Cosmology

Question 1

regard galaxies as ___ test ___

Answer 1

cosmic/particles

Question 2

galaxies follow a ___ and ___ distribution

Answer 2

homogeneous/isotropic

Question 3

___ in the microwave background radiation is ___ in all directions

Answer 3

temperature/the same

Question 4

some time ago all galaxies we see today must be at ___ point

Answer 4

the same

Question 5

motion of galaxies is due to ___ forces acting on them by other objects superimposed with general ___ caused by expansion of space

Answer 5

gravitational/receding velocity

Question 6

___ force much stronger than ___ force

Answer 6

EM/gravitational

Question 7

___ and ___ forces exert no significant forces between atoms as they are ___ ranged

Answer 7

strong/weak/short

Question 8

___ and ___ forces influence over very large scales as it is a ___ distance to decay and vanish

Answer 8

electromagnetic/gravitational/long

Question 9

___ is the dominant force as the attraction of very massive objects is felt over vast distances

Answer 9

gravity

Question 10

gravitational attraction makes a uniform distribution of mass ___

Answer 10

unstable

Question 11

small fluctuations in ___ attract more than their surroundings

Answer 11

density

Question 12

universe looks the same in every position

Answer 12

homogeneity

Question 13

universe looks the same in every direction

Answer 13

isotropy

Question 14

___ implies ___ but not necessarily the reverse

Answer 14

isotropy/homogeneity

Question 15

universe with uniform distribution of matter rotating around some point looks ___ but it is not ___ as its rotation velocity differs in different directions

Answer 15

homogeneous/isotropic

Question 16

Olber’s paradox: if the universe were infinite, every ___ will eventually intersect a star somewhere

Answer 16

line of sight

Question 17

we assume the universe is:
finite in ___ (modern view)
infinite in ___
___
___
space is ___

Answer 17

time/
space/
static/
homogeneous/
euclidean

Question 18

hubble flow is relevant only on ___ scales

Answer 18

large

Question 19

___ velocity: velocities induced by ___ effects of structures which have detached from hubble flow

Answer 19

peculiar/gravitational

Question 20

___ velocity dominates over hubble flow for ___

Answer 20

peculiar/galaxies

Question 21

___ coordinate is a coordinate system that expands with space

Answer 21

comoving

Question 22

energy density of universe is dominated by ____ matter and does not include contributions from ___ and ___

Answer 22

non-relativistic/photons/dark matter

Question 23

test bodies move along ___ trajectory - not necessarily a ___ line

Answer 23

shortest/straight

Question 24

matter tells space how to ___, space tell matter how to ___

Answer 24

curve/move

Question 25

proper separation of two events is ___ and independent of observer

Answer 25

invariant

Question 26

___ specifies rules that govern how distance is ___and ___ in a given space time

Answer 26

metric/defined/measured

Question 27

positive curvature ___ universe

Answer 27

closed

Question 28

negative curvature ___ universe

Answer 28

open

Question 29

flat curvature ___ universe

Answer 29

flat

Question 30

friedmann,___ and ___ equations are not all independent

Answer 30

acceleration/fluid

Question 31

some particles have such ___ interactions that they would pass through without being ___

Answer 31

weak/reflected

Question 32

relativistic particles are called ___ in cosmology, and they have large ___ motions

Answer 32

radiation/random

Question 33

___ pressure: a particle moving towards the right will meet a counterpart particle with the same ___ moving towards the left

Answer 33

radiation/momentum

Question 34

non-relativistic particles have ___ random motions

Answer 34

negligible

Question 35

any of the friedmann, acceleration and fluid equations can be derived from ___

Answer 35

the other two

Question 36

dark energy does not participate in ___ interactions so its existence is inferred through ___ effects and density remains near ___ as the universe expands

Answer 36

EM/gravitational/constant

Question 37

as universe expands, newly created space has ___ energy as density can stay constant

Answer 37

vacuum

Question 38

in a vacuum, pairs of particles and antiparticles are ___ and ___ after a short time

Answer 38

created/annihilate

Question 39

critical density is an ___ estimate of the density in the universe and is very small

Answer 39

order of magnitude

Question 40

density greater than critical density ___ universe

Answer 40

closed

Question 41

density equal to critical density ___ universe

Answer 41

flat

Question 42

density less than critical density ___ universe

Answer 42

open

Question 43

density parameter is roughly the ___ of a given matter species to the universe's expansion rate

Answer 43

fractional contribution

Question 44

expansion halts at ahalt and universe starts to ___ eventually collapsing back to a ___

Answer 44

contract/singularity

Question 45

k=0, density par0.=0 then universe would ___ forever but its rate ___ as time passes

Answer 45

expand/diminishes

Question 46

k<0, density par0.<0 the universe ___ forever but at an asymptotically ___ speed

Answer 46

expands/constant

Question 47

attractive gravity between matter tends to ___ expansion but can be reversed if there is enough matter

Answer 47

slow down

Question 48

ahalt gets closer to 1 if density par0. ___, adding more matter more quickly ___ and ___ expansion

Answer 48

increases/slows down/reverses

Question 49

open universe: expands forever and approaches an ___ or ___ universe in the distant future

Answer 49

empty/constant

Question 50

closed universe: expansion ___ and ___ in future

Answer 50

halts/recollapses

Question 51

flat universe: expands forever, expansion rate becomes ___ in the distant future

Answer 51

smaller

Question 52

___ becomes dominant energy as we go to earlier times

Answer 52

radiation

Question 53

in a ___ universe, density par. of matter species i is the fraction of the total density contributed by the species

Answer 53

flat

Question 54

as long as we are not too close to the ___ time, the expansion history can be well approximated by the ___-component solution

Answer 54

equality/single

Question 55

when we observe objects at red-shift we are seeing the universe ___ than is it today

Answer 55

younger

Question 56

Hubble constant as a state parameter is the current Hubble ___

Answer 56

expansion rate

Question 57

Hubble constant as a cosmological parameter directly determines ___ and ___ scales in cosmology

Answer 57

distance/time

Question 58

luminosity of cepheids calibrated in our own galaxy allows us to calculate ___ to cepheids in other galaxies

Answer 58

distances

Question 59

___ speed is found to correlate with total galaxy luminosity

Answer 59

rotation

Question 60

path of light from distant galaxies can be bent by the ___ field of an intervening massive galaxy

Answer 60

gravitational

Question 61

time flows at different rates in places of different ___

Answer 61

curvature

Question 62

standard candles are astronomical objects with known ___ (regardless of their distance)

Answer 62

luminosity

Question 63

provided the ___ is high enough, other particle species than photons can become ultra relativistic and become radiation

Answer 63

temperature

Question 64

small fluctuations mean universe at last scattering is not exactly ___

Answer 64

homogeneous

Question 65

photons play ___ role in present-day dynamics of the universe

Answer 65

negligible

Question 66

there is a point beyond which photons dominate the ___ content of the universe

Answer 66

energy

Question 67

if timescale for reactions is short compared with the age of the universe then ___ is reached

Answer 67

thermodynamic equilibrium

Question 68

timescale for interactions is ___ to square of Fermi's weak coupling constant

Answer 68

proportional

Question 69

if neutrino species is larger than 3 then at a given temperature, density rel is___ hence Hubble parameter is larger. At given temperature Universe is ___ thus freeze out occurs at ___ temperature

Answer 69

larger/younger/higher

Question 70

longer half-lie implies ___ weak coupling tau and so smaller reactions and ___ freeze out

Answer 70

smaller/earlier

Question 71

luminosity of galaxies is total luminosity of ___ they contain

Answer 71

stars

Question 72

massive stars produce more ___ per unit mass so mean value M/L depends on fraction of stars that are more or less ___

Answer 72

light/massive

Question 73

close universe: light rays from opposite sides of hot spot ___ each other

Answer 73

bend towards

Question 74

flat universe: light rays from opposite sides of hot spot ___

Answer 74

do not bend at all

Question 75

open universe: light rays from opposite sides of hot spot ___ each other

Answer 75

bend away from

Question 76

closed universe: structures appear ___ and therefore ___ (CMB peak towards ___)

Answer 76

larger/closer/left

Question 77

open universe: structures appear ___ and therefore ___ (CMB peak towards ___)

Answer 77

smaller/further/right

Question 78

positive galaxy correlation indicates that galaxies ___

Answer 78

clump together

Question 79

zero galaxy correlation function implies that galaxies are ___ distributed

Answer 79

randomly

Question 80

___ matter density than environment means it pulls more matter

Answer 80

higher

Question 81

in the ___ model there was a period of very rapid expansion before the radiation-dominated era

Answer 81

inflation

Question 82

horizon size increases with time due to propagation of ___ and the ___ of space

Answer 82

photons/expansion

Question 83

horizon size increases ___ during inflation

Answer 83

exponentially