Lesson Aim To consider the evidence for the Big Bang

theory

Evidence for the Big Bang

The evidence for the Big Bang is circumstantial and is inferred from what we can observe today.

Some is based on empirical evidence and some is theoretical.

Hence the title Big Bang Theory

(Although there is a lot of evidence to support this theory)

The Evidence: Expanding Universe

The Doppler Effect – if you’ve heard a fire engine (nee-naw, nee-naw) you notice the pitch of the noise changes.

This is the Doppler Effect of sound waves contracting and stretching.

A similar process happens with light.

Doppler Effect

http://www.youtube.com/watch?v=imoxDcn2Sgo&feature=related

Edwin Hubble

The Hubble telescope observed that the light coming from distant galaxies was all shifted towards the red light of the light spectrum.

This somehow enables scientists to identify the source of the light

Think of it as light carrying a certain signature (Or an mp3 file creating info on when it was

created) This is known as the cosmological red shift

This cosmological red shift implies an expanding universe – as light waves would have come from the same source and is expanding outwards away from the original source

Einstein A few years earlier Einstein

argued that all systems in the Universe had a finite source of energy

Energy in the Universe is not infinite therefore the Universe could not have existed for all eternity

The logical conclusion of this is that the Universe must have had some sort of beginning

Implications

Everything in the Universe appeared to be expanding away from a central point so there must have been a starting off point (a beginning).

Einstein’s theory of relativity supported this view.

Cosmic Background Radiation

Think of a sparkler on Bonfire night. You light it and it gets very hot and also heats up whatever is around it.

The Big Bang obviously created a huge amount of heat and this is still around today

This heat is called cosmic background radiation

Cosmic Background Radiation

Think of a sparkler on Bonfire night. You light it and it gets very hot and also heats up whatever is around it.

The Big Bang obviously created a huge amount of heat and this is still around today

This heat is called cosmic background radiation

Cosmic Background Radiation

Back in 1965 astronomers picked up radio signals from the universe – a sort of background fuzz

They identified this as cosmic background radiation

This provides evidence that the Big Bang actually happened

Cosmic Background Radiation

Back in 1965 astronomers picked up radio signals from the universe – a sort of background fuzz

They identified this as cosmic background radiation

This provides evidence that the Big Bang actually happened

Cooking a Universe

Is it possible to eat a meal (without knowing the ingredients) and then guess what was in it and how it was made??

Cooking a Universe

We can do something similar with the Big Bang There are 117 elements in the periodic table The amount of elements in the Universe points

towards a Big Bang 90% of the elements are Hydrogen atoms – this

is exactly what we would expect if the Universe had started with a Big Bang

Discussion Point

If the Big Bang theory is correct, what might this mean for religious beliefs???

6 minutes

“If the density of the universe one second after the Big Bang had been greater by one part in a thousand billion, the Universe would have recollapsed after 10 years. On the other hand, if the density of the Universe at that time had been less by the same amount, the Universe would have been essentially empty since it was about 10 years old. How was it that the initial density of the Universe was chosen so carefully?”

Professor Steven Hawking

Now, read page 63 in the purple book and answer the questions.