Sun Radiation: On Land and Sea




BACKGROUND

The sun radiates light and heat onto the world we live in (and other bodies in our solar system). The amount of the sun's radiation that reaches the surface of the earth over a period of time is called "insolation". The light of the sun dispels the darkness, making everything visible to our eye. The sun warms our planet as well. Our earth is just the right distance from the sun so that we are not boiled or completely frozen as are some of the other planets in our solar system. That was God's plan for our world. How much heat is received from the sun is dependent upon a number of different factors. The nature of the surface is one such factor. Soil and water absorb heat differently. It takes more heat to raise the temperature of water one degree than to raise the temperature of soil the same amount. Scientifically this is called the "specific heat capacity" of a substance. Also, soil loses heat more rapidly. Other factors also play a part, such as darkness of color, transparency and evaporation. The behavior of land and sea masses in response to the sun's radiation in turn affects climate.  The temperature of water and soil affect the air temperatures near them. Areas near the ocean or other large bodies of water, for example, usually have a milder climate. Movement of air as breezes is also affected by differential heating, but that is for other investigations.

INVESTIGATION   

PLACE TO BEGIN
How does the temperature of water change over time when exposed to the sun?  How does the temperature of soil change over time when exposed to the sun?  How do these two materials compare?  What happens to their temperatures when they are no longer exposed to the sun?

MATERIALS
Equal-sized water-proof containers (such as plastic shoeboxes), soil sample(s), water, thermometers (2)

DIRECTIONS
Fill one shoebox with soil and the other with water. Fill the boxes to the same level. Pick a time of day when temperatures are increasing.  Measure the initial temperature of the soil and of the water and record them. The temperatures may be different, but the main interest is in the change of temperature over time. Place the boxes side by side in the sunshine. Every 1/2 hour (or other time period) record the temperature of each again. Remove the thermometers between each temperature reading to prevent the sun from hitting the thermometer directly. When inserting the thermometers, wait a couple of minutes for the temperature to steady and shield from direct sun at this time. Determine the change of temperature over time.  At a later time, when air temperatures are declining, repeat the process to see whether soil or water has the greatest change in temperature at this time.

GOING FURTHER
Does the color of the soil make a difference? [Compare dark & light soils, soil and sand etc.]
Is there a difference between wet and dry soil?
If water is colored wtth food dye is there a difference compared to clear water?
How does the temperature of the air near water compare to that further away (but in the same general location)? [Both locations should be in the sun. Be sure to shield the thermometer from direct sunlight when taking these measurements.]

DEVOTIONAL   

Read Ephesians 4: 17-32. In this passage, comparison is made between those who are living a sinful life who have their hearts "hardened" and those who are "new creations", dedicated to living a life pleasing to God. The former live apart from the truth and refuse to change. On the other hand, those who allow the Holy Spirit to work in their lives no longer follow sinful ways but instead seek to have a changed attitude and grow in Christlikeness. One could compare this to how the sun affects different materials. God is like the sun figuratively providing light and warm. Those refusing to respond to God are like adobe that hardens with the heat of the sun. Christians who follow the Holy Spirit are like wax that is melted and molded into a useful shape. It is the same sun, but different responses.

APPLICATION QUESTIONS
1. Do you read the Bible regularly to find out what is pleasing to God?
2. For what sinful thoughts or actions do you need to ask forgiveness and stop doing?
3. Can you think of some ways that the Holy Spirit could help you be more like Jesus?

Sing the chorus, "Spirit of the Living God, Fall Fresh on Me". 
YouTube link

CREATIVE ACTIVITY   

Take some Play-doh or modeling mixture to make a sun face. (Recipes can be found online to make your own.) First make a ball and then flatten it on some wax paper to make a circular shape. The size of the ball determines the size of the sun face. Cut into the edge of the circle to form "rays". Shape features of a face with your fingers. When finished, place the sculpture in the sun until it is hardened. [Note: the photo above is of a large example. Unless you have a kiln, you probably want to do a much smaller one.]



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