Origin of the Universe
Big Bang Theory
Big Bang Theory
• Scientists now believe that the universe had a definite
beginning, and it will have an end.
• The ‘best’ explanation for the existence of the universe is
currently the Big Bang Theory.
• The Big Bang is thought to be an explosion from a
SINGULARITY (a single point of density – where all
known space was compressed into an infinitely small
• This happened 12-15bn years ago (12,000,000,000-
• They don’t really know what the singularity was or ‘how
long’ it had been there.
• Unlike Steady State Theory, the universe is not
‘filling up’ as it expands – the galaxies are
moving further away from each other, with more
• In the first second after the explosion, gravity
and electro-magnetism were ‘created’.
• In the first minute the universe had grown to
1million billion miles (1,000,000,000,000) across
• In the first 3 minutes, the heat (10 billion degrees
celsius) causes nuclear reaction with lightest
particles to make 98% of all matter in the
• The Big bang was thought to produce 2 main
types of particle: matter and anti-matter.
• Matter and anti-matter in equal quantities cancel
each other out. The surplus is what the universe
is made of.
• After 500,000 years, particles from atoms
• 500,000 years after that, atoms and molecules
start to gather together and form galaxies and
• Out of the first stars came H, He, C, O
• Our solar system is about 4.5 billion years old.
Evidence Supporting the Big Bang
1. Hubble’s Law: the speed of the galaxies
moving away from each other causes a
change in the light spectrum, ‘red shift’.
2. Background radiation: We can still detect
radiation from an explosion of this size – the
radiation is the same everywhere on earth (TV
3. Composition of Older Galaxies: Analysis of
light from galaxies towards the ‘outside’ of the
universe confirm theories about the early
universe. They are made up of approx 93% H,
7% He, and trace Li
1. Cosmologists cannot follow the evidence
right back to the origin of the Big Bang
2. There is observable evidence to count
for 90% of the explosion (10.5bn years) –
no light to be measured from other 10%
3. The other 10% is only ‘known’ through
hypothetical mathematical simulations –
they are only theoretical.
Religious Use of the ‘Gap’
1. As science is not 100% certain about the
cause of the Big Bang, it is reasonable to posit
God there (no evidence against this) – this is a
‘God of the Gaps’ approach
2. Some facts about the world might always be
beyond science – even if we do figure out all of
the processes behind how we got here, it still
does not answer why we are here. There
could always be an ultimate power behind it
all. This is an area of faith.
1. Spontaneously created from nothing (like
Quarks appear to be) – all natural laws
etc have developed randomly over time
2. There are basic laws / creative powers
‘behind’ nature that explain how it has
come do develop the way it has. This
creative power is the final explanation of
the universe (which some people also