Some scientists have more imagination than most fiction writers. Take Alexander Feigel of the Weizmann Institute of Science in Israel for example. He thinks that objects can move by being pushed by "virtual photons" appearing spontaneously in a vacuum. Nature has the story, "Movement from nothing." The most amazing thing with this theory is that it doesn't violate any fundamental law of physics. Read on.
Feigel says that objects can achieve speeds of several centimetres an hour by getting a push from the empty space of a vacuum.
How can this be possible?
Feigel draws on the well-established notion that empty space does contain a little bit of energy. This ‘vacuum energy’ is a consequence of the uncertainty principle -- one of the cornerstones of quantum mechanics.
Because of the uncertainty principle, subatomic particles or photons can appear spontaneously in empty space -- provided that they promptly vanish again.
Then he looked at the effects that these virtual photons would have on the momentum, a quantity generally accepted as 'conserved', meaning that if something moves in a direction, another one must take another one.
He showed that the momentum of the virtual photons that pop up inside a vacuum can depend upon the direction in which they are travelling. He concludes that if the electric field points up and the magnetic field points north, for example, then east-heading photons will have a different momentum from west-heading photons.
So the vacuum acquires a net momentum in one direction -- it’s as though the empty space is ‘moving’ in that direction, even though it is empty.
So far, it's just a theory, but it could be possible to measure this effect.
Feigel estimates that in an electric field of 100,000 volts per metre and a magnetic field of 17 tesla -- both big values, but attainable with current technology -- an object as dense as water would move at around 18 centimetres per hour.
Please contact him if you have the right lab.
By the way, what would be a possible use of such an effect?
Feigel thinks it should theoretically be possible to make use of the effect to shunt tiny amounts of liquids around on a lab chip, for example. Such small-scale experiments could be useful for chemists interested in testing thousands of different drugs at the same time, or for forensic scientists who need to do analyses on tiny amounts of material.
The results of this research work have been published on January 16, 2004 by Physical Review Letters under the title "Quantum Vacuum Contribution to the Momentum of Dielectric Media." Here is the abstract -- in scientific language.
Momentum transfer between matter and electromagnetic field is analyzed. The related equations of motion and conservation laws are derived using relativistic formalism. Their correspondence to various, at first sight self-contradicting, experimental data (the so-called Abraham-Minkowski controversy) is demonstrated. A new, Casimir-like, quantum phenomenon is predicted: contribution of vacuum fluctuations to the motion of dielectric liquids in crossed electric and magnetic fields. Velocities of about 50 nm/s can be expected due to the contribution of high frequency vacuum modes. The proposed phenomenon could be used in the future as an investigating tool for zero fluctuations. Other possible applications lie in fields of microfluidics or precise positioning of micro-objects, e.g., cold atoms or molecules.
Sources: Philip Ball, Nature, February 2, 2004; Physical Review Letters, January 16, 2004