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Practical Gravity Shielding for Spacecraft?
Anonymous Coward writes, "I saw this site today:
'The Gravitational Spacecraft from Fran De Aquino
Warping to the deep space...'
A researcher in Brazil says that it can be done. What do you think? Anyone working in this area care to comment?
The site can be found
here." Slashdot has no official editorial position on the feasibility of gravitationally shielded spacecraft, but if anyone wants to send us a review unit, we'll gladly put it through its paces and do a writeup about it.
@@ how do you know?
@@ have you seen a photon
@@ i have not
I suspect you have. I've seen billions of them.
dylan_-
--
Igor Presnyakov stole my hat
Yes in fact we do know that photon's have gravitational mass in the sense that photons generate a gravitational field just like other matter.
Yes photons have zero rest mass in the sense that a positive rest mass would result in infinite energy given that they travel at the speed of light. However photons are not in fact at rest and can never be at rest and do in fact have mass.
That photons have mass is easy to deduce from their possesion of energy and the equivalence of mass and energy. Moreover they must produce a gravitational field as they are affected by gravitational fields (gravitational lensing) and so by conservation of momentum must in turn generate a gravitational field.
Marriage is the "pseudo-ethics" that cloaks the messy truth of sexuality in the raiment of propriety -- it's "Don't Ask,
I'm hoping that someone can clarify this for me: I'm certainly not a Physics major, but if two particles come near each other and recoil from each other as a result of a graviton exchange, wouldn't that be a bit backwards from what actually happens? Namely, gravity is attractive (I think we all can agree on that!) and so it would seem that the absorption of a graviton would cause a particle to accelerate towards whence the graviton came.
Now, in my silly little physics-naive head, the only way to make this work with Conservation of Momentum would be to postulate that gravitons have negative mass. Is this so? Just curious. Last I heard the existance of the graviton proper hadn't yet been affirmed by observation and in fact this whole bit about integrating quantum mechanics and gravity was still causing some fair number of very intelligent people to bang their head against very solid objects.
I'd appreciate it if someone could screw my head on straight with regards to this: how does a graviton work? Might gravity actually not exhibit wave/particle duality? Please shake a clue stick in my direction.
David E. Weekly
David E. Weekly
Code / Think / Teach / Learn
h4x0r for
Anyone remember the old Ray Harryhausen movie where the mad scientist painted gravity-blocking paint over the space capsue? An I can't find an IMDB link or similar, so here's a private page about it.
I note from your formula that the gentleman's science reduces to BS. : )
I see even classic Slashdot is now pretty much unusable on dial up anymore.
They can't cancel each other out because the spin operators won't.
Why not do a review of something interesting?
I recommend Robert Forward's "Indistinguishable from magic" for a start. At least his devices, as impossible as they seem, are based on real science that could potentially be built with a future technology.
Regards,
Ben
My usual seat in the cluetrain is at A HREF="http://pub4.ezboard.com/biwethey.ht
Seriously - bending the topic from anti or shielded gravity to communications - a real scientist wrote a piece of fiction which (iirc) implied that if gravity could be modulated we would be able to communicate at the speed of light squared. So, if one of a pair of objects could be made to appear to change mass, how long does it take for the other one to 'feel' the change in force??
try { do() || do_not(); } catch (JediException err) { yoda(err); }
Seriously, any page that has the phrase "Free Energy" should never gain the honour of a /. story...
This story is to Greenglow as crop circles are to NASA's breakthrough propultion initiatives.
Anyone got a URL for the LightShip project? (A mirrored vehicle propelled by pulsed, groung-based lasers)
While slashdot can hardly be expected to be an expert in all areas of science, or to be a perfect, much less final, judge on the merits of specific scientific or pseudoscientific theories, I do think some common sense can be excersized in seperating speculative pseudo-science from hard science.
Perhaps a pseudo-science category, with an appropriate x-files or flying saucer logo, would be in order for articles such as this, which are on (or beyond) the fringe of conventional science. Save the scientific icon and category for hard, well established scientific articles.
This would IMHO boost slashdots credibility when publishing headlines for scientific articles, without censoring the more speculative (and often nonsensical) stories which, while having perhaps little scientific merit, do give some wonderful ideas for science fiction/fantasy stories...
Of course, there would be the incessant "this belonged in the other category!" arguments, but at least a nominal effort to seperate the wheat from the chaff would be a net positive, IMHO.
The Future of Human Evolution: Autonomy
May I suggest The Elegant Universe by Brian R Greene?
It offers an excellent, laypersons explaination for Special and General Relativity, Quantum Mechanics, String Theory, Superstring Theory, and M-Theory. It explains these theories and their ramifications in terms easilly understood, as well as their limitations.
You may not like Quantum Theory (Einstein didn't like it either), but it has been demonstrated to be correct, as far as it goes, as has General Relativity.
I too wish there was some way off this rock in our lifetimes, and there may well be if we get off our butts and build a space habitat or two. But, alas, unless M-Theory contains some interesting suprises for us over the next few decades (and it very well could), while we may make it into space, it is unlikely any of us will have the pleasure of walking beneath an alien sun, unless medical science delivers that immortality serum I've been asking for for years now, and we're willing to make a journey of hundreds or even thousands of years.
The Future of Human Evolution: Autonomy
- Well, they are, inasmuch as anything else is. A body in motion will tend to stay in motion. Other than that, they aren't perpetual motion machines, in the sense that you cannot get energy out of them indefinately, sooner or later they drop into their lowest energy state, and you can't get any enegy out of them (even if theydo still have a non-vanishing momentum)
- Not sure I see the diffrence. Every two particles with mass experiences an attractive force between them proportional to the product of the masses, and inversely proportional to the square of the distance between them. The force is towards the other particle, (this is easily demonstrated) so I'd guess you'd call it a "pull".
- This isn't a QM question, it's a relativity question (so is the last one, I guess), but I'll give it a shot anyway. It is the speed of light (in vaccum) that's constant. Multiple experiments have demonstrated this. A consequence of the effects that make the speed of light constant is that nothing can travel faster than light (also well demonstrated).
- This makes very little sense to me. Electrons are (mostly) conserved. (there are some processes that create/destroy electrons, but they all conserve charge, and/or other things related to charge). Why the universe has equal amounts of positive and negative charge is a somewhat open problem in science, but is a little deeper than your question goes...
heck me too, just this aint it. But the solar systems big 'nuff for my lifetimeQuantum physics and Newtonian physics. It sounds like you want the quantum world to be governed by the newtonian rules. I'm sure someone will correct me if I'm wrong, but that won't happen unless both fall under a Unified physics ruleset.
If you want a good general idea of why quantum physics is so odd, it's cause stuff always gets weird at extremes.
Bad Mojo
Bad Mojo
"If you can't win by reason, go for volume." -- Calvin
It's a bird!
:)
It's a plane!
It's, it's... Why, it's an anti-gravity donut stack delivery system. The future is looking good for law enforcement!
I like that java animation though. That's pretty cool. And probably the most technically impressive piece of the site.
-- What you do today will cost you a day of your life.
1) The website on AOL is someone paraphrasing De Aquino's work. De Aquino's own website isn't any better, but the papers in peer-review journals seem to be much better. Sometimes any of us can sound like a fool without a good editor.
2) I'm not sure you're interpreting 'gravitational mass' as Aquino intended. Specifically, De Aquino has papers addressing addressing the (non?) equivalence of gravitational and inertial mass (e.g.) as an underpinning of his (her) theories.
3) How do you reconcile the stress tensor and the type of gravitons you espouse (spin = 2, and therefore require quadrupolar transitions to be emitted) with the fact that gravitons must escape from black holes? It would seem that this type of graviton could not (as far as I can tell)? (Yes, gravitons interact with gravity. Hence the fact that gravitational fields have their own 'mass equivalence' induced gravitational fields.)
__________
If you can go to bed, knowing you did a valuable thing today, you're very lucky. If you can't... it's not bedtime
you talk about the two as if they were seperate things.. but in fact if you can control gravity you effectively have time travel cinched. If you take einstein's equations and make the variable for effective mass negative, you wind up with the time variable becoming negative as well. They said something like that in physics class. Or maybe that was when you're travelling faster than the speed of light..? Um, never mind. It isn't important. Trust me, i'm right. And if you don't believe me, i can make some pictures in KPT Bryce for you that will prove my correctness beyond a doubt.
Anyway, it is well known that there is a definate link between gravity-based travel and time distortions. The government scientists at Area 51 have been doing extensive testing and refining of aircraft with a gravity-based engine based on technology recovered from crashed alien spacecraft. It has been well documented that exposure to such technology frequently results in "lost time"-- things in the general area of the gravity engine temporarily move at a faster rate through time than the world around them, causing them to wind up having short amounts of time "disappear". We know this information, by the way, because agent Fox Mulder of the FBI was able to infiltrate Area 51 after the reality warping in the general vicinity after a gravity-based spacecraft malfunctioned overhead his car on the highway outside area 51 and crashed caused, causing Mulder and a high-ranking Area 51 official to temporarily swap minds in an episode spanning two weeks. As a result we were able to get much information about this fascinating technology that is directed gravity propulsion.
-mcc-baka
INTELLECTUAL PROPERTY IS THEFT
Irritable, left-wing and possibly humorous bumper stickers and t-shirts
(1) Very possibly. But the theory itself is still cracked.
:) Most importantly, string theory can correctly predict aspects of the low-energy behavior of black holes which show up when classical GR starts to fail. (Hawking's "information paradox" is such an issue)
(2) Nonetheless, de Aquino claims that the null mass of the photon (the vanishing of its inertial rest mass) implies that it is outside the effects of gravity. I argue that the way de Aquino referred to the mass of the photon as having to do with gravity is simply wrong.
(3) This is a good question and one that bugged me for a long time. The real answer is that the graviton picture - the approximation that the gravitational field can be decomposed into small excitations which behave more or less like free particles, with some additional interactions - is only valid in the limit of weak gravitational fields. For black holes and similar strong fields, the self-interactions of the gravitons are so strong that they can no longer even approximately be thought of as particles.
This actually is fairly closely associated with why quantum theories of gravity are hard. Basically one can show that a quantum field theory of spin-2 particles is inconsistent. It reduces to something consistent in the low-energy approximation, where gravity can be thought of as the exchange of individual gravitons. But as soon as the self-interactions of gravitons becomes significant, this picture of gravitons as particles stops producing meaningful predictions.
And this is exactly the point where we have to turn to our one well-defined and reasonably well-understood theory of quantum gravity: superstring theory. While this theory is not experimentally verified, there is substantial reason to believe it will be. (Which I won't go into now
So it's possible to calculate the gravitational properties of black holes using string theory and then back away and say: If I'm far away from the black hole, it just looks like an ordinary gravitating object, gravity is weak, and the graviton approximation should apply. Indeed it does; it turns out that, from far away, the black hole looks like a uniform sphere of radius equal to its event horizon, and as far as a distant observer is concerned, it does indeed emit gravitons from this distance. But all information about the internal structure of the black hole is kept within its event horizon; we can't see inside the horizon using these gravitons.
Yonatan
You are describing a radiometer, and the reason a radiometer spins is due to the black/white surfaces. Light hitting the black surface is absorbed, heating the air next to it, and causing an imbalance. It is not due to any kind of 'photonic pressure'.
Recall that his intent is not that radiated photons act as a propellant, but that they negate graivty, acting as a shield, to block gravitons.
http://linquirer.tesla.cx
So what exactly is the speed of gravity? I've always wondered about that one?
For some reason he's not using photons, he's using electrons in a 60HZ dual coil (two ELF antennas in a coil -- look at the diagrams and the coils are only connected at one end).
He doesn't describe the kind of table, room construction, or anything else which eliminates magnetic effects. Nor whether the materials might bend or expand when heated, causing the coil to lift itself by bending the input leads (and hundreds of amps should cause some heating...).
If you look at the links and credits in the pages, you end up with the JLN Labs page. Full of other interesting "technology" tips.
You are smarter than that.
;)
And there's another for the "Crackpot Theories" department.
Seriously, he's probably just bored and wanted to watch all the knees jerking.
The Signal/Noise ratio can be improved in two ways. Remaining silent is the OTHER way.
As might be evidenced by one or two "black holes" out there...
--The basis of all love is respect
So what exactly is the speed of gravity? I've always wondered about that one?
The speed of light, or slightly slower; gravitational waves are governed by similar constraints to the permittivity/permissivity constraints that govern light in normal space (ie. same medium, different units).
Simon
Coming soon - pyrogyra
I find this kind of story entertaining in a sick sort of way but my take on all these crackpots is that someday one of them will be right and they will get ignored. We've seen it before and well see it again.
I've read about quantum physics since I was about 10. I still don't buy it. I love Dr Feynman's books on sub particle physics made easy. One part I like the best is he makes a statement that any physical law that is complicated in the past has been untrue (early chemistry, astronomy, etc) but then goes straight into some of the most bizarre stuff in modern science. I think he was one of the few scientist that would have gladly thrown away all they knew about a subject if it was replaced by something simple and correct.
My basic problems with modern quantum physics include:
1) Electrons seem to be perpetual motion machines.
2) Does gravity push or pull and how would one prove it? If it pushes that would sure explain why all the Zero G crystal can be duplicated on earth.
3) Speed of light seems to lock down lots of physics. Is it the speed of light or the speed of gravity that is the limiting factor?
4) There always seems to be enough electrons.
I guess I'll be like the rest of the geeks and keep wishing that some one will find some way to get off this rock we call home before I die of old age.
Momentum, energy, mass and so on get a bit mixed up once you start dealing with special relativity.
In short, photons have no rest mass. However, they do have both momentum and energy, as those two are very much related in special relativity. Anything with mass or kinetic energy has momentum.
Therefore, being hit by a photon does give you a push, and shooting a photon off does make you recoil. Though not much. This is the principle behind light sails.
Here's a quick calculation of the power needed to run a 100% efficient spacecraft near the Earth (warning: very rough. =)
E=.5mv^2=.5m(10t)^2=50mt^2. (rounding, etc).
So in one second, E=50m=500,000J for a 10,000kg spacecraft... Thus, at LEAST 500,000J/s=500,000W must be used to counter the falling spacecraft, by basic conservation of energy.... That's 5,000 100W lightbulbs... This is going to be a BRIGHT spacecraft.
Where is he going to get all this energy?
PLEASE correct any wrong assumptions/simplifications... Just throwing this out there....
Yes, but it would take an infinite amount of energy to counteract the mass-increasing effects of lightspeed, so we're right back where we started.
-NOC Monkey (OOK!) Experience is what allows you to recognize a mistake the second time you make it.
Move along, citizens. Nothing to see here. Just another inventor of perpetuum mobile.
--
Industrial space for lease in Flatlandia.
I think I caught the first booboo he made. Photons *do* have a rest mass of zero. But uh, they tend to travel at the speed of light relative to all frames of reference (or so I hear :). Because of some relativistic quirks, this gives them a slight mass.
Consider the speed at which the earth is spinning AND the speed at which the earth is revolving around the sun (about 18000miles/second).
Yes I realize how a TV works. How it works
makes perfect sense. A big coil that influences
the path of a stream of electrons.
I never said coild don't have uses. I just have
doubts about their ability to "nullify gravity".
Seriously...he is talking about photons...nearest
I can figure he plans to just shove so much
current through the wires that they glow like a
light bulb....then why use insulated wire? Where
will the light go?
Certainly that much heat (if thats what he
is doing) would burn righ tthough any
insulation I know of...furthermore the high
temperature would cause the metal to oxidise
very readily in normal atmosphere.
Yes it "seems bogus". No thats not a logical
statment. Its a gut feeling based on presentation,
and the fact that AFAIK the basic premise is
flawed. (not to mention that people have been
playing with putting huge currents into coils
of wire for a long time and mysteriosluy noone
has noticed this ability of theirs to
"nullify gravity".
"I opened my eyes, and everything went dark again"
correct and incorrect.
radiometers spin because the light is absorbed
by the black surface....which heats it up. Thus
when air (there is a small amount of air still in
the glass tube...very low pressutre) strikes the
black surface, it is heated and moves away with
greater force,...thus pushing on the black side
more than the cooler white side.
In the low air pressure (and thus low air friction
) environment...this is enough to make it spin.
However....
If you pump out even more air...thus lowering
the air pressure even more...this effect becomes
much less...and the fins actually DO spin in
the opposite direction.
"I opened my eyes, and everything went dark again"
I understand that those posting these news stories can't have full background knowledge on every bit of science involved, and that some things will sound good until the message board quickly fills up with what turn out to be really obvious flaws in the 'article'. Even so, shouldn't this have been taken with a grain of salt? An AC submits the story ($10 says it was the authors of the website), it's nothing more than a concept writeup on a user homepage, it has not even a GLIMMER of scientific scrutiny (doesn't come through scientific-news channels, no sign of it being submitted to any journals or universities or the like) ... the obvious prejudice of the AOL account isn't even NEEDED here.
Sure, it's possible that someone will come up witha revolutionary scientific breakthrough independantly, and publish it on their web site before the scientific community can applaud it. But what are the odds? If you really want to put up stories like this, go ahead, but don't pretend this is real science. Entertaining sci-fi, sure ... but c'mon, light being affected by gravity is knowledge just BARELY above high school physics.
You know what to do with the HELLO. ...
Help create an open-source world
Gravity Shielding, Anti-Gravity a while Back. Am I the only one to see the conspiracy going on here? Its an attempt to draw all the LINUX geeks into space on 'ISS Linux' and have the 'ISS Enterprise' shot it down?
-- Note: These Comments are Generated by ME! Not You! ME!
It looks like he is manipulating formulae in an odd manner...
And it looks like he is glossing over most, if not all, of General Relativity when it comes to spacetime, tensors, etc.
Even so, where do these photons come from? At what frequency do they have to be? At what power? Probably be so intense they'd ionize, if not completely shred, every atom nearby, including you and your spaceship. And he talks about cross-sections between the photon and graviton... Talk about mixing relativity and quantum mechanics! Not good...
At some level, this is all trickery, like Cold Fusion. Most physicists knew immediately that Pons and Fleishmann did not produce the level of neutrons they claimed, because if they had they would have been dead.
Now, I have heard a talk about negative matter (and negative anti-matter) which react like (-m) instead of (+m) in F=ma and F=GMm/r^2. But when a (-m) piece of matter runs into (+m) matter, they anihilate leaving E=0 ! Maybe the guy needs some of this stuff to build his shield. Dunno how tho... Even odder negative matter generates negative photons ...
Eric Aitala
www.f1m.com
hehe
Eric
Eric Aitala
www.f1m.com
Unfortunately for the poor crackpot - there are quite a few problems with his physics.
;-). (Light sails accelerate extremely slowly - and this guy wants to make something accelerate at 9.8m/s^2) Oops.
1) Photons _do_ interact. (Maxwells equations are linear - but theses are only an approximation of reality.) If you use relativistic quantum mechanics - you will find that there is a fourth order diagram where two photons can interact via the exchange of electron / positron pairs. This means that his parameter U is not zero as he claims.
2) Photons do have zero rest mass - however photons contain energy (E=hf) This means that they contribute to the Stress-Energy Tensor T_ab
Now G_ab = 8Pi T_ab Where G_ab describes the curvature of space-time. This means that if you have alot of photons - you can curve space. This means that his approximation of zero graviational mass for photons is also wrong.
3) For his machine to work - it needs to radiate photons. Now this costs energy. I don't think he has calculated the amount required
There is one final hint that something is wrong. At the bottom of the page are the plans for a perpetual motion machine - always a tip off....
"Would you like a cold drink with that Sir? Yes, yes, for the sake, of the future, of all mankind, I will have, a sm
The momentum formula p=mv and many other classic formulas only apply to non-relativisic velocities, generally meaning they'll give acceptable answers when v ~0,1c (10% of light speed).
//ASCII algebra suck, I know
The relativisic expression for momentum (p) is mv * gamma, where gamma is something called the Lorentz factor, (1-(v/c)^2)^(-1/2)
If you insert the values for a photon, m=0 and v=c, you get p=0/0.
As all who have studied higher math whould know, the answer 0/0 doesn't really say us much, it could be virtually anything. 0/0 usually means we have to use other methods to find our answer.
To make a long (algebraic) story short, the formula for a photon's momentum is p=E/c, where E is the photon's energy. E is expressed by hf (h=Planck's constant, f=the lights frequency), thus giving us p=hf/c or p=h/lambda(=wavelength)
Dixi
---
It seems slashdot.org is slashdotted all the time
A poster in a previous article was right. Slashdot has achieved the quality of weekly world news. The submissions often have spelling and grammatical errors, and I think pretty much everyone, however idle they may be, has something better to do than look at this tosh. Maybe if I write up a dodgy page about free energy machines using some error ridden maths (remember folks, often mathematical errors are difficult to find), and explain how men in black helicopters are stopping me from saving the world with it, I'll get slashdotted. Of course, these men in black helicopters are hired by the EVIL M$, who the Slashdot crowd ridiculously seem to believe to be worse than mining companies, agri-business, banks, and military-industrial complex corporations.
IANAPP (I Am Not A Professional Physicist), but I believe I can answer some of your questions.
:)
> 1) Electrons seem to be perpetual motion machines.
Not really, it only seems that way. Entropy (slow loss of energy due to friction, gravity, magnetic fields and other elements opposing the current state) does happen, but is not observable in any way that a human would be able to notice, except for mathematically. The electromagnetic interaction between a proton and an electron provides the centripetal force necessary to maintain the electron in a stable orbit. The amount of gravitational attraction generated by an electron is so small that the orbit will not decay naturally for billions of years. Note that in this case, when the orbit decays, instead of falling inward toward the proton, like a spaceship around a planet, the electron will actually fly away from the proton.
2) Does gravity push or pull and how would one prove it? If it pushes that would sure explain why all the Zero G crystal can be duplicated on earth.
All particles push on objects they collide with, however in the case of gravitons, my understanding is that they push on the fabric of space-time rather than the physical objects. This could be seen as a mathematical hack, though, since in effect this is the same as the object itself warping space-time, as per Einstein.
3) Speed of light seems to lock down lots of physics. Is it the speed of light or the speed of gravity that is the limiting factor?
It seems to be the speed of light. And it's not really a lock-down, just a natural limiting factor in many equations. In a hyperbolic formula, one could say the asymtopes of the equation are limiting factors in much the same way.
4) There always seems to be enough electrons.
I don't think I understand the question here
Enough electrons for what? There are atoms with fewer electrons than protons - they're called ions. You could just as well say there always seem to be enough protons, or gluons, or quarks, or photons, etc., etc. It doesn't mean anything.
In post-9/11 America, the CIA interrogates YOU!
In the future, it would be nice if Slashdot authors quietly discarded any "revolutionary physics" that have been posted up on web pages for some 2 years yet never mentioned in any scientific journals.
Think about it. Do you really think Slashdot is going to be the place where the Real anti-gravity breakthrough is going to hit first (esp. since this "research" is claimed to have taken place YEARS ago)? How many of these crappy web pages do we have to see posted on Slashdot before we figure out the pattern?
If nothing else, search for the phrase "free energy". That should be an immediate and conclusive clue that this article might not be all it's cracked up to be.
Not quite. A photon's momentum is related to its wavelength by the following relation:
p = h / lambda
so (p^2 * c^2) - E^2 = -m^2 * c^4 =>
((h^2 * c^2 ) / lambda^2) - E^2 = -m^2 * c^4
c / lambda = frequency, so:
h^2 * frequency ^2 = -m^2 * c^4
and h * frequency = energy (for photon)
so E^2 - E^2 = -m^2 * c^4, and c != 0,
so m must equal 0.
Unless you can demonstrate that either
h*frequency != Energy for photon
or h / lambda != momentum, both of which
have been established experimentally, you
cannot say a photon has mass (also see the logic in my previous reply to another poster).
Doug
Venn ist das nurnstuck git und Slotermeyer? Ya! Beigerhund das oder die Flipperwaldt gersput!
At first, this looks like a silly idea, using directed photons to counteract gravity. But, as shown by Einstein's mass-energy equivalence equation (E=mc^2), but expanded to include an object's momentum (p):
(p^2 * c^2)-E^2=-m^2 * c^4
Then we solve it for mass:
-(SQRT((p^2 * c^2)-E^2)/c^4)=m
Shows that a highly energetic photon _can_ have some mass. The problem is that the energy need is so high that any really significant change in the local measure of (g) would take enormous amounts of energy, most likely needing a direct-conversion reactor to genereate any usable mass. To give some scale to this, the fission of a single U-235 nucleus gives off enough energy to set off a mousetrap. And remember, a fissioned nucleus is not completely consumed. Only a small fraction of the mass is converted into energy. For a device like this to work, we would need to generate more energy than has been produced throughout all of human civilisation.
Nice use of Bryce, tho...
-NOC Monkey (OOK!) Experience is what allows you to recognize a mistake the second time you make it.
BS (Fig.1)
where B is a gravitating body and S is a grav-shielded spacecraft.
As the spacecraft has zero mass, it has zero potential energy with respect to the body. Now let's switch our shields off.
What happens? The spacecraft starts falling.
B<---S (Fig. 2)
This is because the spacecraft instantly acquires potential energy. This energy can be utilized when the spacecraft falls onto the body and emits lots of heat upon impact.
B*S (Fig.3)
(* signifies the great thermal explosion.) Let's switch our shields on again (presuming we've survived the impact). The craft starts to float away from the body.
Switch them off, we fall and generate more heat. On again, float away. Off again, falling, generating heat. Cycle through Fig. 1--3 ad libitum.
What we have is a perpetuum mobile of the first kind. Unless the energy required to switch the shields on and off is more than the energy we can generate. In this latter case, the shield is useless (what potential energy do you have with respect to the Andromeda galaxy?)
Note how we don't care about the exact means of establishing the gravitational shield. Use any method. Energy conservation means you cannot win.
Of course there's a smallish possibility that energy conservation does not hold. In which case we're better off fitting our cars and homes with perpetuum mobile. This has much more sense than exploring distant worlds.
--
Industrial space for lease in Flatlandia.
Ok...basically he has 2 coils next to eachother.
Look at the diagrams...thats all it is. A big
metal tube with a couple of wire loops inside...
looks like 2 or 3 turns each.
Now....he claims to be throwing 300 A into
this sucker...depending on voltage...thats a
shitload of juice. Perhaps he is producing a
magnetic feild strong enough, and properly
oriented so that the coil is actually being
suspended above the electronics in the scale
below it?
I dunno...it all seems really bogus. AFAIK the
generally accepted theories of Gravity state that
Mass warps space in 3 dimensions. So light is
effected by gravity only because the space it
is taveling thorough is bent (ie it follows
a straight line in a curved space).
Personally...I am very quick to call this pure
bunk. Its just too pretty. I notice he claims it
has been tested...yet there are no pictures of
the actual device...just diagrams.
It should also be mentioned that just because the
math works, doesn't mean it physically works.
You can play with math and make a good case for
"white holes" (ie the opposite of a black hole..
it spews out matter and never takes any in)
however...its just because the math works both
ways...there is no evidence that a white hole
would actually exist.
Perhaps this guy is just a crackpot...I would be
interested to see more evidence myself. Another
criticizm is...where are the photons comming
from? He is talking about radiation etc...yet
all he is really doing is dumping ALOT of current
through a couple of coils that are near eachother.
I am definitly skeptical.
"I opened my eyes, and everything went dark again"
Is it me or is it rather courious that these so called scientists have an AOL web page? I mean if they are reputible at all, won't they have a web page URL that either:
1] belongs to a commerical company
2] a university
but AOL? camon, no smart people comes out of AOL. no self respecting scientist would publish stuff on AOL.
Any crack pot [with some physics courses] can generate some mumble jumble drawing and formula and stuff. I won't belive it till its published in any reputible Science/Physics Journal [no, not the Playboy Science Section. The reputible journals have people that will analysis it and only publish the ones that are acutally true or promising, not any mumbe jumble. With the web, you can publish anything.
BOTTOM LINE: wait till its published in a scientific journal, that way its gone through some peer review and we can be sure its not all crap!
-- Note: These Comments are Generated by ME! Not You! ME!
Not proton, PHOTON.
Photons are massless, and do not exert gravitational force. Light does respond to gravity, however, since it is just following the shortest path of a deformed fabric of space.
Photons have to be massless, otherwise they would have infinite energy:
E = mc^2 * gamma
gamma = 1 / sqrt( 1 - (v^2 / c ^ 2))
insert c for v, and you get a zero in the denominator, thus any particle which travels at c must be massless.
Doug
Venn ist das nurnstuck git und Slotermeyer? Ya! Beigerhund das oder die Flipperwaldt gersput!
Almost correct. Photons have zero rest mass, but they also have energy. The deformation of spacetime in general relativity is measured by the stress-energy tensor, to which photons may contribute. So photons do exert a gravitational force. -- just another astrophysicist reading Slashdot instead of reducing his Keck data
OK, some physics perspective on this...
One-line summary: These guys are better at graphics than they are at physics. No, it doesn't work.
Since the discussion below is a bit more technical than I usually send to Slashdot, here's a brief summary:
* No, it doesn't work. There are in fact some very fundamental reasons why it can't be made to work, either.
* It can be shown (through some fairly messy math) that it is not possible to cancel gravity by introducing other particles, unless you somehow had negative-mass particles to strap to your spaceship.
* Even if you could do all of this, how would you hold a sphere of photons in place?!
The rest of this is a bit heavy, so you may just want to skim. If you want to get a fairly easy-to-manage and good intro to this topic, you may want to check out Rindler's _Introduction to Relativity_.
Okay, on with the show. There are three basic problems with this suggestion.
Problem 1: "Photons have a null gravitational mass." It is true that the rest mass of a photon is zero. (The rest mass of a particle is the mass of that particle as measured by an observer at rest with respect to it. Special relativity tells us that objects with nonzero rest mass must travel slower than light, and objects with zero rest mass travel exactly at the speed of light.) However, the "effective mass" of an object for gravity purposes is <i>not</i> its rest mass. The quantity which generates gravitational fields is a more complicated quantity called the stress tensor, which is nonzero any time there is energy or momentum in a system. Photons definitely have a nonzero stress tensor and as a result do produce gravity.
In fact, because of the way the stress tensor is defined, it is impossible to entirely cancel it with <i>any</i> configuration of masses, unless you somehow had something with a negative mass. If you find something like this please let the rest of us know; there are several well-known, mathematically valid, ways to design superluminal drives based on them. However there are also several results that quantum mechanics prevents the formation of more than infinitesimal quantities of such matter.
So that's problem one; photons don't have "null mass" (whatever that means) and so don't automatically cancel gravity. On to
Problem 2: If we had a shell of photons around our ship, they could exactly cancel the gravitons. Not quite. First of all, I should say that gravitons are the smallest quanta of gravity and are in many ways analogous to photons. (In the language of general relativity, where gravity is a stretching of spacetime, a graviton represents a localized deformation of spacetime. Similarly, a photon represents a local deformation of the electromagnetic field, which is the particle physics way of stating the fact that light is an electromagnetic wave.)
Now, the way gravity works (in graviton language) is that gravitons can be emitted or absorbed by anything with a nonvanishing stress tensor. (The bigger the stress tensor, the more easily this happens) So say two massive objects are moving along; Alice (having a nonzero stress) emits a graviton, and recoils by conservation of momentum. Bob (also having a nonzero stress) absorbs this graviton, and also recoils. So effectively both Alice and Bob have changed their momentum, i.e. exerted a force on one another.
Now, say I wanted to cancel this out with some shell of Mystery Particles which would give the exactly opposite forces. These particles would have to do a couple of things:
* First of all, they had better travel at the speed of light so that they arrive at the same time as the gravitons in order to cancel them out. So these had better be massless. (See note above)
* Second, they should be able to interact with any particle that has mass, and they should interact equally strongly with any two particles of the same mass. (e.g., if our mystery particle hit electrons twice as hard per unit mass as they did protons, they wouldn't just cancel the gravity, they would also knock about everybody's particles quite a bit.)
Now it turns out (and this would require some lengthy tangents to explain in detail) that these two conditions are enough to <i>uniquely</i> specify the properties of this particle! In particular, the particle must have zero mass, and (for those of you with some physics background) have spin 2 and be symmetric tensor fields. These are exactly the same as the properties of the graviton, which isn't surprising since these things have to cancel them. But...
* It's fairly straightforward to show (using a bit of field theory) that forces mediated by spin-2 symmetric particles are always attractive. (Like gravity, and as opposed to electromagnetism. EM is mediated by photons, which have spin 1 and can be either attractive [opposite charges] or repulsive. [like charges]) So unfortunately, no Mystery Particles can cancel out gravity.
OK, and just in case this isn't enough, one other point:
Problem 3: Even if you had some magic way of getting around this, e.g. introducing multiple species of graviton and giving them some extra interactions which let them exactly cancel gravity while somehow not affecting the ordinary operation of gravity in <i>any way</i>, (Which, incidentally, doesn't work; if these particles are just like gravitons, they should be produced in nature just like gravitons and so would be everywhere) How the hell are you going to keep a bunch of massless particles sitting in a perfect shell? They're <i>massless</i>. They tend to fly away.
(OK, and now a more technical note for those of you who bothered to read this far: There is actually one other possible way to satisfy the constraints for a mystery particle, allowing it to couple to matter identically to gravitons without also being a graviton. Namely, the particles can be part of a multiplet of particles which are related to gravitons by some continuous symmetry [discrete symmetries would just give multiple graviton species] and so all matter would have to couple universally to them as well. This could be done even for particles that did not have spin 2.
But some math prevents this from working. If we want our mystery particle not to have spin 2, the symmetry must relate particles of different spin. By a key result known as the Coleman-Mandula Theorem, the only way to achieve this is with a type of symmetry known as supersymmetry. If you do this, you find that it is possible to construct a complete suite of particles called a "gravity multiplet," consisting of the graviton and several particles with spins ranging from zero to 3/2, all of which couple universally to matter and do everything we wanted.
So does this solve it? Well, not quite. The condition for these supermultiplets to cancel gravity is very well-known; it's called the BPS condition, and it says that the objects exerting the forces on one another have to obey very specific relationships between their charges (electric and other) and their masses, as well as some requirements about their relative shapes and orientations. When you work it all out, there are a few very specific configurations where this happens, but (1) It doesn't happen for arbitrarily shaped objects like spacecraft, and (2) All of this would require that supersymmetry be present and unbroken in nature. This would have some <i>really</i> visible experimental consequences, e.g. atoms looking pretty much nothing like they actually do. Such a symmetry is quite definitely ruled out.
So I'm afraid that there's nothing of this sort that can cancel out gravity. Sorry...
Yonatan
You guys have lots of money now. Hire a freaking science consultant already. A responsible site that claims to be "News" does not put this story under the category of "Space" (thankfully it was not posted under "Science"). Put it under "Humor" or "Crackpot Theories".
It's time to realize that there is a lot of bogus stuff out there. Please don't be fooled. You are smarter than that.