Our Universe What it is like, how it started, how it evolved to its current state, and how it will end

First, let’s look at some of the objects we might find if we explored our Universe

Where do we live?

Where is the Earth?

The Solar System

Q: What is a STAR?

Our Sun is a star!

Stellar Facts A star is a big ball of burning gas Our Sun is a very average star When we look out into the night sky, many of the stars we see are very similar to our own sun In fact some of these stars also have planets, just like our own Solar System

What is this?

What is it made of?

MANY STARS

MANY STARS SOME SUN-LIKE

Galactic Facts Stars tend to group together to form galaxies Galaxies contain hundreds of thousands of stars At the centre of most galaxies is a massive black hole! Our sun is part of a galaxy

You are here!

Our Galaxy from the Earth

We live on the Earth The Earth is a planet in the Solar System, orbiting our star which we call the Sun The Sun is part of a galaxy When we look out into the sky at night, all of the stars we see are in our galaxy But our galaxy is just one of many…..

Galaxies: Hubble Space telescope image

‘Zoom out’ - galaxies form filaments and voids

It is hard to comprehend the size of the Universe! We will now all help make a scale model of the solar system to get an idea of the distances we are talking about

IN THE BEGINNING…….

EVERYTHING!

EVERYTHING!

STARTS EXPANDING….. EVERYTHING! ENERGY INCREASING, BECOMING LIKE A BOMB…….

Tick tick tick……

BOOM!

The Big Bang Not really an ‘explosion’ Universe expanded rapidly as a whole (Universe is still expanding today as a result of the Big Bang) Matter was created in the form of tiny particles (protons, neutrons, electrons) Too hot for normal ‘stuff’ to form (eg atoms, molecules)

COSMIC ‘SOUP’

COSMIC ‘SOUP’ PROTON NEUTRON ELECTRON

300,000 Years Later….. Universe much cooler, atoms start to form….. Hydrogen, Helium, normal ‘stuff’

Universe is now a GAS

Universe is now a GAS HELIUM HYDROGEN

GRAVITY!

Gravitational Collapse We started with a uniform gas Small regions became more dense The denser regions had larger gravity and started to pull other particles towards them The gaseous Universe began to look ‘clumpy’

Formation of Structure! The Universe began very hot & dense following the Big Bang. As it expanded and cooled, large clouds of gas could be compressed by gravity, forming stars and galaxies..

Gravitational Collapse Regions with more particles (higher density) become gas clouds Gas clouds become stars and galaxies Galaxies congregate together in filaments, groups and clusters

But we are inside one of these galaxies, so all we see are the nearby stars. We can see other galaxies if we use a telescope

Cosmic Microwave Background Radiation! Shows that the universe is nearly the same temperature in every direction. Indicates a massive explosion-like event occurred in the universe about 13.7 Billion years ago! http://www.astro.cornell.edu/~rbean/images/cmb_popup.jpg

The BIG BANG! Evidence: The universe is expanding. The amount of gas in the universe matches with what should have been created by a big bang. We see dim microwave radiation coming from every direction… an afterglow!

The Gemini Telescope

Working Timeline since BB

Future? The Universe is still expanding All galaxies are moving apart The ‘explosion’ of the big bang is still happening! It may contine expanding forever Or is may stop expanding, and fall inwards in a big CRUNCH!

What have we learned? The Universe started with a BIG BANG Gradually the particles were drawn together under GRAVITY to form STARS and GALAXIES Many stars have planets around them The fate of the Universe is uncertain…

THE END