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Significance:
Water vapor in the sky is responsible for the natural greenhouse effect that keeps the Earth warm enough for life to exist. Clouds formed from water vapor play a major role in controlling the temperature of the Earth. The activities in this project demonstrate that the open sky, while very cool, is much warmer than space and that cumulus clouds are much warmer than the sky.
Project Links:
Supplies Needed:
1. Non-Contact Infrared (IR) Thermometer. This is an electronic thermometer that uses a heat sensor installed inside a plastic housing to measure the temperature of objects from a distance. Infrared thermometers measure the temperature across an area known as the field of view or look angle, an invisible cone between the instrument and the object or substance whose temperature is being measured. A look angle of 1:1 means that 1 meter away the thermometer "sees" a spot 1 meter across. For best results use an infrared thermometer with a look angle of at least 6:1. This means that 1 meter away the thermometer "sees" a spot 1/6 meter across.
Many different kinds of IR thermometers are available from industrial
suppliers and online dealers. The least expensive at the time
this writing are around $45 (less from some discount sites). A key feature
to look for is the look angle, which describes the cone viewed by the IRT.
A 6:6 look angle means the instrument sees a 6 foot diameter circle when
held 6 feet away from an object. The range of the IRT, especially the
minimum temperature, is also important for this project. Gun-style infrared
thermometers are easier to use, since you can point the thermometer where
you like while watching the temperature display. You can find many infrared
thermometers by searching online.
Caution: When using an IR thermometer equipped with a laser, switch the laser off if possible. If the laser cannot be switched off, place a small piece of dark tape over its port to block the beam. When using the IR thermometer with the laser switched on, never point the laser at anyone or at a shiny surface. Never point the laser beam at your eyes!
Always keep an infrared (IR) thermometer in a protective case to protect it from dust and to keep from scratching its readout. If it did not come with a case, you can store it in a clean sock.
An IR thermometer is operated simply by pointing it at anything whose temperature is to be measured. Press the power button to activate the thermometer and read the temperature from the display. Most infrared thermometers will allow you to switch between Celsius and Fahrenheit scales. Various IR thermometers have different operating controls, so be sure to read the instrument's instructions. Most IR thermometers have a "hold" mode. This allows you to point the thermometer at an object, measure its temperature and read the temperature when it is convenient.
Test the IR thermometer by pointing it at your hand, your clothing, a book and a light bulb, and notice the temperature differences. Next, point the IR thermometer at the floor and then at the ceiling. Warm air is lighter and rises. Thus, the ceiling will usually be warmer than the floor.
2. Notebook or Spreadsheet. Pencil or pen and notebook or, alternatively, a clip board with a spreadsheet arranged like this:
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DATE |
TIME |
SKY TEMPERATURE | CLOUD TEMPERATURE |
SKY (CLEAR, HAZY, CLOUDS, ETC.) |
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Note: Mention of commercial products and suppliers does not imply that they
are endorsed by NASA or the author. You can find many sources for
conventional and IR thermometers at retail stores and by searching the web.
Procedure:
The temperature of the air and everyday objects is usually given using the Fahrenheit or Celsius scale. In the Celsius scale, The freezing point of water is 0 degrees and the boiling point of water is 100 degrees (at sea level). In the slightly older Fahrenheit scale, the freezing point is 32 degrees and the boiling point is 212 degrees. Scientists and people in most countries use the Celsius scale. While the Fahrenheit scale is going out of style, its advantage is that it provides nearly twice the resolution of the Celsius scale. Both Celsius and Fahrenheit scales are used in the projects that follow.
Here are the formulas for converting between Celsius (TC) and Fahrenheit (TF):
Celsius (TC) = (5/9) x ( (TF) - 32)
Fahrenheit (TF) = (9/5 x (TC)) + 32
Here are spreadsheet formulas you can use for making these conversions:
Various online calculators like this one allow you to convert from Fahrenheit to Celsius or Celsius to Fahrenheit.
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