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Astronomy > Big bang and early universe > Flashcards

Big bang and early universe Flashcards

1
Q

Describe big bang

A

•occurred everywhere-all space
•is a process/era, not a point
•may have followed in from an earlier phase

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2
Q

What does universe expanding mean for past of universe?

A

•it was all much closer together-big bang
•or it has gradually been created as it expands-steady state

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3
Q

What were earliest attempts to test bb v ss?

A

•used numbers of radio sources per volume as function of redshift
•if universe not evolving should not change
•favoured bb

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4
Q

Why is cosmic microwave background evidence for bb?

A

•uniform across sky
•if interpreted as black body then temperature about 3 K
•as predicted by bb cosmology

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5
Q

What happens when you heat up gas enough?

A

Plasma
•free electrons and protons
•scatters photons so opaque

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6
Q

What happened when universe cooled?

A

•electrons bound to protons(recombination)
•universe became transparent and photons escaped-travelling ever since

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7
Q

When was universe hot enough for plasma?

A

380,000 years after bb

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8
Q

How does CMV preserve density structure?

A

Tiny variations in temperature

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9
Q

How much do hot spots caused by gravitational redshift vary?

A

1 part in 10^5

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10
Q

What are structures visible in density pattern of early universe?

A

Progenitors of galaxies

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11
Q

What measured CMB spectrum?

A

COBE space telescope
•perfect black body spectrum

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12
Q

What must any theory of the universe confront?

A

CMB measurements such as temp fluctuations, energy, shape measures

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13
Q

What completely killed steady state theory?

A

CMB measurements

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14
Q

What are the four known forces?

A

Gravity, electromagnetism, weak and strong nuclear

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15
Q

What are known forces believed to be?

A

Aspects of one underlying force

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16
Q

What is proof for general relativity?

A

Black holes

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17
Q

What is proof for quantum mechanics?

A

Zero point energy

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18
Q

Are GR and QM compatible?

A

No but both compatible with classical physics

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19
Q

What theory do we need to understand QM and GR?

A

Quantum gravity

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20
Q

What is zero point energy?

A

Quantum theory implies density fields have tiny fluctuations

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21
Q

In early universe what do fluctuations mean?

A

•early universe incredibly dense
•small fluctuation in high density field can be very large
•so in early universe fluctuations large enough that they should be black holes

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22
Q

What is Grand Unified Theory(GUT)?

A

Theory combining strong and electroweak forces

23
Q

What happened in GUT era?

A

Gravity and GUT force only forces acting

24
Q

What happened at end of GUT era?

A

GUT Force split into strong and electroweak force

25
Q

What was the inflation era?

A

A short but ultra-rapid acceleration of cosmic expansion

26
Q

How long did inflation era last?

A

10^-36 seconds and made scale factor 10^26 times bigger (size of atom to solar system)

27
Q

What was inflation era driven by?

A

One or more scalar fields going through a transition and releasing energy

28
Q

What are motivations for inflation?

A

•cosmic structure
•horizon problem
•flatness

29
Q

What’s the link between inflation and structure?

A

Could have blown up atom sized fluctuations in density to solar system sized ones- progenitors of structure today

30
Q

What is the universes horizon?

A

14 billion light years away but horizon changes with time

31
Q

What did inflation expand?

A

A tiny region that was close together in thermal equilibrium

32
Q

Can the universe as a whole have an overall curvature?

A

Depends on matter of density compared to a critical value

33
Q

What is flat geometry?

A

A special case where density perfectly matches expansion

34
Q

What shape is universe if p<pcritical?

A

Hyperbolic

35
Q

What shape is universe if p>pcritical?

A

Spherical

36
Q

What predicts flatness of universe?

A

Inflation
As space enlarges quickly it gets closer and closer to flat. So any pre inflation curvature would be flattened out and only detectable on scales larger than horizon

37
Q

What happened at end of electroweak era?

A

Electroweak force split into electromagnetic and weak forces

38
Q

What happened during electroweak era?

A

Particles continuously created and annihilated (soup of fundamental particles)

39
Q

How can we reach energy of electroweak era?

A

In particle accelerators above 10^15K. W and Z boson behaviour matches theories

40
Q

When did photons become dominant energy?

A

When universe cooled and spontaneous creation of particles stopped. (Particle era)

41
Q

What happened to quarks in particle era?

A

Coalesced into protons and neutrons

42
Q

What happened to matter and antimatter in particle era?

A

Annihilated

43
Q

What is baryon asymmetry?

A

In particle era, for every billion anti-protons there was a billion and one protons

44
Q

When was universe hot enough to produce nuclei(nucleosynthesis)?

A

<5 minutes

45
Q

What happens to neutrons at high temps?

A

Convert to protons and vice versa

46
Q

Why is proton production favoured at lower temps?

A

Neutrons more massive so need more energy to produce

47
Q

What did protons and neutrons fuse to form in nucleosynthesis era?

A

Deuterium and then deuterium fused to form helium

48
Q

What era was after nucleosynthesis?

A

Recombination (formation of CMB)

49
Q

What happened after recombination?

A

Dark ages( 500M years of not much)

50
Q

What happened during dark ages?

A

Tiny over dense regions in CMB maps slowly pull more matter towards them by gravity, growing. Then grow enough so smallest ones can start to form stars

51
Q

When does galaxy formation begin?

A

In first billion years after bb

52
Q

What is the current era?

A

Dark energy era

53
Q

What is dark energy era?

A

When matter decreases below density of dark energy

Astronomy (23 decks)

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