Lecture 1: Life, the universe and everything

Question 1

When did the precambrian start?

Answer 1

Around 4.6 billion years ago.

Question 2

Ga…?

Answer 2

billions of years ago

Question 3

Ma…?

Answer 3

millions of years ago

Question 4

When was the hadean in the precambrian?

Answer 4

4.6 -> 4.0 Ga

Question 5

When was the Big Bang?

Answer 5

The end of the Cumbrian period about 13.75 billion years ago.

Question 6

Immediately after Big Bang there was very little variation in the composition of the universe…

What was the % of hydrogen and helium?

All the elements that were heavier…

Answer 6

Hydrogen (98%)
Helium (2%)

All the elements that were heavier further up the periodic table were formed subsequently-> without these, planets could not form.

Question 7

How are heavier elements formed?

Answer 7

As a result of stellar fusion as temperature and pressure increase (inside stars).
Very massive stars can produce elements as heavy as iron.

Question 8

What is a supernova?

Answer 8

Very massive stars get older.
Burn up their fuel.
Eventually collapse.

Question 9

Whats in interstellar space?

Answer 9

Gas - h2 and he 
Interstellar dust
Carbon (graphite) and organic compounds
Water (ice)
Silicates (Mg and Fe)

Question 10

‘Star factories’

Answer 10

Vast dust and gas clouds

Concentrated in spiral arms of galaxies

Question 11

Development of solar nebulae

Answer 11

Pressure waves cause the local aggregation of gas and dust.
Often due to nearby supernova.
Gravitational attraction increases cloud density.

Question 12

When did the solar system form?

Answer 12

4.568 billion years ago (know because of radiometric dating).

Question 13

How were stars like the sun formed?

Answer 13

As gas and dust becomes denser it begins to spin and eventually flattens
More attraction = higher temperature and pressure
If enough matter material will ignite = sun

Question 14

How are rocky planets formed?

Answer 14

Solar wind clears light material in star formation.
This forms gas giants beyond ‘frost line’.
Inner solar system becomes enriched in heavy elements to form rocky planets.

Question 15

What was the iron catastrophe?

Answer 15

Planet differentiates
Heavy to core
Lighter to surface

Question 16

What are the layers of the earth like?

Answer 16

Inner core: solid, iron-nickel alloy
Outer core: liquid iron-nickel alloy
Mantle of metal rich silicates
Thin silicate crust

Question 17

What is a self exciting dynamo?

Answer 17

Solid inner and liquid outer core case a self exciting dynamo- convection in molten outer core interacts with Earth’s rotation.

Question 18

What does a self exciting dynamo do and what does that mean?

Answer 18

It generates a dipolar magnetic field.
This helps protect the planet.
Shield against solar storm-> deflecting ionised particles from solar wind.

Question 19

What was the Hadean?

Answer 19

The first 600 My of Earth History.
Very dense greenhouse atmosphere.
Very vigorous mantle convection.

Question 20

What are carbonaceous chondrites?

Answer 20

Non-volatile material of the solar nebula meteorites that formed in oxygen-rich regions of the early solar system so that most of the metal is not found in its free form but as silicates, oxides, or sulfides.

Question 21

How are elements heavier than iron formed, and the type of event that is responsible?

Answer 21

They are formed during supernova explosions of dying stars.
When the star has “burned” everything but iron, it has used up all its fuel.
The heat and radiation that have streamed outward preventing collapse under force of immense gravity, stop flowing.
Causing collapse = SUPERNOVA.
The forces of the explosion drive iron nuclei into each other, supplying the energy needed to force the iron nuclei to fuse into heavier elements.

Question 22

Why are carbonaceous chondrites important?

Answer 22

They contain water-bearing minerals which is evidence of water moving slowly through their interiors not long after formation.

Question 23

How can we account for the compositional differences between the Earth and the Moon?

Answer 23

The Moon is thought to have formed from the debris of a small planet of different composition that collided with the Earth.