Casimir Starcraft: Zero Point Energy
November 18, 2009 16 Comments
The Casimir force arises from one of those unlikely sounding real world manifestations of quantum mechanics. It begins with considerations of what exactly is a vacuum. In the classical everyday sense we think of a vacuum as what is left after we have removed all of the stuff, molecules atoms etc. But that still leaves photons, so if we remove those as well – including all the thermal energy then surely we should now have an absolute vacuum which contains precisely nothing. Therein lies the problem. Heisenberg’s uncertainty principle, describes the limitation on the knowledge of pairs of parameters in terms of Planck’s constant; most well known being position and momentum. An equally important pairing is energy and time, and quantum mechanics forbids the precise independent knowledge of these two parameters. The absolute energy of a system is thus unknowable as a single parameter, including the unique value of zero. So we cannot have a vacuum of absolute zero energy because it violates the uncertainty principle.
The theoretical physics resolution of this paradox is to assume the existence of virtual particles which pop out of the vacuum and wander around for an undefined time and then pop back – thus giving the vacuum an average zero point energy, but without disturbing the real world too much.
One of the most remarkable results of Quantum Field Theory is the existence of vacuum fields, particles and zero-point energy. Vacuum is not a tranquil void but a quantum state made up of matter fields and energy fields.
The Casimir force has a long tradition in relationship to travel and exploration. In the distant past the old seafarers of the ocean going nations were aware of a force with the ability to cause problems to ships just as they were being moored and all of the hazards of sea travel were assumed to be over. These old sailors knew that to moor two large ships parallel to each other was to court disaster, as a mysterious force would cause them to crash together. We now know that the cause of this force is the difference between the wave energy between the ships and the wave energy beyond them. Because the wavelength of a wave between the ships is limited by their separation there is a cut off in the wave energy density between the ships, which is less than the energy density in the unlimited regions beyond them, and hence this imbalance provides a force, which moves the ships together. A similar force was deduced by the Dutch physicist H.B.G. Casimir in 1948, to exist between pairs of conducting parallel plates with small separation due to their interaction with electromagnetic radiation and the resulting difference in wave energy density, in an exact analogy to the old sailors story. Casimir also realised that the same analogy applied to the interaction of real objects with zero point fluctuations, or vacuum energy.
The relationship between the Casimir force and transport doesn’t stop with square-rigged sailing ships. There could be important implications for space travel. It turns out that the energy density of vacuum fluctuations is almost infinite and all pervading. If one could find a method to exploit this limitless energy source one could build a space drive, which extracts its energy from the vacuum and enable spaceships to reach the stars. The requirement would be to influence the interaction of the Starship with the vacuum fluctuations in its direction of travel differently to the interaction with the vacuum fluctuations in its wake, perhaps by using attractive and repulsive configurations. The resulting imbalance might then be persuaded to cause propulsion; however such concepts for Casimir drive interstellar starships is clearly very far in the future.
NASA addressed these issues with the Breakthrough Propulsion Physics Program (which is now currently unfunded). Its aims were to specify the problems that need to be addressed to create a “Space Drive” (Marc Millis – NASA Glenn)
The aim was to use “Horizon Mission Methodology”, in which impossible hypothetical mission goals, consistent with firmly established physics were used in an attempt to force paradigm shift, and not simply provide incremental extrapolations from existing solutions.
The Goal is obviously far from fruition but along the way one might be able to identify affordable research in order to make measurable progress
The following links will take you to further discussion of these points.
Spacetime at the Planck scale is topologically nontrivial, manifesting a granulated structure, which has been described as Quantum Foam. A better description may be “like the bubbles at the top of a glass of Champagne”; New droplets emerge from the Champaign and old droplets vanish to give a dynamic medium. It is the ineraction with this dynamic medium that causes the Casimir force on real world objects. Another manifestation of this dynamic quantum medium is it’s potential to interact with the atom beams in atom interferometers, one of the observations expected from the HYPER project. (see Fundamental Physics Links. ) Also see Giovanni Amelino-Camelia paper in Nature Vol 410. for possible effects in interferometers such as LISA.