The transactional interpretation of quantum mechanics is applied to the “interaction-free” measurement scenario of Elitzur and Vaidman and to the Quantum Zeno Eﬀect version of the measurement scenario by Kwiat, et al. It is shown that the non-classical information provided by the measurement scheme is supplied by the probing of the intervening object by incomplete oﬀer and conﬁrmation waves that do not form complete transactions or lead to real interactions.
One of the great and persistent technological dreams of science fiction has been the invention which would nullify or reverse the force of gravity. H. G. Wells in The First Men in the Moon did it in 1901 with Cavorite, a substance which shields objects behind it from gravitational lines of force. James Blish in the Cities in Flight series used the Spindizzy, a device which converts rotation and magnetism into gravity fields and forces. And, of course, "floaters", "null-g speeders" (...) and "grav sleds" have abounded as techno-props in science fiction stories for many years. (shrink)
This AV Column is about the Universal Solvent of modern physics which we call antimatter, and about a bottle in which it can be and has been kept. However, before getting to the hardware I want to talk about antimatter as it relates to the fundamental symmetries of the universe.
Then, as soon as my column was safely submitted, hot new results on antigravity appeared. The lead article in the January 6, 1986 issue of Physical Review Letters had the unassuming title: "A Reanalysis of the Eötvös Experiment" by E. Fischbach, et al. Two days later the New York Times ran an article with the headline: "Hints of Fifth Force in Universe Challenge Galileo's Findings" describing the importance of Fischbach's work. Peculiar experimental results from terrestrial gravity measurements and from the (...) behavior of "strange" K-mesons (kaons) had been explained by a new theory proposing a "hypercharge" force, a new fifth force of nature which is gravity-like but which repels rather than attracting nearby masses. This new antigravity force is the subject of this AV column. (shrink)
As the author of these columns describing cutting edge physics and astronomy, I get quite a few letters and E-mail from readers who are more interested in Â“over-the-edge physics and astronomyÂ”. One recurring theme is various alternatives to the standard model of Big Bang cosmology. Perhaps the universe is not expanding; itÂ’s just that light Â“gets tiredÂ” on its path from far away and loses some of its energy. Perhaps quasars are closer than we think, particularly since some of them (...) appear to be linked to closer galaxies. Perhaps relativity is wrong, and itÂ’s the speed of light that is different in different parts of the universe or changing with time. Perhaps quasars are the tailpipes of nearby alien spaceships, and they have such large red shifts because we only see them when they are moving away from us. And so onÂ…. (shrink)
Last Saturday I made my first journey into virtual reality . I walked with giant strides around a city called Seattle. I leaped the Columbia Center, the tallest building in the city, with a single bound. I dove beneath the surface of Puget Sound and watched a pod of whales heading north toward Canada. I hovered above the Space Needle, then dropped inside to enjoy its panoramic view and to examine its structural details. I raced a Washington State ferry across (...) the Sound from Seattle to Bremerton. I caught up with it just as it approached the Bremerton dock and was able to watch the docking operation from a perch on the roof of the bridge. Then I flew back across the Sound and peered down into the Kingdome, looking in vain for a winning team. Finally, I pointed my magic glove across the Sound to the Olympic Peninsula, flew there, and examined a group of towering snow-capped peaks from all angles. I did all of this without leaving a small building on the campus of the University of Washington. (shrink)
Two years ago, astrophysicists studying Type Ia supernovas discovered that our universe is a much stranger place than we had imagined, with invisible vacuum energy accelerating its expansion.Â (See my column about this in the May-1999 Analog.) However, new astrophysical observations from the BOOMERanG experiment (BalloonÂ Observations Of Millimetric Extragalactic Radiation and Geomagnetics), a balloon-borne cryogenic microwave telescope measurement that flew at an altitude ofÂ about 24 miles over the Antarctic, indicate that our universe is also rather ordinary, in that (...) its space is maximally flat.Â The term Â“flatÂ” as used here means that the space of our universe is neither positively curved like a ball or negatively curved like a potato chip.Â It appears that in our universe, the tendencies of space toward positive curvature from gravitational attraction and towards negative curvature from expansion kinetic energy are precisely in balance, leaving space on the average completely free of curvature. (shrink)
to energies of 160 GeV/nucleon, a total energy of 33.3 TeV (3.33 × 1013 electron volts) for each lead nucleus. Now, with a week of beam time remaining, we are working very hard and the experiment is beginning to collect good data. In this column, I want to describe the situation here at CERN. I'll return to the experiment after that.
The largest flying creature alive today is the Andean condor Vultur gryphus. At maximum size it weighs about 22 pounds and has a wingspread of about 10 feet. But 65 million years ago in the late cretaceous period, the last age of dinosaurs, there was another larger flying animal, the giant pterosaur Quetzalcotalus. It had a wingspread of over 40 feet, the size of a small airplane. Other pterosaurs were also quite large. The pteranodons of the late jurassic period, the (...) classic flying dinosaurs of magazine illustrations, had a maximum wingspan of about 33 feet. (shrink)
Albert Einstein taught us that c, the speed of light in vacuum, is nature's ultimate speed limit, the highest speed at which matter, energy, and information can travel through space-time. In several AV columns I've discussed ways for getting around this annoying natural law, the law that SF writers and fans most wish to violate. Two AV columns discussed the possibility of getting around the lightspeed limit by popping through a trans-spatial wormhole shortcut. See [ Analog-6-89, "Wormholes and Time Machines"] (...) and [Analog-5-90, "Wormholes II: Getting There in No Time"]. Two others discussed the possible use the faster-than-light nonlocal handshaking implicit in quantum mechanics for FTL messages and travel. See [Analog-11-86, "The Quantum Handshake"] and [Analog-9-88, "Paradoxes and FTL Communication"]. Both of those methods, however, are beyond our present technology, and the latter is probably impossible. (shrink)
In October-2010 the headlines of the science press were dominated by the announcement of the discovery of a â€œGoldilocks Planetâ€, Gleise 581g, which has a mass not too different from that of the Earth and has an orbit squarely in the middle of the habitable zone of its parent star. It was supposed to be not too hot, not too cold, but just right for the evolution of life. Steven Vogt of UC Santa Cruz, the lead author of the paper, (...) was quoted (out of context) as saying, â€œThe chances of life on the planet are 100%.â€ Now that some of the dust has settled concerning this reported discovery, Iâ€™d like to have a look at the work behind the announcement and consider its present status. (shrink)
We human beings have evolved with brains that have amazing capabilities for rational thought, pattern recognition, judgment, creativity, and imagination, none of which can be readily duplicated by the best computer simulations. However, there is one area, in which the human brain is sadly lacking: the ability to accurately assess probabilities and act on these assessments. The successes of lotteries, Las Vegas, and tribal casinos provide ample evidence that when it comes to estimating the odds and acting accordingly, we humans (...) as a species are really deficient. We think that â€œwinning streaksâ€ are real, that slot machines are â€œoverdueâ€ for a jackpot, that the past pattern of random events somehow influences the odds for the next event. (shrink)
The purpose of this AV Column is to describe a physical paradox involving what seems to be an loophole in a well established physical law, the famous Second Law of Thermodynamics. The 2nd Law states that the amount of disorder (entropy) always either increases or remains constant for any isolated system of particles, whether they are gas molecules or light photons. An yet, as we will see, laser physicists seem to have provided us with a way of making the 2nd (...) Law work backwards for a system of photons, so that the disorder decreases. (shrink)
The "four-wave mixer", a laser technique for reversing the motion direction of light waves so that they can be turned around and returned to their point of origin was the subject of my last Alternate View column (ANALOG, June-1985). In this AV column I want to go one step further by examining a hypothetical kind of time-reversed light wave which should actually go backward in time. As we shall see, such backward waves could be used to send information from the (...) present to the past, resulting in a sort of "poor man's" time travel. Recent science fiction novels like Jim Hogan's Thrice in Time and Greg Benford's Timescape have been based on backwards-in-time communication and the situations that might arise from it. In both books a world disaster is averted by sending a message to the past. In Timescape a side-effect of the signalling prevents Lee Harvey Oswald from assassinating President Kennedy, irreversibly altering the course of events after 1963. (shrink)
This column is a followup to a previous Alternate View column [Analog, June-'89] about "wormholes", faster-than-light travel, and time machines, which was based on a spectacular theoretical breakthrough in general relativity. It described how a sufficiently advanced civilization might construct a stable wormhole (a curved-space shortcut between one region of space and another) and use it both for faster-than-light travel and for time travel, with no laws of physics violated in the process except causality (the principle that a cause must (...) precede its effects). (shrink)
Why is gravity so weak? Why are the color forces between quarks so strong? In the standard model of particle physics, why are there so many different energies at which distinct fundamental forces are supposed to "unify", and what determines these widely separated energies? The answers to these questions may be provided by extra dimensions curled into loops a millimeter around. In other words, our universe may be only a millimeter across, in directions we are not yet able to perceive. (...) In this column we'll consider millimeter-size extra-dimensional loops and their implications. (shrink)
I live in Seattle, the city which last Fall was host to two major international conferences of interest to science fiction readers: The Annual International IEEE Symposium on Virtual Reality (VRAIS- 93) and The 5th ACM Conference on Hypertext (Hypertext-93). I was able to attend both conferences, and I'll use this column to provide an overview of what I learned there.
My previous Alternate View column (ANALOG 9/84) described the widely accepted "inflationary scenario" of modern cosmology in which our Universe is just one among very many "bubble universes", all popping out of the general medium of the Big Bang like bubbles forming in a glass of beer. Somewhere perhaps there are many universes more or less like ours, some very similar to and others radically different from the universe we call "home".
If you measured the radiation present in our environment with sufficient sensitivity, you would find that the Earth is a rather radioactive place. Radon (half-life 3.82 days), a radioactive inert gas that decays by emitting energetic 8 MeV alpha particles, is..
EPR experiments demonstrate that standard quantum mechanics exhibits the property of nonlocality , the enforcement of correlations between separated parts of an entangled quantum systems across spacelike separations. Nonlocality will be clarified using the transactional interpretation of quantum mechanics, and the possibility of superluminal effects (e.g., faster-than-light communication) from nonlocality and non-linear quantum mechanics will be examined.
The territory of time travel has, from the days of H. G. Wells to the mid-1980's, been the exclusive province of writers of science fiction and fantasy. SF critics have even argued that time travel stories are so scientifically unlikely that they should be considered fantasy, not science fiction.
In the December-1989 issue of Analog, I wrote an AV Column entitled “Cold Fusion, Pro-fusion, and Con-fusion” that described and gave my opinions about the recently announced “discovery of cold fusion” by Stanley Pons and Martin Fleischmann. These University of Utah electro-chemists claimed that by electrolyzing D2O (heavy water) on a tabletop, they had produced the nuclear fusion of deuterium (mass-2 hydrogen) nuclei..
Nanocon 1: The First Northwest Conference on Nanotechnology was held at the University Plaza Hotel in Seattle, Washington, on February 17-19, 1989. The conference was sponsored by the Seattle Nanotechnology Study Group and the University of Washington Student Nanotechnology Study Group. This AV column is a report on the conference.
This Alternate View column marks three milestones: This is the 3rd anniversary of my start as an AV columnist for Analog, this is the 20th AV column I've written, and it is also the 7th anniversary of my first publication in Analog. I enjoy writing these columns on scientific subjects, but it can be frustrating. Science is continually changing as new experimental results and observations are made, as new ideas and theories are conceived and old ideas are rejected. Often by (...) the time an Alternate View column on some new development in physics or astronomy appears in these pages the field has already progressed further and there is more to be said. So this third anniversary column will be used as an occasion for a backward look at some of the subjects covered in previous columns and articles, giving an update on more recent developments. An index of my first 20 AV columns and articles is provided below. This can be used as a reference guide to indicate which topics were discussed in which columns and articles. (shrink)
The path to a new discovery in physics is often a very twisted one. The subject of this Alternate View column is an example of this process. A major accelerator, built with with the prospect of discovering super-heavy elements, is now being used in an experiment to produce "super-atoms" with very large electric fields, and this work has quite unexpectedly revealed what looks like a new and mysterious particle. It is reminiscent of the SF of the 1930's where one of (...) the standard science gimmicks was the discovery of a new element with amazing properties. It also sounds a bit like the Paul Preuss novel Broken Symmetries, where the plot revolves around the discovery at a large accelerator laboratory of a mysterious new particle. But this is real science, folks. Honest! (shrink)
On a mountain top on a clear moonless night the brilliant stars strewn across the sky press down almost oppressively, the Milky Way so full of them it seems about to burst. And yet, we have been learning in the past decade that the visible matter of the universe, the stars that we see, represent only a tiny fraction, perhaps less than one part in 200, of the mass of the universe. The question of what the remainder of the universe (...) is made of is called the Dark Matter Problem. It is one of the most vexing in modern physics. (shrink)
This column is about the apparent quantization of cosmological red-shifts, the persistent astronomical observation that the red-shifts and velocities of distant galaxies are not randomly distributed but rather grouped in clumps of similar values. About eight years ago I had considered an AV column on this mysterious phenomenon, but after looking at the data then available I decided against it. As an experimental physicist I've seen too many "structures" in poor-statistics data that vanished as the statistics improved. Over the years, (...) however, the red-shift data has improved to the point where the evidence that this is a real effect is now fairly convincing. So here it is, a persistent and puzzling astronomical observation that does not fit with our present understanding of the laws of physics and the universe and that has no accepted explanation. (shrink)
I'm an experimental physicist. The basic physics research I do is funded primarily by the U. S. Government. As I write this, it is less than two weeks before the 1993 Presidential Inauguration. The new Clinton Administration is still of an unknown quantity. A new Presidential Science Advisor with excellent qualifications, Dr. John H. Gibbons, has just been appointed, but little is know about the science policies of the new administration.
This column is about a new development in the theory of wormholes. At Vanderbilt University, David Hochberg and Thomas W. Kephart have discovered that gravity itself can produce regions of negative energy. Within these regions, we may conjecture, stable wormholes may form naturally, particularly during the early Big Bang. A wormhole is a geometrical shortcut in curved space-time with the topology of a cup handle which, in principle, allows movement from one point in space-time to another without the necessity of (...) traversing the intervening space-time interval. This provides a physical basis for two traditional gimmicks of science fiction: faster-than-light travel and time travel into the past and the future. (shrink)
This year I am on sabbatical at the Max Planck Institute for Physics in Munich, Germany, which by a happy coincidence was also the site of the 17th Texas Symposium on Relativistic Astrophysics held here two weeks ago (December 12-15, 1994). I was able to attend the Symposium, to learn quite a bit about the present state of astrophysics, and to contribute a paper co-authored by SF writers Forward, Benford, and Landis and wormhole theorists Visser and Morris [see my recent (...) AV column on this in the mid-December-94 Analog]. (shrink)
The plane of the present is a concept that is useful for discussing the various paradigms of time. Here by ‘plane of the present’ we mean the temporal interface that represents the present instant and that forms the boundary between the past and the future. We use the geometrical term ‘plane’ to indicate an extended surface in the space-time continuum, as opposed to a ‘point’ on some time axis. This point/plane dichotomy is intended to raise issues of extension and simultaneity (...) and to examine the degree to which these are meaningful concepts from various physical viewpoints. We will show by example in the present work that the plane of the present is a pivotal concept that offers considerable power in differentiating between various views of the nature of time. The concept of time within the main stream of physics thinking has followed a rather convoluted path over the past three millennia. Anticipating the modern motion picture, Zeno of Elea (c.490-c.430 B.C) questioned whether time should appropriately be viewed as a continuously flowing river, or should more properly be considered as a rapid sequence of stop-motion ‘freeze-frames’, in effect rendering geometrical each instant as a separate infinitesimal point on the line of time. Adopting this view, he asked how physical motion could occur. He argued paradoxically that motion is not possible, since it appears to happen only between the frozen frames of time instants.1 From the viewpoint of Zeno, the plane of the present would be simply the last and most recent in this sequence of freeze-frames. It would be that frozen instant, spanning the universe, which changes progressively as the instant we call ‘now’ becomes the frozen past and future possibility freezes into the ‘now’ of present reality. We note that the plane of the present as a concept does not resolve the arrow paradox that Zeno raised. It only provides a way of thinking about it. (shrink)
Light speed, c = 3 × 108 meters per second, is the ultimate speed limit of the universe. The welltested physics orthodoxy of special relativity tells us that nothing can go faster than c. When any massive object with rest mass M (taken to be in energy units) has velocity v=c (or relativistic velocity ß = v/c = 1), the object's mass-energy becomes infinite. This is because the relativistic..
I'm sure you know the plot: a lost magical formula has eluded the wisest practitioners of the arcane art down through the ages. Now a cabal of young upstarts, with disdain for conventional wisdom and working against all odds, discovers the key ingredients that make the magic spell work, with spectacular results.
Gravity is an extremely weak force . Consider two spheres that are close together, each with one kilogram of mass and one coulomb of electric charge, i.e., one unit each of charge and mass in Standard International Units. There will be electrical repulsion pushing them apart and gravitational attraction pulling them together, but which is bigger? It’s no contest: the electric force between these spheres is 1.35 x 1020times stronger than the gravitational force. But perhaps this difference is so large (...) because Standard International Units depend on some rather arbitrary choices on the size of units. What about fundamental particles? (shrink)
This column is a milestone. In 1983, while I was on a one year sabbatical at the Hahn Meitner Institute for Nuclear Physics in what was then West Berlin, I received a letter from Stan Schmidt informing me that Jerry Pournelle had decided that he no longer wished to be an Alternate View columnist for Analog and asking if I was interested in taking over as the AV columnist and “alternating” with G. Harry Stine.
About 22 years ago, the physics world was briefly rocked by claims of evidence for a new “5 th force”, based on reanalysis of data from an early 20 th century experiment. Baron Roland von Eötvös, a Hungarian nobleman, had performed extensive measurements of the correlation between inertial mass and gravitational mass and published them in 1922. The lead article in the January 6, 1986 issue of Physical Review Letters had the unassuming title: "A Reanalysis of the Eötvös Experiment" by (...) Ephriam Fischbach, et al. Two days later the New York Times ran an article with the headline: "Hints of Fifth Force in Universe Challenge Galileo's Findings" describing the possible implications of Fischbach's work. (shrink)
Neutrinos are very peculiar particles. About 610 trillion neutrinos produced by the sun are passing through your body in the second it takes to read this line. If it is night where you are, the neutrinos from the sun are passing through the earth in order to reach you. Because neutrinos have no electric charge and little or no mass, they interact with matter only through the two weakest forces, gravity and the weak interaction. They can pass through solid matter (...) almost as freely as through vacuum, and light years of lead would be needed to absorb them. (shrink)
Wormholes are shortcuts through space time, constructs of general relativity (GR) that appear to offer a physics foundation for faster than light travel and even for travel back in time. They first appeared in the physics literature in 1935, when Albert Einstein and his colleague Nathan Rosen discovered that implicit in general relativity is a tunnel like structure in the topology of space time connecting two separated regions. Einstein and Rosen were actually trying to explain fundamental particles like electrons and (...) proton. They suggested that if lines of electric flux were threaded through such a structure, the flux would be trapped and one end would appear to be an isolated positive charge and the other end would appear to be a negative charge. Later, however, general relativity was used to calculate the masses of such “particles” and it was realized that they would be have a mass of at least a few micrograms, far heavier than the mass of an electron or proton. (shrink)
Science fiction writers, to avoid undue delays in the story's plot line, need a way of beating the speed of light speed limit of the universe. Most readers of this magazine are familiar with the gimmicks that have been used for faster than light travel: warp drives, detours through hyperspace, matter to tachyon conversion, trans spatial jumps, and dives past the singularity of a rotating black hole. But perhaps the faster than light mechanism which has the best credentials in orthodox (...) physics is the wormhole, also known as a Schwartzschild wormhole or an Einstein Rosen bridge. (shrink)
The transactional interpretation of quantum mechanics is summarized and various points concerning the transactional interpretation and its relation to the Copenhagen interpretation are considered. Questions concerning mapping the transactional interpretation onto the Copenhagen interpretation, of advanced waves as solutions to proper wave equations, of collapse and the quantum formalism, and of the relation of quantum mechanical interpretations to experimental tests and results are discussed.
Agendanken experiment is proposed for distinguishing between two models accounting for the macroscopic arrow of time. The experiment involves the veloeity revesal of components of an isolated system, and the two models give contrasting predictions as to its behavior.
Copenhagen interpretation of quantum mechanics deals with these problems is reviewed. A new interpretation of the formalism of quantum mechanics, the transactional interpretation, is presented. The basic element of this interpretation is the transaction describing a quantum event as an exchange of advanced and retarded waves, as implied by the work of Wheeler and Feynman, Dirac, and others. The transactional interpretation is explicitly nonlocal and thereby consistent with recent tests of the Bell inequality, yet is relativistically invariant and fully causal. (...) A detailed comparison of the transactional and Copenhagen interpretations is made in the context of well-known quantum-mechanical Gedankenexperimenre and "paradoxes." The transactional interpretation permits quantum-mechanical wave functions to be interpreted as real waves physically present in space rather than as "mathematical representations of knowledge" as in the Copenhagen interpretation. The transactional interpretation is shown to provide insight into the complex character of the quantum-mechanical state vector and the mechanism associated with its "collapse." It also leads in a natural way to justification of the Heisenberg uncertainty principle and the Born probability law (P = ii iij*), basic elements of the Copenhagen interpretation. (shrink)
The problem of the direction of electromagnetic time, i.e., the complete dominance of retarded electromagnetic radiation over advanced radiation in the universe, is considered in the context of a generalized form of the Wheeler-Feynman absorber theory in an open expanding universe with a singularity atT=0. It is shown that the application of a four-vector reflection boundary condition at the singularity leads to the observed dominance of retarded radiation; it also clarifies the role of advanced and retarded waves in the emission (...) of very weakly absorbed radiation such as neutrinos. (shrink)