our view of the universe is a limited one because..

.. lights from objects further away than a certain distance

(defined by travel time of light in the lifetime of the universe)

has not reached us

how many light years is our observable universe?

where is it centered?

how old is our universe?

a sphere of radius 13.7 billion ly centered on the earth

our universe is thus 13.7 billion years old

what is the primary evidence for the expanding universe?

the rate of expansion of the universe (according to type 1a supernovae) is

accelerating/decelerating because of __________

rationale for the big bang

when did the universe explode?

based on current size and expansion rate of the universe, (confirmed by systematic measurements)

it exploded about 13.7 billion years ago

the age of the universe if it has expanded since the big bang at a constant rate

equivalent to 1 divided by the Hubble constant

radiation from the hot clouds of the big bang explosion

radiation left over from the big bang (after the universe expanded and cooled)

what is the temperature of blackbody radiation that we receive from the Big Bang?

why is it so cool?

2.7 K

it is so cool because the universe has expanded and cooled since the big bang

also, because of the large red shift

matter composed of antiparticles,

which upon colliding with a matching particle of normal matter

annihilate and convert the mass of both particles into energy.

recombination

the stage, within 300,000 years of the big bang,

when the gas became transparent to radiation

where are the photons that won their freedom when the universe became transparent to photons (during recombination)?

photons released when the universe became transparent to photons have been traveling ever since in all directions.

due to the expansion of the universe, their wavelengths have increased and energies decreased.

now easily observed as 2.7 K CMBR

how do the photons released from recombination supply evidence and support for the big bang?

remember- recombination is when gas became transparent to radiation- thus, universe became transparent to photons

these photons are now CMBR (2.7 K)

temp and distribution of this radiation agree with calculations based on expansion rate of universe

thus- big bang theory

dark age

before what?

after what?

the period of time ...

after the flow of the big bang faded into the infrared and

before the birth of the first stars

during which the universe expanded into darkness

the stage in the early history of the universe when ultraviolet photons from the first stars ionized the gas filling space

the cosmological principle states that, on the largest scales-

1. the _ properties of the universe are the same everywhere

2. the local universe looks __

3. the laws of physics __

1. the physical properties of the universe are the same everywhere

 2. the local universe looks the same in any direction that one observes.

3. the laws of physics are the same everywhere in the universe

if you travel in a straight line in a ___..

you will eventually return to your starting place

((universe does not have a center or boundary))

if you travel in a straight line in a __ universe,

you will continue to see new material forever.

((universe does not have center or boundary))

measurements of the fluctuations in the CMB

how does matter and energy density of the universe affect its curvature?

if density is large?

moderate?

small?

if the avg density of matter/energy is large --> gravity dominates and will eventually close

if density is moderate, the "flat universe" will expand forever

if density is small- expansion dominates- "open universe will expand forever

Big chill

define-

what kind of universe does this relate to?

if the average density of matter in the universe is small,

 then expansion dominates,

the "open universe" will expand forever

Big Crunch

define-

what kind of universe results in this?

if avg density of matter/energy is large,

gravity dominates

will cause closed universe

the big chill and big crunch are results of...

the curvature of the universe

(critical density)

Nonbaryonic Matter

the peculiar circumstance that the early universe must have contained exactly the right amount of matter to make space-time flat.

Horizon Problem

the circumstance that the primordial background radiation seems much more isotropic  

than can be explained by the standard big bang theory

Inflationary Big Bang

a version of the big bang theory

that includes a rapid expansion when the universe was very young

Cosmological Constant

a constant in Einstein's equations of space and time

that represents a force of repulsion

the postulated energy that fills empty spaces

and drive the acceleration of the expanding universe

evidence of dark energy in our universe

that is a repulsive gravitational force

- available matter and energy (including dark matter) are only 30% of the amt required for a flat universe

-dark energy a repulsive gravitational force, would make up for this deficit

-supernovae explosions are dimmer than expected

-which means that our universe is accelerating

-result from the presence of dark energy

Supercluster

a cluster of galaxy clusters

what is the fate of the universe?

((if dark energy increases with time))

a big rip

if the dark energy increases with time

and galaxies, stars, and even atoms are eventually ripped apart by the accelerating expansion of the universe

Large-Scale Structure