= UNSW Foucault pendulum observation
{c}
The University of New South Wales documents an undriven, visitor-started <Foucault pendulum>. A fixed vertical wire and wall line define its initial north–south swing <plane>. The documented comparison one hour later shows reduced <amplitude> and about nine degrees of anticlockwise <precession>. The apparatus swings for several hours without an electromagnetic drive.<The Foucault pendulum by Joe Wolfe>[The Foucault pendulum, opening observation sequence and Our Foucault Pendulum: wire/wall reference, one-hour comparison, no electromagnetic drive]{ref}
\Image[/foucault-pendulum-apparatus-and-latitude.png]
{title=Functional Foucault pendulum apparatus, fixed sighting reference, and predicted latitude dependence; schematic with no historical dimensions}
To turn that demonstration into a quantitative experiment, the following is a proposed measurement protocol. Establish a rigid support with no preferred horizontal swing direction, measure the wire length to the bob's centre, and mark two perpendicular horizontal axes fixed to the building. Start with a small displacement along the sighting <plane>, then release with as little transverse <velocity> as possible. Record the actual launch method; burning a fine restraining thread is one possible proposed release, not a claim about the documented UNSW launch. Keep people clear of the bob and avoid touching the suspension during the observation.
Record the horizontal <position> from above with a stationary, calibrated camera, or sight the bob against the wire and wall line at recorded times. Fit the long axis of each short group of swings to estimate its orientation $\psi$; use the extrema on both sides rather than following the bob's rapidly reversing <velocity>. A swing line has orientation modulo $\pi$, so unwrap successive small direction changes continuously. Rotate no camera or reference between measurements. Record the fast <oscillation period> separately, and compare the slope of $\psi(t)$ with the <Latitude law of Foucault precession>. Repeat launches along different directions and monitor <ellipses>, pivot motion, and air currents before attributing the slow change to <Earth's rotation>.
Back to article page
