16 - Cosmology

Question 1

What is redshift?

Answer 1

The increase in wavelength/decrease in frequency of the light of an object that is moving further away from us

Question 2

How do you calculate redshift?

Answer 2

z = redshift (no units - ratio)
- z = v/c – recessional velocity/speed of light
- z = change in wavelength/original wavelength

Question 3

What is Hubble’s Law?

Answer 3

He measured redshift - noticed almost all galaxies showed redshift … theyre all moving away … universe is expanding

Question 4

How did Hubble use redshift to calc velocity?

Answer 4

Plotted a graph of velocity against distance, concluded V is directionally proportional to D

Question 5

What is Hubble’s equation?

Answer 5

v = H x D
(velocity = H x distance)
((km/s = km/s/mpc x mpc))

Question 6

What is the current value of the Hubble constant?

Answer 6

68km/s/mpc

Question 7

How do we calculate the age of the universe using Hubble’s constant?

Answer 7

Hubble’s constant is the inverse/reciprocal of time, so the age of the universe is the reciprocal of Hubble’s constant

Question 8

pt 2. How do we calculate the age of the universe w/ Hubble’s constant?

Answer 8

• Convert km/s -> pc/s. 3.1x10^19km in a pc - divide by that number
• Hubble constant = 68/3.1x10^19 = 2.19x10^-18
• AOU in S = 1/H(s) = 4.57 x 10^17s
• Convert into years - 60 x 60 x 24 x 365.25 = 31557600s in a year
• AOU in years = age in s/s in year = 1.4x10^10 = ~~ 14 billion

Question 9

How do we know Hubble’s constant is the inverse/reciprocal of time?

Answer 9

• Rearranging Hubble’s equation to make H the subject, we get H = v/d
• This is similar to the equation of speed: s = d/t
• Dividing both sides of these equations we get: v/d = d/dxt -> v/d = 1/t
• so h = 1/t … time = 1/H

Question 10

What is the Steady State theory?

Answer 10

• Universe is expanding
• Matter is being created
• Density is constant
• No beginning or end
• Not much evidence to support it

Question 11

What is the Big Bang theory?

Answer 11

• Universe is expanding
• All matter & energy created in the ‘bang’
• Universe started from a singularity point
• Lots of evidence to support

Question 12

How does the expansion of the universe support the SS & BB theory?

Answer 12

BB:
- Matter has been spreading out/further apart & away from the singularity point
SS:
- Matter created as its expanding

Question 13

What are quasars?

Answer 13

• Stands for quasi-stellar objects
• Appear like stars, actually ancient galaxies with an active galactic nucleus (AGN)

Question 14

Why are quasars important as evidence for the Big Bang?

Answer 14

• Can tell a lot about the early stages of the universe because of age; estimate star formations & what the universe was like at that time
• More common in early universe - supports evolutionary nature of the BB
• Their formation fits with models of the BB

Question 15

What is CMBR?

Answer 15

• Stands for Cosmic Microwave Background Radiation
• Microwaves all around us in equal concentration
• Heat remnant of the Big Bang, the background temperature of the universe

Question 16

Why is the discovery of CMBR important as evidence for the Big Bang?

Answer 16

• ## It tells us what happened to all the heat in the universe from that time

Question 17

How are the further studies of CMBR - COBE, WMAP & Planck - important as evidence for the Big Bang?

Answer 17

COBE:
- COsmic Background Explorer
- Picked up fluctuations in CMBR … universe is not uniform
- Produced a grainy image of these fluctuations
WMAP:
- Wilkinson Microwave Anisotropy Probe
- Produced HQ image of previous fluctuations
Planck:
- Refined this evidence
- Produced even HQ image of fluctuations

Question 18

What is the Hubble Deep Field?

Answer 18

• An image of “empty” space
• Shows a huge amount of galaxies with large amounts of redshift & a high number of disturbed/irregular galaxies

Question 19

How is the Hubble Deep Field important as evidence for the Big Bang?

Answer 19

The huge amount of redshift it shows signifies:
- Universe is expanding, everything is moving away
- Universe was more crowded than it is now
- Gives us more knowledge about the rate of galaxy/star formation over the age of the Universe
- Irregular galaxies show collisions occurred frequently in early universe

Question 20

What is Dark Matter?

Answer 20

• Believed to be close to “normal” matter
• Spread throughout the universe
• Accounts for 85% of the universe mass - greater than what we can see
• “Holds” galaxies together (pulls them closer)
  ^- Slowing down the expansion of the universe

Question 21

What is Dark Energy?

Answer 21

• Believed that 70% of the universe is Dark Energy
• Pushes everything further away
  ^- Driving the expansion of the universe

Question 22

Do Dark Matter & Dark Energy actually exist?

Answer 22

• Most scientists believe Dark Matter, however we can’t see it
  ^- Hasn’t been found yet
• Dark Energy has not found or proven - it’s undetectable

Question 23

What are the 3 current future universe models?

Answer 23

• The Big Crunch
• The Big Rip/Yawn
• The Cyclic Universe

Question 24

What is The Big Crunch theory?

Answer 24

• The universe will stop expanding
• Everything gets pulled in by gravity & dark matter
• Starts collapsing until it’s a single point

Question 25

What is The Big Rip/Yawn theory?

Answer 25

• The expansion of the universe continues & accelerates
• Everything is eventually torn apart

Question 26

What is The Cyclic Universe theory?

Answer 26

• It continuously cycles through the Big Bang and Big Crunch with no real end
• Bang -> Crunch -> Bang -> Crunch etc…

Question 27

What is the most likely future universe theory?

Answer 27

Ends with The Big Rip
^- Universe is currently expanding at a constant rate