The quantum vacuum has fascinated physicists ever since Hendrik Casimir and Dirk Polder suggested in 1948 that it would exert a force on a pair of narrowly separated conducting plates. Their idea was eventually confirmed when the force was measured in 1997. Just how to exploit this force is still not clear, however.
In recent years, a new way of thinking about the quantum vacuum has emerged which has vastly more potential. And today, one physicist describes how it could be used to create propulsion.
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Before we discuss that, let’s track back a little. According to quantum mechanics, any vacuum will be filled with electromagnetic waves leaping in and out of existence. It turns out that these waves can have various measurable effects, such as the Casimir-Polder force.
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The new approach focuses on the momentum associated with these electromagnetic fields rather than the force they exert. The question is whether it is possible to modify this momentum because, if you can, you should receive an equal and opposite kick. That’s what rocket scientists call propulsion.
Today, Alex Feigel at the Soreq Nuclear Research Center, a government lab in Yavne Israel, suggests an entirely new way to modify the momentum of the quantum vacuum and how this can be exploited to generate propulsion.
Feigel’s approach combines two well-established ideas. The first is the Lorentz force experienced by a charged particle in electric and magnetic fields that are crossed. The second is the magnetoelectric effect–the phenomenon in which an external magnetic field induces a polarised internal electric field in certain materials and vice versa.
The question that Feigel asks is in what circumstances the electromagnetic fields in a quantum vacuum can exert a Lorentz force. The answer is that the quantum vacuum constantly interacts with magnetoelectric materials generating Lorentz forces. Most of the time, however, these forces sum to zero.
Hwever, Feigel says there are four cases in which the forces do not sum to zero. Two of these are already known, for example confining the quantum field between two plates, which excludes longer wavelength waves.
But Feigel says the two others offer entirely new ways to exploit the quantum vacuum using magnetoelectric nanoparticles to interact with the electromagnetic fields it contains.
The first method is to rapidly aggregate a number of magnetoelectric nanoparticles, a process which influences the boundary conditions for higher frequency electromagnetic waves, generating a force.
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The second is simply to rotate a group of magnetoelectric nanoparticles, which also generates a Lorentz force.
Either way, the result is a change in velocity. As Feigel puts it: “mechanical action of quantum vacuum on magneto-electric objects may be observable and have a significant value.”
The beauty of Feigel’s idea is that it can be easily tested. He suggests building an addressable array of magnetoelectric nanoparticles, perhaps made of a material such as FeGaO3 which has a magnetoelectric constant of 10^-4 in a weak magnetic field.
These nanoparticles simply have to be rotated in the required way to generate a force. Feigel calls it a magnetoelectric quantum wheel.
Of course, nobody is getting a free lunch here. “Although the proposed engine will consume energy for manipulation of the particles, the propulsion will occur without any loss of mass,” says Feigel. He even suggests, with masterful understatement, that this might have practical implications.
So here is a high-risk idea with a huge potential payoff. The question is: who has the balls to try it?
