GL SNAPSHOT

Sun Angle Team

 

DAY ONE

 

What is ÒSun AngleÓ?

Sun angle is the angle between the horizon, or ground, and the sun.  Although you could guess, you can also measure simply with an instrument you will build, a clinometer.

 

 

WHAT DO YOU THINK?

 

Warm-Up Question 1: Is it hotter on Earth when the Sun is low on the horizon  - the edge of the earth you see - or when it is higher overhead? Write your thoughts below.

 

 

 

 

 

Warm-Up Question 2:  How can there be times during the same day when the Sun angles are the same? Write your thoughts below.

 

 

 

 

Warm-Up Question 3:  At noon on one day like today, is the sun angle the same anywhere on earth? (Is the sun just as high above the EarthÕs observed edge anywhere?) Write your thoughts below.

 

 

EXPLORE

 

1. Cut out the paper representing the sunÕs rays. 

2. Hold it in different positions above the EarthÕs surface.

3. In each position, count how many ÒraysÕ fall on the study site.

 

READ (Do we want them to read this or discover it?)

 

What Affects Sun Angle?

Sun angle depends on several factors. First, the Sun angle depends on the time of day. The Sun is low in the sky in the morning and evening and therefore its angle from the horizon is low in the morning and evening.   The Sun is highest in the sky at about noon and therefore the Sun angle at any time of year is greatest at about noon. We call this time solar noon.

 

The Sun angle also depends on the time of year. During the winter the Sun angle is smaller than in the summer. (The amount of time the Sun can be seen in the sky is shorter during the winter. The Earth spins at the same rate regardless of season, so the Sun cannot get as high in the sky during the winter.)

 

Sun angle depends on latitude. At the North and South poles, the Sun can never ever be straight overhead, with a Sun angle of 90 degrees. As you move closer to the equator, the Sun angle at solar noon gets larger and larger.*

 

 

DAY TWO

 

Building and Using a Clinometer 

 

What is a clinometer?

A clinometer is an instrument used to measure height, using angles of elevation. We will use a clinometer to measure the angle between the horizon and an object.

 

Materials

Protractor Template paper copy

Manila folders

Glue

Straws

Tape

Pins (or other means of poking a small hole)

Pieces of string 20 cm long

Steel nuts

 

 

Construction

  1. Glue the Protractor Template copy along an edge of a manila folder making sure that the edge of the paper is square with the edge of the folder.
  2. Cut around the outside of the protractor. Carefully remove any rough edges.
  3. With a pin, poke a hole through the protractor at the center mark of the straight edge.
  4. Tape a straw along the straight edge so that a little bit of the straw extends past each end of the protractor.
  5. Push a string through the hole and tie a knot large enough so the string cannot pass back through the hole. Adjust the knot and string until the string swings freely along the face of the protractor copy.
  6. Tie a nut to the free end of the string.
  7. Check that the weighted string swings freely. If it does not, try tilting the clinometer slightly until the string can swing freely.

 

 

Procedures

  1. Light, temperature, and Sun angle measurements should be taken at the same location on the study site and approximately two (2) meters above the ground. Therefore, the three teams must identify an appropriate location at the study site. The Sun Angle Team must ensure that the Sun is not obstructed by trees or buildings at the agreed-upon location.

 

!!!! SAFETY ALERT: It is essential you never look directly at the Sun!

 

  1. While one team member holds the meter stick, another team member should position the clinometer one (1) meter above the ground. A third team member should hold a blank piece of paper behind the clinometer. Again, do not look directly at the Sun!
  2. Aim the clinometer at the sun and hold the paper behind the clinometer so that the tube of the clinometer casts a shadow on the paper. Hold the clinometer steady so that yet tube casts a dark, uniform, circular shadow on the paper and the light intensity of the Sun is focused in this circle. Make sure that the string moves freely.

 

  1. Each team member should make at least one measurement with one of the clinometers. Record each reading and the time and date it was made in your journals.
  2. Average the readings from each observer to obtain your final reading. If there are large disagreements, discuss the readings. Could the readings differ because of variations in the clinometers themselves? Did they vary because of differences in how team members took their readings?
  3. Check your final value to make sure it is reasonable. Remember, when the Sun angle is zero degrees, the straw is parallel to the ground. When the angle is 90 degrees, the straw is pointing straight up.
  4. Submit your reading to the Global Lab database.

 

DATA PAGE

 

Measurement of angle

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

 

X measurements of angle

 

Discussion of any differences

 

 

 

 

 

 

 

 

 

 

 

 

 

 

THE CLINOMETER TEMPLATE