William Herschel

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Slide 1

Space Infrared Telescope Facility (SIRTF): The Herschel Experiment

Dr. Michelle Thaller

thaller@ipac.caltech.edu

SIRTF Science Center

California Institute of Technology

sirtf.caltech.edu

Dr. Denise Smith

Dan McCallister

Origins Education Forum

Space Telescope Science Institute

Slide 2

The Origins Program

Origins:

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

Slide 3

The Discovery of Invisible Light

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.

Slide 4

The Herschel Experiment: A Classroom Activity

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)

Slide 5

Herschel Experiment Set-Up

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.

Slide 6

Results

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.

Slide 7

Team Roles

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