big bang

The big bang theory is a theory scientists have accepted as a possible explanation for the universe creation

Before the big bang there was no universe, no matter, no space. Absolutely nothing

  1. The Big Bang: 13.7 billion years ago EVERYTHING erupted from a single point called the singularity

  2. Inflation: 10^-35 seconds after the big bang. In less than a second the universe rapidly expanded

  3. Fundamental forces appear: 10^-43 seconds after the big bang gravitation and electromagnetic and strong and weak nuclear forces appeared. This is called the Planck Era

  4. Creation of Subatomic Particles: The particle era occurred 10^-10 - 10^-3 seconds after the big bang when the universe rapidly cooled forming atoms with protons, electrons and neutrons

  5. Creation of Atoms: 3 seconds after the universe continued to cool down to 3000ºc and plasma ended. The first atomic nuclei formed were primarily hydrogen and helium

  6. Light shines:  10,000 years after, due to plasmas disappearing and atoms appearing photons move freely and light shone. This is called the Radiation era

  7. Galaxies and stars form: 300million years after gases merged together forming the first stars and galaxies

  8. Solar systems form: 5 billion years ago the solar nebula, a spinning disk of dust and gas formed our solar system

  9. Planets form: 4.5 billion years ago first dying stars produced heavy elements were pulled together by gravity to produce new stars and planets

  10. Life begins: 3.5 billion years ago Earths atmosphere formed and the first life appears as microscopic bacteria like organisms

 

Evidence of the big bang:

 

-Cosmic Background Radiation (CBR)

-Key pieces of evidence of the big bang includes CBR, electromagnetic waves detected throughout the universe left over from the intense heat of the early stages of the big bang

-The universe used to be extremely hot and heat left behind a glow

-If big bang was accurate the glow should still exist today

-In 1965 engineers tracking communication satellites accidentally discovered CBR as there were background signals interfering with their measurements

-When trying to find the signal's source it was deduced it was coming from every point of the sky confirming it was CBR

-Once the universe was too hot to contain atoms and once cooled nuclear fusion began fusing hydrogen nuclei to helium atoms and released energy uniform throughout the universe

-The energy released as light waves that were stretched to low energy waves called microwaves which are now known was CBR and the oldest signal we can detect on Earth

 

 

-Redshift:

 

-Hubble's Law Describes the relationship between the distance of galaxies and their velocity, indicating that the universe is expanding.

-Galaxies are moving away from us; the farther they are, the faster they recede.

-The expansion supports the Big Bang theory, which posits that the universe originated from a hot, dense state.

-Light from distant galaxies shifts to longer wavelengths (red) due to their motion away from us; indicates an expanding universe.

-As galaxies move away, light's wavelength stretches, lowering its frequency.

-Some galaxies may exhibit blueshift (light appears blue), indicating they are moving toward us due to gravitational attraction.

-Hubble's Law and the observed redshift of light provide critical evidence for the continuous expansion of the universe since the Big Bang.

 

Composition of the universe:

-The big bang explains the presence of hydrogen and helium along with other evidence

-As the universe expanded then cooled down abundance of elements were created by nuclear fusion

-Ratios of hydrogen, helium and other elements are measured by scientists, and by studying distant galaxies and old stars it was concluded that our universe used to be 73% hydrogen and 25% helium

-When calculating the ratio of hydrogen and helium in todays universe based on the early universe's conditions, the ratios (3:1) were almost the exact match, supporting what the big bang states about the early compositions of the universe

-In conclusion with its high proportions of helium and hydrogen along with other elements formed through nuclear fusion

 

 

Life cycle of a star:

  1. Nebula: a star starts off as a big cloud of dust and gas mostly hydrogen

  2. Protostars: Gravitational forces pull the particles of the nebula closer together increasing temperature and density. The friction caused by the particles brushing past each other produces more heat and light is emitted

  3. Main sequence star: Eventually hydrogen nuclei gain enough energy that they start to fuse when they collide. This forms heavier, helium nuclei. this process is called nuclear fusion and the star is now known as a main sequence star.

The next stage of the star depends on its size, they can either be the same size as the star or larger depending on its initial mass.

For stars the same size

  1. Red Giant: The fusion of larger nuclei causes an increase in the thermal energy store at the stars core making it expand into a red giant

  2. White dwarf: At the end of the red giant stage, the fusion stops and the gravitational forces are stronger than the expansive forces. This imbalance causes the star to collapse inwards and the outer layers of the star are expelled and left over core is known as the white dward. White dwarf stars are very bright and very hot as all their energy is condensed to a small core

  3. Black dwarf: Over time this energy is emitted into the surroundings and the star gets dimmer and dimmer until it turns into a brown and then a black dwarf star

For stars bigger than the sun

  1. Red supergiant: The fusion of larger nuclei in the main sequence star causes an increase in the thermal energy store in its core. This increase causes the star to rapidly expand

  2. Supernova: The fusion of nuclei up to the size of iron causes the core to become more dense and when the supergiant runs out of fuel it collapses. The shockwaves resulting form this collapse cause the star to explode into a supernove, and when a supernova runs out of fuel its core is so heavy that it graviational forces pull the outer layers of the star towards the centre causing it to collapse

  3. Neutron stars and black holes: At the centre of a supernova the particles form an incredibly dense core. Most supernovae collapse to form neutron stars and fusion does not occur in this stage. The largest supernovae form black holes and gravity in black holes is so strong that not even light can escape