Chapter 22- Makeup of the Universe

Question 1

what does “the universe was very dense and hot” mean

Answer 1

that the universe was full of particles and radiation

Question 2

cosmic microwave background

Answer 2

• electromagnetic radiation as a remnant from an early stage of the universe in Big Bang cosmology
• evidence of BBT

Question 3

what does it mean that we needed to wait of universe to become transparent

Answer 3

-the time of Recombination: the universe cooled enough for neutral atoms to form

Question 4

ho long did we wait for the microwave background to start

Answer 4

380,000 years

Question 5

cosmological redshift

Answer 5

-photons were stretched

Question 6

isotropic

Answer 6

same in all directions

Question 7

we know that cosmic microwave background is isotropic, so what can we infer

Answer 7

that Big Bang evidence is everywhere in the sky

Question 8

closed (sphered) universe geometry

Answer 8

• positive curvature

- mass density exceeds critical limit

Question 9

flat universe geometry

Answer 9

• zero curvature

- mass density equals critical limit

Question 10

open universe geometry

Answer 10

• negative curvature

- mass density less than critical limit

Question 11

what suggests that the universe is flat

Answer 11

angular separation of temp fluctuations

Question 12

what are the two problems with our universe

Answer 12

1) isotropy problem

2) Flatness problem

Question 13

what is the isotropy problem within the universe

Answer 13

• the uniform appearance of cosmic microwave background creates a problem
• how did all parts of the observable universe achieve a common temp
• to have a common temp things have to touch and some parts of the universe are just now coming in contact

Question 14

what is the flatness problem within the universe

Answer 14

• if the density is greater than 1 then the universe would end in a Big Crunch
• if the density is less than 1 then the universe wouldn’t have enough matter to form
• how did the density magically equal one

Question 15

inflation in the universe

Answer 15

universe expands by rapid factor (faster than the speed of light)

Question 16

planck epoch

Answer 16

• unknown physics
• need a theory of everything to describe this epoch
• all 4 forces of nature would have been unified

Question 17

dark matter

Answer 17

-an undirected form of mass that emits little or no light. but whose existence we infer from its gravitational influence

Question 18

dark energy

Answer 18

an unknown form of energy that seems to be the source of a repulsive force

Question 19

evidence of dark matter

Answer 19

• galactic rotation curves
• gravitational lensing
• cosmic microwave background

Question 20

makeup of universe

Answer 20

73% dark energy
22% dark matter
4% He/H
other stuff is stars and radiation

Question 21

what we DO know about dark energy

Answer 21

• there is more of it than anything else

- it acts like antigravity