HOW THE UNIVERSE BEGANYear 11 Physics – The Cosmic Engine

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Syllabus Glossary

Syllabus references

Outline the discovery of the expansion of the Universe by Hubble, following its earlier prediction by Friedmann

Identify that Einstein described the equivalence of energy and mass

Identify data sources and gather secondary information to describe the probable origins of the Universe

Where did the universe come from?

The Big Bang theory

The expanding universe Cosmic background radiation

The expanding universe

Scientists who have contributed to the expanding universe Albert Einstein Aleksandr Friedmann Edwin Hubble

Albert Einstein

Special theory of relativity

The speed of light Equivalence of

energy & mass Energy can be

converted into mass Mass can be

converted into energy

E = mc2

Evidence for Einstein’s theory Predicted that light rays can be warped by

space-time and should curl around stars (gravitational lensing) Gravitational lensing of distant quasars has been

studied by astronomers using the Hubble telescope Predicts that time should run slower near an

object as large as a planet Tested and verified in 1962

Predicted that the universe is expanding but Einstein believed in static universe so he put a cosmological constant in the equation to make the universe static

Aleksandr Friedmann

Read Einstein’s work but thought his cosmological constant was wrong, so he tried to solve Einstein’s equations

Assumed that the universe is the same no matter where we look

Friedmann’s maths proposed two models: (1) closed universe and (2) open universe

Closed universe

Time and space have a beginning and an end

Time and space both began with a big bang and will end when gravity stops the universe and pulls everything back into one point – “ the big squeeze”

The universe is finite and the expanding universe is due to space expanding

Open universe

Universe began with a big bang and will continue to expand forever

Time and space has no end

How do we know the universe is expanding?

In 1912, Vesto Slipher examined the spectrum of light produced from a nebulae

Found that the light from the nebulae had frequencies lower than normal light

The light from the nebulae was more shifted towards the red end of the spectrum – red shift

What is redshift?

Remember: light travels at the same speed regardless of how fast you are travelling

Light is made up of different colours; red has the lowest frequency and blue/purple has the highest frequency

Redshift is when light moves towards the red end of the visible light spectrum

The electromagnetic spectrum

Redshift continued ...

http://youtu.be/FhfnqboacV0

Redshift in the universe

The left spectrum is the transmitted frequency of light from a star

The right spectrum is the observed frequency of the star from Earth

The spectral lines are shifted towards the red end

Shows star is moving away from us

Edwin Hubble

Hubble used the redshift idea to propose his expanding universe model where the universe is like an exploding bomb

He also came up with the Hubble constant (Ho) Rate at which universe is

expanding Used to estimate the

size of the universe

Summary The big bang theory proposes that the

universe exploded out of a hot dense point.

The big bang theory is supported by the expanding universe model which various scientists have contributed to Einstein – equivalence of energy and mass

(E = mc2) Friedmann – closed and open universe Hubble – spectral lines and Hubble constant

Redshift demonstration

1. Go to www.tale.edu.au/tale4students

2. Save code: X03RO