the stars and planets and the energy that flows between them even space and time were created at the Big Bang No one really knows why it happened and to this day it remains one of the great mysteries of science The start is the Big Bang 13 8 billion years ago 13,799,000,000 years 377 thousand years 377,000 years after the Big Bang Atoms form and photons of light travel freely Through time the Universe spread out in all directions and began to take shape From the swirling energy tiny particles popped into existence After a few hundred thousand years they collected together into atoms the basic building blocks of everything we can see in the Universe Also at this time light was released and free to fly through the Universe Wowee
It wasn’t until hundreds of millions of years later that the atoms collected together into great clouds from which the first generation of stars was born These stars collected together into galaxies and the Universe started to become the one that we see in the sky at night today The Universe is still expanding now and will carry on getting bigger and bigger forever 200 million years 200,000,000 years after the Big Bang The first stars form 500 million years 500,000,000 years after the Big Bang The first galaxies form Fact You can hear the echo of the Big Bang yourself Just listen to a detuned radio one crackle in a hundred is made by leftover light from the Big Bang stretched over billions of years into radio waves 5
