Z-Man

Because it is wrong. You have still not pointed out a concrete error in N_las's pictures. Well, yes. Precisely. And kind of obvious, you can't get back to Earth if you move away from it. That's why you (let the information) switch warp ships or do some manoeuvres to turn around while continuing to move backwards in time according to Earth's rest frame.

Err. Yes. It's a thing called 'projection'. You project away, ignore, the two spatial dimensions that are not relevant to the situation at hand. 2D space/time drawings are the perfect tool for explaining what Lorentz transformations do. If you think your imagination is superior to them in this case, sorry, chances are your imagination is wrong.

Ah! The discrepancy in the calculation I pointed out is only a result of very poor rounding for the presentation. 9.66*10-39 is apparently best approximated to 10-39. Oh well. Still, it's numerology, especially given that both the unrenormalized vacuum energy density and mass of the (observable?) universe can differ a lot depending on how you calculate them. The other coincidences pointed out in the paper are, I'm afraid, normal. Orbital speeds near a black hole are close to the speed of light by nature. The proton radius is naturally closely related to the typical times the strong force acts under. And so on. Perhaps we should concentrate on Figure 1? It certainly looks the most impressive. First, we isolate three data points. 1. The lowest one, the Planck mass and length. By definition, the Planck length is about the Schwarzschild radius of a black hole with Plack mass. 2. The Schwarzschild proton. Again, by its definition, the radius is the Schwarzschild radius corresponding to its mass. 3. The universe. As we know, it has pretty close to critical density, give or take a factor you won't see on such a log-log plot. That, too, means its (observable) radius is close to the Schwarzschild radius corresponding to its (observable) mass. That those three would fall on a line is no coincidence. The Schwarzschild radius is proportional to the mass. That proportionality line would be the true significant line to draw in the plot, and it's not mysterious at all. All the other data points are below that true line because they are not black holes, sometimes missing by ten orders of magnitude. The log-log plot best fit line hides such vast discrepancies. What he really discovered is that noting can be more massive than a black hole of the same size, most things are not black holes, and those structures big enough to be noticed can come relatively close. Two more things about the plot. Note that the two galaxy cluster points and the universe also seem to lie on a line with a much larger slope. Again, no coincidence, that are the scales where the almost uniform density of the universe starts to kick in. But it does not fit into his unified scaling law, so it is ignored. Missing from the plot, things he included in the other plot from the video (the one that's not in the paper, about the relation between object size and typical frequency): living things. That's because they'd be way, way below the line. As would be planets, nebulae, red supergiants or star clusters. Ok, I give him the nebulae, they are clearly unusual enough to drop, but the others? No, there's no a priori reason.

No, not really. Undesirable consequences, no matter how nasty they may be, are no reason to assume something is impossible. Chances are that nature has a way of dealing with them either shortly before they are created (and yes, there is a well defined shortly before) or when they are created. We just don't know what it is yet. It may even be harmless.

Sorry, that's meaningless mumbo-jumbo. It was not. It's on most top ten Things Physics Has to Get Straight lists. It's ignored in particle physics because unless you take into account gravity, the base energy density does not matter. Except... he gets it wrong by a factor of 10. From the video, the Mass of the universe is 10^55g, the proton volume 10^39cm^3, vacuum energy density 10^93 g/cm^3. That gives a proton mass of 10^54g. Plus, as he states that the mass of the universe is just enough to make the whole universe a black hole, that mass includes the fake dark matter, otherwise it does not add up. Sorry, that's pure numerology. Combining random numbers to find coincidences.And he claims the force between protons is really the gravitational attraction between the proton black holes. Well, sorry, with any mass he attributes to them, that force would be way stronger than what is observed. Again, something that is very well known known. This time, however, not a problem. Energy conservation does not apply to cosmology.

Yes. Note that I did not claim it can be created After all, it relies on the existence of speculative states of matter and our ability to suitably control them. But without good reason, you can't claim something is impossible, either. I can, for example, state that it is impossible to divide an arbitrary angle into three parts using only ruler and circle. We have proof for that. But we don't have any theorems regarding the impossibility of creation of closed timelike curves, not even under the strictest conditions on matter fields. So you don't get to use anything like that as a serious argument.

The thing is, you can. Accelerate your craft normally to .5 c (relative to Earth) in the negative x direction. Engage warp at 10c relative to your current rest frame into the positive x direction. Congratulations, you're already moving backwards in time relative to Earth's reference frame. See N_las's pictures. Now you disengage warp, turn your ship around to .5 c into the positive x direction, engage 10c warp into the negative x direction, disengage and break down to 0 relative to Earth. Make the warp phases long enough, time it right and you are now back at earth at an earlier time. You're still only breaking global causality, though. The important bit is the bolded one. You have to assume the warp drive is capable of getting you to superluminar speeds relative to whatever is your current rest frame. The Alcubierre drive would do precisely that. And what's superluminar in one reference frame can go backward in coordinate time for another. Still, you can't use that argument to declare such a drive is impossible. Global causality violations are a bit like spacetime singularities. They are both very annoying, but if you can't rigorously prove they can't be created, you have to deal with them. You can't claim stellar collapses don't happen because that would create a singularity, you can't claim any kind of FTL can't happen because that would cause causality problems. You can use it as a motivation for further research in that direction, sure, but you need to find a more fundamental reason. "I don't like B, it sounds horrible. A would imply B, so A can't be true" does not cut it. Back on topic, I did the parallel transport calculations for arbitrary constant weak gravity fields. Nothing unusual happens. Your velocity at the end of warp has three contributions: 1. The original velocity before warp 2. The acceleration you would have picked up if you were a regular Newtonian particle moving along the warp path in Newtonian gravity 3. A tiny term due to the spatial part of the curvature. Zero if your initial velocity is zero. If your warp direction is identical to the classical ingoing velocity, this bends your velocity by half the value it bends the direction of a photon going down your warp path. Unless both your warp factor and your initial velocity are huge, the third term can be safely ignored. For large warp factors, the second term can also be ignored. Dunno. How does KSPI's warp drive operate? If it's "velocity relative to the sun stays constant during the warp jump", it's probably accurate enough.

That's a magnetic solar sail and has nothing to do with gravity. It may indeed work, the question is whether you can actually create a field large enough with little enough power consumption to make it worth it.

Please tell me this is satire.

Hubble's law is only an average law and kicks in at much larger distances; local movements can override it. Hills and mountains don't contradict the fact that overall, the Earth is pretty round.

It's possible, but you need to fool the PS4 into thinking the mp3 stream is actually a regular file on a regular file system on a regular USB stick. The AVM Streaming Stick is the only product I know that does something like that, and all the webpages I find about it are only in German... In short, you are probably going to be better off just using a second device for streaming your music. On a second set of speakers or mixed in with the PS4 audio, whatever works better for you.

It's your SciFi universe, so if you think it is cool, then yes, it can work. In this universe, it's pretty much on the same reality level as the Warp Drive; you're doing pretty much the same thing with a slightly different result. For your antigravity, you need some kind of exotic matter we don't have yet in sufficient quantities. For the ship to move at apparent FTL from the point of view of outside observers, you need to be able to manipulate spacetime in front of the ship quickly enough. Those are the exact same unsolved problems the Alcubierre drive has.

Did you check the second derivative at the Extremum? Looks like you found the point of maximum total dv for your landing strategy (which, as N_las points out, is not optimal in itself).

You should probably show us your calculations. If I'm not horribly mistaken, for minimal landing (and return) dv, you orbit as low as you dare. It's where your total energy is minimal among non-crashing orbits, and also the spot where old Oberth says your dv to energy change conversion rate is optimal.

Oh, right. That variation would be observable. It sounded differently in your first post, like the structure of the entire sky would change due to velocity addition. Still, we would just perceive and describe it as a seasonal change in relative position of the sun and the "mysterious blob of stuff". At least on one hemisphere, the blob would still be visible through most of the year, just sometimes only in the morning or evening.

In order to get the yearly variations you describe, Earth's orbit velocity around the Sun would also need to be close to c.

Formally, yes, scalar fields are densities. Though not always charge or mass/energy densities. What kind of density a field is depends on the interaction with other fields and itself. Here, it's ... just Higgs. (Nitpick protection: "Scalar" is taken to mean "Scalar wrt space/time transformations".) With that broad description, yes. Though probably not a very efficient one. Nothing about the Higgs field makes it particularly well suited for the task. No. First, the Higgs field is complex and only its absolute values matter. So making it negative relative to its current value changes nothing. Secondly, the state it is in now is the ground state*. Any changed configuration would have a higher energy, not the lower energy the various exotic states of matter for stable wormholes and warp drives require. And that's before the machinery required to change the field's value is taken into account.* Hopefully. It may be a metastable state that can decay into an even lower state. If that is the case, the decay event would be a bad day for everyone, so triggering it should be avoided.

Kinetic energy is not conserved here. "Grabbing" something is an inelastic collision and usually transforms kinetic energy into heat. What is conserved, though, are linear and angular momentum, and the effects of that are exactly what orcman describes.

It has to be pointed out that the 'particles popping in and out of existence' picture is about as suitable for reasoning about quantum vacuum effects as the 'series of tubes' picture is for the Internet. With that in mind: They are most certainly not aligned with any large object that just happens to be near on astronomical scales. The QED vacuum is Lorentz invariant. Any hypothetical device using the QED vacuum as propulsion "medium" will have to have a trust/power ratio that is independent of the current velocity.A bit more detail on the virtual particles: The virtual particles always pop in in groups, the most frequent one being electron, positron and photon. Total momentum of the group is always zero, as is total energy (1). That is true wherever they appear and from whatever frame of reference you measure their effects. The momenta of the individual particles that contribute to your process depend on your process: the higher your general energy scale, the higher the momenta of the virtual particles you have to take into account. In this case, the energy scales are really, really low; the virtual particles will still mostly have relativistic momentum, though (2). Note that I carefully avoid discussing speed/velocity. That is a property virtual particles simply do not have in any meaningful way. Very naively put, they are simply not around long enough to get two position measurements done that differ by more than the inherent quantum uncertainty of the measurements. 1: That is, of course, classically impossible. That is the reason why they have to vanish again before the universe notices something is amiss. 2: If you are violating classical laws to spirit an electron into existence, you may as well ask for a little more and get an electron with a lot of momentum.

True. And of course, they're also absorbed a tiny bit by air itself. However, there is very little air and water in there and quite a lot of metal, and the air just has to let things through, the metal needs to reflect the waves. I should have said that the direct heating was negligible.

That doesn't work for a couple of reasons. Microwaves do not heat the air, they heat the metal of the cavities. That then would need to heat the air, which happens with a delayed response. Then the heated air does not escape immediately, it only escapes at a speed proportional to the pressure differential, which only slowly builds up as the temperature rises. And from what I read, the cavities of the Cannae thing are quite tightly sealed up, any holes would be tiny. So there would be a delayed response, too. Also, if thermal expansion produces thrust somehow here, there should be an opposite thrust while the device cools down. Maybe too small to measure, it does not need to be symmetrical. And the thrust should vanish once everything is heated up to equilibrium. I can't say whether they left the devices on for long enough to rule that out, though.

Well, that is a basic assumption you have to make in order to define what it means to be expanding faster than light. If you drop that, you also lose cosmological time as a good universal coordinate time. And if you allow arbitrary foliations into spacelike submanifolds, you can measure FTL "expansions" in Minkowski space. That said, if you just assume uniform expansion and homogeneity for the observable part of the universe and a bit beyond, some bits of objects on our past light cone are bound to be now moving away faster than light for a pragmatic definition thereof. The CMB origin, for instance. Something quite drastic would need to happen out there to change that.

It is a good control for a limited but important set of possible false positive effects, things the Chinese team completely failed to address. For example, what if the wave guide used to feed the power to the resonator causes the thrust once it is powered on, or the electronic components also mounted on the rotating frame? The resistor test mostly excludes that possibility. Any measured effect comes from the cavities. And yes, the immediate response pretty much rules out thermally induced air currents. My personal shortlist of ordinary explanations: 1. Interactions with the Earth's magnetic field. Essentially, if you have a metal plate and put some AC through it and a magnetic field is present, the field is going to "deflect" the current and cause eddies. Those will have a unidirectional magnetic moment (the magnetic field breaks time reversal symmetry, that's why this is allowed to happen), which then interacts with the magnetic field again and cause a torque. 2. Near field effects. Less likely because cavities even made out of paper-thin copper are quite good at completely containing GHz waves, and near field effects would require some radiation to escape. They'd need to tunnel through leaky seams or escape via... 3. Vibrations. A very long shot, but there will be oscillating stress on the cavity walls. They are in the GHz range initially which would be strongly damped, but apparently GHz sound is something that exists and has been researched.

The universe is still expanding, and it has no border. So yes, this is still happening, you just have to start out with larger base distances than you had to back in the early days, err, attoseconds.

I think you're not doing your frame transformations properly. Let's look at it, replacing the baseball with a star. All quantities are to be interpreted as measured far away from the star where you can assume space is sufficiently flat and vector transport around the star is possible. Three objects pass the star with identical initial travel direction and projected distance to the star: A) a spaceship at the speed of .99c a spaceship at the speed of .9999c C) a photon Now, of course, the following is true: A will receive a bigger direction change than B and B will receive a bigger direction change than C. However, both spaceships are sufficiently fast that the difference is negligible. In regular situations (weak gravity fields guarantee that), trajectories depend smoothly on the initial 3-velocity, after all. If the photon is going to be deflected by 1 degree, A is not going to be deflected by 2 or 3 degrees, rather maybe 1.02 a most. In the reference frame of the star, the 3-velocity change is going to be similar in all cases, and certainly, the deflection the photon receives is a lower bound for the spaceships. Math time. Notation: lower case letters are scalar values, upper case letters are vectors, 3 or 4 components by context. c = 1. In case there is a stray u, I mean v. Let's say before the encounter, the 3-velocity of a spaceship in the star's rest frame is is V = (v, 0, 0) and after the encounter, it's V' = (sqrt(v2 - ε2), ε, 0). They have the same length, so the same ɣ-value of ɣ = 1/sqrt(1-v2). ε is small compared to v, but has a lower bound. Those 3-velocities correspond to the 4-velocities U = (1, v, 0, 0)ɣ and U' = (1, sqrt(v2 - ε2), ε, 0)ɣ, still in the star's reference frame. The Lorentz transformation matrix from the star's rest frame to the rest frame of the spaceship before the encounter is (Sorry, can't write this better on the forum) ɣ , -ɣv, 0, 0 -ɣv, ɣ , 0, 0 0 , 0 , 1, 0 0 , 0 , 0, 1 Easy to check by pushing U through it and getting out (1,0,0,0). What does it do to U'? It gets transformed to ( ɣ2(1-v sqrt(v2 - ε2) ), ɣ2(-v + v sqrt(v2 - ε2) ), ɣε, 0 ) and if you apply the small epsilon approximation to turn sqrt(v2 - ε2) to v - ε2/2v, this simplifies to U'' = ( 1 + ɣ2ε2/2, -ɣ2 ε2/2v, ɣε, 0) What we have calculated here is an approximation of the 4-velocity of a spaceship that was initially at rest, but then is passed by a star moving by at relativistic speed -v at some predefined distance. And clearly, the change from (1,0,0,0) grows with ɣ, which grows with the energy you put into the moving object. The term dominating under normal conditions is the ɣε jerk in y-direction. If you check where the values come from, ε is proportional to the star's rest mass, so ɣε is proportional to the star's total energy measured from the initial rest frame of the spaceship. Heck, you're not even just receiving a jerk towards the passing object of magnitude ɣε. At high (very, very high) enough ɣ values, the star starts to significantly pull you along with it. ... Huh. At about ɣ > 2/ε2, the spaceship is even going faster than the star after the encounter. I did not expect that. Yeah, it's essentially just a gravity slingshot, but I would not have thought it was possible to transform an infinitesimally small deflection into one. The OP is of course right, this IS weird And entirely possible I screwed up at some point.