Week 1: How to build a planet: formation of the Universe

Question 1

How have people’s perceptions of the Earth’s place in the Universe changed over the centuries (what is
geocentrism/heliocentrism)?

Answer 1

Before people perceived the Earth as the centre of the Universe- believing everything all revolved around Earth=geocentric model
Now people perceive the Sun as the centre of the Universe- believing Earth and the their planets revolve around the Sun= heliocentric model

Question 2

What is the basic architecture of our Universe and its components?

Answer 2

Sun lies at the centre of the Universe
Earth and other planets orbiting around it
our sun is one of 300billion stars in Milky Way Galaxy
our solar system includes eight planets: Mercury, Venus, Earth, Mars (=inner planets) Jupiter, Saturn, Uranus and Neptune (=outer planets) ordered from closest to sun to furthest
All are much smaller than the sun
Milky way= looks like a flattened spiral with vast curving arms (earth sits near the outer edge of on of these arms) that slowly swirl around a glowing disk-like centre.
Estimated a trillion galaxies sit within the Universe

Question 3

How old is the Universe?

Answer 3

13.7 billion years

Question 4

What event does the Big Bang theory describe?

Answer 4

The formation/expansion of the universe
(stretching with space not expanding into pre-existing space)
no origin of expansion

Question 5

What is the evidence that the Universe is expanding?

Answer 5

Red shift= the further a planet the redder it appears as the light waves are shifted to the red end of spectrum
light from distant galaxies are slightly red in colour due to ‘red shift’

Question 6

Why has the Universe cooled as it has expanded?

Answer 6

lost heat as its expanded

Question 7

How has the rate of expansion changed since the Big Bang?

Answer 7

Universe is expanding at an accelerating rate because of dark matter

Question 8

What is astronomical redshift, and how is it different to the doppler effect?

Answer 8

Doppler red shifts due to the light source moving relative to the observer
BUT

Astronomical redshifts are ‘expansion redshifts’ due to the expansion of space itself

Question 9

What is Hubble’s Law?

Answer 9

The faster a galaxy is moving away the farther away it is

Question 10

What is Hubble’s constant and how is it measured?

Answer 10

the ratio of the speed of recession of a galaxy (due to the expansion of the universe) to its distance from the observer.
redshift= hubbles constant/ speed of light x distance
z= Ho/c x d

Question 11

What sequence of key events occurred in the first 380 kys after the Big Bang in the history of the Universe?

Answer 11

1. First Moments (0-10 seconds): hot and dense
   2.Nucleosynthesis (3 minutes)
   3.Photon Decoupling (380,000 years)
   4.Era of Recombination and Formation of the Cosmic Microwave Background (CMB)
   5.Formation of Cosmic Structures

Question 12

Which is the earliest epoch visible today?

Answer 12

Photon epoch

Question 13

What are the four fundamental forces?

Answer 13

1. strong
2. electromagnetic
3. weak
4. gravitational

Question 14

What energy field is responsible for particles having mass? How does it confer mass?

Answer 14

Higgs field

Question 15

In which era did the first normal matter form?

Answer 15

Hadron epoch

Question 16

What elements were formed through primordial nucleosynthesis?

Answer 16

Hydrogen, helium and lithium

Question 17

What is recombination and how did it effect the ‘transparency’ of the universe?

Answer 17

Photon decoupling occurred (ionised hydrogen and helium atoms captured electrons and formed neutral atoms) so the universe became transparent to light

Question 18

Why was the era known as the ‘dark ages’ dark?

Answer 18

There was dominantly dark matter in the universe which neither emits nor absorbs light and a diffuse fog, this matter clumped together under the influence forming web like structures

there was no stars formed yet to give off light

Question 19

What is the composition of the currently observable Universe: what is dark energy, dark matter and normal matter?

Answer 19

Dark Energy= A force that is causing the rapid expansion of the universe when it should be slowing down.68.5%
Dark matter= Matter composed of particles that don’t reflect, absorb or emit light. It forms a web on which normal matter builds.26.6%

Question 20

What % of normal matter is made up of hydrogen and helium?

Answer 20

75% hydrogen
25% helium

Question 21

What role did dark matter play in the formation of the structure of Universe?

Answer 21

more dark matter= more galaxies