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#161 |
Penultimate Amazing
Join Date: Feb 2005
Location: Shanghai
Posts: 10,311
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I don't see how anything the violates conservation of momentum could work with any interpretation of quantum mechanics.
If conservation of momentum is violated it means very new physics. That would be great, but, let's put it this way: if the pilot wave interpretation allowed for violations of conservation of momentum then it would have been given even less credence than it was/is. |
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#162 |
Knave of the Dudes
Moderator
Join Date: Jul 2010
Posts: 12,499
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"The president’s voracious sexual appetite is the elephant that the president rides around on each and every day while pretending that it doesn’t exist." - Bill O'Reilly et al., Killing Kennedy |
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#163 |
Philosopher
Join Date: Oct 2003
Location: Charleston
Posts: 5,426
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By the same logic, any other element of another QM interpretation could carry momentum. Maybe the wave collapse in copenhagen can carry away momentum. If pilot waves generated by just bouncing some photons around generated momentum, I'd think that type of thing would already turn up in accelerators.
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#164 |
Penultimate Amazing
Join Date: Dec 2010
Posts: 18,783
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I have previously seen one comment suggesting that they'd get better thrust by strapping a lightbulb to the back of the spaceship than they would through the proposed mechanism, although the actual supposed thrust is much greater than a photon drive. I suspect it's really just another variation on "because quantum". Certainly, the only people who actually have expertise in quantum mechanics I've seen talking about it have said that it's nonsense.
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I don't trust atoms. They make up everything. |
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#165 |
Uncritical "thinker"
Join Date: Jan 2007
Location: UK
Posts: 17,190
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Originally Posted by Squeegee Beckenheim
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OECD healthcare spending Expenditure on healthcare http://www.oecd.org/els/health-systems/health-data.htm link is 2015 data (2013 Data below): UK 8.5% of GDP of which 83.3% is public expenditure - 7.1% of GDP is public spending US 16.4% of GDP of which 48.2% is public expenditure - 7.9% of GDP is public spending |
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#166 |
Guest
Join Date: Nov 2010
Posts: 12,673
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Here's one without someone else's leading questions from incredulity, so we can add our own.
http://arc.aiaa.org/doi/10.2514/1.B36120 Snopes' conclusion
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#167 |
Penultimate Amazing
Join Date: Dec 2010
Posts: 18,783
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If the results were clear and the experiment was carefully controlled and the published paper was detailed in explaining those controls and if it had been replicated in several labs by several teams with the same level of care then it would be harder to say that it couldn't be true because of conservation of momentum and instead be looking to determine how it doesn't violate it, or how it's possible for it to be an exception to it. The mechanism is much less important than whether or not it actually does what is claimed of it. If it doesn't, then there's nothing to explain.
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I don't trust atoms. They make up everything. |
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#168 |
Penultimate Amazing
Join Date: Dec 2010
Posts: 18,783
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I don't trust atoms. They make up everything. |
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#169 |
Guest
Join Date: Nov 2010
Posts: 12,673
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I was decrying the quality of the "annotations" in the annotated version. It seems to me not many people responding to the thread have even read the paper. I'm just an overeducated carpenter, it isn't difficult to understand.
From my reading and with other science I know this thing seems like it could be our locomotive to develop the solar system, or it could be the animal magnetism and phlogiston of our time. I don't know yet, obviously, and I'm not willing to plug my ears with fingers and yell "sounds like woo" about the device. The testing methodology seems sound. My criticism of the criticism annotations stems from my looking at the comments and screening out the utterly insignificant lab-science noobism first, and finding not much else. Questions can be useful, but answers more so. |
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#170 |
Guest
Join Date: Nov 2010
Posts: 12,673
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#171 |
Uncritical "thinker"
Join Date: Jan 2007
Location: UK
Posts: 17,190
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I don't disagree with your view, but I'd consider the entire history of experimental science as further evidence. Any claimed effect uses a mechanism that violates this, just as when it was announced that neutrinos seemed to be travelling slightly faster than light, that was sufficiently extraordinary that more attention was paid to the experimental method - and a source of error was detected.
If something doesn't overturn the whole of physics, then it needs less verification. |
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OECD healthcare spending Expenditure on healthcare http://www.oecd.org/els/health-systems/health-data.htm link is 2015 data (2013 Data below): UK 8.5% of GDP of which 83.3% is public expenditure - 7.1% of GDP is public spending US 16.4% of GDP of which 48.2% is public expenditure - 7.9% of GDP is public spending |
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#172 |
Penultimate Amazing
Join Date: Dec 2010
Posts: 18,783
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This is the issue - it doesn't. Every criticism of the paper says exactly the same thing (and I've read three, and had one in person from my father, who is a physicist who has been called upon to be a peer-reviewer himself) - there's not enough information. There's not enough data points, and there's not enough said about the set-up or the potential sources of error and how they've been mitigated for the results to actually mean anything.
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I don't trust atoms. They make up everything. |
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#173 |
Penultimate Amazing
Join Date: Dec 2010
Posts: 18,783
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It is evidence. But it doesn't matter. The reason the "violating the speed of light" thing you mention got the publicity it did is precisely because the experiment was done with the care and attention to detail is was. And it's worth noting that in that case the researchers were saying "we're sure we've made an experimental error, but we can't find it so we're publishing what we've got to see what everybody else thinks".
Were these experiments being carried out with that much care and attention to detail you'd have physicists champing at the bit trying to recreate the experiment for themselves, rather than most of them ignoring it and those who aren't saying "it's possible there's something there, I suppose, but this experiment isn't good enough to demonstrate that so it's most likely experimental error". |
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I don't trust atoms. They make up everything. |
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#174 |
Uncritical "thinker"
Join Date: Jan 2007
Location: UK
Posts: 17,190
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OECD healthcare spending Expenditure on healthcare http://www.oecd.org/els/health-systems/health-data.htm link is 2015 data (2013 Data below): UK 8.5% of GDP of which 83.3% is public expenditure - 7.1% of GDP is public spending US 16.4% of GDP of which 48.2% is public expenditure - 7.9% of GDP is public spending |
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#175 |
Graduate Poster
Join Date: Apr 2011
Posts: 1,257
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In addition to any other objections, I find it odd that no one seems to have picked up on the fact that a working Em drive violates energy conservation, and in a big way.
The heart of the matter is that, if constant power gives constant acceleration, input energy is linear with time, as is velocity, but kinetic energy goes as time squared. An example: Let's say we have a slightly improved Em drive with an efficiency of 1N/kW. This is installed on a 400 kg vehicle, with a power source which is a 200 kg Cassini-class RTG (5 W/kg) so thrust is 1 N. Acceleration is 1/400, or 2.5 x 10^-3 m/sec^2. After 800,000 seconds (9.26 days) velocity is 2,000 m/sec, so kinetic energy is 800 GJ. By coincidence, total energy input is 1 kW times 800,000, or 800 GJ. But here's where things get hinky. After 1.6 Gsec the velocity is 4,000 m/sec and KE is 3200 GJ. However, the RTG has only produced 1600 GJ, so the vehicle has acquired twice the energy put into the drive. Worse, the effect continues to grow with time, and if it weren't for relativistic effects would continue unchecked. It's true that this doesn't apply to conventional rockets, reflected in part by the decreasing acceleration produced by a fixed exhaust velocity as velocity increases, with the characteristic limiting factor being the exhaust velocity. However, the equivalent to exhaust velocity for the Em drive has to be c, yet the energy imbalance shows up at much lower velocities. This does not seem at all reasonable. Nor does the prospect of a working perpetual motion machine. |
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#176 |
Philosopher
Join Date: Oct 2003
Location: Charleston
Posts: 5,426
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Been mentioned several times on this thread. If you put some of two counter-rotating wheels, you can actually easily extract energy as soon as the rotational velocity passes the break even point.
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The woods are lovely, dark and deep but i have promises to keep and lines to code before I sleep And lines to code before I sleep |
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#177 |
Graduate Poster
Join Date: Feb 2007
Posts: 1,300
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The latest, also this article links to a just released NASA paper. http://m.phys.org/news/2016-12-mars-...sses-nasa.html
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#178 |
Penultimate Amazing
Join Date: Mar 2003
Posts: 39,010
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I suspect you are a sandwich, metaphorically speaking. -Donn And a shot rang out. Now Space is doing time... -Ben Burch You built the toilet - don't complain when people crap in it. _Kid Eager Never underestimate the power of the Random Number God. More of evolutionary history is His doing than people think. - Dinwar |
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#179 |
Pi
Join Date: Nov 2005
Posts: 14,446
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A very sensible article - or, at least, it appears to be to my untrained brain.
http://www.sciencealert.com/there-s-...pulsion-expert |
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#180 |
Penultimate Amazing
Join Date: Nov 2002
Location: Directly under a deadly chemtrail
Posts: 19,791
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Well, Thunderf00t has busted it...
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What a fool believes, no wise man has the power to reason away. What seems to be, is always better than nothing. 2 prints, same midtarsal crock..., I mean break? |
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#181 |
Penultimate Amazing
Join Date: Dec 2010
Posts: 18,783
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I just watched the whole video and the only interesting or new part was where he said that with the efficiency reported in the paper that even with a nuclear reactor it'd be at the break-even point with rocket fuel, meaning that rocket fuel is still the better way to go. But since he didn't provide any numbers to back that up, it's not really a useful thing to say.
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I don't trust atoms. They make up everything. |
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#182 |
Neoclinus blanchardi
Join Date: Jul 2001
Posts: 2,155
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Quote:
Would someone fetch me some |
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#183 |
Penultimate Amazing
Join Date: Jan 2003
Posts: 22,755
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I don't get the part about how it could make space travel extremely swift. My understanding is that if it isn't just some sort of measurement error, the amount of thrust generated is minuscule. You could generate more thrust by exhaling (not that you could do that in space, but just to illustrate how much thrust we are taking about here).
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#184 |
Pi
Join Date: Nov 2005
Posts: 14,446
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Ignore.
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"I am a Jedi, like my father before me*" *Until such time as it all gets really dark and I abandon my sister and my best friends. When the going gets tough, the tough go hide on an island. Dave Skywalker #Notmyluke |
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#185 |
Philosopher
Join Date: Mar 2008
Posts: 6,255
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The article you quoted is messed up. Even if EM drive works as described, it will make a difference only for trips to Jupiter and farther, where years of acceleration really add up. To Mars EM drive would take significantly LONGER (although perhaps cheaper) than chemical rockets.
Ion drives suffer from the same tortoise-hare issue: anywhere closer than asteroid belt, bare wins. |
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#186 |
Graduate Poster
Join Date: Feb 2007
Posts: 1,300
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Consider the amount of thrust generated using ion propulsion. Deep Space 1 probe used it. The thrust generated was equal to about one sheet of paper. The Dawn probe took 4 days to go from 0 to 60 miles an hour. Even if the thrust is lower for the E M Drive, over time speed can amount greatly.
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#187 |
Apathetic Agnostic
Join Date: Apr 2004
Posts: 1,578
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Also (assuming for the sake of argument the thing actually works) there's no reason to think the version currently being tested is the most efficient version of the drive. Changing the materials used, the shape of the cavity, or the microwave frequency generated could all result in higher efficiency.
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#188 |
Graduate Poster
Join Date: Feb 2007
Posts: 1,300
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#189 |
Philosopher
Join Date: Oct 2003
Location: Charleston
Posts: 5,426
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The woods are lovely, dark and deep but i have promises to keep and lines to code before I sleep And lines to code before I sleep |
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#190 |
Illuminator
Join Date: Apr 2013
Location: Oklahoma
Posts: 4,085
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This is a skeptic forum. So it is acceptable to call it fake/experimental error until there is more evidence to the contrary.
Without new physics, it certainly is impossible. One day maybe we will have new physics like when Einstein surpassed Newton. But it will take something big like that to explain how the drive could even possibly work. |
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#191 |
Penultimate Amazing
Join Date: Mar 2007
Posts: 16,879
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You have to supply electrical power to the drive to get your thrust (assuming there is thrust.) The the amount of gained kinetic energy is less than the supplied electrical energy, there you are not getting free energy.
And this might be the observation that makes us go looking. If these three teams are right and there is thrust once they have finally eliminated every possible error, then it has to do it and maintain the laws we already know, that means it's time to start looking for whatever else it is emitting that is taking the energy away and would balance the equations, just as they did with the Neutrino. |
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#192 |
Philosopher
Join Date: Oct 2003
Location: Charleston
Posts: 5,426
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The amount of energy you need to add to the em drive to get a specific delta v is constant. 10 m/s to 15 m/s takes just as much time and energy as 15 m/s to 20 m/s. Kinetic energy increases as the square of the velocity. This means that there must be some break even point where the liner graph of expended energy intersects the polynomial graph of stored kinetic energy. Once past that point the energy of the system increases faster than the input energy. Not to mention to mention all the energy bring lost to heat.
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The woods are lovely, dark and deep but i have promises to keep and lines to code before I sleep And lines to code before I sleep |
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#193 |
Graduate Poster
Join Date: Jul 2010
Location: Silicon Valley
Posts: 1,281
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#194 |
Philosopher
Join Date: Aug 2002
Location: Denmark
Posts: 5,234
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#195 |
Philosopher
Join Date: Oct 2003
Location: Charleston
Posts: 5,426
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<tin hat on>The reason the EM drive results have been so small and inconsistent is due to our high rate of speed (and changing rate of speed) in relation to the ether.</>
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The woods are lovely, dark and deep but i have promises to keep and lines to code before I sleep And lines to code before I sleep |
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#196 |
Penultimate Amazing
Join Date: Apr 2003
Location: 16 miles from 7 lakes
Posts: 11,032
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"Political correctness is a doctrine,...,which holds forth the proposition that it is entirely possible to pick up a turd by the clean end." "I pointed out that his argument was wrong in every particular, but he rightfully took me to task for attacking only the weak points." Myriad http://forums.randi.org/showthread.php?postid=6853275#post6853275 |
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#197 |
Pi
Join Date: Nov 2005
Posts: 14,446
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"I am a Jedi, like my father before me*" *Until such time as it all gets really dark and I abandon my sister and my best friends. When the going gets tough, the tough go hide on an island. Dave Skywalker #Notmyluke |
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#198 |
Graduate Poster
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#199 |
Philosopher
Join Date: Jun 2010
Posts: 5,997
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High-mass small-thrust setups aren't suited for hohmann transfers. You won't have one take you to Mars by itself.
What they are suited for is shaving down the rocket equation by shlepping stuff around when it's convenient. You can get by with a much smaller rocket if you can offload most of the dv into an unmanned EM-drive tug (or what have you) that spends years towing your spaceship out to just under Earth escape velocity before you board and go. |
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#200 |
Pi
Join Date: Nov 2005
Posts: 14,446
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"I am a Jedi, like my father before me*" *Until such time as it all gets really dark and I abandon my sister and my best friends. When the going gets tough, the tough go hide on an island. Dave Skywalker #Notmyluke |
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