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A Cheap, Easy
Earth Science Demo


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From 101 Effective Earth Science Demonstrations Using Only One or Two Items, by William Johnston, with Mark Francek
Source: Janice VanCleave: Janice VanCleave's Astronomy for Every Kid: 101 Easy Experiments that Really Work (1991), page 22.
Objective
To demonstrate why Venus has such a high temperature.

<TABLE border=0 cellSpacing=0 cellPadding=7 width="100%"> <TR> <td bgColor=#ffffcc> About the Authors Bill Johnston is a science teacher in southeastern Michigan. Mark Francek is an earth science educator at Central Michigan University. See more Earth Science Demos. </TD></TR></TABLE>

Standards
Objects in the Sky (sky object properties, locations, and movements); Earth in the Solar System (position, properties of sun, earth, its moon, and the other planets); Interactions of Energy and Matter (Waves have energy and can transfer energy when they interact with matter.); Light, Heat, Electricity, and Magnetism (light absorption); and Transfer of Energy (light transmission and absorption).
Materials

• two thermometers
  
• one lidded jar large enough to hold one of the thermometers
  

Procedure

1. Place one of the thermometers in the jar and secure the lid.
   
2. Place the jar and the second thermometer near a window receiving direct sunlight.
   
3. Observe the temperatures of both thermometers after about twenty minutes.
   

The Science Behind It
The temperature of the thermometer inside the jar will be higher than the temperature of the thermometer not in the jar. Solar radiation given off by the sun contains both visible and infrared light waves. Infrared light waves are given off by objects that are hot. In this demo, the jar represents the atmosphere of the planet Venus. The majority of the light reaching the surface of Venus becomes absorbed; heating the planet. The surface then radiates that heat energy as infrared waves. Because the atmosphere is extremely thick, however, the infrared waves become trapped. Those trapped infrared waves heat the surface of Venus to more than 800癋. Because of the extremely high temperatures, rocks on the surface of Venus glow red.
Article by William Johnson, Mark Francek
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