Slashdot Mirror
Fuel Free Spacecrafts Using Graphene
William Robinson writes: While using a laser to cut a sponge made of crumpled sheets of Graphene oxide, researchers accidentally discovered that it can turn light into motion. As the laser cut into the material, it mysteriously propelled forward. Baffled, researchers investigated further. The Graphene material was put in a vacuum and again shot with a laser. Incredibly, the laser still pushed the sponge forward, and by as much as 40 centimeters. Researchers even got the Graphene to move by focusing ordinary sunlight on it with a lens. Though scientists are not sure why this happens, they are excited with new possibilities such as light propelled spacecraft that does not need fuel.
Now they just need to figure out how to use this to make hoverboards and we'll be all set.
So they'd need to carry hydrogen and split off its electrons or something to neutralize the charge.
(T>t && O(n)--) == sqrt(666)
Where the heck those extra electrons came from? Absorbing photon momentum (more efficient solar sail) sounds feasible, but "accumulating electrons" from nowhere and then emitting them in one direction (where light came from) ... less so.
Paul B.
We already have solar sails, but this could make them work much better. Real question is what happens if you paint one side. A solar sail with one side painted and the other painted with graphene might be really cool.
excitingthingstodo.blogspot.com
So it's not really fuel free, the fuel just happens to be on the ground (or wherever you put the laser).
In that it fails to mention the object was macro-scale, the resulting movement is greater than that would be expected from momentum of the photons, and was not due to ablation of the material. This is far more interesting that pushing tiny things around with a laser.
All great discoveries can be summed up with three simple letters... WTF
Lets test your hypothesis by creating a slashdot poll.
Mod me down, my New Earth Global Warmingist friends!
Does this mean we'll finally get a version of the Crookes Radiometer that works as a light pressure engine and not just a heat engine? All this space nonsense is abstract to me, I want something I can hold in my own damn hands!
Void rays.
Mod me down, my New Earth Global Warmingist friends!
"The most exciting phrase to hear in science, the one that heralds new discoveries, is not Eureka! (I found it!) but rather, 'hmm... that's funny...'" - Isaac Asimov
Some days it's just not worth chewing through the restraints.
Interesting method of waging war in space -- make mines out of objects that use their electrons to move into position -- then anytime a neutrally-charged object comes near them -- BOOM
Where the heck those extra electrons came from?..."accumulating electrons" from nowhere and then emitting them in one direction...
Isn't that the opposite of what the phosphors used in a CRT do when hit by electrons? Is it too much to think the reverse is possible?
Having read the article, they've already ruled material vaporization out.
Clearly it collects the electrons from the hydrogen particles in the interstellar gas. Of course, the now-charged hydrogen gas follows it around until it gains critical mass and... FOOM! New sun!
Well, CRT face is (weakly) grounded, so e- kinetic energy can excite atom for subsequent photon emission, but its charge will happily leak into the ground.
There is no "ground" anywhere next to flying spacecraft!
Actually, on reading the preprint, yes, electrons come from under the Fermi level, get lost in the process and graphene foam (or, spacecraft carrying it) *will* become charged -- it was pointed out in the article as well, but I did miss it on quick read.
AC below actually paints a rather dramatic picture of what can happen next! :)
Paul B.
A quick search on converting photons to electrons turned this up:
http://cleantechnica.com/2013/...
A new discovery by researchers at the ICFO has revealed that graphene is even more efficient at converting light into electricity than previously known. Graphene is capable of converting a single photon of light into multiple electrons able to drive electric current.
So that could be where the extra electrons are coming from.
Better known as 318230.
Maybe from this other recently discovered process?
http://cleantechnica.com/2013/...
Better known as 318230.
So they'd need to carry hydrogen and split off its electrons or something to neutralize the charge.
Actually this could provide more thrust. Use sunlight to propel the craft until it has built up a large enough electric charge that the efficiency of the thrust begins to drop (since it will take an increasing amount of energy to expel the electrons from something with a large positive charge) and then introduce a stream of neutral gas into the sponge. This should strip the electrons off the gas and the remaining positively charge ions will then be repelled by the positive graphite and provide even more thrust.
Of course this means that you need to have a fuel source but it's likely to be far more efficient than current rocket fuel plus there it no need for it to be something explosive like hydrogen - you could probably use Xenon which is a noble gas and so extremely inert and so a lot safer.
Combine it with an EM drive: double the speed & double the mystery. Maybe if you mix baffling with confounding you get a multiplier effect instead of just doubling. (That's the way the entropy seems to work with compounded software bugs.)
Table-ized A.I.
isn't this already know? how is this different to a light sail?
I figured this out when I was like seven years old. You just hook up one of these to a space ship and fly straight to Jupiter.
https://upload.wikimedia.org/w...
You are welcome on my lawn.
Where the heck those extra electrons came from?
They could easily come from all the material which is surrounding the graphite. As the charge builds up on the graphite due to all the electrons being expelled it will develop an increasingly strong electric field eventually will pull electrons from the walls of the chamber. Since the vacuum will also not be perfect the remaining gas molecules could also transfer charge by moving back and forth between the graphite and the chamber walls.
A similar effect exists in the LHC where the electrons are 'helped' to leave the walls by synchrotron radiation hitting the walls of the beam pipe and are then dragged along by the electric field of a bunch of protons forming a electron cloud. This effect is one of the primary limiting factors on the number of protons we can have in an LHC beam.
That may be correct but the article you linked has an incredibly misleading title. This process does not convert photons into electrons it simply imparts the photon's energy to one or more electrons which, in the case of thrust, causes them to be ejected from the graphite. The coupling of electrons to photons is extremely well understood, in fact it is the second most accurately tested scientific theory ever discovered (the first being special relativity). The only way to create electrons from photons is to also create an equal number of positrons. However this requires far higher energy processes ~1 MeV of energy which is many orders of magnitude higher than the energies involved in visible light and would easily break apart graphite which is something they ruled out.
Isn't this just plain photoelectric effect but the novel thing is that thrust is generated because the electrons are apparently all released in the same direction?
So I imagine it isn't really 'fuel free' in the sense of that it would still need some source of electrons eventually.
I'm just sharing a curious idea that came to my mind while reading the summary, what if we mount laser on the spacecraft that got a "graphene sail". I mean, AFAIK laser doesn't generate any trust (if it was the case, we could probably use fuel-free laser engine). And laser on graphene generate trust.
Please help me find where's the error, my brain hurt.
Elok
It is a related principle, photons have momentum and it can be transferred to atoms to increase their kinetic energy, but it is only when it happens coherently that you notice anything more interesting than heat.
light pushes the fins of a radiometer in a vacuum - could this be a similar phenomenon??
http://upload.wikimedia.org/wi...
Furthermore, their ability to second-guess the credentialed experts is improved exponentially by posting AC.
Do you ever get the paranoid feeling that someone is occasionally modifying the laws of physics in order to advance the plot?
"Oh look, they're going to be stuck on Earth for an excruciatingly long time due to the exponential-propellent-scaling problem. Let's add a new capability to graphene that will give them a work-around for that."
I claim that two years ago the exact same graphene experiment would have shown no unexpected results; but now in 2015 we see this suspiciously useful behavior appear. I'm not sure how to test my hypothesis though :)
I don't care if it's 90,000 hectares. That lake was not my doing.
Galileo would have been fucked on this site.
Not to worry, he had religion to take care of that for him.
I've fallen off your lawn, and I can't get up.
I wonder if they've weighed the sponges. One possibility is that the sponges are deteriorating in a particular direction, thus engaging in conventional "stuff out one end makes you go the other way" propulsion. And also becoming traditional "will get used up" style fuel in the process. :)
Though it'd be all kinds of awesome if it was creating coherent motion out of energy delivered by photons without wearing out. Now *that* could be a space drive.
I've fallen off your lawn, and I can't get up.
The EM drive is pseudoscientific rubbish. Conservation of momentum is a buzzkill and there's no way around it. As for this discovery, one of two things will happen:
1. They will 'discover' that it uses no reaction mass, in which case it can safely be discredited as pseudoscience.
2. They will discover that there is indeed reaction mass involved. Actually that's what it says there in the article: "Instead, they think the graphene absorbs laser energy and builds up a charge of electrons. Eventually it can't hold any more, and extra electrons are released" If this is confirmed it means that you can't run this for very long because you build up a positive charge and you need to balance this by gaining electrons from somewhere (interstellar gas maybe?) or ejecting positive ions.
If electron ejection is happening then it's really nothing new; we've known that electron guns can propel objects in space. This might lead to new, more efficient ways of using that effect, though. Still, I doubt that the thrust is going to be anywhere near useful for, say, a manned spacecraft. It might be extremely useful for satellites and probes.
A fool and his hard drive are soon parted.
Galileo is still fucked on this site. Practically every time his name comes up a bunch of mean-spirited posters say everything that happened to him was his fault because he was a jerk. So instead of concentrating on the message they attack the man. The Pope was right to excommunicate him and ban his books, because he insulted people.
It doesn't 'violate' charge conservation. You build up a positive charge as you run. Pretty soon the positive charge becomes so huge that your thruster ceases to work. You can make it work again by neutralizing your charge.
A fool and his hard drive are soon parted.
Well, there might be some sort of principle for a new and better ion drive of some sort buried in there. Its all certainly worth investigating, as any "WTF!" moment of this sort is. The hype about reactionless drives certainly is drivel though, and it seems your average peruser of online science fora has little or no clue about small things like Noether's Principle, which pretty well guarantees nobody is violating Conservation of Momentum, ever.
"Malo periculosam, libertatem quam quietam servitutem." -- Jefferson
I'm only saddened because this means I can't have a window on my computer case in the future. The light that enters will cause my graphed based transistors to overheat.
You don't really have to have much knowledge about anything to second guess experts in any field. Just hold to the rule that "all amazing results are caused by inaccurate measurement, poor sampling, cognitive leaps or coincidence" and you'll be right 70% of the time.
The actual breakthroughs will be so old hat by the time they have been tested properly that nobody will talk about them and you'll never eat crow.
Remember, cynicism and wisdom lead to the same result most of the time, only wisdom is so much harder to learn.
When Argumentum ad Hominem falls short, try Argumentum ad Matrem
Article says they tested for that, and the tests show that the material is not losing atoms. It seems (according to further tests) that the graphene sponge is absorbing energy from the directed light (they repeated the experiment with sunlight and a traditional lens, with similar results) and finally reaches some sort of critical mass, and sheds electrons in a stream, rather than in random directions, resulting in thrust. If this whole hypothesis pans out, the difficulty in making a space craft that makes use of this phenomenon is that it would eventually build up a large positive charge, which would eventually damage the craft, if it can't be dealt with.
I've decided to Diversify my Holdings. I've divided my cash between my left and right pockets, instead of all in one.
Welp, I've got a laser pointer and a table, you find us some graphene sponge and a vacuum chamber, and we'll test it. Which is the whole point of this. Its literally:
"Hey scientists of the world, we pointed a laser at some graphene, and something weird happened. Here's what we did, will you give it a go and see if we're tripping balls, or have discovered something awesome?"
I've decided to Diversify my Holdings. I've divided my cash between my left and right pockets, instead of all in one.
Conservation of momentum is a buzzkill and, as far as we know there's no way around it.
Here, fixed for you. A good scientist knows the limits of what he know, while others like you tend to be simple religious shitreaded fanatics with dogmas.
related? http://en.wikipedia.org/wiki/R...
However, electrons are very nearly massless, so unless they're somehow exciting them with massive amounts of energy, the propulsion from the electrons is unlikely to be significant.
It depends on what you compare it to. Since this process was hitting the graphite with photons it makes sense to compare the thrust produced to that created purely by bouncing photons off a material. Electrons might be light but they have more mass than a photon and so the thrust should be significantly higher.
No, the electrons go through a circuit, which is the entire point.
In a CRT, the output of the flyback transformer is a really high voltage, which connects to the CRT face through a heavily insulated plug. If you take a look at any CRT, there's a thick heavy cable in the middle of the body that runs to the flyback transformer. Inside the CRT, the electron gun is at negative potential and it's slowly accelerated past the deflection coils, then it basically accelerates due to the electric field from the gun to the front of the screen. It hits the phosphor which imparts energy into the phoshor atoms which then do the whole higher-energy state thing and they drop back down to ground state that emits a photon of a specific color.
The electron that hit the phosphor returns back via that nice flyback cable to complete the circuit. Otherwise the screen wouild quickly dim as the phosphor layer takes on a highly negative charge.
Yes, I got the polarities right. Remember electrons flow from negative to positive.
What about creating the reaction mass from the photons of the laser?
Patents Drive Free Software as Hurricanes Drive Construction Industry
I'm pretty sure Galileo wasn't attacked by the church for any of his scientific work.
Required reading for internet skeptics
I'm no physicist, but I'm pretty darn sure a spaceship's gotta move a whole lot further tan 40 cm to get anywhere.
File under 'M' for 'Manic ranting'
Incidentally, mass effect game universe. Engines eventually reach full charge cloud, which needs to be neutralized by dispersing it into atmospheres of planets en route. We could do the same.
http://en.wikipedia.org/wiki/G...
I would call that attacked for his scientific work. He was placed on house arrest (for life) in 1632.
"So long and thanks for all the fish."
No. Nobody has noticed this. You're the first. Thank god you're keeping scientists of the world grounded.
"Old man yells at systemd"
Do you ever get the paranoid feeling that someone is occasionally modifying the laws of physics in order to advance the plot?
Only when I observe the magnetic pattern of the sea floor, and realize we're more than 500,000 years overdue for a magnetic pole flip -- stopped flipping about the same time life demonstrated intelligence. I hope we don't have to pay back the "good fortune" of having our cosmic-ray-shield maintained. Oh, I also get a bit paranoid when thinking of how much it would cost to break up that would-be planet between Mars and Jupiter into manageable chunks for manufacturing materials with no gravity-well tax. And, also when I think about how we have more water cached in Ceres (dwarf planet in the asteroid belt) than exists on Earth, that's just too much "good luck", there's got to be a catch. I hope they didn't have to tow the no-EM-field sparse atmosphere training ground (Mars) very far, it is just about perfect for figuring out how to live in the next step outwards (asteroid belt). How much would a moon full of methane go for on the intergalactic market, do you think? What about a sub-brown dwarf (Jupiter) to complete a gravometric laboratory kit? Saturn's got diamond rain... yikes. Surely they can't charge us for that absolutely huge moon made of the same exact elements as Earth with features clearly visible with the naked eye beaconing us to take a closer look and make the first steps along the red carpet to the stars that's apparently been rolled out for us. The welcome sign has to at least be free, right?
I do believe the Anthropic Principal is enough to explain how we were so "lucky" to find ourselves springing to life in the lush environment of a Goldilocks Zone, but when I examine the rest of this solar system it just seems way too conveniently laid out for us. It's uncanny how if I were to design a solar system for a space faring race to emerge from, this one would pretty much fit the bill completely.
He definitely was attacked for his scientific work - heliocentrism was banned and Galileo had been investigated multiple times. However he did himself no favours by putting the pope's words into the mouth of a character called Simplicio who is depicted as a fool.
No, it's not pseudoscience.
If a researcher perfoms an experiment and gets a very strange, unexpected result, what should he do? Say "that result is clearly impossible, so I shall just disregard it"?
No, he will try to repeat the experiment, gather data, and try to figure out what's going on. Maybe (most likely) there's a perfectly valid explanation within existing scientific frameworks, maybe it's a setup or measurement error, or maybe, just maybe, this is a new effect that hadn't been discovered yet. So the scientist tries to figure that out, and tells others about the experiments so they can try the same thing and see if they get similar results.
That's how science works.
I'm sure you would have called the theory of relativity "pseudoscience" back in the day of Newtonian physics. New things do get discovered sometimes. As long as it's being researched using scientific methods, that's science and not pseudoscience. Yes, they probably will be wrong. That doesn't mean it's not science.
If I read this correctly, the decisive advantage this has over conventional solar sails, is that instead of turning a fraction of the (feeble) momentum of photons into useful movement (basically by bouncing photons around), this discovery turns (apparently, most of) the energy of those photons into a coherent emission of electrons, which give off orders of magnitude more useful momentum.
So, it's not quite a solar sail, but rather a very very very light and efficient solar-powered electron cannon.
Maybe we deserve this world ?
What they don't say, is that the graphene sponge was used by Qui-Gon to clean up Anankin's wound. And since the midi-chlorians hate lasers (or light-sabers, for that matter) cutting through them, they preferred to move the sponge away.
Mystery solved. You heard it here first.
So they discovered that if you shoot something at something, something moves? Is one of them named Zeke, and was the discovery made in his backyard?
Good explanation thanks.
http://ghostbusters.wikia.com/... It's ghosts! Got to be.
Liberty - Security - Laziness - Pick any two.
Yeah i read that bit too and i get it now... however doesn't that mean the effect also diminishes as the charge builds? eventually completely stopping.
Sounds like it basically need a battery, i wonder if that could be solved by coupling this with a photovoltaic material? Sorry my solid state physics kinda sucks :P
LoL... no i does work, photovoltaic and photoelectric are different effects of the same phenomenon right? i guess there is not simple closed form way to get those electrons back without getting all fusiony.
The plural of craft is crafts - when you're talking about embroidery, woodcarving & the like.
When you're talking about vessels, it's just craft.
At the bottom of the
Exactly my thought. Someone answer this?
Elok
http://en.wikipedia.org/wiki/S...
And maybe he will describe the effect so well in an equation that some bored patent clerk will call it a transformation and assume it is one of the fundamental laws of the universe....and then everybody will spend the next 100 years talking about him.
"I opened my eyes, and everything went dark again"
Well, as long as your space travel goal is 40cm or less, we've got you covered!
It's kind of like expecting to do work on an iPad. Sure, you can do all sorts of things, as long as your standards are low enough and your definition of "work" is exceptionally loose.
Is it just my observation, or are there way too many stupid people in the world?
Has this been confirmed by a second party ?
If the graphene is throwing off electrons to generate the propulsive force, it hardly seems likely that this could provide a long term propulsion system. If you add photons to graphene and emit electrons, wouldn't the graphene get seriously positively charged, which should limit how many more electrons can get thrown off?
Set up a Slashdot server on board the space ship. You'll have an unlimited supply of negativity, so much so I think if you dumped a cup of tea on it the ship will instantly jump to ludicrous speed.
If conservation of momentum were not true, it would break 99.999% of our understanding of physics.
FTFY.
If man's law defining conservation of momentum is found to have a loophole, then physics as defined by the universe will work the same way it always has. It's just our definition that's been broken, which would mean that every other theory we've created that's been supported by this law would have to be brought back to hypothesis and reworked into a new theory of how things work based on new evidence.
To think that it's unlikely that conservation of momentum will be discovered to have a loophole we didn't understand doesn't make you the 'religious shitreaded fanatic' [sic]. I also highly doubt that we'll find that loophole, even with this new discovery, and I feel that all the laws of physics have been fairly solidly proven thus far that they can be safely presumed to be a certainty. That said, I would not be so arrogant to say that if it were discovered that one of our laws was flawed that physics has been broken. I would only say that man's understanding of physics has been shown to be flawed and that we must come to understand that flaw so that we can rework a more complete understanding of the physics of our universe that correspond with this new information.
Only when I observe the magnetic pattern of the sea floor, and realize we're more than 500,000 years overdue for a magnetic pole flip ...
The underlying process seems to be random, so we're not necessarily 500,000 years 'overdue'.
The recent weakening is 'within spec'. If it does flip, it could do so rather quickly.
Tiller's Rule: Never use a word in written form that you've only heard and never read. You will end up looking foolish.
I thought the same thing. Maybe it's not the low mass that matters, but the high surface area that's enabling it to trap a lot of air inside.
I've been hearing about the hypothetical possibility of spacecraft where at least part of the drive capacity is fueled by energy beamed to it from earth or some other large "stationary" (i.e. not attempting to change orbit) object in the form of laser light, for ages.
That doesn't make this any less neat - it sounds like what they've found, if they can harness it from theoretical science to proper working technology, is a much more *efficient* way of consuming the energy being thus beamed - but the basic idea of creating such a spacecraft is not new. Still cool though, if it makes the idea more likely to actually be attempted.
it's stuff like this that makes science interesting and fun.
see something odd ball happening,
test, test, and test again to make sure it's happening,
tell everyone that you are seeing this,
let them test it to...
someone's bound to figure out why, and they
get the co-explanation.
someone else get's to figure out how to use it,
everyone wins.
if you see me, smile and say hello.
Yup. And we have an extensive understanding of physics. We know it's incomplete, and that some of it has to be wrong, but it predicts observations with tremendous accuracy and in general works extremely well over a very wide range of conditions.
If we throw out conservation of momentum, we essentially trash all that and have to start all over again. This would be more fundamental than relativity or quantum physics. With the exception of black-body radiation, neither touched everyday life. We now have people talking about reactionless drives that are fairly simple, which means variations of physical law over space that are significant enough to affect everyday life.
It's conceivable that momentum isn't conserved, but it's far too soon to be hypothesizing that seriously, and it's going to take REALLY, REALLY strong evidence to change that.
"When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes
Massive generalisations do not the non-asshole make.
Obviously this is worth following up. It's apparently repeatable by the original experimenters. People are going to try it in their own labs. Assuming it can be replicated, people are going to try to figure out exactly what's happening. This is precisely as it should be.
On the other hand, there's a lot of nonsense being thrown around by people who don't know what they're talking about.
"When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes
Anytime Galileo is brought up it's as proof that the Church is/was anti-science; which is patently false. Don't get pissy because your example is bad.
Unless there's a flaw in "Noether's Principle;" a possibility that is and should never be left out of scientific research.
Just because a foundational principle is wrong, doesn't mean everything else is broken. The law or theorem could just be flawed. I don't understand your zero-sum way of thinking here.
Its not that kind of a thing. It demonstrates that LOGICALLY there is a correspondence between conservation laws and symmetries of nature, and shows that Conservation of Momentum is logically equivalent to the universal equivalence principle (all physical laws apply the same at all points in space). This is fundamental and if it weren't so then LOGIC ITSELF fails. Its not some law of physics that might or might not exactly be true or only holds in some specific conditions. Either Conservation of Momentum is universally true everywhere, or there are no consistent laws of physics, and if this is not so then logic itself is meaningless.
So, any time you have a 'theory' which violates one of the known universal conservation laws, then its pretty much insta-quack. Its always worth being careful about the fine print, because concepts like 'conservation of momentum' can get quite slippery in Relativistic Mechanics for example. This means that when something fantastic that breaks these conservation laws seems to happen what you will find is that the books ARE balanced, but it might not always be in a really obvious way.
"Malo periculosam, libertatem quam quietam servitutem." -- Jefferson
I doubt that.
When someone says, "Any fool can see
If they are asserting the same claims as the EM drive. Then i hope so.
reactionless propulsion in a vacuum means free energy. Literally it is an over unity device. Yea pretty safe to call bullshit if that is what is claimed.
Oh and this is in newscientist. If you want shit science stories its the place to go. For good stuff, not so much.
If information wants to be free, why does my internet connection cost so much?
If momentum is not conserved. Neither is energy nor relativity. So all those experiments must be in error somehow... or your wrong. Forces are *between* things, so momentum is conserved. So is energy and its all relative.
A good scientist doesn't waste time on bullshit. And violating momentum conservation is bullshit.
If information wants to be free, why does my internet connection cost so much?
What I understand is that the lasered piece of graphene shoots out electrons, creating a thrust. But what happens when there are no more electrons ?
Moreover, stripping off all these electrons will ionize the material, which would either cause nuclei to detach as well (like with a plasma thruster) or the resulting positive charge will eventually end up pulling back all the ejected electrons, negating the thrust.
Of course, he was attacked by the scientific community, not the church. The other natural philosophers were the ones that lodged the complaints. Until he pissed them off theologically, he had the support of the church. And house arrest, well, gee, he got to stay in the medieval equivalent of a five-star hotel for the rest of his life. I'm sure everyone would like that kind of a sentence.
reactionless propulsion in a vacuum means free energy. Literally it is an over unity device. Yea pretty safe to call bullshit if that is what is claimed.
Well, except for the energetic laser that acts as an outside source of energy, yeah.
Cue the speed of light jokes....
There was no "ground" anywhere next to my computer when I had it running from a battery-powered inverter, but the CRT monitor worked fine in this arrangement and I don't glow in the dark.
Kid-proof tablet..
Or, it just means that we found a way to convert energy to momentum directly. No free lunch as you'd still have to supply energy to convert into momentum.
Preconceived ideas and bigotry is always anti-science. Some of the other elements of religion might not be.
Is this a good point to mention that momentum isn't conserved in General Relativity. GR deals with curved space-time, so this probably isn't surprising. There's translational variance of space. However there's still a conserved quantity: the stress–energy–momentum tensor.
Actually, after RTFA, it appears that they confirmed a flow of electrons away from the graphene. That would imply that momentum is being conserved.
Does a car pushing against a road break conservation of momentum? Does a boat with a propeller in the water break conservation of momentum?
The only reason we use reaction engines in space is that we haven't found anything to push against in space. But who's to tell that EmDrive isn't doing precisely that?
That depends on what foundational principle is wrong. Not having laws of physics vary significantly from place to place is pretty basic, and conservation of momentum follows from that. If momentum is not conserved*, every law of physics will have to be re-examined to figure out exactly how it applies.
*Yes, in fact, I do know that I'm using "space" and "momentum" here like they were real things, and that things get more complicated when considering relativity. It's still going to have an impact that big.
"When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes
Nope... If there is no reaction mass, then its over unity regardless of how much energy it consumes in some characteristic time. It is easy to prove.
If information wants to be free, why does my internet connection cost so much?
Gravity is a force *between* things. You fall to earth and the earth falls up to you.
If information wants to be free, why does my internet connection cost so much?
True, but that is getting a little pedantic for the level of discussion here.
If information wants to be free, why does my internet connection cost so much?
If the hypothesis is correct then this IS NOT a "fuel-free" engine -- it's using electrons as reaction mass. The novel feature is simply the means by which they are accelerated and the fact that an accelerator isn't required to collimate the beam into a coherent stream, i.e. they don't fly off randomly in every direction as electrons normally would do upon reaching ionization potential.
Wonder what the average age distribution is on slashdot...
> maybe it's a setup or measurement error, or maybe, just maybe, this is a new effect that hadn't been discovered yet.
Science consists of performing experiments, gathering data, coming up with a set of competing explanations for the observed data, and then conducting more experiments to obtain proof in favor of or against the competing hypotheses.
The key is the 'coming up with explanations' part. Anything that violates conservation of momentum is NOT an explanation. It creates far, far more problems than it solves. If you're even willing to consider it when ANY other option is available indicates that you are biased, not the other way around.
It's only when all other options have been exhausted that you should even think about considering violating conservation of momentum. And if you're at that stage, you are incredibly screwed because now you have to revise ALL of physics, not just your little experiment.
If you think that an honest unbiased scientist should waste even 1% of their time contemplating violation of conservation of momentum, it's you who are being biased and dishonest.
A fool and his hard drive are soon parted.
Physics IS our understanding of the Universe. "Our understanding of physics" means something completely different.
A fool and his hard drive are soon parted.
From the New Scientist article, they talked about the possibility that the incoming photons boil off electrons from the sponge, and most of those electrons were emitted in the opposite direction of the light beam, generating more thrusts than can be accounted by just the light pressure alone.
They also raised the issue that, if that were actually the case, you would end up with a dangerous level of positive charge. Without being able to neutralize the charge, this would not make for a good propulsion system.
The fact that the apparent diameter of the Moon and the Sun are virtually the same, resulting in nearly perfect solar eclipses, is also rather surprising, although I don't know that any science breakthrough comes out of that. (Lots of beauty, for those who can fly their Learjet up to Nova Scotia to see the total eclipse of the sun. Also nice if you want to avoid being burned at the stake by King Arthur. And I suppose that's how the Sun's corona was discovered.)
Wait. I'm confused. If it's spitting out electrons that are *part* of it, yes, it'd go positive. It'd also be losing mass (and changing composition) which puts it right back into the "I am fuel and will run out" category.
But if the electrons are merely the photons re-directed out one edge here, then it's a conduit, like a wire, not a charge reservoir or source. Just as a wire doesn't constantly gain positive charge because electrons are moving along it, I don't see why this stuff would either.
And if the photons are coming from outside... well, there's no reason for something that arrives and then leaves to change the net charge of the thing it is passing through/by/along/whatever. Again, just like a wire.
Or do I have this all wrong?
I've fallen off your lawn, and I can't get up.
I'm sure glad Einstein devoted more than 1% of his time to prove that time flows differently for different observers, speeds cannot be simply added together, momentum has to be calculated differently, etc.
Except Einstein didn't immediately jump to "classical physics is wrong" just to get a kick out of it. Einstein was aware of the experiments that were inconsistent with the classical way of thinking. He correctly realized that relativity was the least improbable theory that fit all observations.
A fool and his hard drive are soon parted.
Look, it's Slashdot 1. They've gone plaid!
Ion drives have the same issues and there are mitigation techniques available.
Matter and energy are equivalent. Regardless, it's a moot point as the article states that electrons are being emitted by the graphene, and it is these electrons which are suggested to be the source of the thrust.
This kind of 'thruster' simply can't work in any practical way.
Actually that depends. As you remove the electrons the charge will build up which means that you have an increasing electric field. Providing that you kick out the electrons with sufficient energy to escape the field the field will continue increasing and will reach the point where it will breakdown even in vacuum.
For a high enough field strength virtual electron-positron pairs will gain sufficient energy as they are pulled apart to become real. The electron will be attracted back to the craft to neutralize some of the positive charge there and the positron will be repelled out into space creating even more thrust. The result is that after achieving a critical charge the charge will stop increasing.
However you will need a huge charge build up to get this far and you would probably need high energy gamma rays to give the electrons sufficient energy to escape the intense electric field required (otherwise they will not leave the material). Since you are, at this point, essentially converting energy into mass and flinging it out the back of the craft I also expect that your net thrust would be no different than just reflecting the incident photons.
Well, for myself.. all I can say is.. WOW!!!
matter and energy may be equivalent. But neither is momentum.
If information wants to be free, why does my internet connection cost so much?
Momentum is a form of energy.