1. The universe

Question 1

Origin of the universe (6)

Answer 1

1- Big bang, formation of energy (radiation)
2- Fast expansion, lowering of density and temperature
3- Formation of elementary particles, formation of H and He
4- Gravitation turns essential: clusters of dust
5- Formation of the first black hole, formation of galaxies
6- First generation of stars

Question 2

What is the age of Universe?
What is the age of Earth and the moon?
How we know the age of the solar system and the Earth?

Answer 2

The birth of universe was in the big bang (13.7 Ga)
The age of the Earth is 4.54 billion years
And the age of the moon is 4.527 billion years
These ages are based on evidence from radiometric age dating of meteorite material and is consistent with the radiometric ages of the oldest-known terrestrial and lunar samples.

Question 3

How do galaxies and solar systems form? (9)

Answer 3

1. Supernova explosion
2. Atoms gather to a gas-dust cloud after the explosion
3. A rotating cloud is formed
4. If enough matter exists, a star forms in the centre of the cloud
5. The gravity causes more matter to gather in the sun
6. Gravitation causes heating of the sun
7. Nuclear fusion starts (H and He)
8. The bulk of the gasses are transported out of the solar system due to radiation
9. Stable equilibrium between gravity and radiation pressure

Question 4

How did Earth and the moon form?

Answer 4

1. The dust that circulates around the central star gathers in bodies that grow larger and larger - (cold) planets form
2. Meteorite impacts cause further planet growth
3. Heterogeneous accretion (first Fe, Mg & Ni, then silicates, finally water & gas)
4. Complete melting of the core and mantle of the Earth through radioactive decay (the most important source of heat on Earth)
5. The moon got in the way
6. Impacts with meteorites caused growth of Earth
7. Mars-size body impacts with Earth and their debris was transported out into space
8. The moon was formed by aggregation of Earth and impact debris

Question 5

What is the effect of impacts on the young Earth?

Answer 5

Impacts caused growth of Earth.
The Moon-forming impact and the decay of radioactive elements probably caused much of the Earth to melt. Melting allowed iron and other dense matter to sink toward the Earth’s center and form the core. Lower density (lighter) matter floated upward to form the mantle and crust. Release of trapped gases (mostly water) from within the Earth gave rise to the oceans and an early atmosphere.

Question 6

Resume formation of the universe, solar system, Earth and moon in few words:

Answer 6

• The universe was formed by an explosion called Big Bang and is in continuous expansion.
• Our solar system was caused by a supernova explosion, the explosion of a star.
• Earth was formed by gathering of materials from supernova explosion and meteorite impacts.
• The moon was formed when a Mars-size body impacts with Earth.