K^2

I don't think there's a problem having a microscope camera, a basic experiment camera, and an exterman camera. These things are small, light, and only need to take up power when taking picture, which isn't much even then. You have a point on moving optics. But I think we might be able to use a head from an optical drive for it. The lens in it has enough travel for our needs. If it gets stuck, we will simply be limited to a fixed focal plane, which is hardly worse than starting with fixed optics to begin with. It's worth experimenting with, at least. Edit: Just to clarify. Ideally, you want multiple moving lenses, so that optics still properly compensates for aberrations. But if you just need tiny adjustments, you can get away with a single moving lens in the middle of the assembly without loss of quality.

I can't think of any. Unity would be my recommendation as well. Primarily, because it's very scalable and is heavily used in industry. Whether you'll decide to do something else later as a hobby, or if you'll want to make a career out of it, Unity experience is going to be very valuable. No reason to waste time with anything else for a project like that. Oh, and Unity is very portable. Whether you end up making a 2D or 3D game, you can port it to Windows, Linux, OSX, iOS, and Android out of the box.

Main reason to go with more than a simple sensor for the camera is because we want to compress images, and rad-hard CPUs with enough power to do compression will a) eat through a lot of power even when idle, and be very expensive. I would rather have a camera capable of on-board compression as a stand-alone unit. If we can find the funds to upgrade to a rad-hard camera, great. If not, we are risking only to lose the camera. Not the whole mission. That said, the camera doesn't have to be anything fancy. The earlier suggestions about something like Go Pro are total overkill. We can't handle data rates for the quality where we'd need this, and it has a whole bunch of stuff we don't need, including its own battery. I have a tiny robotics camera that does VGA stills and handles JPEG compression on board. I can use that for early testing. We can later get something slightly fancier, so as to get better quality images. Microscope is a separate story. I think our best bet is buying a cheap microscope and cannibalizing its optics for a custom solution. Though, I'm not entirely sure what exactly we are looking, and how we are going to get what we are interested in in the focal plane, without anything else getting in the way. But again, worst case scenario, we won't get microscope data. So long as we are getting clean readings from all of the sensors, we should still be able to estimate biomass growth pretty reliably. I think, key word in almost everything we do is reliability and redundancy.

Treldon, that NOAA link is in the bull's eye. Thank you.

They are. They all give exactly the same result. Always. Like I said, it might be more work in one than the other. But all interpretations will give you the same answer. They make the same predictions, and they will either all pass or all fail any particular experimental test. There is no known way that is practical. We don't know if there is a different, practical way to achieve these. But more importantly, it's theoretically possible. That means, there are no fundamental contradictions with these things happening. If we find a moon made out of cheese, we will be stunned with such a find. But it would not invalidate any of our science. In this thread, we are fundamentally talking about curvature of space-time. FTL only works in curved space-time. Time travel is only knwon to work in curved space-time. Gravity is just a side effect of such curvature. My analogy is entirely fair. You are just trying to restrict the problem to simple flat space-time picture you have some understanding off. Time travel doesn't work in that simple picture. No sh*t. That's why we have to discuss more complicated situations.

They are mathematically identical and are a part of a theory. Another theory can have its own set of interpretations, but it will not have any bearing on these, even if some of the interpetations sound like they are the same thing. If I had to wager on future developments in Field Theory, I'd say that we are going to find that principle of superposition is bogus. It's too specific, and looks too much like linearization. So I'm guessing, and that is a conjecture, that we simply don't see the non-linear behavior at energies we have access to. In that case, the corrected, general field theory will have a distinction between a single history or multiple histories. But that won't prove or disprove MWI. Even if we find that due to decoherence or something else the worlds collapse to single history, it would still allow use of MWI to explain some local phenomena.

I think you are picturing this a bit wrong. If you are in a frame of reference that's severely dilated and your clock slows, do you expect to watch the clock actually run slower? No, you are time-dilated as well. Your internal clock slows as well. All of your thoughts run slower. Your metabolism runs slower, everything. From perspective of your brain, the clock runs at the same rate. It's everything else in the universe that appears to run faster. Edit: Heh, ninja'd. Yeah, you got it.

Working on it, working on it. If you want to help save me some time with it, one of you can try and do some search for data available on Earth's magnetic field. I'd prefer a parameterization, like what is done with gravity, but if all you can find is a high rez map, that's a start.

Technical Ben, you are still arguing on things that you don't understand. This conversation can be way more constructive. We cannot prefer one interpretation over the other. So long as they are interpretations of the same theory. We can, and should, prefer one theory over the other, or they are the same theory. With me so far? You start out with the correct statement, and then BAM go on to make a completely unrelated conclusion which happens to be false. If MWI makes a prediction, Quantum Mechanics makes the same prediction. In some interpretations, it's just more work to demonstrate it. We only use MWI to get to the result faster. The result is the same. Quantum Mechanics and General Relativity are both the most precisely tested theories we have. Nothing comes even close to the amount and precision of testing that was done on these two. General Relativity predicts time travel as a possibility. Quantum Mechanics predicts how conflicts are resolved. If you don't think we can make predictions based on that, you do not understand anything about how science works, or why it is useful. Quantum Mechanics and General Relativity predict time travel and FTL to be possible. There is no theory that predicts otherwise. The way science works is that you'd have to prove that it's impossible in order to overthrow the standing theories. Not the other way around. Makes action to be extreme. Extreme in the mathematical sense. Action does not vary with minor variations in path when it is extreme. Usually, it means that action is maximum or minimum, but that's not a strict requirement. I'd take a glance at Principle of Least Action. In classical Mechanics, least action is the extremum we are looking for. Article talks about that at least briefly. The solution to a rotating black hole is the Kerr Metric. The feature you're looking for is closed timelike curves (CTC). Same article talks about naked singularity case, where there is no event horizon, and you can actually use such a singularity as a time machine by following a CTC trajectory. These solutions are known to be unstable, so they will not exist naturally. Whether stable configurations with CTC exist is still being researched. We do know that stable configurations exist if we assume negative energy densities are possible. Hence the Alcubierre Drive, traversable wormholes, etc. They all have that as a requirement for a stable configuration. Of course, stability of the solution isn't exactly a strict requirement either, if we are looking for something artificially generated. Really? So how much energy is required to keep Earth going in Circles around the Sun? No, for the same reason. You just need space-time that's sufficiently curved to send it the "wrong" way. You got yourself confused somewhere along that way, but I'm not untangling that mess. You should probably avoid anything with the word "symmetry" in it until you learn more about the significance of symmetries in physics. Start with Noether's Theorem. You are confusing GR time, which is a coordinate, with Statistical Mechanics time, which is essentially an evolution parameter. They can both be used for time travel, but for completely different reasons. Seriously, this is messy in physics. We need more terms than just "time". There are three or four completely different, only slightly related concepts we call "time". In relativity, they got it sorted with "map time" and "proper time". We need that for other "times". That's because you need to learn the difference between theory and interpretation, then learn some Quantum Mechanics, and then learn how the interpretations arise.

@Ravenchant. How far along are you in your studies? I can probably use another set of eyes to look over the equations of motion. But I don't want to scare you with graduate level mechanics if you haven't had a classical mechanics course yet. Though, theory isn't critical here, it's mostly just Diff Eqs. If you'd like to take a crack at a few checks, I can write out what you'd need. The moss mission is designed for LEO. The sat's orbit will eventually decay, resulting in total disintegration and sterilization of the experiment during reentry. If we can put together a beyond-LEO mission in the future, that one will almost certainly focus on propulsion and navigation, and there will not be a biological payload.

The universe is 14 billion years old and 90 billion light years across. Good place to remember intermediate value theorem. You are convoluting two different concepts, and you are completely wrong on both of them. First of all, theory does not have to explain how things work. It has to make correct predictions. Quantum Mechanics is a Scientific Theory. It has multiple interpretations which imply different, but indistinguishable sets of fundamental reality. The goal of scientific theory is not to probe that reality, but merely predict what our measurements are going to be. And all interpretations make identical predictions. Again, this is not uncommon in science. Quantum Mechanics is just the most blatant example. Second issue is causality. Just because you can't imagine a world without causality, doesn't mean the real world has to follow your rules. Causality is routinely violated on micro-scale, and there is absolutely no reason to suppose that it has any fundamental properties on large scales. We just happen to live in a fairly flat part of space where things are pretty casual on scales we observe. That's all. You are simply projecting your expectations on the rest of the world, and the rest of the world doesn't work that way. Light does not follow the shortest path. You are stuck on high school explanation of refraction. It has very little to do with actual physics of light or relativity. Light takes path that exteimizes its action. So does anything else. For light, the action is proportional to the proper distance traveled. And that works out to be the local maximum in relativity, which happens to be zero for light, or anything else that is light-like. The "instant" you are talking about is proper time. In flat space-time, proper time of FTL trajectory would, indeed, be negative. But we are not dealing with a flat space-time. There is a metric involved, and that metric is the reason why ship's own world line remains entirely time-like. In other words, it keeps accumulating positive proper time. Again, you are arguing out of ignorance alone, and it would be more constructive if you asked questions about things you don't understand, rather than assert things that aren't true and keep trying to prove them. False analogies. Traveling backwards in time is nothing like changing directions. The conjugate quantity to time is energy, not momentum. Again, ignorance. The whole point of superposition principle is that things cannot self-interact. Detecting something from another world would prove both MWI and QM wrong.

Somebody should actually compute the thickness of the tank walls in that original proposal, just for giggles. You can have all the ISP you want, but it won't do you any good if your mass ratio is practically unity.

Aether did not fit with many experiments. Michelson-Morley was specifically designed to disprove aether. The Geocentric model is a fair comparison, though. Here you are making a mistake. It's not that we don't have information. We fundamentally cannot have that information. The interpretations are indistinguishable. Just like Geocentric view isn't wrong. There is absolutely no way you can say that "X is center of the universe." But having Earth go around the Sun rather than the other way around does make the math easier. Heliocentric model is simpler and more elegant. It is no more or less wrong than Geocentric model. They are equivalent. The only way MWI will ever be proven wrong is if entire QM is wrong. If you trust predictions of Quantum Mechanics, you trust that MWI is an adequate description of the universe. And if you start arguing for distinction between "There are multiple worlds" and "Universe behaves in every way as if there are multiple worlds, but there aren't," you should be having that discussion with theologists and philosophers, not scientists. The most important aspect of this is that Quantum Field Theory can look after time travel paradoxes in any interpretation. MWI just makes it easiest to visualize what is happening. It's easy to understand something showing up from alternative future and preventing that alternative future from happening than it is to work out how it even took place in other interpretations. If you'd like to get a feel for what it's like, try to work through the logic of Delayed Choice Quantum Eraser under Copenhagen. It works, but it's almost impossible to understand. In MWI, it is a trivial effect. So is Quantum Teleportation. Whether you like the idea of many-worlds from philosophical perspective or not, MWI is a valuable tool, and it makes valid predictions. So if MWI is fine with time travel, real world is fine with time travel. Total nonsense. Again, you are trying to look at it as a philosophical question. Next, you'll be telling me that Achilles cannot catch up with a turtle. And we have observed FTL to be possible, because we have observed Universe expanding faster than light. Just like General Relativity predicts it should. Because GR states that light limit is purely local and does not apply globally. Which means you can travel faster than light with respect to a remote object, such as the place you are going to. And we see it actually happening, and it is what Alcubierre Drive does as well. I'm sure it's fun to make blanket statements like that in other places, but until you can read and understand at least the Alcuberre's original paper, you really shouldn't be talking such nonsense on a science forum. It makes you look foolish.

I can set up some software for people to use that's literally just requiring an amateur radio station tuned to correct frequency and hooked up to an audio jack on PC. Data rate won't be great, but I'm sure we'll find enough volunteers that would be able to receive position updates and some other data from the sat on regular basis. Visual tracking would be helpful as well, even if merely to confirm that it passed terminator when we predicted it should, which can be done by anyone with a telescope or a good set of binoculars.

It's called entropy. The number of future states is nearly infinitely higher than the number of past states. That means that there is that much more branching into the future than into the past. This is basically the reason memory works in the first place, and why you can remember yesterday, but not tomorrow. There should be some branching into the past, but it is by definition indistinguishable from random loss of information. For the record, if you think you disproved MWI, you would have also disproved Quantum Mechanics in general, because all interpretations are mathematically identical. If there is something wrong with MWI, there is something wrong with Copenhagen Interpretation, and any other interpretation you can come up with. It would mean that QM is fundamentally wrong. Feeling lucky? N_las has actually proven that it does work this way. I can confirm that with the exception of initial mistake with rocket's direction, his proof is correct. Your argument is, "No, I still don't think that's how it works." Since you don't seem to be capable of producing an actual proof, what exactly are your qualifications to say that it's wrong? Mine are graduate work in Relativistic Quantum Mechanics.

Yeah. It's basically the modern equivalent of a philosopher's stone. Perhaps destined for the same fate. But I'm sure we'll at least stumble on something else that is no less useful along the way.

You have my seal of approval on that, for what it's worth. 2D diagrams are entirely legitimate for working out almost everything in Special Relativity*, and great deal of General Relativity. Even gravity can be demonstrated to arise in a 1D + time world. And warp drives, other than the actual warp bubble, can be entirely worked out in SR. * There are SR topics, like acceleration and scattering, that require at least two spacial dimensions.

Sure there is. It's called a centrifuge. The whole thing is industrial quality bull****, though. From the whole video, the only factually correct statements were about Faraday, Maxwell, and the twist terms in Einstein Field Equations. The later, however, are not actually responsible for spin, despite sharing some qualities. And even that, essentially, is due to the fact that both spin and twist terms arise from non-Abelian gauge theory. While electrodynamics and gravity are due to Abelian gauges. Long story short, saying that twist terms are responsible for spin because they share qualities is just as misguided as saying that electromagnetism is the cause of gravity, because the two are similar. Though, there are certain individuals who don't seem to know better. *cough* Anyhow, the "secret" to manipulating gravity is the same as that for manipulating electromagnetic fields. And that's neutral currents. The reason electric motors work is because we can push a lot of current through a neutral wire. If you can give me a (nearly) massless wire that can carry through it a few billion tons of mass per second, I can build you a gravity generator out of a motorcycle engine. Unfortunately, this comes down to needing exotic matter with negative mass, which is the same requirement as warp drives and stable wormholes. There are some hints of these things being possible, and hopefully, we'll get there eventually, but revelation for something like that won't come from a cheap YouTube video that wasn't even dubbed properly.

The diagrams look like it's been fixed, but original example had time shifts backwards. If you are flying towards an event, it appears to have happened earlier. So both rockets need to be departing away from Earth. It still causes a "paradox", but honestly, time travel isn't an issue with real physics. The fact that you prevent event's cause using a CTC resolves itself trivially in field theory. Like many things in QM, it's easiest to understand from MWI perspective. All you did was create another branch in the many worlds. One that is, admittedly, a bit odd for anyone involved. But there are no fundamental contradictions in logic anywhere.

Possibly, but that's kind of irrelevant. Can't heat at more than 100% efficiency. We either have enough power, or we don't. Dedicated heaters won't make a difference.

You can't really use warp drive to time-travel directly. You essentially need two objects traveling at FTL times to actually close the loop, and they have to communicate under conditions under which two Alcubierre ships can't. So you need something else going on. Or you can use a region of space-time that's warped to begin with to complete a CTC. Bottom line is, FTL of any kind violates causality, but it doesn't automatically mean a practical time machine. Not that a real time machine would cause any serious problems to underlying physics.

Virial Theorem. Learn it. Understand it. Use it. When applied to circular orbit, it says that you need to double your kinetic energy to escape. Moon's average orbital velocity is just over 1km/s. That means the escape velocity will be just over 1,400m/s. No need to remember a bunch of formulas and constants. If you know one, you know the other. And since sqrt(2) is very close to 1.4, you can do the math in your head.

You can always use magnetotorquers for heat in the worst case. It's just as efficient as any other electric heater.

Lets start with the fact that entropy is a conserved quantity. It's a trivial proof in QM, but a more general proof exists that covers classical mechanics as well. (It is based on Liouville's Theorem, if anybody cares for the math.) What increases is the coarse-grained entropy, which is far more important for how we perceive time, so the heat death is still a heat death, even if fine-grained entropy is conserved. Anyways, these are just things to keep in mind when talking about 2nd law. The answer to OP's question is actually much simpler. The entropy density goes to zero as volume of the universe tends to infinity. The total (coarse-grained) entropy over all of space still increases.

I don't know why I bother. "Causality" is stuck in everyone's head like it's a universal absolute of some sort. For the second time in this thread alone. It's a local feature. Global causality is completely optional.