  We present measurement results demonstrating that a conducting lead sphere
exposed to electromagnetic (e/m) waves in the infrared (IR) regime, is
attracted by e/m waves. The result may seem surprising and against conventional
wisdom that electromagnetic wave forcing should lead to a repulsive force.
Nonetheless, all our experiments show that the attractive force can be
determined quantitatively, and that they are reproducible. Our experiment setup
is a Cavendish torsion-balance experiment with lead spheres, one of the spheres
intermittently irradiated by IR light. Because the Cavendish experiment is well
known, simple, and readily available, the results can be easily verified or
falsified. However, to avoid Bernoulli and other external forcing effects, the
entire experimental setup should be placed in a vacuum chamber. In our case the
experiments were performed at \approx 4 \cdot 10^-7 mbar. One of the 20 g lead
spheres was intermittently irradiated by infrared radiation from a lamp covered
by an aluminium foil. Two independent experiments (V1 and V2) are described.
Besides showing that wave energy and momentum transfer leads to attraction, we
also describe some experimental requirements and constraints. The lamp was
powered on during 10 or 12 s, the power changing between 8, 16, and 26 W. All
measurements, including those affected by lamp out-gassing, shows that the
attracting force on the lead sphere increases with increasing irradiative
energy. From the V2 experiment, preceded by lamp "baking" to eliminate
repulsive out-gassing forces, the irradiative energy 8.7 Ws on the sphere
resulted in a total force 2.9+/-0.5\cdot 10^-9 (N). From the V2 experiment we
also derive a power law relation between incident radiation energy (W) and the
attractive force, corresponding to F=2.8\cdot 10^-10 W^1.1, with R^2=0.95.
