How have later scientists refined the Cavendish experiment to measure the gravitational constant?

Since the late 19th century, scientists have significantly refined the Cavendish experiment to measure the gravitational constant (G) with greater precision. While the original apparatus used a torsion balance to measure the deflection of a rod, modern iterations have introduced several sophisticated techniques:

• Improved Materials: Researchers have replaced traditional wires with thin metal ribbons or fused silica fibers to create more stable suspension systems.1
• Measurement Methods: Beyond simple deflection, scientists now utilize:
  • Period Measurement: Introduced by Carl Braun in 1897, this method measures changes in the oscillation period of the balance when attracting masses are moved, which can be determined more precisely than deflection.1
  • Servo Control: The deflection of the balance is maintained at a constant position using a servo control system.1
  • Resonance and Acceleration: Techniques involving resonant oscillations or the direct measurement of the acceleration of suspended masses have been employed to isolate the gravitational force.1
• Environmental Control: Modern experiments continue to address the extreme difficulty of isolating tiny gravitational forces from extraneous disturbances, a challenge first noted by Henry Cavendish.123