Question 1: What observations can you make about the values in this table? Particularly, do you see any pattern between the distance (in AU) and the amount of light that reaches the planet? Do you see any pattern between the distance (in AU) and the light travel time? (For this last question, it's easiest to notice the pattern if you look at the planets further out than the Earth and compare the light travel time for those planets compared to Earth's light travel time.)
|
Planet
|
Distance from Sun
|
Amount of Sunlight
|
Light Travel Time
|
|
|
(AU)
|
(Earth = 1 unit)
|
From Sun (minutes)
|
|
|
|
|
|
|
Mercury
|
0.4
|
6.25
|
3.8
|
|
|
|
|
|
|
Venus
|
.07
|
2
|
5.8
|
|
|
|
|
|
|
Earth
|
1
|
1
|
8.3
|
|
|
|
|
|
|
Mars
|
1.5
|
1/2
|
12.45
|
|
|
|
|
|
|
Jupiter
|
5
|
1/25
|
41.5
|
|
|
|
|
|
|
Saturn
|
10
|
1/100
|
83
|
|
|
|
|
|
|
Uranus
|
20
|
1/400
|
166
|
|
|
|
|
|
|
Neptune
|
30
|
1/900
|
249
|
|
Pluto
|
40
|
1/1600
|
332
|
|
|
|
|
|
Question 2: You have likely heard of radar. What are 2 or 3 applications of radar that you have heard of in your life? What can radar tell an observer about some object, whether it is an airplane, a car, a cloud?
Question 3: Do you think radar could be used to find the distance to a neighboring planet? Why or why not? Do you think radar could be used to find the distance to neighboring stars? Why or why not?
Question 4: Assuming the planets are all lined up on the same side of the Sun as the Earth, use the time data from Table 1 and do the following:
Calculate the time it would take for a radar signal to travel from Earth to Mars. ______________ minutes
Calculate the time it would take for that radar signal to travel back to Earth. _______________ minutes
Calculate the total radar signal travel time from Earth to Mars and back._______________ minutes
Do the same for a radar signal to Pluto and back. _________________ minutes = ____________ hours
Question 5: What are some limitations that you can foresee when trying to use the radar method to find the distance to distant objects - planets or stars? (You may have, in part, answered this question earlier.)
Question 6: If the object is further away, is the angle larger or smaller? Make a sketch, similar to that shown but with the object further away to show how the angle changes.
Question 7: The distance from the Earth to the Moon is 384,400 km; the diameter of the Moon is 3474 km. Calculate the angular size of the full Moon as we see it in the sky. How does your answer compare to the value given in the text and/or lecture notes. (Look it up if you need to.)
Question 8: A U.S. quarter (coin) is about 1 inch in diameter. If you were to hold it up so that it was covering the full Moon, how far (in inches) must you hold it away from your face so that it would pretty much cover the Moon exactly?(That is, at what distance does a quarter have an angular size equal to the Moon's.) Is your arm long enough to do this?(If you happen to see a full Moon sometime and have a quarter in your hand, try this out.)
Question 9: Find the definition of stellar parallax in the text or somewhere. Summarize here. And then, explain briefly how stellar parallax is similar to the simple task you just performed.
Question 10: Why do the distant stars seem to (almost) never change their positions relative to us?
Question 11: When observing your finger's "motion" when you open and close your two different eyes, what characteristic or aspect of that "motion" would you measure that could give you information about how close or far your finger is from your eyes?