The pull that every object with mass has on every other object is real enough to measure on a tabletop — if you build the right instrument. A torsion balance detects this force by letting a suspended beam twist toward nearby masses. Build a balance arm from a thin pine strip with lead weights at each end, suspended by vegetable fibre from twine. Place two large paving stones near the lead weights. The gravitational pull between the stones and the lead causes the beam to twist slightly. The challenge is the support fibre — natural fibres respond to humidity and tear under stress, so selecting and preparing the right fibre takes patience and repeated testing.