The Big Bang

Question 1

What was the Big Bang?

Answer 1

An event which birthed the Universe

Question 2

How would I describe the universe?

Answer 2

Started from a point, known as the singularity, and matter was condensed from the energy that resulted from this. To this day, the universe remains expanding and cooling

Question 3

Who proved that the universe was expanding?

Answer 3

Edwin Hubble

Question 4

What were the first fundamental particles formed?

Answer 4

Leptons, neutrinos, and quarks + zero mass particles like gluons and photons

Question 5

How did the fundamental particles form other particles?

Answer 5

As the temperature decreased, the quarks collided with each other to form hadrons, like protons and neutrons.

Question 6

What was the force that initially came from the birth of the universe?

Answer 6

The unified force

Question 7

What was Hubble able to prove?

Answer 7

Able to prove that the further away the galaxy was relative to the Eaerth, the greater velocity of the galaxy
v = Hd

Question 8

What is cosmic redshift?

Answer 8

Redshift of the wavelengths of radiation due to the expansion of space

Question 9

What are the differences between cosmic redshift and doppler effect?

Answer 9

Dop. effect depends on relative velocity of source and observer at the time light is emitted
- cosmic redshift occurs after the light has been emitted due to the expansion of space

Question 10

What is luminosity?

Answer 10

Power emitted by a star - stars are assumed to be black bodies

Question 11

What is brightness of a star?

Answer 11

Refers to how bright the star appears from Earth - measure of the intensity

Question 12

Explain the formation of the Big Bang theory.

Answer 12

13.7 billion yrs ago, a singularity expanded, creating space, time, energy and matter. The Big Bang was the birth of the universe at the beginning of time.
#1 = expansion and cooling
#2 = gravity

Question 13

What was the first phase of evolution?

Answer 13

Expansion led to cooling as the energy of the universe was spread - allowed energy to be converted into matter - formed quarks, leptons - decayed to form protons, neutrons and electrons

Question 14

What was the second phase of evolution?

Answer 14

Gravity led to the gas in the universe collapsing into giant clouds and eventually forming the stars and galaxies we see today

Question 15

Explain the process of the universe

Answer 15

• inflation
• post inflation - expanding and cooling at a slower rate
• nucleosynthesis = protons & neutrons form helium
• recombination = further cooling to form neutral atoms
• reionisation = first stars form

Question 16

What are the three main pieces of evidence to support Big Bang Theory?

Answer 16

1. Expansion of universe
2. Abundance of light elements
3. Cosmic microwave radiation in background

Question 17

How did abundance of light elements prove the existence of the universe?

Answer 17

Energy –> matter —> p, n, e-
At high temp, hydrogen -> fusion –> He –> formation of light elements = nucleosynthesis

Question 18

How does cosmic radiation prove big bang?

Answer 18

Universe filled with charged particles (q, L)
- absorb and emit radiation
- radiation (photons) coupled to matter
- radiation and matter were in equilibrium
then recomb, the radiation recoupled from matter - nuclei formed neutral gas - universe became transparent
- radiation was not interacting with matter

Question 19

How does gravity prove big bang?

Answer 19

Universe was filled with neutral gas - as gas cooled kinetic energy, the gravitational forces show that there is an uneven distribution of matter
- links to accretion

Question 20

What is accretion?

Answer 20

Process by which denser objects attract matter due to their gravity
- variations in strength - mass is pulled by denser regions - stronger gravity - uneven distribution of clouds

Question 21

What is up the top on the hertzsprung russel diagram?

Answer 21

Supergiants, then giants, then main sequences, and bottom white dwarfs

Question 22

What is the stellar evolution?

Answer 22

Mass - determine their position, evolution, process inside the star, etc.

Question 23

Summarise the formation of a star

Answer 23

1. Cold giant cloud –> undergoes accretion
2. PE => KE
3. Temp increases, radiation emits - forming protostar
4. Further collapse leads to high temp, hydrogen fusion, collapse continues, fusion releases energy resulting in radiation pressure

Question 24

The mass determines whether the star sits in the main sequence

Answer 24

High mass will be larger so higher temp as they collapse, meaning the rate of fusion is higher leading to higher luminosity