BIG BANG THEORY

Big Bang theme song

Sam Neill, Star Stuff

OUR BEST GUESS AT HOW THE UNIVERSE BEGAN…

• Most widely accepted theory of the beginning of our

universe among scientists at the present

• Nobody was alive to see it therefore it is our best guess

• Explains the observations we can make on earth with

our current technology.

MAIN PREMISE:

• The universe began with a gigantic explosion

about 13.8 billion years ago

• Nothing existed before this NO time, NO space

• Out of nothingness came everything in the

universe and it started to expand

AN INTRIGUING MODEL…BUT RAISES LOTS OF QUESTIONS

• What happened immediately after the Big Bang?

• Will the universe continue to expand forever?

• Does the universe have an edge?

• What is the evidence that supports the Big Bang theory?

WHAT HAPPENED WHEN…

1. BB often described as an explosion but is different in one way. Explosions fly outward into empty space that was there before the explosion. With the BB there was NO SPACE for it to expand into. (Universes don’t always fit into our everyday intuitions!)

2. BB happened 13.8 billion years ago

3. Universe was too hot right after explosion for subatomic particles to form. There were subatomic particles present (protons, electrons, quarks etc…) but they were moving so fast due to the heat that they didn’t form atoms

WHAT HAPPENED WHEN CONT…

3. As the universe cooled the particles slowed down and combined with each other to form Hydrogen atoms (380 000 years after the Big Bang). It was so hot the Hydrogen atoms gave off radiation. This radiation is known as Cosmic Background Radiation (CMB). We can measure this light today…more about that in a future class.

4. As the universe continued to cool the Hydrogen atoms could condense and form stars.

5. Condensation/ cooling allowed for all other bodies in the universe to form.

EVIDENCE FOR THE BB THEORY

• Cosmic background radiation is evident

• faint radiation left over from the first hydrogen atoms to form right after the explosion itself

• Red shift of wavelengths of light from distant galaxies

• Expansion implies universe was smaller in past

PROBLEMS WITH THE THEORY?

• There was nothing, then there was something. From where did it come?

• All matter in the universe in a pin sized package???

We’ve come along way from believing the earth was flat… What will be the next big discovery to help us understand?

Homework: Watch two Khan Academy videos “Big bang introduction” and “ Birth of stars”. Write a paragraph about things that interest you or questions you don’t understand.