Why do the wheels of the calorimeter turn? There are
two explanations one argues to turn in the direction of the dark
surface, one in the other. It actually depends on the vacuum.
In a full vacuum, the photons at the bright surfaces reflect more and
push the surface so that it moves towards the dark part.
However, if there is still some air in the bottle, then there is
more thermal expansion of air at the darker side pushing it towards
the bright reflective part. This is what happens.
Here is a movie made in our garden. You see the Emily Dickinson flower
(a bit sad at the moment as it is hot) and the Mary Cummings stones
(shiny glimmer stones which look precious but the Mary Cummings park
as the neighboring parts of Woburn are full of shiny nice stones like that.
I would when running around in the last few months often come back with
a pebble for decorating the garden. You see also a butterfly visiting
the set-up while filming.
Here is a Mathematica implementation of the Calorimeter:
