Where did we come from? Are we alone?
Space Infrared Telescope Facility
Exploring the universe in the infrared
Planned launch: December 2002
Expected lifetime: 5 years
A Fortunate Accident
In 1800, while placing thermometers in each color of the solar spectrum, Herschel places his “control” thermometer just outside the red end of the spectrum.
Result: the thermometer outside the visible spectrum registered the highest temperature!
The first detection of invisible light, which Herschel called infrared (“beneath red”) light.
Objective: To perform a version of the experiment of 1800, in which a form of radiation other than visible light was discovered by the famous astronomer Sir Frederick William Herschel.
Target Audience: Grades 7-9, easily extended to higher grades (10-12)
Place a sheet of white paper inside a cardboard box
Tape three thermometers together and place inside box
Cut a small notch in the top of the box and position a small glass prism so that the spectrum is projected inside the box
Arrange the thermometers so that one is just outside the red end of the spectrum, with no visible light falling on it
Do not look directly at the Sun.
After approx. 10 minutes, the thermometers show a 10 degree difference:
The highest temperature is found outside the visible spectrum, where infrared light is falling on the thermometers.
The thermometers will register differences almost immediately.
The Herschel Experiment can be done in groups of 2 to 4. Team members can be assigned the following roles:
Box-keeper – makes sure the thermometers are positioned properly and holds box if necessary
Timekeeper – announces times for temperature measurements
Measurer – reads the temperatures of the thermometers
Recorder – records the temperatures on the observation chart
Adjust the prism in the notch until a broad spectrum is achieved.
Place thermometers in the blue, the yellow, and next to the red portions of the spectrum for 30 to 60 seconds, until a temperature difference is observed.