outlines a clean, falsifiable experiment that can unambiguously test the temporal invariant
prediction.
2. Why 1 Hz is Dirty – But Not Unambiguously
Precision torsion balances (such as those used in the EötWash experiment or for measuring the
gravitational constant ) are usually operated at much lower frequencies (mHz to tenths of Hz)
to avoid seismic and thermal noise. Nevertheless, when a pendulum is actively driven at 1 Hz,
the following contaminants are known to appear:
2.1 Nyquist aliasing
If the data acquisition samples at a rate , any signal component above the Nyquist frequency
is folded back into the measured band. For a 1 Hz signal of interest, sampling at
would place the Nyquist limit exactly at 1 Hz, leading to severe aliasing (a pure 1 Hz
input can appear as a DC offset or as an arbitrary low frequency). However, this is trivially
avoided by oversampling: with , the Nyquist limit is above 50 Hz, and no aliasing of
a 1 Hz signal occurs. Modern microcontrollers easily achieve 1 kHz sampling, so aliasing is a
solvable problem, not an intrinsic obstacle.
2.2 Parasitic pendular (swinging) modes
A torsion pendulum is suspended by a thin fiber. If the driving force is not perfectly aligned with
the torsional axis, or if the fiber is slightly asymmetric, the drive can couple into translational
swing modes. For a fiber of length , the pendular frequency is For
, . Therefore, a 1 Hz drive can easily excite the swing mode if any
misalignment exists. That swing mode will appear as an anomalous peak in the torsional signal
because the optical readout cannot perfectly distinguish pure rotation from horizontal translation.
This artifact is eliminated by:
•
Balancing the pendulum mass symmetrically and using a fiber with high torsional
stiffness (low swing resonance) or, conversely, by designing the fiber such that the
pendular frequency is far from 1 Hz (e.g., gives ).
•
Using a second, independent sensor (e.g., a lateral position sensor) to monitor and
subtract the swing component.
•
Verifying that the anomaly disappears when the drive amplitude is reduced to zero (no
artificial excitation of the swing mode).
2.3 Environmental microseisms
Building vibrations, HVAC systems, walking on floors, and even computer fans often have sharp
spectral components near 1 Hz. These vibrations act as a direct displacement of the suspension