New kids on the block Endre Kajari and his crew at the University of Ulm in Germany have now arrived to bust that all up. They have shown that in the realm of quantum physics, there can be wild variations between gravitational mass and inertial mass.
From the article at MIT's Technology Review...
Their thinking begins by pointing out the important distinction between kinematics, which is concerned purely with motion not how it arises, and dynamics which focuses on the origin of motion. In the classical world, this has no bearing on the effects of inertial and gravitational mass.Dare we say "intertial drives" or at least "inertial dampeners"? Hyperspace, here we come! :-P
However, in the quantum world, the way states are prepared has huge significance. They point out, for example, that the wave function of a particle in a box does not depend on mass at all whereas the energy wave function of a harmonic oscillator depends on the square root of the mass.
That leads to an interesting idea: that it is possible to create combinations of gravitational and electromagnetic boxes and oscillators in which inertial and gravitational mass play different roles.
It turns out that physicists already play with exactly this kind of set up: the so-called atom trampoline, in which a matter wave falls under the influence of gravity but is bounced by an electromagnetic force. They calculate that the energy eigenvalues of the atom are proportional to the (gravitational mass)^2/3 but to the (inertial mass)^-1/3.
That's an amazing result. The kind of energy spectroscopy of atoms or Bose Einstein Condensates that can spot this difference ought to be achievable, if not now, then very soon within the next few years.
If successful, these kinds of investigations will provide an entirely new way of studying the nature of mass and, perhaps more importantly, of investigating the puzzling relationship between general relativity and quantum mechanics.
Seriously though: this is very, very cool stuff and I'm looking forward to seeing what comes of it.