1. Space and Astronomy Study Guide Standard 1
Earth Science

2. What things move around in the night sky and why?
Moons, comets, asteroids, planets; because they are closer than the stars

3. Explain how we know objects in the sky are so far away.
Because they move less. (Parallax – remember your car)
Because they appear smaller (think head squishing)

4. What does gravity do? It pulls all matter in the universe together.
Depends on mass and distance.

5. What is a nebula? A cloud of dust and gas.
Forms solar systems and stars.

6. What are the stages of the formation of our Solar System?
Nebula
Gravitational Collapse
Spinning
Flattening to Disk
Fusion
Accretion of Planets

7. What kinds of objects are in our solar system?
The Sun
8 Planets
3+ Dwarf Planets
240+ Moons
Small Bodies (Comets, Asteroids, Gas, Dust)

8. How are stars formed?
Nebula
Gravitational Collapse
Fusion

9. What two gases are present in our Sun, and most stars?
Hydrogen and helium.
In the Sun 75% hydrogen and 25%. Helium.

10. Explain what fusion is.
When small elements join (fuse) to make larger elements.
The most common kind is hydrogen combining to make helium.

11. How are planets formed?
By condensation of cooling pieces of gas and dust around the sun.
Spinning
Flattening to Disk
Accretion of Planets

12. Name 6 differences between inner and outer planets.
Size
Density
Atmosphere (Thick & Light, Thin & Heavy)
Distance from Sun & Spacing
Compostion (Gas vs. Rock & Metal)
Number of Moons
Bonus: Rotation Speed

13. Explain why the inner planets are so different from the outer planets.
The solar wind blows light material farther out while gravity keeps the heavier material close.
As a result the inner planets are heavy and the outer planets are light.
There is more light material so the light planets are bigger.

14. Explain how old the Solar system is and how we know this.
At least 4.6 billion years old
This is the age of the oldest rocks and meteors determined with radioisotope dating.

15. Why are there more crater impacts on the moon than on the earth?
The Earth has an atmosphere and plate tectonics that weathers away craters.
The moon is dead and has no erosion.

16. What causes the seasons on earth?
The seasons are caused by the earth’s tilt.

17. What is the Earth’s rotation?
It is the time it takes for earth to turn one time on its axis.
One day. ~23.93 hours.

18. What is the Earth’s Revolution around the sun?
The time it takes for Earth to make one orbit around the sun.
One year days