Instructions: You and your group are going to find the answers to the following questions about the Earth and how it was measured. You may use: your textbook, Dictionary, Encarta, Encyclopedias, Britannica.com, the Almanac…etc.
What shape is the Earth?
1. Provide one piece of evidence which illustrates the Earth is a sphere and is NOT flat.
2. Who was one of the first people to realize this (Hint: It wasn’t Columbus – much before his time people understood the Earth was round).
3. In what year (or around what year) did this person first understand the principle of a spherical Earth
How do we move in Space?
4. Provide one piece of evidence which illustrates Heliocentrism over Geocentrism. (First, you’ll have to figure out what those two terms mean. Use a dictionary if you don’t know) (Hint: “seasons” is not the answer because that could be a result of the sun getting closer or further from us)
5. Who was the first person credited with this discovery (of Heliocentrism)?
6. In what year did this person publish his results?
7. Who was the first person credited with the idea of Geocentrism?
8. In what year did this person publish his results?
9. How many years elapsed between the idea of Geocentrism and the idea of Heliocentrism?
10. How many years elapsed between the idea of Heliocentrism and today?
11. What evidence did Galileo use to prove Heliocentrism? (He did not create the idea of Heliocentrism, but he did provide excellent evidence that it was the true motion of the planets).
12. In what year did Galileo make this proof?
Real data about our Earth:
13. What is the radius of the Earth in Km and miles (Hint: If you can find only one, you can easily convert the answer. 1.609 Km = 1 mile)
14. What is the circumference of the Earth? (Hint: C = 2 p r)
15. Who is credited with first figuring out the radius and circumference of the Earth?
16. In what year did he figure this out?
17. What is the difference between a longitude line and a latitude line?
18. What is the latitude of the Equator? (Hint: It is a number)
19. What is the latitude of the North Pole? (Hint: It is a number)
Gravity – Some really attractive questions!
20. State the Universal law of Gravitation. (p. 172 of physics textbook). When answering this question, be sure you say something about both MASS and DISTANCE as they relate to Gravity.
21. Who figured this law out? About what year did he do this?
22. What are the only two factors which affect the influence of gravitational force (F)?
23. What is the inverse square law? Copy the diagram on p. 175 and explain it. Realize that butter is used in place of either the force of gravity or light – light also decreases as inverse square of the distance.
24. Write the Universal Law of Gravitation Equation. Include the constant, G.
25. Find the mass of the Earth in Kg by using the Universal Law of Gravitation Equation (in #24) and the following information: An 80.0 Kg person is standing 1 radius away from the center of the Earth (answer to #13 converted into meters!!!!)
26. In what year did Cavendish perform his experiment to find G? Look in an encyclopedia.
27. What is the mass of the Earth – in tons. Look in an almanac.
28. Draw a diagram of Von Jolly’s method for measuring G and explain how he did that (p. 173).
29. Which is stronger: Gravity or Magnetism? Offer one example which you could show in class how one is stronger than the other.
Applying what you’ve learned
Measuring the Earth from your own backyard:
You are trying to measure the circumference of the earth, just like
Eratosthenes did many centuries ago. All you have is a meter stick which you
can place vertically in the ground at solar noon on March 22nd (March 22nd is
the day of the spring equinox. The day when the sun is directly overhead of
the equator at solar noon. In San Clemente, the sun will NEVER be directly
overhead – at any time of year).
When you place the stick in the ground, you notice a shadow which is 0.66
m long. Use your knowledge of geometry and SOHCAHTOA to figure out angle
q
(see drawing below).
2. What is the Latitude
of San Clemente? Look at the above drawing to help you figure it out.
Don’t use any outside sources.
Your friend is doing the same experiment as you at his home on the equator. He
discovers at solar noon on March 22nd that there is no shadow at all from his
meter stick.
3. Now, all you need to know is the distance from you to the equator to figure
out the circumference
of the Earth. Use the following website and record the Latitude and
Longitude of San Clemente.
http://www.indo.com/cgi-bin/dist
4. How far is it from you to the equator. To do this, you will need to know
the latitude of the equator (see question #18 on the previous page) and you
will need to know the longitude of San Clemente (see question #3 above).
Your answer needs to be in both Km and miles!
(remember 1.609 Km = 1 mile)
5. Why did you need to know the longitude of San Clemente as well as the
latitude of the Equator to answer #4? How come you couldn’t just enter 0
N and 0 W?
6. If a circle is 360o
, and the angle between San Clemente and the equator is _____ (see question #2
above).
What percent of the Earth is the distance from San Clemente to the equator?
(Hint: The angle between the North pole and the equator is 90o
. This is 25% of the total amount of a circle)
7. You know the distance from San Clemente to the equator. You know the
percentage of the circle this number represents. Show your work and determine
the circumference of the entire earth! Answer in both Km and miles.
8. Find the Percent error between your answer and the actual circumference of
the Earth (you found the circumference in question #14 on the previous page).
(Remember: Percent error = (½
actual – predicted
½
predicted) x 100.
Do this for both miles and Km.
1. Draw the stick/shadow set-up and use SOHCAHTOA to determine angle
q
.