A tractor beam is a device that can attract one object to another from a distance. The concept originates in fiction: The term was coined by E. E. Smith (an update of his earlier "attractor beam") in his novel Spacehounds of IPC (1931). Since the 1990s, technology and research have labored to make it a reality, and have had some success on a microscopic level. Less commonly, a similar beam that repels is known as a pressor beam or repulsor beam. Gravity impulse and gravity propulsion beams are traditionally areas of research from fringe physics that coincide with the concepts of tractor and repulsor beams; tractor beams developed by mainstream researchers and engineers are generally not based on gravity, and practical designs typically use electromagnetism and/or motion of a medium.
Physics
A force field confined to a collimated beam with clean borders is one of the principal characteristics of tractor and repulsor beams. Several theories have predicted that repulsive effects do not fall within the category of tractor and repulsor beams because of the absence of field collimation. For example, Robert L. Forward of Hughes Research Laboratories showed that general relativity theory allowed the generation of a very brief impulse of a gravity-like repulsive force along the axis of a helical torus containing accelerated condensed matter. The mainstream scientific community has accepted Forward's work. A variant of Burkhard Heim's theory by Walter Dröscher, Institut für Grenzgebiete der Wissenschaft (IGW), Innsbruck, Austria, and Jocham Häuser, University of Applied Sciences and CLE GmbH, Salzgitter, Germany, predicted a repulsive force field of gravitophotons could be produced by a ring rotating above a very strong magnetic field. Heim's theory, and its variants, have been treated by the mainstream scientific community as fringe physics. But the works by Forward, Dröscher, and Häuser could not be considered as a form of repulsor- or tractor-beam because the predicted impulses and field effects were not confined to a well-defined, collimated region. The following are summaries of other notable experiments and theories that resemble repulsor and tractor beam concepts:
1960s In July 1960, trade magazine Missiles and Rockets reported that Martin N. Kaplan, a research engineer at Ryan Aeronautical Company, had conducted experiments that could lead to an ability to direct an anti-gravitational force toward or away from a second body. In 1964, physicists Leopold Halpern of the Niels Bohr Institute and B. Laurent of the Nordic Institute for Theoretical Physics indicated general relativity theory and quantum theory allowed the generation and amplification of gravitons in a manner like the laser. They showed, in principle, gravitational radiation in the form of a beam of gravitons could be generated and amplified by using induced, resonant emissions.
1990s – Podkletnov experiment In 1992, Professor Yevgeny Podkletnov and R. Nieminen, of the Tampere University of Technology, claimed to have discovered weight fluctuations in objects above an electromagnetically levitated, massive, composite superconducting disk. Three years later, Podkletnov reported the results of additional experiments with a toroidal disk superconductor. They reported the weight of the samples would fluctuate between −2.5% and +5.4% as the angular speed of the superconductor increased. Certain combinations of disk angular speeds and electromagnetic frequencies caused the fluctuations to stabilize at a 0.3% reduction. The experiments with the toroidal disk yielded reductions that reached a maximum of 1.9–2.1%. Reports about both sets of experiments stated the weight loss region was cylindrical, extending vertically for at least three meters above the disk. Qualitative observations of an expulsive force at the border of the shielded zone were reported in the Fall of 1995. Several groups around the world tried to replicate Podkletnov's gravity shielding observations. Italian physicist Giovanni Modanese, while a Von Humboldt Fellow at the Max Planck Institute for Physics, made the first attempt to provide a theoretical explanation of Podkletnov's alleged observations. He argued that the shielding effect and slight expulsive force at the border of the shielded zone could be explained in terms of induced changes in the local cosmological constant. Modanese described several effects regarding responses to modifications to the local cosmological constant within the superconductor. Ning Wu of the Institute of High Energy Physics (Beijing), used the quantum gauge theory of gravity he had developed in 2001 to explain Podkletnov's observations. Wu's theory approximated the relative gravity loss as 0.03%, or an order of magnitude smaller than the reported range of 0.3–0.5%. C. S. Unnikrishan, Tata Institute of Fundamental Research, Mumbai, showed that if the effect had been caused by gravitational shielding, the shape of the shielded region would be similar to a shadow from the gravitational shield. For example, the shape of the shielded region above a disk would be conical. The height of the cone's apex above the disk would vary directly with the height of the shielding disk above the earth. Podkletnov and Nieminen described the shape of the weight loss region as a cylinder that extended through the ceiling above the cryostat.
… excerpt ends here. Continue reading the full article.
