Lecture 1: Life, the universe and everything Flashcards
When did the precambrian start?
Around 4.6 billion years ago.
Ga…?
billions of years ago
Ma…?
millions of years ago
When was the hadean in the precambrian?
4.6 -> 4.0 Ga
When was the Big Bang?
The end of the Cumbrian period about 13.75 billion years ago.
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…
Hydrogen (98%)
Helium (2%)
All the elements that were heavier further up the periodic table were formed subsequently-> without these, planets could not form.
How are heavier elements formed?
As a result of stellar fusion as temperature and pressure increase (inside stars).
Very massive stars can produce elements as heavy as iron.
What is a supernova?
Very massive stars get older.
Burn up their fuel.
Eventually collapse.
Whats in interstellar space?
Gas - h2 and he Interstellar dust Carbon (graphite) and organic compounds Water (ice) Silicates (Mg and Fe)
‘Star factories’
Vast dust and gas clouds
Concentrated in spiral arms of galaxies
Development of solar nebulae
Pressure waves cause the local aggregation of gas and dust.
Often due to nearby supernova.
Gravitational attraction increases cloud density.
When did the solar system form?
4.568 billion years ago (know because of radiometric dating).
How were stars like the sun formed?
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
How are rocky planets formed?
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.
What was the iron catastrophe?
Planet differentiates
Heavy to core
Lighter to surface
What are the layers of the earth like?
Inner core: solid, iron-nickel alloy
Outer core: liquid iron-nickel alloy
Mantle of metal rich silicates
Thin silicate crust
What is a self exciting dynamo?
Solid inner and liquid outer core case a self exciting dynamo- convection in molten outer core interacts with Earth’s rotation.
What does a self exciting dynamo do and what does that mean?
It generates a dipolar magnetic field.
This helps protect the planet.
Shield against solar storm-> deflecting ionised particles from solar wind.
What was the Hadean?
The first 600 My of Earth History.
Very dense greenhouse atmosphere.
Very vigorous mantle convection.
What are carbonaceous chondrites?
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.
How are elements heavier than iron formed, and the type of event that is responsible?
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.
Why are carbonaceous chondrites important?
They contain water-bearing minerals which is evidence of water moving slowly through their interiors not long after formation.
How can we account for the compositional differences between the Earth and the Moon?
The Moon is thought to have formed from the debris of a small planet of different composition that collided with the Earth.
