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Astronomy 101 > Final Stretch 2 (50% of Final) > Flashcards

Final Stretch 2 (50% of Final) Flashcards

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1
Q

What does an explosion suggest about the big bang and the universe?

A
  • Most distant galaxies from the point of explosion moving away fastest
  • Less massive galaxies move faster
  • Earth would have to be located at ‘ground zero’
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2
Q

What does an expansion suggest about the Big Bang and the universe?

A
  • most distant galaxies from PoV appear to be moving away fastest
  • No dependence between a galaxy’s recessional velocity and mass
  • Expect a random distribution of mass
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3
Q

Was the Big Bang an explosion or an expansion?

A

An expansion

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4
Q

What is the reasoning for the myth to suggest that the universe is not expanding?

A
  • Light loses energy as it travels which causes the redshift
  • This would make galaxies seem to be moving away from us when in reality they are stationary
  • This was theorised by Zwicky
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5
Q

Why is it hard to argue that light ‘gets tired’

A
  • There is no mechanism to prove how or why this would happen
  • It cannot explain the blackbody spectrum of the CMB
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6
Q

How can we test the theory of tired light?

A

Tired light predicts that supernova explosions should have a duration independent of their distance from Earth, while the Big Bang theory says that the explosions further away will las longer as light is redshifted.

The big bang model has shown to be true

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7
Q

What is the steady state theory?

A
  • The theory that the Hubble constant has, indeed been constant all throughout time
  • New matter is created in a ‘c-field’ as the universe grows so that the density of the universe remains constant
  • Jets observed around things like quasars and black holes can be potential sites of growth
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8
Q

How can we test the steady state theory?

A

Distant universes should look the same as nearby universes. BUT this it not the case

CMB also proves that the universe use to be hot and opaque

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9
Q

What does MOND stand for?

A

Modified Newtonian Dynamics

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10
Q

What is MOND?

A

The theory that we may simply just not understand gravity

  • inventing DM seems like a little bit of a stretch
  • Newton’s law of gravity is wrong when it is applied to very weak gravitational forces. This explains the orbits of peripheral stars in spiral galaxies
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11
Q

Is MOND plausible?

A

It was only invented to make the numbers work, but it cannot actually be disproven so it is still plausible

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12
Q

How many stars are there in the Milky Way?

A

Around 1 billion

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13
Q

How many stars can you see from a dark, clear spot?

A

Around 6,000

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14
Q

How was the Hubble Deep Field taken?

A
  • 10 Day exposure

- Tiny fraction of the sky (size of a grain of rice)

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15
Q

How old did the redshift of certain galaxies suggest they were in the Hubble Deep Field?

A

12 billion years old

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16
Q

How was the Hubble Ultra Deep Field taken and what does it suggest?

A
  • 1 million second exposure
  • Size of a grain of sand in the sky
  • Through infrared detection, we can see 700mn years into the past
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17
Q

What is on way that galaxies can grow?

A

They can merge with other smaller galaxies

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18
Q

Who tried to make a map of thee universe using the data from the Hubble ultra deep field?

A

Hochra and Geller

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19
Q

How did they build a map of the universe?

A
  • picked a slice of the sky and counted + measured distances to the galaxies within it
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20
Q

What was unique about the first strip that Geller and Hochra measured? What was it called? How big was it?

A

It was in the shape of a man

It was called homunculus

It was 700mly long

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21
Q

What did the homunculus suggest about the universe?

A

That it was not the same in all directions

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22
Q

What did a larger survey of galaxies in the universe prove?

A

That the universe had an overall cosmological principle to it.

There was a Great Wall in the Southern Hemisphere as well as in the northern hemisphere

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23
Q

What is the Sloan Digital Sky Survey?

A

Wanted to measure the brightness of 100MN objects and form a 3D map of the universe.

Would do this by measuring the redshift of certain galaxies

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24
Q

Why does the universe have a honeycomb shape to it?

A

Over time, gravity would pull H and He into this shape

25
Q

What is the Hubble graph?

A

A graph of velocity of the galaxies moving away against the distance from us. The further away they are, the faster they move

26
Q

If the expansion of the universe is slowing down, will the Hubble Constant be bigger or smaller than in the past?

A

H will be smaller, even though it was bigger in the past

27
Q

What did investigations of supernovae reveal about the nature of the universe?

A

There were multiple experiments involving the measurement of luminosity and distance of supernovae

They all came to the conclusion that the universe was accelerating

28
Q

What is the primary theory that suggests the cause of this acceleration?

A

Dark Energy

29
Q

What is Dark energy?

A

some kind of repulsive gravitational force that pushes the universe to expand

30
Q

What are the 3 DE related ways that the universe could end?

A

DE could stop, causing a Big Crunch
DE will remain constant and causes consistent expansion
DE will become stronger and rip the universe apart in a Big Rip

31
Q

How much of the universe is made up of DE?

A

69%

32
Q

What is one possible cause for DE?

A

It is caused by repelling particles

33
Q

What is the flatness problem?

A

The theory that, as the universe expands, the actual density of the universe should decrease. This means that thee universe should change over time

UNLESS omega = 1, in which case the universe will remain the same

34
Q

Why does omega = 1 mean that the universe will be the same as it expands?

A

Its a very special case, and there is a formula that only works when omega = 1

35
Q

What is the difference between DE and DM

A

DE pushes things apart

DM keeps things together

36
Q

what happens to the size of the universe over time?

A

The size of the observable universe grows over time. This means that we ave to wait longer to see stars that are far away

37
Q

What is the ‘Horizon Problem’?

A

How can widely separated regions of the universe be in such amazing thermal equilibrium

38
Q

What must happen in order to form a blackbody spectrum?

A

The atoms must collide many many times

BUT, they are currently millions of lightyears apart

39
Q

At some point in the past, everything was closer together. Does this solve the Horizon Problem?

A

NO

40
Q

What is the solution to the Horizon Problem?

A

Inflation

41
Q

who came up with the theory of inflation?

A

Alan Guth

42
Q

What was the inflation era?

A

The era where the universe grows 10^100 times in about 10^-35 seconds

43
Q

In the inflation era, how big would an atom become?

A

10^85m (our universe is only 10^27)

44
Q

What happens to the shape of the universe after inflation?

A

The observable universe has grown so much that it appears flat

45
Q

What does inflation demand omega to be?

A

1

46
Q

What would omega be without inflation?

A

0.9 at 1sec AB and therefore 10^-14 today

47
Q

What does inflation mean about the speed of light?

A

The universe can expand faster than thee speed of light?

48
Q

What does inflation not tell us?

A

What caused it

49
Q

What did Linde say about the universe?

A

If a universe just popped into being out of nowhere before, why has it not happened since?

50
Q

What does quantum mechanics possibly explain about the cause of inflation

A

At a tiny, tiny scale, particles move in a random, foamy state. Maybe one of these bubbles just kept on going and our universe is just one of these fluctuations

51
Q

What is the relationship between Inflation and the cosmological constant?

A

Inflation does not work without it

52
Q

What do the variations in the clumps of CMB indicate?

A

The conditions of the early universe

53
Q

Why is Antarctica a good place to do astronomy?

A

humidity is almost 0 and the water absorbs the radiation

54
Q

What did BICEP discover

A

trick question

They thought they discovered patterns in the CMB to describe inflation, but they were premature in making this judgement

55
Q

What do Planck and HST disagree on and why?

A

the value of H

No one knows why

56
Q

What is the gap between the theory over the amount of DE and the actual amount of it?

A

theory predicts there to be 10^120 times more DE than Matter, but in reality there is only 2.2x more

57
Q

What does string theory say about the number of particles>

A

there is not 17 types of particle, but instead only one string-type particle

58
Q

How do strings explain protons and neutrons?

A

they vibrate in a way that mimics them

59
Q

What is the issue with string theory?

A

THERE IS NO PROOF

Astronomy 101 (15 decks)

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