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How the Universe evolved

Science and Religion in Schools - Unit 4aThe Scientific Account of the Beginning

The Big Bang The old Steady State theory

has now been rejected The universe and all the

structures in it has evolved - things have changed over time

The initial events are still mysterious, but we understand the broad outline of history from the first few seconds onwards

Simple starting points The universe is 13.7

billion years old This images dates

from 300 000 years into history

It shows how matter was arranged in the universe

Red means lower density of matter, blue means higher

Very little structure in the early universe

Clusters of galaxies Galaxies are grouped in

collections or clusters Gravity is pulling these

galaxies together Sometimes galaxies collide

(see later) On the largest scales,

clusters of galaxies are grouped into superclusters

Between superclusters there are vast empty regions of space

The large scale structure of the universe

This picture has been generated by computer using information from special telescopes

Every ‘dot’ is a cluster of galaxies

The ‘filaments’ and ‘voids’ can be seen

Colliding galaxies 63 million light years from

Earth, two galaxies are seen colliding

Left hand image shows an over-all view and the galaxies are seen again in more detail on the right

Star formation can be seen along the arms where the collision is taking place

Such collisions were frequent in the early universe and may have had a lot to do with how stars formed

Triggering star formation

Galaxies in collision 500 million light years from Earth

One of the two objects on the right punched a hole through the main galaxy on the image

A ring of bright, hot,young stars has been formed as a result of the shock wave from the collision

Star formation in gas clouds

M16 Eagle nebula 6,500 light years from Earth

Long, thin pillars of gas At the end of each

pillar, there is a star forming

Another image of the Eagle nebula - in close up

The ‘fingers’ can easily be seen

Life of a star Stars are giant balls of ‘burning’

gas - mostly hydrogen Nuclear reactions in their cores

generate energy They also ‘fuse’ light elements

(like hydrogen and helium) into heavier ones (like carbon and oxygen)

Without stars there would be no life as we understand it

We need their warmth, the planets that orbit them and the elements they create

Death of a star When stars die, they shed material

into space This includes the heavier elements

made during the star’s life As new stars form, they pull these

elements towards them

Stars explode Sometimes stars die by

exploding (supernova) In these gigantic events, the

exploding star can be brighter on its own than a whole galaxy

The explosion blasts elements into space

Heavy elements (iron etc) are made in these explosions

The start of solar systems These are images of stars in the

Orion nebula Each star (red dot) is about a

million years old and surrounded by a ring of dark material

The dark material will probably go on to form planets

It is the heavier material left over from when the star formed

Evidence for planets The star is Gliese 229,

about 18 light-years away

It is 20-50 times heavier than Jupiter, but only about the same size

It is roughly the same distance from its star as Pluto is from our Sun

Another possible planet 450 light years from Earth It is about 2-3 times the size of

Jupiter Could be a background star

(perhaps 2% chance) Possible planet is about 210

billion km from the stars and moving at 10 km/s

Recipe for life Origin of life is not well

understood Perhaps the formation of

organic molecules in the chemical bath of the Earth was triggered by lightning

Perhaps Earth was ‘seeded’ with organic molecules from space

Seems likely that to take hold, life would need a set of circumstances not found on all planets

Oxygen is a clue to the presence of life

DNA Self replicating molecule Twin helix (coil) with the two arms

cross-linked to each other The two arms can be un-coiled and

each can reproduce the other Segments of DNA can also link

chemically to specific amino acids Amino acids assembled in sequence

build proteins Sequences of DNA can hence make

specific proteins DNA contains the information to

build copies of itself and specific chemicals within the organism

Cells A vital step in the evolution of life All living forms are composed of

one or more cells In complex forms, cells contain

nuclei and organelles Organelles carry out various

functions within the cell Nucleus contains DNA molecules

coiled up into chromosomes Cells probably evolved to protect

the DNA from the environment

The tree of life Evolution well established as a

biological theory Links Mendel’s idea of genes with

Darwin’s natural selection Mutation of the gene gives rise to

changes in the organism These changes can be beneficial

(more offspring) or not (fewer offspring)

Beneficial changes are passed to offspring

Gives rise to biological diversity

The brain The most complex system known

to science One million billion synaptic

connections Constructed out of the same

material as the rest of the universe (carbon, oxygen, nitrogen etc as made by stars)

The seat of consciousness that understands the universe