Cosmology and Big Bang

Question 1

studying universe methods

Answer 1

observations - deep survery of galaxies (100s of millions mapped), background radiation, and element abundances.

simplified theoretical models - examples include homogeneity, isotropy, etc.

computer simulations

Question 2

observational facts on recession of galaxies

Answer 2

fact 1: except for some near ones, light from all galaxies is redshifted.

fact 2: redshift is proportional to distance.

Question 3

recession of galaxies (hubbles law of 1929)

Answer 3

from hubble plots of recession speed vs. distance we get [v = H x D].

everything is moving away from everything else, everything looks like the center but there is no center.

distance is stretching because universe expansion happening at 70 km/s/Mps = 700 km/year/ly.

tracing back universe, it must have started from a point (big bang).

Question 4

evidence for big bang

Answer 4

expanding universe (hubble law)

cosmic microwave background radiation

abundance of elements (big bang nucleosynthess)

Question 5

big bang is twofold

Answer 5

first part if the initial creation event: point from which universe began to expand, Gamow (1940s) proposed universe began in an explosive event giving birth to matter space time, etc. 13.8 billion years ago.

second part is the entire physical model/scenarios of universe’s evolution from t=0 onward; expansion, cooling, nuclear reactions, radiations, etc.

Question 6

big bang theory beginning

Answer 6

very dense very hot beginning, first energy produces particles, then protons fuse to make helium (plus a little lithum and berilium) during first 3 minutes of universe

380,000 years later hydrogen forms; matter.

full model traced evolution of universe in time.

Question 7

future of the universe

Answer 7

depending on matter/energy/density:

eternal expansion/big rip, collapse/big crunch, equilibrium

Question 8

big rip

Answer 8

universe expands infinitely, expansion accelerates overtime until everything tears apart.

Question 9

big crunch

Answer 9

gravity slows and expansion reverses, universe contracts back to a hot/dense state, possible reversal of big bang.

Question 10

equilibrium

Answer 10

universe stabilizes, balances forces prevent expansion or collapse, stability is long-term