To observe the gravitational tidal pull of the Moon and the
Sun using a simple home built device, I propose to use a pair of rigid coupled
The top one, hinged from above is a direct pendulum.
The bottom one, hinged from below, is an inverted pendulum.
The two are coupled in a way that the instability of the bottom pendulum
is compensated by the stability of the top one.
The device is extremely sensitive to horizontal forces.
This sensitivity can be used to detect the horizontal
components of the tidal pull of the Moon and the Sun.
These components are smallest for a body, Moon or Sun,
on the horizon or at the vertical,
and reach a maximum when the body is around 45 degrees above or below the horizon.
Developing The Model
A mathematical model of the device
and its physics looks promising. Tidal forces could produce deflections as large
as 1/10 th of a millimeter.
I also looked at some other topics related to this design.
Building The Device
An outline sketch of the device is shown on the left.
It consists of a pair of glass strip pendulums coupled through small magnets.
I am also preparing a
more detailed description.
The frontend detector uses a paper flag attached to the top pendulum
and oscillating between a bright diode and a phototransistor.
This displacement measurement technique is the same used in by the magnetic
The frontend signal is then amplified and plotted.
The circuits used are again similar to that of the magnetic gravimeter,
minus the feedback circuit.
At this time I am recording without any amplification.
Temperature compensation is also needed. At this time I have only temperature monitoring in place, but no control feedback.
Once temperature control is in place the frontend signal can be amplified
and still remain within the range of the position detector. That's something
I still have to do.