  For over a century, two rival descriptions of electromagnetic field momentum
in matter have co-existed, due to Abraham and Minkowski, respectively. We
propose a set-up for measuring the difference between Abraham's and Minkowski's
predictions in optics. To wit, a set-up is proposed in which the transient
"Abraham force", a consequence of the Abraham energy-momentum tensor of 1909
may be measured directly. We show that when a train of short laser pulses is
sent through a fiber wound up on a cylindrical drum, the Abraham theory
predicts a torque which, by inserting realistic parameters, is found to be
detectable. Indeed, the same torque when calculated with the Minkowski tensor
takes the opposite sign. Numerical estimates show that with a typical torsion
pendulum set-up and standard laser parameters, the angular deflection is in the
order of $10^{-3}$ rad, which is easily measurable and even visible to the
naked eye. Although its prediction is a century old, the Abraham force has
proven experimentally elusive, and to our knowledge no macroscopic experimental
demonstration of the difference between the predictions of the two mentioned
energy-momentum tensors exists at optical frequencies.
