Transcript Origins Of The Universe

Friday, April 8, 2016
Stars
 To understand the life cycle of stars
The Universe
 What is the origin of the Universe?
 A lot of evidence and information has been gathered about the
universe, and observations have led to the development of the Big
Bang theory
 The theory states that originally all the matter in the universe was
concentrated into a single incredibly tiny point
 This began to enlarge rapidly in a hot explosion, and it is still
expanding today – this Big Bang happened about 15 billion years
ago
Big Bang
 Since all galaxies appear to be moving apart at a rapid rate, this
suggests there was an initial explosion – the Big Bang
 All the matter in the Universe must have been compressed into a
very small space, which exploded and expanded around 15 billion
years ago (and is continuing today)
 The age of the Universe can be estimated by the current rate of
expansion (although accuracy is a problem as it is difficult to
identify if this expansion has been slowing)
 The rate of expansion is important as this will decide the future of
the Universe (gravity slows the expansion down…)
Future Of The Universe
 The fate of the Universe depends on how fast the expansion is, as
well as the total mass within it (tricky to identify as our
observations of how much mass are much lower than our
predictions – most mass is probably contained within black holes
/ dark matter etc… which become difficult to identify)
 Depending on the rate of expansion and mass of the Universe two
possibilities exist (excluding the steady state theory):  The Big Crunch – if there is a critical mass compared to the
expansion then the Universe will eventually stop expanding
and begin contracting (which could be cyclic…)
 Constant expansion – if the mass is below the critical point
then the Universe will expand forever
Stars
 Stars go through many stages in their lives
 Protostar – star formation initially from clouds of dust and
gas where gravity makes the dust and gas spiral together
 Main sequence star – a stable period where the force of
gravity is balanced by an equal outward pressure caused by
nuclear fusion
 Red giant – star runs out of hydrogen and eventually swells
then cools, finishing ‘life’ as a white dwarf
 Red super giant – very large stars run out of hydrogen and
swell and then explode in a supernova, finishing ‘life’ as a
neutron star or black hole
Stars