  This activity has been developed as a resource for the "EU Space Awareness"
educational programme. As part of the suite "Our Fragile Planet" together with
the "Climate Box" it addresses aspects of weather phenomena, the Earth's
climate and climate change as well as Earth observation efforts like in the
European "Copernicus" programme. This activity uses a simple analogue for the
power of radiation received at a given distance from a star. A photovoltaic
cell is connected to an electric motor. Depending on the power received on the
cell, the motor begins to move. It changes also its speed with respect to the
distance between the cell and the lamp. This can be interpreted as a model for
a planetary system and its habitable zone. The "engine of life" moves as soon
as the receiving power is big enough to sustain its operation. The distance,
where the motor stops, can be interpreted as the outer edge of the habitable
zone. As a second activity, the students will reconstruct the orbits of a real
exoplanetary system by drawing a scaled model. In addition, they will calculate
and superimpose a realistic circumstellar habitable zone and discuss its
elements.
