Astronomy Review 5
1. What two areas do almost all comets come from?
The Oort Cloud and the Kuiper Belt
2. Why can’t the comets we see have originated here in the inner solar system?
They would have melted by now. Most comets melt within a few thousand
years.
3. What gets hit with more asteroids and meteoroids, the Earth or moon?
The Earth, it is a much bigger target.
4. What is actually adding heat to the Earth’s core?
Radioactive decay of elements like uranium and radium.
5. Why would asteroids almost always be moving faster when they collide with the
Earth compared to ones that collide with the moon?
The Earth’s gravity is much greater so they would be accelerated more by
Earth’s gravity.
6. How do we know the age of the Earth?
We use “radioactive dating” to determine the age of the oldest rocks.
7. Which planet in our solar system has the greatest density?
Earth is most dense followed by Mercury, Venus, Mars then Jupiter.
8. How do we know what the interior of the Earth looks like?
Earthquake waves traveling through the Earth create a picture of the
interior.
9. Into what layer of the Earth is the deepest hole ever drilled my man the crust,
mantle, inner core or outer core?
The Crust
10. Which element on the periodic table is thought to comprise most of the Earth’s
core?
iron
11. Why hasn’t the Earth’s core “cooled down” in the past 4 billion years?
Two reasons, more heat is constantly being added by nuclear decay and
there has not been enough time.
12. What is lunar regolith?
Shattered rock and soil. Caused by impacts.
13. What do we call the time period required for half of a sample of radioactive
material to decay away?
The half life of the material.
14. What are the four layers of the Earth?
Crust, mantle, the liquid outer core and the solid inner core.
15. How does the diameter of the Moon compare to the Earth?
The earth is 4 times larger or you could say the moon is ¼ the size of the
earth.
16. What is the lunar feature known as a rille?
Lava Tubes
17. If a rock has a volume of 5 cm3 and a mass of 22.5 grams, what is its density?
4.5 grams/cm3
18. How can we tell that the highlands of the moon are older than the maria?
The maria have far fewer craters.
19. What evidence do we have that the core of the Earth consists mostly of iron?
The Earth’s magnetic field, Earth’s high density and the fact that iron is so
common in our solar system.
20. A rock is found that contains equal amounts of potassium 40 and its daughter
isotopes. If Potassium-40 has a half life of 1.25 billion years how old is this rock?
If half of the Potassium-40 has been converted to daughter isotopes than
one half life or 1.25 billion years have passed since this rock formed.
21. What are the two types of seismic waves that travel through the Earth from an
earthquake?
Earth quakes create p-waves and s-waves.
22. What is more dense, rock or iron?
Iron is much more dense than rock.
23. How old is the Earth and how do we know?
4.5 billion years. We have found rocks on Earth that are 4 billion and on the
moon that are almost 4.5 billion years old.
24. How many times does the Earth rotate on its axis per year?
One more time than the number of days. 366 times in a 365 day year.
25. What two reasons are there for the core of the Earth being so hot?
There hasn’t been enough time for it to cool and radioactive decay is still
generating heat.
26. Where on Earth is the Earth’s magnetic pole located?
About a 1000 miles from the geographic poles. The north pole is in Canada.
27. What protects us from the bombardment of solar particles?
Earth’s magnetic field deflects solar particles around the Earth.
28. Why is there so little iron here on the surface of the Earth?
Most of the iron sank when the Earth was molten.
29. Where does Earth’s atmosphere end?
It doesn’t abruptly end but just slowly gets thinner and thinner.
30. What is the depth of the deepest hole ever drilled on Earth?
7 to 8 miles deep.
31. What happens to radioactive materials over time?
They decay into smaller less massive elements.
32. The moon has many features that look like rivers, what are these called and what
created them?
These are called rilles and were created by flowing lava.
33. What are two possible sources of Earth’s atmosphere?
Volcanoes and Comets are thought to be the sources of most of our
atmosphere.
34. Almost all rocks in Earth’s crust contain this most common element in Earth’s
crust.
Oxygen, the most common element on Earth
35. Why is it that we don’t see many craters here on Earth?
The atmosphere stops most small objects and erosion eliminates the craters.
36. How long does it take Earth to rotate 360 degrees on its axis?
23 hours 56 minutes and 4 seconds
37. What do scientists use radioactive rocks for?
Determining the age of the rocks
38. What does the fact that seismic “S” waves do not pass through the center of the
Earth tell us?
Since “S” waves do not travel through liquids we know that the Earth must contain
a partially liquid core.