The Big Bang Theory and Solar Nebula

The Universe

Where do we live?

Where are we located?

• 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…..

The Solar System

Question??

What is a STAR?

What is a Star?

• A star is a big ball of burning gas

• 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

Galaxies

• 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

Galaxies as seen with the Hubble Space Telescope

The Big Bang Theory

• How did everything start?

• How long ago did this happen?

In the Beginning

All the mass and energy of the universe

EVERYTHING!

EVERYTHING!

ENERGY INCREASING, BECOMING LIKE A BOMB…….

STARTS EXPANDING…..

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’

PROTONNEUTRON

ELECTRON

COSMIC ‘SOUP’

• Universe much cooler, atoms start to form…..

• Hydrogen, Helium, normal ‘stuff’

300,000 Years Later…..

Universe is now a GAS

Universe is now a GAS

HYDROGEN

HELIUM

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’

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

If we could view the Universe from outside, if would look like this:

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

The Gemini Telescope

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