L1B

Question 1

Hubble’s Law

Answer 1

Objects in space are moving apart

Question 2

Big Bang Theory Evidence

Answer 2

1. Hubble’s Law

Measures this doppler effect to describe how objects in space move apart from one another
If objects are moving apart, they must have started together at a single point

2. The universe is permeated by background radiation

This background radiation is believed to be the fading afterglow of the Big Bang

Question 3

Nucleosynthesis

Answer 3

creation of nuclei from pre-existing nucleons

Question 4

Big Bang Nucleosynthesis

Answer 4

• will create forms of hydrogen and helium (and some lithium)
• Few minutes later – cooled below 109 K*, no more nuclear reactions possible, until stars

Question 5

Stellar Nucleosynthesis

Answer 5

• Stars are fueled by fusion of H to He. As stars age, other elements burns to fuel the star
• Combining helium with other elements creates many more

Question 6

Nebulae

Answer 6

are stellar nurseries

Question 7

Galactic Nucleosynthesis

Answer 7

• Cosmic rays collide with heavier atoms

- Atoms break apart into fragments via spallation

Question 8

Origin of the solar system

Answer 8

1. Hot origin – comet collision:
   - Proposed a “hot origin” of the planets from a collision between a comet and the sun
   - Earth initially very hot, but as it cooled, molten rock hardened
2. Nebular hypothesis:
   - Condensation of a hot gaseous nebula in progressive stages
   - As centre of nebula (sun) rotated and contracted, gas ejected form rings
   - Rings condensed to form molten balls, which cool and harden into planets (oldest planets farthest from the sun)
3. Cold origin – planetesimal hypothesis:
   - Gravity of star that passed close to the sun lead to the extraction of a succession of solar gases
   - Orbiting material cooled and condensed into particles that accreted into small bodies (planetesimals)
4. Modern nebular:
   - Planets as byproducts of star formation
   - Local instability in nebula causes gravitational collapse into central sphere
   - Laws of physics shape a central sphere (proto-star) surrounded by disk
   - Planets formed by accretion, starting with micron sized grains into larger bodies

Question 9

Chemical versus Physical Layering (differentiation)

Answer 9

Chemical:
- refers to the composition 
-Core: metallic iron, high density
-Mantle: rocky, intermediate density -Crust: rocky, low density
– Oceanic: thin but denser
– Continental: thick but lighter

Physical:

• refers to the material properties
• Inner core: solid
• Outer core: molten
• Mesosphere (mantle except the upper mantle): solid
• Asthenosphere (upper mantle): weak and plastic
• Lithosphere (uppermost mantle plus crust): strong and rigid