-Velocity-

Since they claim they are exchanging momentum via gravitational interactions, it's not FTL. Theoretically, gravity is carried by gravitons, which have zero rest mass, so they travel at c. So the speed of gravity is the same as the speed of light and the speed of the strong force and the maximum speed at which two spatially separated things can effect each other - c. The weak force is carried by particles that do have (quite high) rest masses, and so it cannot travel at c, but I don't know what its actual propagation velocity would be. Because the weak force is so short-ranged though, who really cares, I guess.

You simply cannot know this as it requires knowing all the extremophiles of Earth, all their characteristics, and all environments available on extraterrestrial bodies. Underground niches on Mars may very well exist. And they don't have to be exactly the same as those on Earth, there are a lot of environmental factors that are irrelevant to an organism, and even within those environmental factors that DO matter, there is of course an acceptable range. Given the huge number of environments on Earth, if there is a place on Mars that has the proper chemicals, energy source, and reasonably fresh water, then there's a reasonable probability that there is at least one organism on Earth that could live there. We need to get to one of those recurring slope lineae and find out for certain whether they are water, and if so, find out if there is anything already living in it, and measure the pH, salinity, etc. THEN we'd have a better idea.

It's very unlikely for any Earth organism to survive an impact on Europa. It's a long trip in a harsh environment, and the surface is harsh too, with very strong radiation. Europa has no atmosphere to cushion an impacting rock- they just smash into the surface at full velocity. Jupiter's high gravity also makes things even more difficult, because an incoming space rock is accelerated to even higher velocities. No extremophile can survive being vaporized on impact.

This popped up today- http://www.gizmag.com/space-elevator-lunar-lift-liftport/35119/ Interesting, they think can apparently just use Kevlar for the lunar elevator ribbon. Now, this group is almost certain to fail, but what if some space-faring nation or someone like SpaceX decided to try to tackle it? You would completely eliminate the need for the actual lander spacecraft. Once the space elevator is in place, it's just a fully resusable, solar powered structure. A major problem with transporting people though would be that it takes a very long time to travel up and down the tether- it still takes like a whole month even if your cable car moves at the speed of a bullet train. A crazy idea- what if instead of a single cable, you actually had like a conveyor belt? So the car does not actually move on the belt, the belt itself is moved- you wheel it up by turning one way, and wheel it down by turning the other. You could reduce the trip to like a week if you could get up to like 1500 km/h. For high speed transport, I think that this conveyor approach would be superior, because you can remove the power source and climbing gear (which would have to be pretty beefy for high-speed operation!) from the car itself, and put it on the surface. Also, you could probably reduce cable wear. You'd probably need a more complicated and heavy counterweight station design though.

Even if Pallas completely misses Earth, it's still probably an extinction event. Pallas is not small, and the tidal buldges it raises as it passes Earth may by itself be enough to cause massive earthquakes and volcanic eruptions. I read once that a near miss by Mars would turn Earth's surface entirely molten from the deposited tidal energy, but I don't know if that scales down to Pallas too. Still, it would NOT BE GOOD. Secondly, it may change Earth's orbit enough to significantly alter the climate. Finally, a near miss does not erase the possibility of a future impact. In the "best" case for negating the possibility of a future impact, where Earth ejects Pallas from the solar system entirely, could mean that Earth deposits so much of its orbital energy into Pallas that our perihelion is too close to the Sun for Earth to remain habitable. Even as it currently stands, Earth is supposedly just inside the inner edge of Sol's habitable zone. If we got just a bit closer, the planet will supposedly go into runaway greenhouse mode, like Venus.

As I noted before, space elevators are much easier to build on other bodies in the solar system than on Earth. So they might end up being very useful- for getting things into space from a lunar mining operation, or putting things into orbit from the surface of Mars. Both the Moon and Mars, our top colonization targets, are favorable for building space elevators. Mars has low gravity plus a high rate of spin, which makes it easy to achieve the necessary centrifugal force on the tether required to overwhelm gravity and maintain tension. The Moon, on the other hand, spins much more slowly but has such weak gravity that a space elevator is possible there too. Mars has the problem though of having a moon (Phobos) that crosses below geostationary orbital altitude, so we'd have to deal with that somehow- possibly by just putting the base of the Martian elevator on rails on a track a few dozen kilometers long, so that it could just dodge Phobos when a collision would otherwise result. At least, that would be my first proposal.

Yes, but it would be a weak charge. Most objects WILL in fact have some net weak positive or negative charge, simply because it's easy to knock electrons off or accept them, so it's highly unlikely for an object to be in a perfect balance. However, the charge will always be weak. Positive and negative charges are in equal number in this cosmos, and this balance of charge is also conserved in all interactions that I'm aware of. So it's really hard to make things keep any kind of significant charge separation over time- opposite charges will be attracted, additional like charges will be repelled, and the object will go towards charge neutrality. Though electromagnetism is many, many, many, orders of magnitude stronger than gravity, because there are equal numbers of positive and negative charges in the cosmos and those charges neutralize each other, electromagnetism has little effect on large scale structures. Gravity rules there, because there are no negative gravitational "charges", and like gravitational "charges" attract. However, because electrons are so mobile, they like to flow. When charges move, they and the electric fields they produce get length-contracted by Lorentz transformations. This gives rise to magnetic fields, which, while magnetic fields appear to be something different from electric fields, in reality, magnetic fields are just electric fields disguised by relativistic effects. All of Maxwell's equations for describing electromagnetics can be derived from just Coulomb's law and Relativity. Anyway, I mention this because magnetic fields can have strong astrophysical effects- not nearly as strong as gravity though- and magnetic fields are, in a relativistic sense, nothing but electric fields.

Well, just because the star can live for 100 billion, a trillion years does not mean the planet can. Earth is supposedly only two billion years away from the end of plate tectonics, even if were to somehow retain its oceans for the next two billion years. This is because the planet is cooling, and radioactive decay in the core- which helps to maintain the planet's heat- is dropping. Heck, the planet used to support natural fission reactors when uranium got concentrated enough by natural processes in one area. All that is done with. With plate tectonics ending, supposedly that does really bad things to the carbon cycle, because crust, and the carbon it contains, no longer gets subducted back into the mantle. It could also cause the remaining heat to build up under the crust until it busts through in devastating episodes of volcanic eruptions, like Venus appears to undergo. The brightening Sun is supposed to do in Earth's biosphere before plate tectonics shuts down, and the loss of water may make plate tectonics shut down before the 2 billion year mark is reached. Another problem with planets that maintain life for very long periods is atmospheric- the atmosphere is slowly being lost to space. Water in particular is lost when it undergoes photolysis and the hydrogen escapes. But we're slowly losing the heavier atoms and molecules too. Oh and as your planet cools, you'll lose your magnetic field. Personally, I don't believe that red dwarf planets are good candidates for hosting habitable worlds. You have the extreme stellar flares problem and the problem of tidal locking. The long life of red dwarf stars is not a benefit for habitable worlds, as habitability has its own, independent timescale. However, of course, if red dwarf stars CAN host habitable worlds, even at a reduced rate from orange and yellow dwarfs, the large number of red dwarf stars may make red dwarf habitable worlds relatively common, even if they are not that ideal. That said, potentially, a geo-engineered red dwarf planet could maintain habitability for a VERY long time, if the effects tidal locking were not too severe. Come to think of it, it's pretty much guaranteed that red dwarf planets/systems will be the last places in the universe where life continues to exist, in the very distant future where almost all star-forming hydrogen is used up in all galaxies, as long as there isn't a Big Rip (or vacuum instability event).

It's really hard to know how far we can take our current computer technology. We keep running into "barriers" that we find ways around. I am doing my dissertation on silicon MEMS and working on some carbon nanotube field emission stuff on the "side", so I have some background knowledge- but the field is so huge and I don't work on silicon transistors. But I have heard of some new radical ideas that are currently being explored to help keep extending Moore's law even further. However, eventually, given the fact (unless you believe in souls, which if you do, that's fine, I won't argue) that we have seven billion working examples of intelligent sapient minds, I just find it almost inevitable that we will discover a way to synthetically create one. The first machine intelligence will not be small, but we should be able to eventually make it so. What IS less certain clear to me is whether or not we can make one that can survive a 1000+ year journey. But maybe we can make one that can last long enough AND still be smart enough to do the job of a seed ship MI. Yes, that's what my beliefs are, and as I said, I actually study and work in the field of MEMS. There's a lot of folks that still believe that MEMS will scale something like transistors do with Moore's law as time goes on. But that's simply not the case. Solely mechanical devices simply no longer work when you get to the nano and sometimes even micro scales. For example, stuff likes to stick to each other due to van der Waals forces and the Casimir effect. Moving parts don't work nearly so well as they do on the macro scale. You might find that you drop your iPhone and when you pick it back up, it no longer is able to recognize which side is up. You've pulled the MEMS accelerometer into contact with its mechanical stop, but with enough force that so much of it made contact with the mechanical stop that the van der Waals forces pulled it into permanent contact. Stuff like gears- FORGET about it. Spinning parts- forget about that too. MEMS gyroscopes are made by making a mass oscillate back and forth on springs and measuring lateral displacements. (I saw some research on electrostatically levitating a mass and spinning it to make a gyro, but I think the effort was ultimately met with failure.) And it only gets worse the smaller you go, as many of the machines we use on the macro scale utilize physical relations that scale with volume (radius^3), while there are limits to performance or opposing forces we can ignore up at the macroscopic that become dominant in the microscopic because they scale with surface area (radius^2) or just radius. ANYWAY, to make a long story short, yes, nanotech will almost certainly be largely chemical in nature. The "classic" nanomachine- picture the ludicrous image of a propeller-driven, multi-armed, metallic-looking robotic submarine drilling away at arterial plaque while a red blood cell looms large in the background- is a fantasy. Real nanomachines will resemble life forms, or even BE life forms. In fact, as I've said before on these forums, I believe that life and the living cell itself is naturally emergent nanotechnology. We are nothing but a vast colony of nanomachines working together. Yes, but I still feel it's far more likely that we'll master an intelligence smart enough and long-lasting enough to pilot a seed ship than we'll ever build generation ships. And the level of machine intelligence needed for a seed ship may not be much higher than what we've already got today- of course, our current computers are not anywhere as radiation hardened and reliable enough yet though.

That may in fact be the case. It's hard enough to know where technology is heading, but at least it has to follow the laws of physics, and we probably already know all the laws we can practically make use of. Predicting how society will evolve is MUCH harder, especially because it is reactive to the technologies that may or may not be innovated. And predicting today how society will evolve when/if non-humans join it is pretty much impossible. Who knows. It may be that "we" lose the drive to establish colonies around other stars. I doubt we will lose the motivation to explore however, that is probably inherent in any intelligent being; curiosity is a necessary trait for survival, and all reasonably intelligent animal species have it to some degree. But establish colonies? I'd argue that we're already seeing a push against the drive to expand; people want large tracts of land left as preserves, we punish countries that try to expand their boundaries by force or subterfuge. It's hard to imagine that we will never want to expand to another star system, but what if there are lifeforms already there? By what right do we have to move in and massacre an alien biology and replace it with our own? 100 years ago, that would have been morally acceptable, but today, not so much. We've come to recognize that the oppression or destruction of the weak by the strong, while practiced by nature, is a social evil. Just because nature favors it doesn't make it right; nature is neither right nor wrong it just is, and trying to draw moral lessons from it is foolish. A lot of people will argue that humans are still just humans and don't change, but that's NOT the case when the influence of society is factored in- we're different than we were thousands or even hundreds of years ago because we grow up in a society that favors different moral values, and are "shaped" differently by it. And again, society may include non-humans in the not-that-distant future. So who knows. Maybe, we'll settle the solar system, and come to feel that that is enough. I doubt it, because there should be systems where life cannot evolve but that we could still settle. But, even if we do still want to establish extrasolar colonies, not only does the technology have to get to the point where it's possible, the desire to establish colonies has to exceed the cost of doing so. We probably could have gone to Mars decades ago, but the public's desire to do so never exceeded the cost of going there. And going back to your original point, yes, you might wonder why bring humans at all? Maybe you settle humans and other Earth lifeforms on an extrasolar planet simply because humans want to settle another world. That's reason enough, and no better or worse than any other reason. All drives and desires are ultimately arbitrary.

Tell will tell of course, but I think that sitting here today, in the midst of a continuing revolution in computer technology, in the midst of us seeing AI get ever stronger and stronger, you cannot reasonably believe that it is unlikely for us to ever achieve a truly intelligent machine. The march of technology is clear, and there is no known physics that prevents us. It's like observing the post-war tests of V2 missiles captured from Germany and believing that we'll never walk on the Moon- only worse, because every one of the seven billion human brains on this planet proves that synthetic, practical, truly intelligent thinking machines CAN exist. It's not like nuclear fusion, where we haven't observed a net power gain outside of the cores of stars or thermonuclear devices. A more reasonable question is whether creating such a machine is possible and practical with silicon microfabrication technology or its derivatives. If not, they would likely take a much longer time to be realized, or at least, miniaturized. So while I don't feel that truly intelligent machines are certain to be developed, I just feel that given what we know, it is unreasonable to believe that they are unlikely to be developed, at least eventually. But as we're trying to predict the future here in this thread, we should consider the ALL technologies that are most likely to be developed, not just one. You should NOT try to predict the future by only projecting forward progress in one field of technology, which is what the "generation ship" assumes- mostly it represents only progress in space utilization, really. Instead, when you look at the total SUM of technologies that are most likely to be developed, the idea of generation ships becomes silly and obsolete, because the VASTLY more efficient "seed ship" becomes possible with advanced machine intelligence and genetics/biology. In fact, the seed ship not only becomes possible it appears to become somewhat practical too, assuming we spread out into space and utilize the vast resources out there in the asteroids.

By the time we actually get to the point where we can spare the resources for a nuclear pulse propelled spacecraft to the stars- IF we ever reach that point- the idea of the generation ship is going to seem cute, quaint, and naive. We still have tremendous strides to make in biology and genetics, but our space technology is (comparatively) mature and advancing MUCH more slowly. I honestly see a near zero possibility that generation ships will ever take flight, unless its as a giant space colony that becomes self-sufficient enough to leave, and WANTS to leave. By the time we have the ability to build a generation ship, our advances in biology and genetics will make the whole idea obsolete. The seed of life can be spread via frozen embryos, artificial synthesis of biological components at the destination, etc- there's no need to transport actual living organisms. That would be massively inefficient, and so no one will do it. Why send one giant colony ship to colonize a single system, when for the same resource expenditure, you can send 50 seed ships to settle 50 different systems? As far as the armor goes against dust- how much armor do you REALLY need if you're "just" going 0.01 c or less? If you're going that slow, the armor you need is significantly reduced. A dust grain 10 microns in diameter "only" packs like 10 J of energy. That's not all that much. A composite armor might be the way to go. You sandwich thin, dense barriers with thicker, lightweight ones. First, the dust hits a thin, dense barrier. It breaks up, and starts spreading out into the lightweight, thick material. Then the fragments- slowing down, less concentrated- strike the next thin, dense layer. And so on. Pretty soon the projectile fragments are spread out enough, and slow enough, to not penetrate the next thin dense layer.

You start running into fundamental physical limits. Like you simply cannot form an image with any decent resolution if the camera's lens is too small. Wheels would be a VERY BAD idea. They do not grip and cannot cross the kinds of obstacles that are extremely common in the mesosacles and microscales. Use legs; model your robot off an insect. It might even be easier to just use a real insect itself, and piggy-back onto it. BTW, they are able to remotely control the insect, you can give it like electrical pulses or something similar to steer or prompt it to go in certain directions. I didn't read the caption for the above image, but if I had to guess, they are steering the insect by stimulating its antennae or the stumps where its antennae used to be.

Yea... according to Wikipedia, Orion supposedly tops out at a theoretical maximum Isp of 1e5 s. Say your spacecraft carried 10X its final mass in fuel. That's only a delta-V of 1e5*9.81*ln(10) = 2.3e6 m/s. Your top speed is half that (since you'd like to stop and orbit Alpha Centauri), or 1.13e6 m/s (1130 km/s, 0.0038 c). Your spacecraft takes over 1100 years to reach Alpha Centauri. Orion is great for puttering around in the solar system, but it's not going to get you to the stars. But... assuming we spread out into the solar system and invent intelligent machines, I still say that the stars appear to be within reach. 1100 years may not be such a formidable obstacle eventually, not to an intelligent, self-repairing machine. And the resources to build these kinds of things may be easy to come by, if we are eventually mining the asteroids and building stuff in giant space-based factories. So as I said before, given the continued survival of civilization- a BIG assumption given all the many things that could destabilize us- I think that "we" WILL eventually go to the stars, because we already know of propulsive methods that should work within timescales that seem acceptable to the type of intelligent machines that seem inevitable to me. Humans, of an alternate form- uploaded minds- could even make the trip themselves, if we ever were to master that tech or something like it. Since they would not make the trip in physical form, you could even slow down the processing of their virtual brains so that the whole trip only seemed to take a few days. A sort of virtual time dilation (or time compression ). Maybe they could even have the option of teleoperating a physical robotic body in real time in case they wanted/needed to perform some physical activity on the ship themselves. Anyway, that's the only way I can see of "humans" really ever making an interstellar trip within their "lifetime".

The expansion "force" is not increasing over time, the expansion rate is accelerating. (Not quite sure if "force" is the right word here, since we're talking about the expansion of space rather than movement through space.) A constant expansion force- the classic, fixed "cosmological constant"- would lead to an acceleration in the expansion rate too. Last I checked, our observations are as yet not precise enough to know whether the cosmological constant is truly constant, or is time-varying.

A little pessimistic, at least the idea that "humans" will forever be locked in the solar system. Though forever is a long time, and not matter what happens, it won't be long before we are not what we would call humans anymore. Most people today have very limited imaginations when they think of people of the future- they only think of humans. Historically that would be right, but there are several expanding transformative and largely untapped technologies that could lead to the citizens of Earth being very much non-human in the not-so-distant future. So perhaps in a sense you could be right. And on a longer time scale, millions of years, current "humans" are certain to cease to exist, even without technological intervention. We'll evolve into something else. Anyway, I'm not terribly concerned about humans not being able to make the trip. That's a specieist viewpoint (discrimination based on species). Why is not enough to be able to send a being that represents our values and culture? Why should we care so much if this being is human or not? If a "non-human" mind respects morality and represents and appreciates our values, under what basis is it logical to discriminate against it? Such discrimination would be just as vile and unjustifiable as antisemitism or white supremacy. If it thinks like us and represents our values, then it IS one of us. There is no known reason such a thing cannot be realized in a machine intelligence , and such an intelligence may be able to make the trip, AND even grow humans (or whatever you want to call our descendants) when it arrives. Oh and finally, given a long enough time span, the stars will come to us.. or at least, a bit closer. If our civilization is truly worthy of settling extrasolar systems, then it should be capable of surviving in our solar system for the requisite millions of years necessary for a close stellar encounter. According to this paper abstract, a star comes within a parsec about once every 430,000 years. So, scaling that probability by the inverse of the space volume, maybe once every 15 million years a star comes within 1 light-year and every 430 million years a star comes within 0.326 light-years. And well... why does fusion pulse look like a dead-end for like 0.1c travel? What is a realistic Isp for it? And that black hole starship idea actually seemed like it might be remotely possible. A mini black hole is able to convert mass into Hawking radiation at a very high efficiency, and if you can keep it fed faster than it decays, AND if you can really practically form one with focused gamma rays, then that seems like it could be a real breakthrough in interstellar travel. It's a long-shot, but at least it may be within the laws of physics and possibly practical, unlike warp drives.

Not realistic at all, considering that IRL they do not exist, and almost certainly cannot exist because they can be used to violate causality, are quite possibly instantly destroyed by Hawking radiation when they exceed c, and would require truly vast amounts of non-existent exotic matter compressed to extremely high negative densities to even construct in the first place.

So maybe you want to build a generation ship. And you're somehow still getting away with 1000 ton spacecraft. You're OK with getting to Alpha Centauri in 500 years time. That will require a top speed of like 2.6e6 m/s, so you'll need a total of 5.2e6 m/s of delta-V. Now your spacecraft's initial mass is "only" 1.5x10^51 kg. You'll need the combined mass of mass of like 400 million Milky Way galaxies to propel your spacecraft. No big deal, right?

No, the specific impulse, from what I've read, is only 5000s. Use the rocket equation- vf = ve*ln(mi/mf) (vf = final velocity, ve = exhaust velocity, mi = initial mass, mf = final mass) ve = 5000*9.81 = ~50000 m/s Say you can put humans to sleep in cryo chambers, so you can get away with "only" a 1000 ton spacecraft payload. You'll want vf of at least like 6e7 m/s so you can accelerate to 10% the speed of light (3e7 m/s) on the way out, and then slow back down at your destination. This is a one-way trip. So, 6e7 m/s = 5e4 m/s *ln(mi/1e6 kg) exp(6e7/5e4) = mi/1e6 kg exp(6e7/5e4)*1e6 = mi mi = 1.4e527 kg.... 1.4x10^527... To put that in perspective, that's over 10^474 times MORE than the mass of the observable universe... which really fails to put it in perspective, honesty. To deliver a 1000 ton spacecraft to Alpha Centauri within a reasonable time span, your spacecraft's initial mass would have to be 140 thousand million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million, million kg. It's a number so large that the human mind cannot truly comprehend it.

The aliens are not stupid. A microscopic examination of the probe would show lacks the complexity to contain an intelligent mind, and isotopic and elemental analysis would show it was powered by the radioactive decay of plutonium 238, whose decay products would still exist, in the correct ratios. It would be a very simple machine to them. Now, perhaps they DO recognize it as a form of life- they might, and some humans already consider machines as having a simple form of sentience. However, they'll recognize that the probe cannot have constructed ANYTHING itself, it didn't have an intelligent mind, and it doesn't appear to have any means of replication. It thus must have been created by something else, something more complex. Meanwhile, if the pictures survive, they show a bipedal creature that uses tools and has five-fingered hands. The most logical conclusion is that these creatures were the ones that created the probe. There are other explanations (such as the message being some sort of deception), but none of them are as simple and likely. You think that the aliens will be so stupid they might not even be able to apply Occam's razor? Without basic logical skills like Occam's razor, science is impossible, and they would never have achieved spaceflight anyway. It's hard to imagine a being that communicates by constructing messages out of metals, ceramics, etc. That is a HIGHLY inefficient method of data storage. Nature abhors such inefficiency. It is this very optimization towards efficiency and common sense solutions that makes it so likely that aliens and humans will have some common ground to communicate. Meanwhile, they'll be smart enough to recognize that the structural layout of the probe is not a message either, it was necessitated by how the probe had to work. They'll know we're an alien species, have very different minds, and thus we need to seek a simple method for writing a message. Sure, they may look for messages in the chemical composition, but they would be absolutely stupid not to recognize as meaningful a clearly-designed pattern scratched into a gold disk, that appears to have no functional purpose. What I AM more doubtful of is whether they would recognize the message as a message to THEM. However, the subject matter of the message, and the context in which it would be discovered, gives a massive hint as to why the message was sent and who it is for. They might have a hard time understanding why we would want to send a message to them, but how is an intelligent civilization ever going to evolve without curiosity, without a drive to explore? Again, we will probably have a common enough background with them that the message's purpose, and its contents are at least mostly understood. Not sensible. There are thermodynamic, chemical, and evolutionary reasons why life should be recognizable. Even highly advanced machine life will still be recognizable as such.

I don't think you give aliens enough credit. We live in the same universe. The aliens are either biological beings that evolved, are artificially evolved biological beings, or are machines that are aware of biological beings and that they exist and how they work. They are not stupid. I'm pretty sure they understand that the same 3 dimensional object can take on a different 2D shape when viewed from a different angle. They're very likely to use vision, though even if they evolved in a cave and have no eyes they'll still have learned about electromagnetic radiation. There are so many pictures of humans that they have to understand that humans are the ones who built the probe. Anything else would not be logical. We show DNA and they'll recognize its ability to be used in chemical life- so they'll know what a human looks like and that they use DNA. I could go on and on, but the point is, aliens and humans would have some very significant things in common- mainly that we all experience the same reality, the same laws of math and physics, and certain basic logic within this reality is universal. Aliens and humans should have some common ground to communicate, and I think it's silly to think otherwise- it's taking the idea that aliens could be very different than us way, way, too far. Though I suppose they could be so far advanced of us that they might not consider the messages they're sending to us true communication, similarly to how we can't talk to dogs but we can crudely communicate with them on a more basic level. What medium could they have printed the photographs in that would actually last billions of years (or even millions of years) in space? Shouldn't radiation break down the chemicals that give the pictures color on astronomical time scales?

My guess is 1g is fairly universal for Earth-like inhabited worlds, within -20% to +50% or so. Assuming a constant density, the surface gravity of a planet increases by the cube root of its mass. We don't know for sure that super-Earths aren't habtitable, though an overly thick atmosphere seems to be likely. You could end up trapping far too much water and gases. That doesn't mean that all super-Earths have to be inhospitable, that just means that a lot of them probably would be. However, we could end up being surprised on this account. At the other end of the spectrum a planet much less massive than Earth will cool off too quickly, losing its geodynamo (magnetic field). It will have a hard time holding onto an atmosphere, and plate techtonics will quickly shut down. A 0.5 Earth mass exoplanet, which is supposedly pretty far on the low end of habitiablity predictions, has a surface gravity of 0.8g, and a 4 Earth mass exoplanet has a surface gravity of around 1.6 g. Again, that's assuming the same density as Earth, but that seems fairly reasonable for ballpark assumptions. These ballpark assumptions can be used to make some other reasonable guesses- for example, alien life adapted to 3g is not likely to exist (or at least, be anywhere near as common as lower-gravity lifeforms like us), as that requires a terrestrial planet with a mass of 27 Earths, which puts you firmly into the range of small gas giants. Retconed by fans or Niven once it was pointed out that his planet did not make physical sense?

Yea, that should work. By burning right when you get to periapsis, you can preserve much of your orbital velocity around Kerbin by escaping its gravity quickly, before it can act to slow you down- so you can obtain large velocities relative to Kerbin. I used a similar concept for a three-stage ion probe I made- I launched it out to around Eeloo, then reduced its periapsis till it was like 1 solar radii. I did not cheat and use massless batteries- I used solar panels, which work even better near the Sun. As I approached periapsis, I did like a five hour ion "burn" to escape the Sun's gravity. I was able to preserve most of my solar orbital velocity at periapsis, plus a bunch of added delta-V from the ion engines. My final anti-solar velocity was just in excess of 70 km/s. 100 km/s would probably have not be hard to achieve, with more ion stages and better optimization (this was my first try), but this was just a simple afternoon "project". Sobering thought- even at 70 km/s, and assuming that all distances in the Kerbal universe are 1/10th that in the real universe, it would still take my "high speed" probe 1800+ years to reach the nearest star to Kerbin, 0.43 light-years away. That's 1 week of continuously running the game at 100000X time compression.

I think it's diamagnetism. http://en.wikipedia.org/wiki/Diamagnetism

Can't they do any basic math? a = w^2*r w = angular rate = 2*pi/(24*3600) = 7.27e-5 rad/s .. r = a/w^2 = 9.81/(7.27e-5 rad/s)^2 = 1.85 million km. Oh... but what does "day" really mean? I don't think that makes sense. A planet that is egg-shaped due to tidal forces, and tidally locked, should be in hydrostatic equalibrium, and the atmosphere would cover everywhere.