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1
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
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