Nowadays folks know his Bolo works, but Dinosaur Beach, Worlds of the Imperium, End as a Hero, and the Retief series were pretty unique for their time. One of my favorite authors.
Dinosaur Beach has to be one of my favorite novels, its a cracking good time travel novel with transhumanism before such was known.
There are several very cool results from String/M-theory, but nothing that can be fully understood without the mathematics. But a theory that fully explains all interactions, including matter fields, with supersymmetry and supergravity arising naturally from it, an explanation of the heirarchy problem, and use of perturbation theory and renormalization for gravitons which are generally non-renormalizable, is interesting.
Loop Quantum gravity is interesting too, especially for its background independence, but it will never explain matter fields, and the semiclassical sector is currently lacking. By contrast, string theory has a natural extension to classical general relativity.
Quantum mechanics is not a theory, it is a set of construction rules for theories that reflect reality. Whatever quantum field theory you construct of whatever operators you care to name (the rules of QM/QFD being most easily phrased in terms of operators), some of those operators do not commute [A,B] != 0, and some of those operators do not anti-commute {A,B} != 0.
We happen to call those bosons and fermions respectively.
String theory, being a quantum field theory including gravity (hence, a superset of general relativity), is also a set of construction rules for theories of reality.
As it so happens, some of those theories produce large extra dimensions of > than the millimeter scale. In general, we characterize those theories by a parameter space, and theories with a parameter space producing large extra dimensions of a particular type *are* disallowed by observation.
If observation disallowed the entire parameter space of string theory, it would be entirely falsified.
Instead, it is something dubbed "The Landscape".
Secondly, it is interesting, but not informative, to listen to opinions of people who have never studied string theory remark on its structure/usefulness.
In fact, string theories do provide some elegant solutions to things like supersymmetric (quantum) gravity (SUGRA), supersymmetry (SUSY), and a good number of other subtle points that are only understood with sufficient background in QFT, GR, etc.
Everyone laughs at "the internet is a series of tubes", but then we get long expostulations about string theory from people that haven't studied it.
Third, remember that the authors of the article (e.g. Lee Smolin) have a somewhat vested interest in denying the usefulness of String Theory, as it allows their own theories (i.e. Loop Quantum Gravity) to be more prominent.
As a matter of my own opinion, LQG has even more difficulties than String Theory, for example, it assumes the spacetime metric is smooth even at quantum scales, and that a classical theory (GR) can be "quantized". As GR is not renormalizable, this is violently at odds with known, tested QFT, which is accurate to 11 decimal places.
Well, gravity is not acceleration, but spacetime curvature. The actual equation is G = 8*pi*T, where G is the Einstein tensor and T is the stress-energy tensor. Since G relates to geometry (the Reimann curvature tensor + Ricci scalar), this directly relates mass-energy (T) to curvature (G).
The curvature of a section of space is defined by its metric. (A metric can be thought of as the generalization of the dot product between two vectors in some space, which therefore relates the two vectors in either a coordinate-free or coordinate basis.) In simple cases we assume space is flat by using the Minkowski metric, which defines simple Lorentz transforms, which can be thought of as rotations from one frame of reference to another.
In complicated cases, space is curved, in which case we use manifolds to describe the topology of space. Topology means that a cofee cup and a donut are identical mathematical objects; manifolds mean that our topology is locally flat, so that we can use the same Minkowski machinery for local points at given spacetime coordinates. The price is we must now use tensors to "rotate" from one frame of reference to another.
You tell if space is curved or flat by its geodesic, which is simply the minimum distance between two points. In flat space it is a line; in curved space it is a curve, which you can measure by defining the geodesic deviation between two neighboring paths. At this point the normal notion of derivative, tangent, and vector are lost, and must be redefined in terms of properties of the manifold as covariant derivatives, parallel transport, and tensors (products of n-forms).
In the example of a sphere: parallel transport is the operation of moving a vector while keeping it pointed in the same direction (preserving its inner product). If you take a vector tangent to the surface pointed north on the equator, move it up to the north pole, back down a line of longitude 90 degrees west, then back along the equator, you will notice your vector ends up in the same location but with a different direction. This difference (non-commutativity of operators) is the hallmark of curved space.
Similiarly, if you wrote a differential equation describing some physics involving these vectors, you would find that it wouldn't hold under the operation described above. But if you replace your derivative operator with a covariant derivative operator satisfying linearity, Leibnitz rule, and other properties, such an equation would hold in all frames of reference.
General relativity is a local theory; it discusses the properties of spacetime at a point, where it is locally flat. Acceleration is really just deviation from a geodesic sketched in spacetime. When you consider a bullet or ball fired or thrown between the two same endpoints, in the everyday frame of reference their curvatures look radically different: the ball has to arc up higher and the bullet travels faster. But if you graph not just x and z, but t in the third dimension, both have the same radius of curvature, because the path of the ball is longer than the path of the bullet through spacetime.
And by the way, you can tell the difference between gravity and acceleration by measuring the cosmic microwave background radiation. Not only that, but since we're at least approximately in a Friedman-Robertson-Walker cosmology, an absolute "cosmic time" can be defined by the evolution of some parameter (CMB, Hubble's constant, etc).
The holographic principle, more generally known as the covariant energy bound (Raphael Bousso, "The holographic principle", Rev.Mod.Phys, 74, 2002), was formulated by t'Hooft and Susskind as the "spherical energy bound." The name comes from the postulate that all physics in a region of space is described by data that fits on its boundary surface, at one bit per Planck area.
There turned out to be problems with this definition; for example, it does not hold for black holes, which ruins the idea as a general cosmological principle. Further refinements giving rise to the covariant energy bound. Even now, it has only been considered for cosmologies that are thought to be "realistic" (in particular anti-DeSitter Conformal Field Theory).
An interesting idea was put forward by my Cosmology professor (Nemanja Kaloper, "Origami World", hep-th/0403208). The basic idea is to solve the gauge hierarchy problem (e.g., why is gravity so weak) by using 6-dimensional anti-DeSitter spaces to generate 4-dimensional gravitons. Unlike versions of string theory, the extra dimensions are not compactified. The intersections of various branes in 3D gives GR gravity, but the 4D bulk propagation produces the very weak gravitational constants. As an added bonus, particular foldings consisting of galaxies "millimeters" away in the bulk create dark matter.
That is, dark matter is the result of the 4-d "shadow" onto 3-space. Or, the Milky way galaxy could generate it's own dark matter simply by being folded in the 4-D bulk.
Any physical theory we come up with now always (ie "must") reduce to observable behavior now. The earth is flat is a good local approximation considering the earth's curvature, until you start sailing and cover continental distances.
The example of "An apple always falls from a tree" is very good. We do not need to know the details of quantum gravity (whatever that may be) in order to predict and describe an apple falling, even though quantum gravity supercedes general relativity and quantum field theory, which supercedes special relativity, flat Minkowski space, and quantum mechanics, which supercedes classical mechanics.
Any theory we come up with had better be reducible to classical mechanics at the right energy scales. All theories have a domain of application, and we keep widening the domain by introducing more and more general theories.
But in the end, we test our general theories against specific observations. There is a beautiful theory of Higg's scalars produced from Nambu-Goldstone bosons "eating" photons in the Standard Model Lagrangian which generates massy and massless fields (and hence mass for all particles which have mass); however, finding the Higg's boson doesn't invalidate the simple observation that an apple "always" falls.
Oh, and by the way, Quantum Field Theory (ie, fully covariant Quantum Mechanics or QM + GR) is proven and tested to a fantastic order of accuracy, 11 or twelve decimal places. It's the most accurately known theory we have, which is why we can tell immediately what cosmological theories are right or wrong by their effect on the Standard Model. We could confirm or eliminate certain string theories if we knew gravitational interactions as accurately as QFT.
So there's a slim to none chance that QFT will prove invalid at anything less than ~10E15 GeV energies, which is the Planck scale at the Big Bang.
The point is you cannot recreate the stream once you measure it.
A qubit from the stream comes in with a value a|0> + b|1>. This means the odds of measuring |0> are a^2 and the odds of measuring |1> are b^2. If you measure a |0> you have just discarded the amplitude |b>; this is what is meant by wavefunction collapse. You would then try to "recreate" the stream by sending out a |0>. However, this is distinguishable from the original a|0> + b|1>, and so your attack fails.
Quantum mechanics involves Hilbert spaces, and they are very very large. A classical bit has only two values, 0 or 1. A qubit has an infinite number of values for a and b, subject to Unitarity, which means their total amplitude doesn't exceed 1. It's possible for the phase information of a qubit to store the entire works of Shakespeare, but you would only ever recover 1 bit.
A 500-qubit system has more information stored in it than there are elementary particles (quarks, leptons, photons, neutrinos, vector bosons, gluons) in the Universe.
The applications to physics is very interesting, especially in Cosmology, where the same idea goes by the name Holography. There seems to be a limit on how much information can be stored in spacetime; the classic example is the Beckenstein limit on entropy for a black hole's surface area. Nowadays, Cosmology and Quantum Field Theory are tied strongly together. For example, in some QFT Lagrangians there are massless scalar axions that couple to photons and can cause distant supernovae to appear fainter, thereby throwing the whole "Universe is accelerating" proposition into question. (I know the above example from a paper my Cosmology professor, Nemanja Kaloper, wrote.)
Oh, by the way, the poster indicating "we can't reliably send 1 photon" is wrong. The original Quantum Cryptography test bed sent out effectively 1/10 photon, using weak amplitudes.
There's a number of inaccuracies/misconceptions here. Let's clarify:
First, the magic of Quantum Cryptography is NOT that the signal cannot be eavesdropped on without being detected -- that's simple non-relativistic quantum mechanics. The trick to QC is that there's an algorithm which can calculate exactly which bits were sniffed, so that a key can be composed of the remaining safe bits. For example, I wish to transmit a PGP private key of 2048 bits. Eavesdropper E picks up half the message. Using QC, I can calculate which part of the message was compromised, and construct the private key of the 1024 bits that are pristine (this is an oversimplification: the algorithm is nondeterministic, but that's the essential point).
Classical switching, such as networks, cannot occur in QC, because no FANOUT operation is allowed. This is a consequence of the no-cloning theorem.
QC can be done with photons, molecules in NMR, electrons, etc. Anything that can be reduced to an EPR pair (or alternately, a Hadamard gate) is a basis for QC.
A quantum computer, by itself, does not give you an O(1) prime-number crunching machine. You need an algorithm which can leverage the strength of the quantum computer. Shor's algorithm does polynomial-time factoring of numbers, and Grover's algorithm does O(sqrt(N)) selection from a list.
Finally, we have a pretty good handle on NRQM and even Quantum Field Theory; quantum mechanics is pretty-well understood in the realm of physics we observe now.
And before someone says "quantum gravity", first tell me what you mean by the term, since it really hasn't been defined yet in terms of physical theory -- meaning there are lots of candidates (string theory, braneworlds, Kaluza-Klein theory, etc), but no results.
It's hard to credit that you know what you're talking about, since from even a 1st year graduate level course in general relativity you'd know that Einstein was barely proficient in differential geometry (he learned it 1912-15, just before GR came out); and since about 1925 Elie Cartan had developed differential n-forms, which is what most practicioners of GR do their work in.
Einstein's physical insight was top-notch. His explanations of Special Relativity have no peer. But we've done quite a bit of reformulation of General Relativity (and that's before you even throw in string theory).
If you have a PhD in Physics, you should be able to tell me the Einstein-Hilbert action and derive the Einstein field equations from it? You should also be able to state the generally covariant Maxwell equations, and calculate the Maxwell stress-energy tensor. Or even something simple, like calculate the Einstein tensor in 3+1 Minkowski space.
Actually, Robert Forward wrote a paper about "negative matter" as an interesting thought exercise in an inertialess propulsion. Negative matter is based upon a 1957 paper by Herman Bondi in General Relativity as a way of explaining certain concepts.
Just like magnetic monopoles, there's no proof of the existence of negative matter. Certainly nothing you can characterize as "strong theoretical evidence" -- just like tachyons, another particle that hasn't been observed or conclusively ruled out.
Another subject of great interest that the late Robert L. Forward wrote at length about in his book Mirror Matter.
First, antimatter "explosions" are actually fizzles, because P-barP reactions at rest tend generate neutral and charged pions and kaons, and neutrinos.
Neutrinos don't interact significantly with matter, so that energy is effectively lost. The neutral pions and kaons interact with the weak force only, and hence carry energy away for quite a distance (kilometers for pions) before they decay into something that does interact with matter. 50% of the time for every charge particle you get m neutral particles, where m>2 (see references
That means that most of your energy is carried kilometers or more away (for the relativistic ones) before decaying into energetic particles that DO cause things to go boom. The energy of the antimatter tends to be dispersed through a rather large volume.
Antimatter is, however, extremely valuable for rockets, due to a unique advantage. The general Hohman-transfer equation, which governs interplanetary flight, has a term exp{V/V0}, where V is the exhaust velocity and V0 is the "mission velocity", defined to be the delta v necessary to achieve a particular orbit.
For example, V0=11.2km/sec for orbit, and ~29km/sec for Saturn. Note that getting into Earth orbit gets you almost halfway to anywhere.
The propellant/load ratio, which is how much propellant per unit of mass you need to get somewhere, therefore depends (exponentially) upon the ratio of V/V0. Now, V is limited in chemical rockets to be at best 7.4 km/s for O1/LH2, so you have a built-in, exponentially growing ratio of rocket fuel you must carry per kilogram of payload. This makes manned flights to Saturn impractical with chemical rockets.
However, an antimatter rocket has no built-in limit on exhaust velocity. Solving the equations, that means that you can get to anywhere on an antimatter rocket with a fuel/payload ratio of 5:1. That doesn't sound great, but it's much better than 100:1 for orbit or 300:1 for interplanetary flights.
And, in fact, with antimatter rockets you can start *thinking* about not using Hohman transfers (which minimize the necessary energy) to get someplace, and can consider minimizing your time instead. You'll need the same fuel ratio, just more antimatter to increase your exhaust velocity V. Forward has a design for a basic antimatter rocket he did research on for the USAF.
Finally, there are ways to store antimatter for weeks at a time, using Pfenning traps and other magnetic facilities.
Antimatter, however, makes a lousy energy source, as it must be fabricated, you get less out of it than you put into it (we're currently.0000001% efficient, according to R.L. Forward's estimates) -- it's essentially an inefficient battery. For the same reason, antimatter is not a particularly good weapon. If you had an "antiproton" particle beam, 99.9% of the energy is coming from kinetic energy, and the inefficiency in handling/storing antiprotons isn't worth the measly 0.1% energy you get out.
Whoops! Right, that's Virginia. I was living in Norfolk at the time, so Virginia, DC, and Maryland mix together on the Beltway.
Well, I left the East Coast shortly thereafter, so as I said, it's been awhile.
The really interesting work some other folks did were Si-Ge laser diodes the size of a flake of pepper, back then.
The radar stuff was kinda cool, but the little I saw of it involved sharp pointed triangles and other polygons of some thickness. I was never sure how they were going to work it into a net.
A long time ago (1986 or so) I worked for a summer at the Night Vision Electro-optics lab at Ft. Belvoir, Maryland. The topic of study was infrared camouflage.
Visual camouflage works by fooling your eye into thinking the object is part of the background. This is done by breaking up profile, matching background colors, and various other tricks.
The same problem exists in the infrared, except you have the additional wrinkle of controlling IR emission (just like carrying around a flashlight blows visual camouflage).
IR happens to be a useful wavelength for detection, because it readily propagates through the atmosphere without loss (over 99% transmission, with exception of two frequencies near 2500 and 25000 where water absorbs and another absorbion band for CO2), and because most objects radiate it (e.g., people, sunlight on the hood of a vehicle, engines, leading edges on wingtips. etc.).
In the 2500 - 25000 nanometer range, to match up with the forested/vegetation background in Maryland, we needed to duplicate the chlorophyl curve, which is the dominant background emission spectra. And, pretty much, they were able to do so, with some expensive nets and other mechanisms. They were trying for an integrated visual/IR/radar camouflage system (the radar folks worked in the same lab).
It's very interesting to read about these paints, since this appears to be the first reasonably viable mechanism for achieving this. They would need a chlorophyl pattern for vegetated regions, a desert pattern for deserts, etc. They would also still need to baffle and reduce IR exhaust, since paint won't help camouflage heated air or hot gun barrels.
The mechanisms previewed so far in the literature (electromechanical gears, electroptical properties) wouldn't likely generate much signature, if any. However, there might be some operation characteristic (e.g., power on) that could be detected with a SQUID (superconducting quantum interference device). However, the SQUID would pick up the spark plugs in the tank long before the electronic signals to the paint.
Actually, Roger Penrose proved that every black hole has a singularity in 1964. It's called, unsurprisingly, the Singularity Theorem.
Since a physical singularity (as opposed to a coordinate singularity) by definition does not follow the laws of physics, a "Cosmic Censorship" principle was proposed stating singularities can only occur inside a black hole, where they cannot interact with the rest of the universe.
Kip Thorne and John Preskill, however, believed that a "naked singularity", devoid of an event horizon, could exist. Steven Hawking made a bet with Thorne and Preskill in 1991 that naked singularities could not exist, but conceded when supercomputer simulations by M. Choptuik showed naked singularities were indeed possible.
Note, I wrote that is the limit for electron degeneracy to prop up the star. I didn't mean to imply a star past the Chandrasekhar limit will collapse to a white dwarf.
Science World says ~1.2 solar masses, in agreement with the figure I posted.
It happens that University of California, Davis physics department has a good cosmology group, and I'm a graduate student here. The last seminar I went to about this topic indicated that the Hubble redshift evidence pretty strongly correlated to an exponential inflation due to the cosmological constant, for what that's worth.
As far as singularities go, Roger Penrose proved the Singularity Theorem back in 1965; therefore, all black holes have singularities.
There is a difference between a coordinate singularity and a "physical singularity", although General Relativity (which equates space curvature with gravity) can make it hard to sort out (the proper techniques involve conformal mapping, again pioneered by Penrose) and of course, path integrals and complex analysis. But to simplify the picture, you don't die by going to the North Pole, even though that is a coordinate singularity in a spherical coordinate system. You will die, however, from encountering an object of unknowable physical properties.
Charged and/or spinning black holes have two event horizons; an inner and outer. The outer event horizon is the one dictated by light rays neither spiralling in nor escaping. The inner event horizon is dictated by a worldline unavoidably encountering the singularity.
Physicists actually have no problem with time travel; see the Novikov
Conjecture, which basically dictates that closed timelike curves are self-consistent (e.g., you cannot kill your grandfather once you are able to travel back in time; you are now in a closed timelike loop, and past and future are subjective). Any FTL travel == time travel, and there are several interesting possibilities. Robert Forward wrote in his "Dragon's egg" books about using a Kerr black hole to travel back in time, and in "Timemaster" about using negative matter to do likewise (negative matter != antimatter; negative matter has negative mass).
Fascinating stuff. The math is actually extremely interesting; one of the perks of studying physics;-) (There aren't many).
--Adam
The Schwartzchild radius is the radius, for a given mass, that will form a singularity. For a ten solar mass star, that is about 30 kilometers.
The Chandrasekhar limit gives the size limit for a star to collapse and produce a white dwarf. Most stars end their lives with a gravitational collapse, but electron degeneracy pressure (from the Pauli exclusion principle) prevents further collapse. However, for stars above ~1.2 solar masses, the gravitational collapse will overcome fermion repulsion, and the collapse will continue. Once the star's density has reached a certain point, it will collapse into a singularity. That density times the star's mass determines the Schwartzchild radius.
The event horizon is delineated by those light rays that will neither fall in nor escape from, the black hole. However, just because you cross the event horizon does not necessarily mean you will strike the singularity. Instead, it depends upon the type of black hole you've encountered.
In actual reality, you'll be fried by the blue shifted radiation coming from the accretion disk around the hole, but let's ignore that quibble.
Black holes have mass, spin, and charge. No other properties are discernable behind the event horizon. The fact that the above properties can be determined without a world-line (that is, information also does not propagate faster than light, and hence cannot escape) says something fundamental about those properties.
An uncharged, unspinning black hole is called a Schwartzchild hole. Once you cross the event horizon, you will unavoidably strike the singularity and perish.
In the other types of black holes, such as the Kerr black hole (uncharged, spinning), Reisnner-Nordstrom (charged, zero angular momentum), and the Kerr-Newman black hole (charged, spinning) it is possible to cross the event horizon without striking the singularity. Instead, you can pass into another universe.
Indeed, it's theoretically possible that you will pass through many universes. This is a one-way trip, however. If you try to get back to where you were, you will encounter the singularity and die.
Actual solution of the Einstein field equations for the holes listed above, however, produce perturbations. These perturbations, so far, cancel out the ability to miss the singularity and enter another universe.
Moving on, Hawking demonstrated that black holes evaporate. Hawking radiation is produced when half of a virtual particle pair appears inside the event horizon. Since both particles are no longer available to disappear under the Heisenberg time limit, the remaining particle acquires real energy. This energy comes from the black hole.
Since the rate of evaporation is proportional to surface area/mass, smaller black holes evaporate explosively. Indeed, no black holes smaller than a proton could exist from the big bang.
Finally, recent research shows that the universe is inflating, due to Einstein's cosmological constant (which, he ironically labelled as his "worst mistake"). That is, Hubble's constant is increasing. There will be no Big Crunch. The universe will expand at a faster and faster rate into nothingness.
There are a lot of good books on cosmology. General Relativity is undergoing a renaissance right now because of all of this important, new information.
The consequences of time travel have been explored a great deal in General Relativity literature.
A conjectured time machine immediately produces a time-loop, which is an inextricable linking of past and future. This is exactly like taking a piece of string and closing it into a circle. Before closure, one could orient the string along some axis and state that part of the string was "ahead" or "behind". However, once you make the loop, only relative, not absolute comparisons, are possible.
Hence "backwards" and "forwards" in time cease to have meaning in a time loop.
A paradoxical event, ie, the Grandfather Paradox, will be prevented from occuring. This is the well-known Novikov Self-Consistency Principle, as detailed by Novikov here:
You cannot have the "free will" to kill your grandfather in the same way you cannot have the "free will" to prevent yourself from falling off a cliff (unless you're Wile E. Coyote;-)
As I've referenced in another discussion concerning Wormhole Physics, time travel = FTL travel, with all of the implications for General Relativity, causality, and engineering. The energies required for large scale "metric engineering" are orders of magnitude larger than available to us even with the entire sun's energy as a budget.
No. Gravity (ie gravitons, Higg's boson scalar field, spin 2 particles, etc.) propagates at the speed of light. There are several relativistic effects that occur because of this, and in fact, that's the whole point of General Relativity.
I think your vector analysis is off. Let's transform to (right-handed) cylindrical coordinates: r, theta, and z, which will naturally express a current flow along a straight wire. Let I = current = I z-hat. Then B = magnetic field = B theta-hat. z-hat X theta-hat is r-hat. Please explain:
How theta-hat, a curvilinear coordinate describing B, has a "longitudinal axis".
How z-hat, the direction of the "axial heat source", is parallel to r-hat, the direction of the Lorentz force.
How Lorentz force = heat. Even if combined with a halogen lamp.
Also, I'd model a halogen lamp as a point heat source (from far away) or as a semispherical or cylindrical mesh, depending upon the lamp configuration. Perhaps the cylindrical configuration is your "axial heat source", but the axis is not very long, and the bulb rather thick (unless they've made a non-standard one). I'm not sure how you're getting a current along this same axis, seeing how the halogen bulb is a very good insulator.
Even the basic physics does not seem to be very credible.
First, an excellent technical reference (that I'm using in this discussion) is Matt Visser's book
Lorentzian Wormholes: From Einstein to Hawking
In general, to create a wormhole one must manipulate the general metric, which is a tensor that describes spacetime (for example, the relatively flat Minkowski metric takes on the form diag(-1,1,1,1) where diag refers to a diagonal matrix). Most "constructed" metrics that produce a wormhole solution have pathological flaws. For example, a Schwartzchild wormhole necessarily occludes the throat with a black hole, which tends to kill off passersby. The Kerr metric solution requires a several solar mass black hole formed into a ring and spun at relativistic angular velocities: how we might accomplish this feat of metric engineering anytime soon is troublesome.
The two most plausible ways of doing so is a Morris-Thorne-Wheeler wormhole, which simply requires exotic matter and violation of ANEC (Averaged Null-Energy Condition), and the Alcubierre spacewarp.
"Exotic" matter is simply matter with negative energy density. All matter and antimatter known has positive mass, and so there's only one way that we know of to get it: the Casimir effect. Briefly, the Casimir effect comes about due to vacuum fluctuations. Even the purest ideal vacuum is not truly empty, but has countless particle-antiparticle pairs appearing and disappearing within the time limits set by the Heisenberg Uncertainty Principle. The continued existence of these virtual particles has a noticeable effect, and is possibly a source of Einstein's Cosmological constant. At any rate, by setting up a parallel plate capacitor, one can reduce the likelihood of the virtual particles appearing, and thereby generate a negative energy density.
Unfortunately, it would take a spherical capacitor the size of the Earth separated by an angstrom (10 E-10 meters) to create a 10 meter or so wormhole using the Casimir effect.
Robert Forward nicely sidesteps this issue by postulating "negative matter" in his novel "Timemaster". As he explained it to me, "Why not?".
Alcubierre's metric contracts spacetime in front of the "ship" and expands it behind. It also requires exotic matter and violating the weak, strong, and dominant energy conditions. Lastly, Pfenning and Ford (1997 Classical Quantum Gravity 14 1743) show that this configuration is rather implausible, and Hiscock (1997 Class. Quant. Grav 14 L188) shows that a backreaction (warp drag) or tuning of the warp field may be required for it to maintain the Alcubierre metric, a difficult proposition given that past and future event horizons are causally disconnected.
In sum, there's really a renaissance occuring in General Relativity, and these issues are discussed in the professional literature. Like everyone else, I'd have to see a publication in the technical literature to consider seriously the claims made in this patent.
Now, with this in mind, after reading the abstract this patent seems to be nonsensical. Examining the claims:
Generating opposing magnetic fields each having a plane of maximum force running perpendicular to a longitudinal axis of the respective magnetic field;
The Lorentz force is given by Il x B, which means that the magnetic force is due to a current, and in general, circulates about the current flow. Due to the cross product, the resultant geometry is not planar. Since we have not discovered any magnetic monopoles, magnetic induction in general forms loops from one pole to another.
generating heat from a heat source along an axis parallel to the longitudinal axis of the magnetic field;
Unless the heat source is a thin wire, it is difficult to imagine an axial heat source. Heat conduction tends to be uniform, and while I'm not a material scientist, it is difficult for me to think of a material that has non-isotropic heat conduction (ie different depending on direction -- a composite material with fibers might do the trick).
generating an accelerator parallel to and in close proximity to the heat source, thereby creating an electromagnetic injection point; and generating a communication signal into the electromagnetic injection point, thereby sending and receiving the communication signal at a speed faster than a known speed of light.
What is exactly meant by "an accelerator"? Why does this magically add up to FTL?
Also note one of the other claims:
It has been observed by the inventor and witnesses that accelerated plant growth can occur using the present invention. For accelerated plant growth, first, you need to create a hot surface that is more than 1000 degrees Fahrenheit. Next, you need a strong magnetic field. Only one device is needed for this function. This allows energy from another dimension to influence plant growth.
Again, there seems to be no basis in which to make this claim. A wormhole would certain create a characteristic signature, even leaving causality problems aside. --Adam
The source material for this story is simply science fiction, to be charitable (more probably it is science fantasy).
There are a number of fallacies in the logic of the article, but here's a brief rundown of a few of them.
1) Determinism is dead.
Everything in the universe has a wavefunction, which is simply a "catalog of expected values" (Schroedinger). Or, simply(*) stated in bra-ket notation:
P = |(a|b)|^2
* This notation is admittedly meaningless without undergraduate QM. However, perhaps I can highlight just one telling mathematical point.
The QM wave equation, which applies to everything, includes terms with imaginary values. This means that rigid mathematical rules are necessary to treat any case of QM (Hermitian operators, orthonormalization, etc), and the above is one of them: you cannot specify something exactly, only its probability. (Mostly true: you can have sharp observables which are eigenstates/eigenvalues, but they quickly convert into mixed states. However, more mathematics will probably obscure the point). Most often this is encapsulated in the Heisenberg Uncertainty Principle.
Determinism is also effectively dead when applied to chaotic systems, which just happens to be most of nature.
From the above principles, talking about scanning the synapses of the brain with perfect accuracy, even given perfect nanobots, is naive.
2) Entropy
Let's examine, as R.P. Feynmann has done, Maxwell's demon. Briefly, this is a microscopic pawl and ratchet affair which allows the ratchet to turn only one way. Due to random vibrations, interactions will occur that cause the wheel to rotate one direction or another. However, due to the pawl, the wheel can only turn one direction. Therefore, we can extract torque from randomness, and build millions of demons to create an extremely efficient (n = 0.5) energy source. True?
Hint: Perhaps I should make a company called Maxwell's Demon Power Systems, write a book, and come out with an IPO.
No. The same randomness will also act on the pawl, and the energy to release the pawl is the same as the amount to rotate the wheel. Therefore, no net rotation.
The point: there is an extremely limited amount of work one can extract from randomness. Information entropy and physical entropy may or may not be the same (this is a matter of debate), but the principles are identically based upon ensembles and microstates. There is a limited amount of information one can extract from an entropic system.
Slashdot Mirror
Nowadays folks know his Bolo works, but Dinosaur Beach, Worlds of the Imperium, End as a Hero, and the Retief series were pretty unique for their time. One of my favorite authors.
Dinosaur Beach has to be one of my favorite novels, its a cracking good time travel novel with transhumanism before such was known.
http://www.dinosaurbeach.com/
There are several very cool results from String/M-theory, but nothing that can be fully understood without the mathematics. But a theory that fully explains all interactions, including matter fields, with supersymmetry and supergravity arising naturally from it, an explanation of the heirarchy problem, and use of perturbation theory and renormalization for gravitons which are generally non-renormalizable, is interesting.
Loop Quantum gravity is interesting too, especially for its background independence, but it will never explain matter fields, and the semiclassical sector is currently lacking. By contrast, string theory has a natural extension to classical general relativity.
Actually, that is wrong.
First, some perspective.
Quantum mechanics is not a theory, it is a set of construction rules for theories that reflect reality. Whatever quantum field theory you construct of whatever operators you care to name (the rules of QM/QFD being most easily phrased in terms of operators), some of those operators do not commute [A,B] != 0, and some of those operators do not anti-commute {A,B} != 0.
We happen to call those bosons and fermions respectively.
String theory, being a quantum field theory including gravity (hence, a superset of general relativity), is also a set of construction rules for theories of reality.
As it so happens, some of those theories produce large extra dimensions of > than the millimeter scale. In general, we characterize those theories by a parameter space, and theories with a parameter space producing large extra dimensions of a particular type *are* disallowed by observation.
If observation disallowed the entire parameter space of string theory, it would be entirely falsified.
Instead, it is something dubbed "The Landscape".
Secondly, it is interesting, but not informative, to listen to opinions of people who have never studied string theory remark on its structure/usefulness.
In fact, string theories do provide some elegant solutions to things like supersymmetric (quantum) gravity (SUGRA), supersymmetry (SUSY), and a good number of other subtle points that are only understood with sufficient background in QFT, GR, etc.
Everyone laughs at "the internet is a series of tubes", but then we get long expostulations about string theory from people that haven't studied it.
Third, remember that the authors of the article (e.g. Lee Smolin) have a somewhat vested interest in denying the usefulness of String Theory, as it allows their own theories (i.e. Loop Quantum Gravity) to be more prominent.
As a matter of my own opinion, LQG has even more difficulties than String Theory, for example, it assumes the spacetime metric is smooth even at quantum scales, and that a classical theory (GR) can be "quantized". As GR is not renormalizable, this is violently at odds with known, tested QFT, which is accurate to 11 decimal places.
Well, gravity is not acceleration, but spacetime curvature. The actual equation is G = 8*pi*T, where G is the Einstein tensor and T is the stress-energy tensor. Since G relates to geometry (the Reimann curvature tensor + Ricci scalar), this directly relates mass-energy (T) to curvature (G).
The curvature of a section of space is defined by its metric. (A metric can be thought of as the generalization of the dot product between two vectors in some space, which therefore relates the two vectors in either a coordinate-free or coordinate basis.) In simple cases we assume space is flat by using the Minkowski metric, which defines simple Lorentz transforms, which can be thought of as rotations from one frame of reference to another.
In complicated cases, space is curved, in which case we use manifolds to describe the topology of space. Topology means that a cofee cup and a donut are identical mathematical objects; manifolds mean that our topology is locally flat, so that we can use the same Minkowski machinery for local points at given spacetime coordinates. The price is we must now use tensors to "rotate" from one frame of reference to another.
You tell if space is curved or flat by its geodesic, which is simply the minimum distance between two points. In flat space it is a line; in curved space it is a curve, which you can measure by defining the geodesic deviation between two neighboring paths. At this point the normal notion of derivative, tangent, and vector are lost, and must be redefined in terms of properties of the manifold as covariant derivatives, parallel transport, and tensors (products of n-forms).
In the example of a sphere: parallel transport is the operation of moving a vector while keeping it pointed in the same direction (preserving its inner product). If you take a vector tangent to the surface pointed north on the equator, move it up to the north pole, back down a line of longitude 90 degrees west, then back along the equator, you will notice your vector ends up in the same location but with a different direction. This difference (non-commutativity of operators) is the hallmark of curved space.
Similiarly, if you wrote a differential equation describing some physics involving these vectors, you would find that it wouldn't hold under the operation described above. But if you replace your derivative operator with a covariant derivative operator satisfying linearity, Leibnitz rule, and other properties, such an equation would hold in all frames of reference.
General relativity is a local theory; it discusses the properties of spacetime at a point, where it is locally flat. Acceleration is really just deviation from a geodesic sketched in spacetime. When you consider a bullet or ball fired or thrown between the two same endpoints, in the everyday frame of reference their curvatures look radically different: the ball has to arc up higher and the bullet travels faster. But if you graph not just x and z, but t in the third dimension, both have the same radius of curvature, because the path of the ball is longer than the path of the bullet through spacetime.
And by the way, you can tell the difference between gravity and acceleration by measuring the cosmic microwave background radiation. Not only that, but since we're at least approximately in a Friedman-Robertson-Walker cosmology, an absolute "cosmic time" can be defined by the evolution of some parameter (CMB, Hubble's constant, etc).
That's not what the holographic principle says.
The holographic principle, more generally known as the covariant energy bound (Raphael Bousso, "The holographic principle", Rev.Mod.Phys, 74, 2002), was formulated by t'Hooft and Susskind as the "spherical energy bound." The name comes from the postulate that all physics in a region of space is described by data that fits on its boundary surface, at one bit per Planck area.
There turned out to be problems with this definition; for example, it does not hold for black holes, which ruins the idea as a general cosmological principle. Further refinements giving rise to the covariant energy bound. Even now, it has only been considered for cosmologies that are thought to be "realistic" (in particular anti-DeSitter Conformal Field Theory).
An interesting idea was put forward by my Cosmology professor (Nemanja Kaloper, "Origami World", hep-th/0403208). The basic idea is to solve the gauge hierarchy problem (e.g., why is gravity so weak) by using 6-dimensional anti-DeSitter spaces to generate 4-dimensional gravitons. Unlike versions of string theory, the extra dimensions are not compactified. The intersections of various branes in 3D gives GR gravity, but the 4D bulk propagation produces the very weak gravitational constants. As an added bonus, particular foldings consisting of galaxies "millimeters" away in the bulk create dark matter.
That is, dark matter is the result of the 4-d "shadow" onto 3-space. Or, the Milky way galaxy could generate it's own dark matter simply by being folded in the 4-D bulk.
Any physical theory we come up with now always (ie "must") reduce to observable behavior now. The earth is flat is a good local approximation considering the earth's curvature, until you start sailing and cover continental distances.
The example of "An apple always falls from a tree" is very good. We do not need to know the details of quantum gravity (whatever that may be) in order to predict and describe an apple falling, even though quantum gravity supercedes general relativity and quantum field theory, which supercedes special relativity, flat Minkowski space, and quantum mechanics, which supercedes classical mechanics.
Any theory we come up with had better be reducible to classical mechanics at the right energy scales. All theories have a domain of application, and we keep widening the domain by introducing more and more general theories.
But in the end, we test our general theories against specific observations. There is a beautiful theory of Higg's scalars produced from Nambu-Goldstone bosons "eating" photons in the Standard Model Lagrangian which generates massy and massless fields (and hence mass for all particles which have mass); however, finding the Higg's boson doesn't invalidate the simple observation that an apple "always" falls.
Oh, and by the way, Quantum Field Theory (ie, fully covariant Quantum Mechanics or QM + GR) is proven and tested to a fantastic order of accuracy, 11 or twelve decimal places. It's the most accurately known theory we have, which is why we can tell immediately what cosmological theories are right or wrong by their effect on the Standard Model. We could confirm or eliminate certain string theories if we knew gravitational interactions as accurately as QFT.
So there's a slim to none chance that QFT will prove invalid at anything less than ~10E15 GeV energies, which is the Planck scale at the Big Bang.
--Adam
The point is you cannot recreate the stream once you measure it.
A qubit from the stream comes in with a value a|0> + b|1>. This means the odds of measuring |0> are a^2 and the odds of measuring |1> are b^2. If you measure a |0> you have just discarded the amplitude |b>; this is what is meant by wavefunction collapse. You would then try to "recreate" the stream by sending out a |0>. However, this is distinguishable from the original a|0> + b|1>, and so your attack fails.
Quantum mechanics involves Hilbert spaces, and they are very very large. A classical bit has only two values, 0 or 1. A qubit has an infinite number of values for a and b, subject to Unitarity, which means their total amplitude doesn't exceed 1. It's possible for the phase information of a qubit to store the entire works of Shakespeare, but you would only ever recover 1 bit.
A 500-qubit system has more information stored in it than there are elementary particles (quarks, leptons, photons, neutrinos, vector bosons, gluons) in the Universe.
The applications to physics is very interesting, especially in Cosmology, where the same idea goes by the name Holography. There seems to be a limit on how much information can be stored in spacetime; the classic example is the Beckenstein limit on entropy for a black hole's surface area. Nowadays, Cosmology and Quantum Field Theory are tied strongly together. For example, in some QFT Lagrangians there are massless scalar axions that couple to photons and can cause distant supernovae to appear fainter, thereby throwing the whole "Universe is accelerating" proposition into question. (I know the above example from a paper my Cosmology professor, Nemanja Kaloper, wrote.)
Oh, by the way, the poster indicating "we can't reliably send 1 photon" is wrong. The original Quantum Cryptography test bed sent out effectively 1/10 photon, using weak amplitudes.
--Adam
Sure ... I'd rather get my security patches from an unknown source ...
There's a number of inaccuracies/misconceptions here. Let's clarify:
First, the magic of Quantum Cryptography is NOT that the signal cannot be eavesdropped on without being detected -- that's simple non-relativistic quantum mechanics. The trick to QC is that there's an algorithm which can calculate exactly which bits were sniffed, so that a key can be composed of the remaining safe bits. For example, I wish to transmit a PGP private key of 2048 bits. Eavesdropper E picks up half the message. Using QC, I can calculate which part of the message was compromised, and construct the private key of the 1024 bits that are pristine (this is an oversimplification: the algorithm is nondeterministic, but that's the essential point).
Classical switching, such as networks, cannot occur in QC, because no FANOUT operation is allowed. This is a consequence of the no-cloning theorem.
QC can be done with photons, molecules in NMR, electrons, etc. Anything that can be reduced to an EPR pair (or alternately, a Hadamard gate) is a basis for QC.
A quantum computer, by itself, does not give you an O(1) prime-number crunching machine. You need an algorithm which can leverage the strength of the quantum computer. Shor's algorithm does polynomial-time factoring of numbers, and Grover's algorithm does O(sqrt(N)) selection from a list.
Finally, we have a pretty good handle on NRQM and even Quantum Field Theory; quantum mechanics is pretty-well understood in the realm of physics we observe now.
And before someone says "quantum gravity", first tell me what you mean by the term, since it really hasn't been defined yet in terms of physical theory -- meaning there are lots of candidates (string theory, braneworlds, Kaluza-Klein theory, etc), but no results.
It's hard to credit that you know what you're talking about, since from even a 1st year graduate level course in general relativity you'd know that Einstein was barely proficient in differential geometry (he learned it 1912-15, just before GR came out); and since about 1925 Elie Cartan had developed differential n-forms, which is what most practicioners of GR do their work in.
Einstein's physical insight was top-notch. His explanations of Special Relativity have no peer.
But we've done quite a bit of reformulation of General Relativity (and that's before you even throw in string theory).
If you have a PhD in Physics, you should be able to tell me the Einstein-Hilbert action and derive the Einstein field equations from it? You should also be able to state the generally covariant Maxwell equations, and calculate the Maxwell stress-energy tensor. Or even something simple, like calculate the Einstein tensor in 3+1 Minkowski space.
The definition of a plasma from Chen's "Introduction to Plasma Physics and Controlled Fusion" is:
Collective Behavior:
Lambda_sub D, Debye Length
N_sub D, number of particles in Debye sphere >>> 1
Quasineutrality:
wt > 1, collision frequency * mean time between collisions with neutral atoms
In other words, collective behavior (determined by temperature) does not make a plasma, sufficient density is required.
Hence Lawson's criterion for fusion once ignition temperature has been reached is density * time > 10^14 s/cm^3 for DT (deuterium-tritium) fusion.
--Adam
Actually, Robert Forward wrote a paper about "negative matter" as an interesting thought exercise in an inertialess propulsion. Negative matter is based upon a 1957 paper by Herman Bondi in General Relativity as a way of explaining certain concepts.
Just like magnetic monopoles, there's no proof of the existence of negative matter. Certainly nothing you can characterize as "strong theoretical evidence" -- just like tachyons, another particle that hasn't been observed or conclusively ruled out.
--Adam
First, antimatter "explosions" are actually fizzles, because P-barP reactions at rest tend generate neutral and charged pions and kaons, and neutrinos.
Neutrinos don't interact significantly with matter, so that energy is effectively lost. The neutral pions and kaons interact with the weak force only, and hence carry energy away for quite a distance (kilometers for pions) before they decay into something that does interact with matter. 50% of the time for every charge particle you get m neutral particles, where m>2 (see references
That means that most of your energy is carried kilometers or more away (for the relativistic ones) before decaying into energetic particles that DO cause things to go boom. The energy of the antimatter tends to be dispersed through a rather large volume.
Antimatter is, however, extremely valuable for rockets, due to a unique advantage. The general Hohman-transfer equation, which governs interplanetary flight, has a term exp{V/V0}, where V is the exhaust velocity and V0 is the "mission velocity", defined to be the delta v necessary to achieve a particular orbit.
For example, V0=11.2km/sec for orbit, and ~29km/sec for Saturn. Note that getting into Earth orbit gets you almost halfway to anywhere.
The propellant/load ratio, which is how much propellant per unit of mass you need to get somewhere, therefore depends (exponentially) upon the ratio of V/V0. Now, V is limited in chemical rockets to be at best 7.4 km/s for O1/LH2, so you have a built-in, exponentially growing ratio of rocket fuel you must carry per kilogram of payload. This makes manned flights to Saturn impractical with chemical rockets.
However, an antimatter rocket has no built-in limit on exhaust velocity. Solving the equations, that means that you can get to anywhere on an antimatter rocket with a fuel/payload ratio of 5:1. That doesn't sound great, but it's much better than 100:1 for orbit or 300:1 for interplanetary flights.
And, in fact, with antimatter rockets you can start *thinking* about not using Hohman transfers (which minimize the necessary energy) to get someplace, and can consider minimizing your time instead. You'll need the same fuel ratio, just more antimatter to increase your exhaust velocity V. Forward has a design for a basic antimatter rocket he did research on for the USAF.
Finally, there are ways to store antimatter for weeks at a time, using Pfenning traps and other magnetic facilities.
Antimatter, however, makes a lousy energy source, as it must be fabricated, you get less out of it than you put into it (we're currently
But it's a wonderful rocket fuel.
--Adam
Whoops! Right, that's Virginia. I was living in Norfolk at the time, so Virginia, DC, and Maryland mix together on the Beltway.
Well, I left the East Coast shortly thereafter, so as I said, it's been awhile.
The really interesting work some other folks did were Si-Ge laser diodes the size of a flake of pepper, back then.
The radar stuff was kinda cool, but the little I saw of it involved sharp pointed triangles and other polygons of some thickness. I was never sure how they were going to work it into a net.
--Adam
A long time ago (1986 or so) I worked for a summer at the Night Vision Electro-optics lab at Ft. Belvoir, Maryland. The topic of study was infrared camouflage.
Visual camouflage works by fooling your eye into thinking the object is part of the background. This is done by breaking up profile, matching background colors, and various other tricks.
The same problem exists in the infrared, except you have the additional wrinkle of controlling IR emission (just like carrying around a flashlight blows visual camouflage).
IR happens to be a useful wavelength for detection, because it readily propagates through the atmosphere without loss (over 99% transmission, with exception of two frequencies near 2500 and 25000 where water absorbs and another absorbion band for CO2), and because most objects radiate it (e.g., people, sunlight on the hood of a vehicle, engines, leading edges on wingtips. etc.).
In the 2500 - 25000 nanometer range, to match up with the forested/vegetation background in Maryland, we needed to duplicate the chlorophyl curve, which is the dominant background emission spectra. And, pretty much, they were able to do so, with some expensive nets and other mechanisms. They were trying for an integrated visual/IR/radar camouflage system (the radar folks worked in the same lab).
It's very interesting to read about these paints, since this appears to be the first reasonably viable mechanism for achieving this. They would need a chlorophyl pattern for vegetated regions, a desert pattern for deserts, etc. They would also still need to baffle and reduce IR exhaust, since paint won't help camouflage heated air or hot gun barrels.
The mechanisms previewed so far in the literature (electromechanical gears, electroptical properties) wouldn't likely generate much signature, if any. However, there might be some operation characteristic (e.g., power on) that could be detected with a SQUID (superconducting quantum interference device). However, the SQUID would pick up the spark plugs in the tank long before the electronic signals to the paint.
--Adam
Since a physical singularity (as opposed to a coordinate singularity) by definition does not follow the laws of physics, a "Cosmic Censorship" principle was proposed stating singularities can only occur inside a black hole, where they cannot interact with the rest of the universe.
Kip Thorne and John Preskill, however, believed that a "naked singularity", devoid of an event horizon, could exist. Steven Hawking made a bet with Thorne and Preskill in 1991 that naked singularities could not exist, but conceded when supercomputer simulations by M. Choptuik showed naked singularities were indeed possible.
--Adam
I meant "black hole" instead of "white dwarf". The limit for collapse to a black hole is ~6 solar masses, but I'm going from memory.
Note, I wrote that is the limit for electron degeneracy to prop up the star. I didn't mean to imply a star past the Chandrasekhar limit will collapse to a white dwarf.
Science World says ~1.2 solar masses, in agreement with the figure I posted.
It happens that University of California, Davis physics department has a good cosmology group, and I'm a graduate student here. The last seminar I went to about this topic indicated that the Hubble redshift evidence pretty strongly correlated to an exponential inflation due to the cosmological constant, for what that's worth.
As far as singularities go, Roger Penrose proved the Singularity Theorem back in 1965; therefore, all black holes have singularities.
There is a difference between a coordinate singularity and a "physical singularity", although General Relativity (which equates space curvature with gravity) can make it hard to sort out (the proper techniques involve conformal mapping, again pioneered by Penrose) and of course, path integrals and complex analysis. But to simplify the picture, you don't die by going to the North Pole, even though that is a coordinate singularity in a spherical coordinate system. You will die, however, from encountering an object of unknowable physical properties.
Charged and/or spinning black holes have two event horizons; an inner and outer. The outer event horizon is the one dictated by light rays neither spiralling in nor escaping. The inner event horizon is dictated by a worldline unavoidably encountering the singularity.
Physicists actually have no problem with time travel; see the Novikov Conjecture, which basically dictates that closed timelike curves are self-consistent (e.g., you cannot kill your grandfather once you are able to travel back in time; you are now in a closed timelike loop, and past and future are subjective). Any FTL travel == time travel, and there are several interesting possibilities. Robert Forward wrote in his "Dragon's egg" books about using a Kerr black hole to travel back in time, and in "Timemaster" about using negative matter to do likewise (negative matter != antimatter; negative matter has negative mass).
Fascinating stuff. The math is actually extremely interesting; one of the perks of studying physics ;-) (There aren't many).
--Adam
The Schwartzchild radius is the radius, for a given mass, that will form a singularity. For a ten solar mass star, that is about 30 kilometers.
The Chandrasekhar limit gives the size limit for a star to collapse and produce a white dwarf. Most stars end their lives with a gravitational collapse, but electron degeneracy pressure (from the Pauli exclusion principle) prevents further collapse. However, for stars above ~1.2 solar masses, the gravitational collapse will overcome fermion repulsion, and the collapse will continue. Once the star's density has reached a certain point, it will collapse into a singularity. That density times the star's mass determines the Schwartzchild radius.
The event horizon is delineated by those light rays that will neither fall in nor escape from, the black hole. However, just because you cross the event horizon does not necessarily mean you will strike the singularity. Instead, it depends upon the type of black hole you've encountered.
In actual reality, you'll be fried by the blue shifted radiation coming from the accretion disk around the hole, but let's ignore that quibble.
Black holes have mass, spin, and charge. No other properties are discernable behind the event horizon. The fact that the above properties can be determined without a world-line (that is, information also does not propagate faster than light, and hence cannot escape) says something fundamental about those properties.
An uncharged, unspinning black hole is called a Schwartzchild hole. Once you cross the event horizon, you will unavoidably strike the singularity and perish.
In the other types of black holes, such as the Kerr black hole (uncharged, spinning), Reisnner-Nordstrom (charged, zero angular momentum), and the Kerr-Newman black hole (charged, spinning) it is possible to cross the event horizon without striking the singularity. Instead, you can pass into another universe.
Indeed, it's theoretically possible that you will pass through many universes. This is a one-way trip, however. If you try to get back to where you were, you will encounter the singularity and die.
Actual solution of the Einstein field equations for the holes listed above, however, produce perturbations. These perturbations, so far, cancel out the ability to miss the singularity and enter another universe.
Moving on, Hawking demonstrated that black holes evaporate. Hawking radiation is produced when half of a virtual particle pair appears inside the event horizon. Since both particles are no longer available to disappear under the Heisenberg time limit, the remaining particle acquires real energy. This energy comes from the black hole.
Since the rate of evaporation is proportional to surface area/mass, smaller black holes evaporate explosively. Indeed, no black holes smaller than a proton could exist from the big bang.
Finally, recent research shows that the universe is inflating, due to Einstein's cosmological constant (which, he ironically labelled as his "worst mistake"). That is, Hubble's constant is increasing. There will be no Big Crunch. The universe will expand at a faster and faster rate into nothingness.
There are a lot of good books on cosmology. General Relativity is undergoing a renaissance right now because of all of this important, new information.
The consequences of time travel have been explored a great deal in General Relativity literature.
;-)
A conjectured time machine immediately produces a time-loop, which is an inextricable linking of past and future. This is exactly like taking a piece of string and closing it into a circle. Before closure, one could orient the string along some axis and state that part of the string was "ahead" or "behind". However, once you make the loop, only relative, not absolute comparisons, are possible.
Hence "backwards" and "forwards" in time cease to have meaning in a time loop.
A paradoxical event, ie, the Grandfather Paradox, will be prevented from occuring. This is the well-known Novikov Self-Consistency Principle, as detailed by Novikov here:
http://www.iap.fr/eas/EAS18/time18/ontime.html
You cannot have the "free will" to kill your grandfather in the same way you cannot have the "free will" to prevent yourself from falling off a cliff (unless you're Wile E. Coyote
As I've referenced in another discussion concerning Wormhole Physics, time travel = FTL travel, with all of the implications for General Relativity, causality, and engineering. The energies required for large scale "metric engineering" are orders of magnitude larger than available to us even with the entire sun's energy as a budget.
--Adam
If you really want to make this happen, you should check out prochange:
http://www.prochange.org
The dolphin mascot is cute.
--Adam
Also, I'd model a halogen lamp as a point heat source (from far away) or as a semispherical or cylindrical mesh, depending upon the lamp configuration. Perhaps the cylindrical configuration is your "axial heat source", but the axis is not very long, and the bulb rather thick (unless they've made a non-standard one). I'm not sure how you're getting a current along this same axis, seeing how the halogen bulb is a very good insulator.
Even the basic physics does not seem to be very credible.
--Adam
In general, to create a wormhole one must manipulate the general metric, which is a tensor that describes spacetime (for example, the relatively flat Minkowski metric takes on the form diag(-1,1,1,1) where diag refers to a diagonal matrix). Most "constructed" metrics that produce a wormhole solution have pathological flaws. For example, a Schwartzchild wormhole necessarily occludes the throat with a black hole, which tends to kill off passersby. The Kerr metric solution requires a several solar mass black hole formed into a ring and spun at relativistic angular velocities: how we might accomplish this feat of metric engineering anytime soon is troublesome.
The two most plausible ways of doing so is a Morris-Thorne-Wheeler wormhole, which simply requires exotic matter and violation of ANEC (Averaged Null-Energy Condition), and the Alcubierre spacewarp.
"Exotic" matter is simply matter with negative energy density. All matter and antimatter known has positive mass, and so there's only one way that we know of to get it: the Casimir effect. Briefly, the Casimir effect comes about due to vacuum fluctuations. Even the purest ideal vacuum is not truly empty, but has countless particle-antiparticle pairs appearing and disappearing within the time limits set by the Heisenberg Uncertainty Principle. The continued existence of these virtual particles has a noticeable effect, and is possibly a source of Einstein's Cosmological constant. At any rate, by setting up a parallel plate capacitor, one can reduce the likelihood of the virtual particles appearing, and thereby generate a negative energy density.
Unfortunately, it would take a spherical capacitor the size of the Earth separated by an angstrom (10 E-10 meters) to create a 10 meter or so wormhole using the Casimir effect.
Robert Forward nicely sidesteps this issue by postulating "negative matter" in his novel "Timemaster". As he explained it to me, "Why not?".
Alcubierre's metric contracts spacetime in front of the "ship" and expands it behind. It also requires exotic matter and violating the weak, strong, and dominant energy conditions. Lastly, Pfenning and Ford (1997 Classical Quantum Gravity 14 1743) show that this configuration is rather implausible, and Hiscock (1997 Class. Quant. Grav 14 L188) shows that a backreaction (warp drag) or tuning of the warp field may be required for it to maintain the Alcubierre metric, a difficult proposition given that past and future event horizons are causally disconnected.
In sum, there's really a renaissance occuring in General Relativity, and these issues are discussed in the professional literature. Like everyone else, I'd have to see a publication in the technical literature to consider seriously the claims made in this patent.
Now, with this in mind, after reading the abstract this patent seems to be nonsensical. Examining the claims:
Generating opposing magnetic fields each having a plane of maximum force running perpendicular to a longitudinal axis of the respective magnetic field;
The Lorentz force is given by Il x B, which means that the magnetic force is due to a current, and in general, circulates about the current flow. Due to the cross product, the resultant geometry is not planar. Since we have not discovered any magnetic monopoles, magnetic induction in general forms loops from one pole to another.
generating heat from a heat source along an axis parallel to the longitudinal axis of the magnetic field;
Unless the heat source is a thin wire, it is difficult to imagine an axial heat source. Heat conduction tends to be uniform, and while I'm not a material scientist, it is difficult for me to think of a material that has non-isotropic heat conduction (ie different depending on direction -- a composite material with fibers might do the trick).
generating an accelerator parallel to and in close proximity to the heat source, thereby creating an electromagnetic injection point; and generating a communication signal into the electromagnetic injection point, thereby sending and receiving the communication signal at a speed faster than a known speed of light.
What is exactly meant by "an accelerator"? Why does this magically add up to FTL?
Also note one of the other claims:
It has been observed by the inventor and witnesses that accelerated plant growth can occur using the present invention.
For accelerated plant growth, first, you need to create a hot surface that is more than 1000 degrees Fahrenheit. Next, you need a strong magnetic field. Only one device is needed for this function. This allows energy from another dimension to influence plant growth.
Again, there seems to be no basis in which to make this claim. A wormhole would certain create a characteristic signature, even leaving causality problems aside. --Adam
There are a number of fallacies in the logic of the article, but here's a brief rundown of a few of them.
1) Determinism is dead.
Everything in the universe has a wavefunction, which is simply a "catalog of expected values" (Schroedinger). Or, simply(*) stated in bra-ket notation:
P = |(a|b)|^2
* This notation is admittedly meaningless without undergraduate QM. However, perhaps I can highlight just one telling mathematical point.
The QM wave equation, which applies to everything, includes terms with imaginary values. This means that rigid mathematical rules are necessary to treat any case of QM (Hermitian operators, orthonormalization, etc), and the above is one of them: you cannot specify something exactly, only its probability. (Mostly true: you can have sharp observables which are eigenstates/eigenvalues, but they quickly convert into mixed states. However, more mathematics will probably obscure the point). Most often this is encapsulated in the Heisenberg Uncertainty Principle.
Determinism is also effectively dead when applied to chaotic systems, which just happens to be most of nature.
From the above principles, talking about scanning the synapses of the brain with perfect accuracy, even given perfect nanobots, is naive.
2) Entropy
Let's examine, as R.P. Feynmann has done, Maxwell's demon. Briefly, this is a microscopic pawl and ratchet affair which allows the ratchet to turn only one way. Due to random vibrations, interactions will occur that cause the wheel to rotate one direction or another. However, due to the pawl, the wheel can only turn one direction. Therefore, we can extract torque from randomness, and build millions of demons to create an extremely efficient (n = 0.5) energy source. True?
Hint: Perhaps I should make a company called Maxwell's Demon Power Systems, write a book, and come out with an IPO.
No. The same randomness will also act on the pawl, and the energy to release the pawl is the same as the amount to rotate the wheel. Therefore, no net rotation.
The point: there is an extremely limited amount of work one can extract from randomness. Information entropy and physical entropy may or may not be the same (this is a matter of debate), but the principles are identically based upon ensembles and microstates. There is a limited amount of information one can extract from an entropic system.
Back to your regularly scheduled Star Trek.