Year 12 Physics - The Big Bang and Universe Expansion

what is the big bang theory

a widely accepted understanding of the origin of the universe

it proposes that the universe originated from a singularity of concentrated energy

when were the 4 fundamental forces created

at the very start of the big bang

what are the 4 fundamental forces

strong nuclear

electromagnetic

weak nuclear

gravity

when and which fundamental force separated first

gravity separated first, leaving the other 3 as a grand unified force

this occured when temperatures cooled to 10³²

when and which fundamental force separated second

strong nuclear

when temperatures cooled to 10 to the power of 27

what was more abundant first

radiation was more abundant than matter

what did expansion cause

the release of energy, hence cooling the universe rapidly and matter could then form

why was it important that inflation was rapid

to prevent the universe from collapsing back into a black hole

what did the fundamental particles form from

radiation

compare particles to antiparticles

they have the same mass but opposite features/characteristics e.g. charge

how were particles intiially made

pair production

the particles would be made with their matching antiparticle

however they quickly annihilated to reform gamma photons

what caused particle antiparticles to decrease

the continuous expansion and cooling

what did a decrease in collisions lead to

a decrease in conversion of matter to collision

imbalance of particles and antiparticles

excess particles resulted in baryogenesis

what is baryogenesis

the combining of quarks

how were hydrogen nuclei formed

protons and neutrons collided to from H-2 nuclei but high temperatures saw these quickly decompose back to the protons and neutrons

H-2 stopped decomposing when temepratures were low enough

H-2 collided with neutrons to form H-3

how was helium formed

H-3 collided with protons to from He-4

when did nucleosynthesis stop

when the temperature had fallen enough so that the energy was insufficient for collisions

how were atoms formed

the temperature cooled enough for nuclei to capture electrons

how did heavier elements form

by nuclear fusion in stars and supernova explosions

how did edwin hubble discover expansion

using large telescopes to obtain long spectral exposure of galaxies

he used the doppler shift of hydrogen absorption lines to determine galaxies velocities relative to earth

what does red shift suggest

that galaxies are receding from earth

explain hubbles law

that the recessional velocity of galaxies is proportional to its distance from earth

what does the reciprocal of hubbles constant represent

used to get the age of the universe

what is cosmic background radiation from

it is remnants of gamma radiation described in the big bang model

as the universe/space expanded, the gamma wavelength increased to that of microwaves

describe the analysis of primordial elements

the amount of H and He isotopes became fixed when the universe temperature was too low for collisions

therefore the mass ratio of H and He can be predicted and compared to the present value

the big bang predicts that the majority of the universe mass is due to H and He