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Gravity Waves

Production of Gravity Waves for Communications and Propulsion Purposes
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The conventional picture of a gravity wave may be called "a moving ripple in the fabric of space-time". A conventional massy object can be said to occupy a region of space-time, each atom of that mass in a different place than any other. If such a mass is encountered by a gravity wave, the wave causes distances between atoms to temporarily shrink and/or expand -- because Space itself shrinks and/or expands as a gravity wave goes by. Various physical properties of the mass will determine how it behaves in response to what can easily be called "a stressful situation". A delicate crystal may shatter, while a piece of rubber may hardly be affected -- flexing it may heat it a bit, perhaps. Actual physical gravity-wave detectors have been built, which operate by detecting the stresses imposed upon a mass, and they seem to work fine.

The primary thing to note in any such event is simply this: It takes energy to affect a mass. Thus if a crystal goblet shatters, the energy required for shattering ultimately came from the passing gravity wave. The second thing to note is a rule which in Quantum Mechanics is called "Time Reversal Symmetry". Any very simple event is reversible, so.... If a large piece of metal experiences detectable distortions of its shape (absorbing energy as it does) when a gravity wave passes through, then should not that mass, suitably distorted, convert some energy into a gravity wave?

There is some reason to think this may be the case. The existing detectors which work on the principle of shape-distortion have been detecting far more gravity waves than can easily be explained in terms of conventional sources (such as black holes). What if they are also detecting such mass-distortions as automobile wrecks, avalanches, trees falling in the woods, explosions of war, and maybe even the hammered nails of the construction industry? Time-Reversal Symmetry is a very powerful idea in Quantum Mechanics, so why can't gravity-wave energy- absorption be reversible? Why not put the notion to the test?

Well, first it must be noted that while there are many ways to distort a mass, there is no immediate reason to assume that all of them may yield gravity waves. Next, careful laboratory experiments have for centuries failed to detect the losses of energy and momentum that could be called crucial clues pointing towards the production of gravity waves. So it must be assumed that only miniscule amounts can possibly be released during ordinary mass-distortions. And yet there is a bit more to keep in mind: When was the last time a careful laboratory experiment tried to track down every last erg of energy involved in something as extreme as, say, an automobile wreck? Equipment sensitive enough to measure all that energy, and tough enough to survive the experience, does not exist!

In favor of the proposed experiment is its simplicity. (For example, suspend an anvil near a gravity-wave detector, and whack the anvil with a sledgehammer.) If it is possible to create gravity waves through extreme mass-distortion, tracking down every last erg at the source will not be necessary, because the detector will detect them! If it isn't possible, the detector will reveal that, too. And thus the first part of the title is explained: If we can both create and detect gravity waves, then they WILL become a communications medium, as an obvious and inevitable result of technological progress.

Let us now take a moment to imagine the preceding experiment from above: The anvil is located at the origin of X and Y axes; the sledgehammer is moved towards it along the X-axis, while the detector is located on the Y-axis. If a gravity wave is produced, it must carry both energy and momentum which originally were part of the sledgehammer's motion. Since we know that momentum is conserved both in magnitude and direction, it is reasonable to conclude that most of the gravity wave will move away from the anvil along the X-axis, and the detector on the Y-axis will not notice much of it. But if there was a second detector along the X-axis, that one should detect the strongest part of the wave. The difference of location is critical, because mass-distortion detectors are extremely sensitive to sound-wave vibrations. The impact of hammer upon anvil will yield a loud noise which may have similar effect at both detectors, but if a gravity wave is also produced, the detection of it should be unequal. The more unequal the detection, the more convincing the test!

The rest of this essay assumes that the experiment will vindicate Time Reversal Symmetry. You may stop reading, and wait for test-results, or you can read the explanation behind the second part of the title.

The key has actually already been presented two paragraphs ago. Imagine a machine which repetitively distorts a mass in such a way as to produce gravity waves. Imagine also that those waves leave the machine always "beaming" in the same direction. As mentioned, they carry momentum, and momentum must be conserved! Thus the machine should be expected to move in the opposite direction as the gravity waves, rocket-like, except that the exhaust of this "rocket" will be very unnoticeable! (But keep your crystal goblets out of the beam-path, just to be on the safe side....)

Time for a dose of reality: How much momentum are we dealing with here? After all, a laser also qualifies as a potential rocket, since photons carry momentum, too. And a laser makes a very poor rocket, indeed, due to the ratio of energy to momentum for photons. Very small amounts of momentum accompany very large amounts of photonic energy. So for any proposed gravity-wave propulsion system, the true key to feasibility is to learn the ratio of energy to momentum for gravitons.

And here is where our knowledge of reality breaks down. Some theories say that gravity waves move at the speed of light, other theories say they move much much faster than that, and at least one hypothesis says they can move at just about any speed at all, including zero! Well, the lower the speed of a graviton, the lower its ratio of energy to momentum, and the more useful it would be for reaction-propulsion -- so let's look at that last notion:

It starts with a consequence of General Relativity which can be stated, "When a mass is destroyed (by falling into a black hole, for example), a gravity wave must appear." Then this hypothesis begins examining a type of mass-destruction which has been called "nullification". That is why this is merely a hypothesis: Nullification requires the existence of "negative mass" -- and as far as we know, there isn't any. However, we also don't know that negative mass absolutely can't exist, which means we are allowed to play with the stuff in a hypothetical way -- at least until we learn better (or, perhaps, actually discover some!).

So what happens when an ordinary mass encounters a negative mass, in the process called nullification? Positive and negative cancel each other out, leaving Nothing behind. -- Except momentum! See for yourself:

------------------(+m)(+v)-----> <-----(-m)(-v)------------------ The masses are chosen to have equal and opposite magnitudes, and are portrayed as moving at equal and opposite velocities. Their total mass is zero, their total kinetic energy is also zero, but their total momentum is a real nonzero amount. If nullification occurs, the masses and their energies dissapear utterly, but all their momentum survives! Now let us choose a slightly different "reference frame" in which to observe the same event: Assume we are moving alongside the negative mass; it will seem stationary. ------------------(+m)(+v)-----------> (-m) The ordinary mass appears to approach the negative mass twice as rapidly as in the other reference frame. It will carry a lot of kinetic energy, while the negative mass has none. Nullification will still destroy the masses, but this time both kinetic energy and momentum survive. Interestingly, exactly the same amount of momentum is left over in every possible reference frame. Can we be dealing with a "quantum of momentum" here? If the thing left over from nullification possesses all the surviving momentum and kinetic energy, mathematically we can divide that Kinetic Energy by momentum (p) and deduce a velocity: ----(GW: v = KE/p)---->

Recall that General Relativity says we can label the thing which leaves the nullification site a Gravity Wave. Recall the change of reference frame which lent velocity to that gravity wave; the original reference frame still gives it none! But since that is the only reference frame where it has zero velocity, is that any reason to abandon the hypothesis? To keep you interested in it, consider a question first raised by Isaac Newton, and the answer not found elsewhere: "Why are gravitational and inertial masses alike?" "Because the graviton is also the quantum of momentum!"

Well, if that hypothesis has any validity at all, then gravity waves can have extremely low ratios of energy to momentum, and thus would be ideal for propulsion purposes. The only thing left to do is to figure out how to make them in vast quantities, beaming away!

Vernon, Jul 26 2000

Vernon's World http://www.halfbake...a/Vernon_27s_20Site
[eagle, Jul 26 2000]

Ostensibly negative K http://boojum.hut.f...nnial/positive.html
A bit of consortium-quality research into the vagarities of absolute zero mash [reensure, Jul 26 2000]

References! http://www.motordyne.com/index.html
Other efforts by other people, on this topic [Vernon, Jul 26 2000, last modified Oct 21 2004]

Synonymous Hypothesis http://www.nemitz.n...rnon/gravtheory.gif
General Relativity used to show how gravity waves can be emitted by stressed matter. (original link broke; this is an "essence" snippet.) [Vernon, Mar 02 2002, last modified Jul 14 2005]

May I trouble you, PS, for another load? http://www.halfbake...m/idea/Clue_20Spray
And the C-B-F would be nice, too. [neelandan, Mar 08 2002]

Woodward Effect http://en.wikipedia...iki/Woodward_effect
Yet another line of reasoning. It doesn't much refer to gravity waves, but does refer to masses under stress. [Vernon, Jul 05 2002, last modified Dec 04 2007]

Synonymous Hypothesis http://web.archive....01%20Manuscript.pdf
General Relativity used to show how gravity waves can be emitted by stressed matter. [Vernon, Oct 21 2004, last modified Feb 05 2013]

CERN - High Energy Physics Facility http://public.web.cern.ch/public/
There is, somewhere here, a lot of information on CPT symmetry breaking. [Detly, Oct 21 2004]

Negative Temperature http://www.phys.nck...eg_temperature.html
Another page on negative temperature. [Detly, Oct 21 2004]

LIGO Homepage http://www.ligo.caltech.edu/
Detection of graviational radiation. [Detly, Oct 21 2004]

First speed of gravity measurement revealed http://www.newscien...s.jsp?id=ns99993232
Measurement of speed of gravitational "information." [Detly]

Speed Measurement Challenged http://www.spacedai...ws/gravity-03d.html
Ah, what fun, the way Science checks its balances.... [Vernon, Oct 21 2004]

Australian Consortium for Interferometric Gravitational Astronomy http://www.anu.edu.au/Physics/ACIGA/
[Detly, Oct 21 2004]

Over in Louisiana (in USA)... http://sam.phys.lsu.edu/
A current experiment involving stressed mass. [Vernon, Oct 21 2004]

NIOBE http://www.gravity....edu.au/bar/bar.html
(Honestly, guys, I'm starting to be shamed by the quality of these web pages....) [Detly, Oct 21 2004]

"how to make them in vast quantities, beaming away!" http://www.halfbake..._2eR_2eT_2eR_2eR_2e
Well, maybe. [Vernon, Oct 21 2004]

A speculation in conceptual logic http://knol.google....on/131braj0vi27a/2#
"Simple" quantum gravitation, using certain of the notions that were posted here years ago. [Vernon, Oct 28 2008]

[link]






       centauri, the gravity wave detectors you are talking about are the latest models, so designed because a lot of physicists couldn't accept the data coming out of the original model. That was a multi-ton cylinder of aluminum, covered with strain gauges. The essay refers to that particular model, and attempts to explain the data. The essay also attempts to make clear that while standard interstellar sources of gravity waves are just fine, those mechanisms may not be the only ways to produce them. Thus, IF a standard gravity wave can affect the aluminum cylinder and distort its shape microscopically, then according to Time Reversal Symmetry, it OUGHT to be possible to distort a mass and produce a gravity wave. The answer to detecting a gravity wave signal from the background is likely to be time, technological development, and sheer power level of the signal. (As a kid, you may have connected two tin cans together with a string. When you spoke into one can, the sound waves vibrated the base of the can, transmitted along the taut string, and then vibrated the base of the other can, allowing communication.) Do note that just because something may be possible, that does not mean it will be practical or widely used. Perhaps gravity wave communications will be restricted to places where nothing else will do (and I don't pretend to know what they might be). The essay is simply a hypothesis, thrown out to the wolves, so to speak. As for sending gravity waves in a single direction, I thought that the essay explained it in terms of the sledgehammer and the Law of Conservation of Momentum. As for how to do it on the scale required for propulsion purposes, that will probably require a technological breakthrough. Hypothetically speaking, the essay might someday prove to be the needed theoretical breakthrough -- provided the wolves don't poke it full of theoretical holes! As for yourself being a wolf, so far you have been offering engineering objections, not theoretical objections.
Vernon, Jul 26 2000, last modified Jul 27 2000
  

       "Time Reversal Symmetry"?
egnor, Jul 26 2000
  

       With respect to interactions among just a few subatomic particles (almost ANY few particles), if you take a movie of the interaction, and then play the movie backwards, that is ALSO an allowed type of interaction, according to the rules of Physics. It is known as Time Reversal Symmetry, and it is distinct from seeing an event in a mirror (Parity Symmetry). Now it may be stretching this to place a gravity wave, consisting of perhaps zillions of gravitons, and a big aluminum cylinder, with its zillions of atoms, in the category of "just a few subatomic particles interacting with each other". Nevertheless, the gravitons in a wave ARE moving in concert, and the atoms in the cylinder are all connected as one object, so in the larger sense, we have one wave interacting with one object. There ARE places in Physics where Time Reversal Symmetry can apply to macroscopic events.
Vernon, Jul 27 2000
  

       It seems to me that the emphasis that existed in the 1950s, in Physics, on three important Symmetry rules (Parity, Charge Conjugation, and Time Reversal), has been neglected lately. Probably that was due to finding a few exceptions. Nobel Prizes were won as those exceptions were found and explained. Nevertheless, for most ordinary particle events, those three rules are just that: RULES. Personally, I suspect that a FOURTH Symmetry rule is waiting to be found and added, but that is another topic altogether.   

       Here is a macroscopic example of Time Reversal symmetry: Suppose you drive your car around a curve in the road. It is certainly possible for you to stop, put the car in Reverse, and drive backwards around that same curve, exactly tracing your original path. Not easy, but possible. Notice that as you drive backwards, Time is still flowing in the normal direction; only the EVENT is occuring backwards, relative to the original event. (Let me be a bit more specific about this event. I am only concerned here about the way frictional forces between tires and road are responsible for making the car follow the curve in the road.) In Physics, T-Symmetry merely states that such events are possible, and can even be expected under various conditions.   

       And no, the best way to disprove a hypothesis OR theory is to conduct some experiment that is suggested, and watch the experiment do something other than what is predicted. So I would like to see someone try the anvil and sledgehammer test described in the essay. By someone who actually has access to those original gravity-wave detectors (which is not me, alas).
Vernon, Jul 27 2000, last modified Jul 28 2000
  

       Since you are saying that only your described experiment could prove/disprove your theory, I guess it's safe for now, and there's no point in really talking about it. Since you're jumping to a lot of conclusions in your original essay, I've decided that I'll jump to one and say that you are wrong, wrong, wrong. The burden of proof on you to prove your theory, not on others to disprove it. Your lack of proper instrumentation is no excuse.   

       If you wish to discuss this further, you can find my address in my profile. (click "centauri")
centauri, Jul 28 2000
  

       Any hypothesis (I do NOT consider that essay to be developed enough to rate as "theory") tries to explain some existing data that otherwise wasn't. The data in this case is the excess numbers of "events" that the original gravity-wave detectors registered. The only other explanation I've encountered for those events was simply that the detectors weren't truly registering gravity waves, but were actually detecting sound waves transmitted to them by the support wires inside the vacuum chambers. As if no efforts at all had been made to damp out external sound vibrations.   

       So one comes up with an alternate explanation -- and then what? It is NOT immediately necessary to conduct experiments. Budget constraints being what they are, it is best to seek a few other opinions; the "two heads are better than one" notion often leads to concepts that were either neglected, and which shoot obvious holes in the hypothesis, or should have been included, and which strengthen the hypothesis. THIS is the stage where that essay fits, and this is the Halfbakery, where such things belong.
Vernon, Jul 28 2000
  

       Well, just because the apparatus might not have been detecting sound waves, doesn't mean that there wasn't some other form of non-gravitic noise at work. And no vibration dampener is perfect. Let's make sure there is no other likely explanation for the results before reaching for the unlikely.   

       From all I've heard, no one has actually proven that gravity waves exist and are detectable. Have I missed something here?   

       Once again, a list of sources would help us all out.
centauri, Jul 28 2000
  

       Gravity waves are predicted by General Relativity in at least two ways, one being the absolute destruction of mass. The original (and modern) gravity wave detectors hope to detect the huge waves that should result when, say, a planet or a star falls into a large black hole. The original interpretation of the aluminum-cylinder gravity-wave detectors was that 99% of the Universe had already been swallowed up, and black holes were everywhere. Due to lack of other evidence in support of that interpretation, the other explanations appeared, concerning sound vibrations. I choose to think that the "interpretation pendulum" swung too far in both directions, as you might expect from the essay here.   

       Then there are other special cases, such as two neutron stars orbiting each other closely. Radio astronomers have detected at least one such pair, and precise measurements have revealed shrinkage in their mutual orbits. Such shrinkage is predicted by General Relativity, and occurs in significant amounts only in "systems" having very massive and fast-moving objects. (In other words, the Earth's orbit is shrinking, too, but so insignificantly as to be ignore-able.) In any "shrinking-orbit system", the orbital kinetic energy that "leaves the system" is supposed to be in the form of gravity waves. The OBSERVED shrinkage is in good agreement with the theory. The implication is that gravity waves do exist, even if we haven't directly detected them.   

       I cannot offer precise references; much of the material I describe comes from things I've read decades ago, and have nothing more than the memories. If I recall correctly, the physicist who built the aluminum-cylinder gravity wave detectors was named Weber, and was at the University of Maryland, during the 1960s.   

       I might mention that one of the things I really like about the hypothesis presented in the essay is the notion that there is such a thing as a "quantum of momentum". EVERY other fundamental thing in Physics (Space, Time, Mass, Energy) has been quantized. Why shouldn't Momentum join the list? Two/three reasons why it SHOULD: I know a general way to describe Gravitation in terms of quantum events, specifically, as a consequence of the exchange of "virtual momentum-quanta" between purely inertial masses. This makes the quantum of momentum the exact same thing as the graviton. It also means that inertial mass is naturally perfectly identical to gravitational mass. As far as I know, NO hypothesis or theory has EVER offered a fundamental explanation for why inertial and gravitational masses appear to be identical, until this one. (Note: Einstein introduced an "Equivalence Principle", between two types of ACCELERATON, one being gravitational, but that is a distinctly different thing from the equivalence of types of mass.) So I make no bones about liking this hypothesis, and am interested in serious commentary.
Vernon, Jul 29 2000
  

       I've thought about gravity from time to time, and although this discussion is a bit over my head, I'll throw my two cents in. Isn't Gravity a function of mass? It would take one hell of a big anvil to get any where!   

       You might be able to find some application for this on a smaller level, i.e. a "piezo gravitronics" amplfier - though how such thing might work is a mystery to me - has a catchy sort of retro science fictiony sound to it though.
Scott_D, Aug 02 2000
  

       Scott, the gravitational force (which is indeed proportionate to mass) is not to be confused with gravity waves. You do not confuse the force between two bar magnets with radio waves, do you?   

       Yet it must be acknowledged that there IS a close kinship between electromagnetic forces and electromagnetic waves -- and therefore a similarly close kinship is to be expected between the gravitational force and gravity waves.   

       Perhaps the simplest way to make the difference clear is to note that the force we observe between lodestones simply IS; we do not have to do anything special to cause that force to exist. Meanwhile, making radio or other electromagnetic waves DOES require that we expend effort of some sort. The effort involves precise manipulation of electromagnetically active objects (electrons, usually).   

       Well, it is to be noted equally that we do not have to do anything special to cause Gravitation to exist. And HOWEVER it might be possible to generate gravity waves, the one certain thing is that energy must be applied to mass in some fasion, whether it be squeezing to death by a black hole, or forcing large amounts to experience large steady accelerations (as in two neutron stars in close orbit).   

       The hypothesis presented here suggests that an ordinary mass may be induced to emit a few gravity waves if it experiences intense CHANGES in the rate of acceleration. Such events are momentary: car wrecks, pile drivers, explosions....   

       I might also mention that this PART of the hypothesis (concerning changes in acceleration) is not entirely original with myself. Some of the theoretical work in this area goes back to the early 1960s. Somehow they had difficulty coming up with a simple experiment to check the idea, however. The sledgehammer-and-anvil test is MY notion.
Vernon, Aug 03 2000
  

       I have no problem with the notion that gravity waves may be generated by applying energy to mass in the suggested manner, I remember reading somewhere that if Faraday had hooked his probes to a brick and struck it with a hammer, he would have achieved similar results. My objection, or observation, is that if gravity operates similar to magnetism via electron, or some other type of particle exchange/polarity that it is a relatively weak phenomona requiring enormous amounts of mass to generate an appreciable amount of gravity - hence impractical from a current technological standpoint. If, on the other hand, it is more akin to a particle in some state of arrested momentum, if I understand you correctly (according to my halfbrained understanding of relativity theory, matter is sort of a slow moving form of energy), then you might be on to something, and the graviton is a sparsely distributed particle of enormous inertia, mass and/or potential energy, and it might be possible to exploit these properties.   

       Please feel free to correct my ignorance, I'm still waiting for the guy with the ant-gravity machine to come hovering by.
Scott_D, Aug 03 2000
  

       Gravitation is indeed a weak force, BUT that does not mean that the fundamental quantum of gravitation, the graviton, itself must carry miniscule amounts of energy and momentum. The portion of the hypothesis that has not been presented is the part that has boringly detailed ideas concerning the emission, motion, and absorption of gravitons.   

       The key notion, however, is that for a "force" to exist, the "exchange particle" (in this case the graviton) must be emitted by one particle, must move towards another, and must be absorbed by that other particle. Electromagnetic forces are very strong because it is easy for electrons to emit photons, and it is easy for electrons to absorb photons. HOWEVER, THAT IS NOT NECESSARILY EQUALLY TRUE FOR GRAVITATION.   

       The hypothesis has reason to suggest that while gravitons may be emitted easily, may carry significant amounts of energy and momentum, and may even have no trouble moving towards other particles, the probability that those gravitons can be absorbed is VERY small. In consequence the gravitational force is very much weaker than electromagnetism.   

       In our favor, however, is that IF gravitons can carry significant amounts of energy and momentum, then we might indeed be able to build a machine that generates a beam of gravitons, and thereby moves in the opposite direction in accordance with Newton's Third Law. AND, we never have to worry about what the graviton beam hits, because hardly any of the gravitons in the beam will ever be absorbed by anything! (Although, as previously described in the essay, we might have to worry a bit about delicate crystals or other matter located in the space that the beam passes through.)
Vernon, Aug 03 2000, last modified Aug 04 2000
  

       reensure, ordinary matter will always have Positive Energy, even at Absolute Zero. Technically, "temperature" is a measure of the average Kinetic Energy of atoms/molecules in a specified environment. THIS can approach zero. But the INTRINSIC energy of the masses of those atoms/molecules will be unchanged.   

       And more precisely yet, due to Quantum Mechanics, even AT Absolute Zero, there remains some "zero-point energy", which for ordinary atoms/molecules will also be Positive.   

       Now, note that the essay presented here makes some remarks about Negative Mass. THIS stuff, if it can exist, will ALWAYS have a NEGATIVE temperature, relative to ordinary matter, thanks to a -m in the equation for Kinetic Energy. (Note: In a prior annotation I made a comment to the effect that I suspected that a fourth Symmetry rule was waiting to be discovered. This rule would cover opposites in phenomena associated with Negative Mass, as compared to ordinary mass. Proof of such a rule has to wait, of course, until/if we get our hands on some negative mass.)
Vernon, Aug 04 2000
  

       Is this a Vonnegut thing? :)
lucidish, Aug 16 2000
  

       PeterSealy: there is a two-thousand word minimum for annotations to this idea. Please edit your annotation accordingly.
PotatoStew, Feb 12 2001
  

       I'm with Peter Sealy on this one! Just scroll to the end then annotate. It's a bit like watching wildlife programmes about the Arctic, nice to know the wildlife is there 'cos it is beautiful and serves a higher purpose but I'm quite happy to leave it to its own devices and get on with my own crazy baking. Wonderful. 10 out of 10.
moonbase, Mar 10 2001
  

       this went completely over my head and all i vaguely pcked up in the hail of quantumumumumum equasions was that vernon thought hat this stuff could be used to communicate   

       can you imagine a mobile phone that included a large anvil and sledge hammer?   

       its all just too confusing :-(
chud, Mar 30 2001
  

       The concept, itself, is brilliant. The applications, while clearly not the major intention, are also great. I don't see time travel. Perhaps my mind is too closed or grounded. What I do see is a warp drive. Light, curved into a ring and then slowed to a snail's pace warping time and space around it. Fire a photon of light at an angle into the space/time soup and it is also swept up in the 'current' but it is on a course to exit the other side of this canal. The light slows to an influencial mass with relation to the craft before exiting the other end. At that time it returns to the speed of light. Equal and opposite, so on and so forth, your craft moves at an opposing velocity. Viola, light speed. Quite a bit more difficult than is typed here, but I worked it out on paper. It works.
algioru, May 25 2001
  

       Great read.   

       But I must ask... Why simply whack a dense object with another dense object?   

       That would be like testing for radio waves by whacking two large charged objects together.   

       My GUESS would be that gravity waves, IF they can be artificially produced in some sort of useful manner (it's not useful at all if we must dump planets in to black holes (or gravastars if you prefer) ), would be that there is some type of vibration/harmonic effect that can be used.   

       Radio waves can be made quite simply.. You take a bar of ferrous material, coil wire around it and excite the coil with alternating electricity.   

       The distance that the radio wave can be detected from, or it's real world power, is NOT necessarily directly connected to the input power. Things such as antenna length (in the example it is only the bar) as well as noise and humidity can dramatically effect what waves will be detected at what distance. But one of the most important is the actual frequency of the wave produced.   

       So, once someone has access to high accuracy gravity wave detector.......   

       First we should simply try whacking something dense with something else dense and see what happens... Like you said. And to assume that gravity waves would move like momentum moves does make sense, but lets not count out inverse reactions or perhaps there is some kind of bizarre quantum effect of some sort that would have the waves branching out in multiple directions .. Perhaps not even simultaneously!   

       But after that, I believe that simply vibrating different materials at different frequencies should be explored (large "tuning" forks). Why? It's the best/cheapest way to cause massive acceleration changes in an object. The tips of a tuning fork in a vacuum can be made to change direction quite easily and rapidly. Also, never underestimate the power of harmonics.   

       Next on the list would be to see if rapidly spinning objects (gyroscopes) use any of their centrifugal force or internal atomic stresses to produce gravity waves. Interaction between multiple objects should also be tested to see if some kind of "amplification" effect or interaction between gravity waves exists.   

       Even though the actual "power" of (as yet to be found/invented) artificial gravity waves might be small, it is entirely possible that they could be far more applicable to real world applications and possibly easier to produce than we might think.   

       Also note that in the near future, optical computer chips will be able to give you a laser gravity wave detector with a laser path that is effectively many many miles long on a chip a few inches square. This would quite possibly enable very sensitive detection of tiny gravity waves.   

       It is in the tiny waves that communication (no lag long distance communication, both earth and space based) and health sciences (MRI like scanning of the human body.. perhaps even down to the molecule) will see benefit.   

       Not to mention some form of "anti-gravity" or gravity wave propulsion.. Or even somehow folding a gravity wave (even a weak one) to such extremes that it becomes a bubble of sorts. This would at the most allow us to reduce "effective mass" and at the least allow for some very exotic experiments as well as propulsion systems or perhaps just reducing the effective acceleration felt by fighter pilots.   

       Hey... It's all half-baked...   

       Until it comes in a cereal box that is..   

       My kid brother just got a calculator out of his. More computing power than what got us to the moon. Remember when "personal computers" were pure fantasy?   

       I can't wait to tell my grandkids about when gravity waves were barley respectable dinner conversation! It will be right after they dig their "Amazing Captain Graviton action figure with Self Levitating Gravity Wave action!" out of the bottom of a Captain Crunch box.   

       :)   

       More tests, more questions.. And more half-baked ideas!
Fifty1Ford, Jan 23 2002
  

       I`ll have a peek into my Carl Sagan book, nothing for now tho..Or should I be reading Iain M Banks?
andrewuk, Jan 23 2002
  

       I just added another link.   

       At this time I know of about five lines of reasoning, from different starting points, to conclude that gravity waves can be produced by suddenly-stressed matter.   

       Experimentation is definitely in order! (gimme a few months....)
Vernon, Mar 02 2002
  

       Just added another link. Make that six lines of reasoning, now. One of the other lines correlates with the Woodward Effect via "changes in the rate of acceleration", as mentioned in a prior annotation here. That other line of reasoning says something to the effect that since a mass as a whole cannot actually instantly change its velocity, then during the time it is experiencing a changing acceleration, it momentarily acts as if it has a little more mass than normally measured. Such changes in mass are the core of the Woodward Effect, which starts its line of reasoning with something called Mach's Principle, a notion designed to explain where inertia comes from. .
Vernon, Jul 05 2002
  

       Ok, so you want to produce gravity waves. I've read about neutron stars doing this, due to their intense rotational speed and their dense mass. Well, what if instead of the car crash or anvil-based experiment, you set one up involving a rotating mass?   

       In physics class they never did explain why the rotating bicycle wheel likes to pull one way over the other...   

       So if "the graviton is the quantum of momentum", perhaps a dense, rotating mass would create some useable gravity waves. For some reason, I am envisioning a sphere inside a shell of another sphere, both spheres rotating in opposite directions but having the same mass. Perhaps some sort of harmonic effect would occur where a directed beam of gravitons would be pushed out. Who knows, it seems simple, usually simple works the best.   

       You'd probably need a lot of energy and dense mass, but not more than the mass you were trying to move, for example, right?   

       Now if you could somehow phase-shift some regular mass out of spacetime such that existed within a gravity "bubble", perhaps the graviton source could work as a propulsion system. I mean you couldn't use a regular rocket, we're not talking about "motion", we're talking about folding the medium and riding the wave so to speak.   

       Crazy.
michaels, Jul 07 2003
  

       michaels, one problem that I have tended to ignore is that of angular momentum. This is what you most probably are dealing with when you talk about rotating neutron stars or bicycle wheels. I have tried to stay away from the angular-momentum angle of this topic, and stick straight with linear-momentum stuff. Not to mention that it seems to me more reasonable to want a linear-momentum communications beam or "rocket exhaust" than an angular-momentum output.   

       That said, I would not be surprised at all if it turned out that there is a distinct quantum of angular momentum, different and more complicated than the linear-momentum quanta mentioned here. In the interests of tackling the simpler stuff first, I recommend the suggested experiment.   

       For those who wonder about sledgehammer-and-anvil communications, or even propulsion, well, keep in mind that I specifically mentioned the "inevitable result of technological progress", knowing full well that such things start out crudely.
Vernon, Jul 08 2003
  

       Interesting idea that the speed of a gravity wave could have any value. The assumption is otherwise (Einstein) that it has the speed of light. Now if it were unlimited, it could become very interesting for communication purposes. So - somebody please test this! Hasse Wi
hawi, Aug 10 2003
  

       A few comments :   

       The bicycle wheel deflects the force because of precession. If you search for the term, you're bound to find diagrams and suchlike.   

       Negative temperature is possible for systems with positive mass, for example, an array of localised quantised magnetic moments, as [reensure] has posted.   

       Special relativity is based on the idea that nothing can exceed the speed of light. General relativity predicts that gravity waves travel at this maximum speed, and no less.   

       The time reversal symmetry you speak of is the subject of a lot of research. After parity (P) was discovered not to be conserved, a lot of exprimentation was done, and it seemed that charge-parity symmetry was conserved, as was time symmetry. It's claimed that the overall CPT (charge-parity-time) symmetry must remain intact, and so any break in CP symmetry would imply that T symmetry is also broken. See CERN link.   

       General Relativity predicts Gravity waves will only be generated by a change in the gravitational field. So, spinning spheres would not emit graivational radiation, because there would be no change in the field. There have been experiments to generate gravity waves by spinning an *asymmetrical* mass - which according to GR should work - but these have yielded no results. I will hunt down and post links soon, but you seem to have a fairly good set of resources posted.   

       Gravity waves carry enourmous energy. The flipside of that is that it takes an enourmous amount of energy to generate even the tiniest gravity wave. One way of thinking about this is that space-time is a very 'stiff' medium, but that's really an analogy.   

       There's also the noise problem. The current laser interferometer gravity wave detectors (LIGO) are so sensitive that even a gradient in air pressure affects their measurements.   

       Theoretically, any wave can be used to communicate, since (almost by definition) a wave is a travelling disturbance of energy. But the reason we don't use tins on string to communicate is, basically, its easier to use EM waves. Using gravity waves might be possible, but not only is it not viable as yet, it's barely even possible to research. But that's not to say it'll never work.   

       These comments are all from either quick research, or my own knowledge of the subject matter, so I'm not trying to be authoritative (it's just the way I write). And I'm probably repeating a lot of what's been said.
Detly, Aug 11 2003
  

       Well, seeing as this argument was swiss-cheesed, I've deleted most of my annotatations.
Detly, Aug 12 2003
  

       Interesting discussion, Detly and sealorator. I'd be quite happy if somebody simply performed the Hertzian-type experiment that I originally described.
Vernon, Aug 14 2003
  

       I've looked around for the paper, but I can't seem to find it. (Even more annoying, I can't find my own essay on the subject, which had the reference in the first place.) But, if I do find it, I'll post it, because it seems very close to what you're thinking of.
Detly, Aug 17 2003
  

       Detly, may I have address of paper you mentioned in your annotation
Eskandari, Oct 29 2003
  

       Dear Detly thanks, I'll try.
Eskandari, Nov 01 2003
  

       Eskandari, if I understand you correctly, then the stuff being discussed in the preceding portion of the annotations is about speed of gravitation. If the Sun was to literally and completely disappear suddenly, would the Earth stay in orbit for 8 minutes (it should if gravitation travels at light-speed), or would it start moving tangentially to its present orbit immediately (instantaneous speed of gravitation), or would some other amount of time pass before that happened? Einstein assumed the speed of gravitation is light-speed, but nobody had any supporting evidence one way or another, until the recent announcement of a measurement.   

       Based on analogies between gravitation and electromagnetism, because we KNOW that electromagnetic waves (photons) only travel at light-speed, and because we have good reason (Quantum Electrodynamics is the most accurately-verified theory in Physics) to be confident that the speed of electric and magnet forces is also light-speed, Einstein and others ASSUME that both gravitational waves and gravitational forces also travel at only light-speed.   

       In the main text of this Idea, however, I present a line of reasoning that indicates that gravity waves might be able to move at any number of velocities. Since it is assumed that gravitational waves are also responsible (as "virtual" entities) for gravitational forces, it becomes an interesting question as to exactly what the speed of gravitation might be. I tend to think that if that line of reasoning is correct, then it will have to be some kind of average, and if that average is light-speed, fine.
Vernon, Nov 03 2003
  

       Vernon, I thout there's some another thing. disappear what means? first, you have to decide what you want to do with our sun, if you put it behind yourself, just we will have another Atlas and nothing will happen for earth, and if you decide to shoot it, it depeneds on how you do it, if you want to change it to energy (conservation), earth will sense it at least in c velocity and you may have no gravity wave or force from disappeared sun, I think earth will have antigravity from disappeared sun and will sense large gravity from what remaines from the world and with all what was in gravitly feild of the sun, depend on where they were relative to the sun, will shoot with speed of expantion of the world . I excluded the speed of disappearing, you wrote suddenly but, suddenly what means? I think it takes a lot of time, because you change spacetime, it dependes on mass and some thing else... And another thing which has made a black hole in my mind is about exchanging mass but not to energy.
Eskandari, Nov 04 2003
  

       Vernon you are quiet, what are you doing?
Eskandari, Nov 05 2003
  

       Eskandari, thought-experiments are often peculiar ideas, and can indeed involve "magic". A famous example is Maxwell's Demon. True, frequently thought-experiments NEED to stay entirely within the bounds of Physical Possibility, but when such a Need does not exist....   

       So, in order to think about the speed of Gravitation, and specifically the attraction between Sun and Earth, it is a conveniently simple idea to think of the Sun as quietly going "poof" and being utterly GONE, courtesy of magic. THEN you go back to hard physics and examine the consequences. Virtual gravitons that HAD BEEN emitted between Sun and Earth continue on their way, but at what rate? The answer should let us figure the amount of time that passes before the Earth's orbital path becomes a tangential straight line (magically ignoring other planets, of course).   

       P.S. I check on the Halfbakery at reasonable intervals, sometimes short and sometimes long. And when I'm working for hours in a place with no Internet connection, the interval can be long....
Vernon, Nov 06 2003
  

       Tiger Lily, I concur with what Detly wrote. However, take a moment to recall the famous thing that Archimedes said, after he discovered the Law of the Lever: "Give me a lever long enough, and a place to stand, and I can move the Earth." (Actually there is an incompleteness to that, since he needed a fulcrum, too.) Anyway, If we grant you an equivalently magical "place to stand" (no reference at all needed to Solar System, why not intergalactic Space?), and sufficient friction, and sufficient strength, then even Detly would agree that you could be at the center of your hog-revolving demonstration. I will also suggest some additional magic, and assume the leash has no mass, although otherwise behaves like some ordinary material. The advantage of that assumption is that then there will be no spin added to complicate the hog's motion, when the leash is released.   

       Now let us consider the moment before you let go of the leash. There is, as Detly indicated, considerable Tension in that leash, which is equivalent to an attractive Force between you and the hog, which merely indicates the amount of effort you are putting into holding onto the leash. (Prior effort put into intially swinging the hog is no longer part of this scenario, due to Law of Conservation of Momentum. Once the hog gets up to appropriate speed, ALL you have to do is hold on to the leash while rotating in place.)   

       Suppose we look at the opposite of what you wrote: If the hog chews through the leash, then the hog immediately is loosed from that Force, and begins moving tangentially from its prior circle. Meanwhile, the leash will continue revolving around you...but you will not notice any difference in the amount of EFFORT you are expending,until, as Detly indicated, the sudden-ending-of-Tension propagates down the leash, at the speed of sound in the material of the leash. --And even if that speed was lightspeed, when dealing with such distances as a hundred million miles, you will be holding on with full effort for several minutes. "Where do you suppose that effort is going?" is exactly as interesting a question as the problem you posed by writing, "I say there isn't enough magic in the universe to make the hog fly around my head the moment I let go of its tether."   

       Well, now we arrive at examining your statement. When you let go, the hog is still at the end of a leash that is under lots of Tension, which IS still equivalent to a Force. The hog will indeed keep orbiting your head, until that Tension is eased -- which only happens via propagation along the length of the tether, something that will take several minutes.   

       Finally, consider the scenario in which the tether simply breaks in the middle. Now the lessened Tension can propagate toward both yourself and the hog, but neither will notice any change in Tension until that propagation is done. The effort you put into holding onto the leash, that seems to be going nowhere, is balanced by the Tension in the hog's section of the leash, that keeps it in orbit. For a short time only, heh heh heh, for both.   

       Possibly there may be a Scientific "Eureka!" moment to be gained from the above. Perhaps, simply because these scenarios involve effort-that-goes-nowhere and Tension-that-seems-to-persist-too-long, well, maybe THAT is the reason why there is such a thing as the Law of Conservation of Mass/Energy, that prevents the Sun from simply going quietly "poof".
Vernon, Nov 07 2003
  

       [Vern] - I spoke to an academic affiliated with the AIGRC (link). I asked him about a "Hertz" style expirement. For those of you who don't know, Hertz was the first person to generate and detect electromagnetic waves predicted by Maxwell decades earlier.   

       Anyway: in his popular* book [title will follow soon...], he gives the analogy of a nuclear submarine on a giant turntable. If you spin it to the very limits of its mechanical stresses (ie. just before the point at which it tears itself apart), you'd only be emitting one graviton every second.   

       So, such an experiment might be possible, but right now, it's in the realm of fantasy. Until we have research neutron stars, anyway...   

       Finally, a few minor things :   

       //There have been experiments to generate gravity waves by spinning an *asymmetrical* mass//   

       I was wrong (as far as I know, anyway). All my efforts at searching for this have turned up nothing, so I must have been mistaken. Oops.   

       //The existing detectors which work on the principle of shape-distortion have been detecting far more gravity waves than can easily be explained//   

       I'm almost certain they've been detecting nothing but noise (eg. seismic noise). But it would be nice if someone closer to these efforts could clarify.   

       --
*Popular as in, not technical. But I'm sure it's very popular.
Detly, Mar 01 2004
  

       Weber claimed to have detected gravity waves - but his results were not repeatable (which means it must be relegated to the world of cold fusion and magnetic monopoles).   

       The interforemter detectors are capable of detecting much lower frequencies, and of much greater sensitivities. Some of LIGOs public papers make for interesting reading (such as its sensitivity charts).   

       The University of Western Australia also worked on a resonant mass detector, called NIOBE.
Detly, Mar 02 2004
  

       If we're going to keep bringing this idea to the top, I want a gravity surfboard so I can ride the waves as this idea cascades towards the bottom.   

       And I hereby declare a momentary monopoly on gravity surfwear....It's not the sport, its the accessories.....
normzone, Mar 03 2004
  

       Thanks [Detly]. But if you hadn't noticed, let me state that I'm pretty sure [Ling] was starting with the standard assumption about light-speed gravitation, and proceding from there (notions of measuring it). Since it was only an assumption, I didn't mind discussing it on that basis.
Vernon, Mar 04 2004
  

       Don't know if this was mentioned...but...   

       If you could somehow resonate a very massive sphere, so that it's resonant movement was in an outward and inward motion from the center of the sphere, you could shine a light beam next to, but far enough away so that diffraction isn't an issuo, the sphere to see if the beams curvature around the sphere changed...following the resonant frequency.
nomel, Jun 09 2004
  

       [nomel], If mass is "connected" to Space/Time such that a passing gravity wave can give up a small amount of energy, to distort the mass, then Time Reversal Symmentry means that that connection is still there, when we stress the mass in an effort to generate a gravity wave. Why should anyone think that such a connection only works one way?   

       I'm not worried about the black holes, thanks to the inverse-square law.
Vernon, Jun 10 2004
  

       " If a connection lets Energy flow from Space/Time to Mass"   

       That's what I'm trying to say. Is there an actual transfer of energy? If the matter isn't moving, just appears to move..but the measurable physical distance doesn't change (which would have to change to somehow gain/lose energy), then energy wouldn't be transfered.
nomel, Jul 02 2004
  

       [nomel], a transfer of energy MUST occur, because energy is required to cause a mass to become distorted. The average solid mass resists compression, so if we discover a Weber Bar to have become compressed, we can be sure some energy has been added to it. Also, since ordinary matter most of the time behaves in a non-perfect way, we can be quite confident there will be some frictional heating of any mass that a gravity wave passes through. Even if this heating is only 0.0001 degree Celsius, it represents energy that had to come from somewhere, and the only candidate would be the gravity wave.
Vernon, Oct 29 2008
  

       If gravity had a particulate nature wouldn't intervening masses be able to block it in a measurable way? Why would water on the far side of a globe receive any gravitons from the moon? Why doesn't a solar eclipse interfere with the orbit of earth? Why are clouds of gas drawn together to form stars? And since this poses the obvious comparison why should we not also need a magneton? Is there a speed of graveton and magneton? If we had a detector, and if there are as few of them as you say what would we detect? Why wouldn't the action of gravitons be rarefied by the intervening objects, gas es and space trash? So many obvious questions that could be answered by observation and yet so much focus on esoteric points. Please address the observable data and 69 the hypothetical.
WcW, Oct 29 2008
  

       [WcW], you need to better understand the "wave/particle duality". The most famous example is the photon, an individual unit of light which exhibits wavy behavior. Gravitons can be expected to be similar to photons in that respect. Gravitons do NOT need to be similar with respect to how easily they can be absorbed.   

       Remember that ElectroMagnetic Force is 10E40 times as strong as gravity (a small magnet can lift a steel pin that the entire mass of the Earth is gravitationally trying to keep on the ground). We are confident that photons of a "virtual" sort are being "exchanged" between objects that experience the ElectroMagnetic Force; the theory of Quantum ElectroDynamics that uses the notion has been tested against experiment to something more than 14 significant figures of accuracy. If a quantum theory is to describe gravitation, then "virtual gravitons" will almost certainly be described as getting exchanged between objects. For gravity to be as weak as it is, some aspect of that exchange needs to be "lesser" (by a large magnitude) than the equivalent aspect of virtual-photon-exhanges.   

       I think part of the difficulty with past efforts to devise a quantum theory for gravity is that if the exhanges happen too seldom, to match the observed weakness of the force, then we might expect to see some sort of jerkiness in the behavior of things interacting gravitationally --and we don't. The virtual gravitons might instead carry appropriately less energy than virtual photons, but then we would need a special rationale for that, because the Uncertainty Principle, responsible for allowing virtual particles to exist, explicitly allows all of them to start their existence carrying quite large amounts of energy. Also, regarding the rate of production of virtual gravitons, we know that it must be directly related to the total mass-energy of any object, no matter what forms that mass-energy takes. I only know of one thing in Quantum Physics that has a chance of connecting mass-energy with graviton-production, and that just happens to be the wave-particle duality. Which means that even a single electron could be associated with 10E20 gravitons per second, leaving the scene seeking to be absorbed as part of an exchange.   

       Well, if we are stuck with a high rate of production of ordinary-magnitude virtual particles, then about the only thing left, for gravity to be such a weak force, is for absorptions to be rather rarer than for photons. Jerkiness gets eliminated due to the fact that even if one in a trillion (10E12) is absorbed between two electrons, that's still 10E8 (a hundred million) absorptions per second. That's just an example, and various factors can allow the absorbed fraction can be a great deal smaller without jerkiness being notice-able. Anyway, with most of them not being absorbed, that would answer your main question about how they can pass through the Earth or the Moon, right?
Vernon, Oct 30 2008
  

       and the failure of magnetism and gravity to be absorbed and consumed in their effect is due to.... conservation of energy, which you would not expect a system that is emitting particles or waves to obey. If gravitation was radiated in random directions and represented a form of energy then 99.9999999 percent of the energy would simply be lost into space and since it cannot be absorbed (i'm just guessing you believe this) then the background level of gravitation should increase as the universe ages. This is an effect we should be able to measure and as yet i haven't heard about an observable change in the strength of gravity in old/young stars. Such an observation would lend credence to the idea but without it we are constructing a model to explain things that haven't been observed.
WcW, Oct 30 2008
  

       [WcW], the conclusion you reached is based on a faulty assumption. The energy of virtual photons and virtual gravitions is not like your ordinary energy; they call them all "virtual" for a reason. It has no effect on real energy UNLESS and UNTIL it is absorbed. Infinite quantities of the stuff can be wasted with no effect at all; its very existence is a temporary and undetectable violation of the Law of Energy Conservation. (And even when virtual energy is absorbed, the effect is, usually, to cause some conversion of real potential energy into real kinetic energy, so Conservation is upheld.)
Vernon, Oct 31 2008
  

       I see absolutely no support for treating gravity as a form of radiation. For a long time I did. However I spoke with a personal friend and we discussed how mater behaves and how radiation behaves. Radiation acts in a linear fashion (remember you propose that this be used for propulsion and communication, this would require linear behavior). If an object is acted on by a radiation from a direct source the effect should be greater on the facing side. If gravity is caused by anything other than mass then the planets being made up of different types of materials, in different states, they should behave differently than expected. Unless you can address the most basic observations you will never be able to harness this force for fun or profit. If you weren't engaged in crankery then this would be as critical to supporting your theory as the unobtanium wand you propose to build.
WcW, Oct 31 2008
  

       oh and if it shares no common behavior with waves or particles as we currently describe them then calling it a "virtual wave" or "virtual particle" is sophistic.
WcW, Oct 31 2008
  

       "If an object is acted on by a radiation from a direct source the effect should be greater on the facing side. "
[WcW], you are still assuming that the facing side will interact with ALL the arriving radiation. Why? Neutrinos from the Sun are detectable at practically the same rate, anywhere on Earth at any time of day, because so few of them interact with the body of the Earth that a detector, no matter where located, remains immersed in a vast flow of neutrinos from the Sun. This well-documented fact provides a precedent for explaining gravity by hypothesizing that gravitons exhibit a similar low (or even lower) absorption rate.
  

       Also, remember that in Quantum Mechanics all particles have some wave-like properties and all waves have some particle-like properties. The word "wavicle" is used sometimes. All the "exchange" particles of the various quantum theories necessarily are wavicles, simply because it is an unavoidable aspect of Quantum Mechanics. Your personal preferences regarding waves vs particles mean nothing.   

       And by the way, WHILE a virtual particle exists, it is identical to an ordinary particle. The only reason we can't detect it is because it either exists for a shorter time, or has a lower energy, than any detector can resolve. By DEFINITION (of the Uncertainty Principle).
Vernon, Oct 31 2008
  
      
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