Reaper

Is there anybody here familiar with the philosophy of David Hume? I've been particularly interested in reading some of his works lately, especially with regards to his treatise on skepticism. In particular, his Natural History of Religion seems to lay the fundamental logical and moral framework for both agnosticism and atheism... Thanks!

Yeah, ok so I realized very quickly that 750 problems a week would be physically impossible to do. I thus scaled it down to a more reasonable number. It will be more realistic goal, like 40 problems a week instead. This equates to about 6 problems per day on average. It will still be quite masochistic (at least at first, when it starts to become trivial I will seek out harder problems or increase the number of them), but at least it is possible and worthwhile.

Hey! It's been a while since I've posted here. Anyways, I've been contemplating on how to create a "training" course, so to speak. It would be designed to help facilitate my learning of topics such as physics, as well as to become very proficient at them. Much like the way people train for physical sport, but instead applied to the mind. The reason I would consider it a "training course from hell" has largely to do with the fact that it is designed to be, well, hellish. Some ideas include: -Doing 750 physics problems a week, in order of increasing difficulty. One wrong answer means that I would have to start over. -Doing some complicated Boundary Value Problems in my head, and keep going until I can get the correct answer at least 90% of the time. -Memorizing large amounts of information, such as thousands of digits of pi, or the names of every single country that has ever existed (past and present). Anybody else have any ideas on how to create the perfect training course?

Exactly. As counter-intuitive as that might seem, there is no reason that it can't behave (at least on a large scale) like any other object without an event horizon. Like Swansont said, gravity is gravity; it's influence depends only on it's mass. Did you even read through any of the articles that I presented to you? That statement is wrong on so many levels. The truth is, we don't really know what goes on black hole (although I can tell you what it is not, a wormhole). General relativity suggests that there should be a singularity at the center, but such objects only represent a failure of General Relativity, not the actual situation.

I don't really think you are understanding what I'm saying. First, your nitpicking terms (it could be semi-fluid or super dense plasma, same difference. Though the word "frozen star" implies solid object....). Besides which, since black holes have no hair, we might as well just treat it as a solid object anyway. So what, exactly, a black hole is made of is irrelevant. And second, transfer of kinetic energy doesn't mean that things will "bounce off" the event horizon. It just means that when things collide, some of that energy will be transferred. A black hole is the same as any other object. Gravitationally, it's pull will be the same as that of an object with the same mass... The scenario that I laid out would probably be the one that would happen. Just get over it. The black hole could either be the mass of a star or an asteroid; if a black hole the mass of the asteroid were to collide with the Earth, it would have exactly the same effect as if an asteroid (even one moving at relativistic speeds...) were to collide. I don't even want to think about what would happen if a black hole with 5 solar masses were to go on a collision course with our planet, although some of the scenarios I laid out earlier would likely occur (e.g. planets getting flung from orbits, Earth vaporized, sun exploding, etc.) Merged post follows: Consecutive posts merged Thank you.

Well, lets see. According to Berekely University: http://cosmology.berkeley.edu/Education/BHfaq.html How is what he is describing not a solid object? More generally, a black hole is the result of a giant star collapsing in on itself. The mass gets compacted into such a small space that the resulting escape velocity near it's surface is greater then that of the speed of light. Thus forming a "black hole" in a metaphorical sense. A much more accurate term is actually a "dark star", but the word black hole sounded so much cooler, so that's what we use. It is not a hole in any sense of the word. It is a solid object, like anything else, except really, really dense. It has a mass, and a speed, thus it has momentum and kinetic energy. Unless you can somehow show that conservation of momentum does not apply, I don't see how the Earth would survive such a collision course (assuming that the gravitational force doesn't rip it apart before it reaches this planet...) ================================================= Here is another fun fact about the term "black hole": ========================================= Here is another good article on the nature of black holes: http://astronomy.swin.edu.au/~gmackie/DarkStar/alpha.html It turns out that people have been speculating about such objects as early as the 1700's! Back then it wasn't clear if light was a particle or a wave, but they already knew it had a finite speed. Therefore, it was hypothesized that there were "dark stars" out there that could only be detected via gravity because it's escape velocity would be that of the speed of light. However, all of Newtonian mechanics would still apply (e.g. it would have mass, speed, momentum, angular momentum, etc.). For relativistic speeds (or extreme gravitational fields), we would use special and general relativity. We can therefore apply basic physics concepts like conservation of momentum to try and guess at what would happen if a massive relativistic black hole were on a collision course with Earth... *NOTE: If I made any mistakes in my reasoning, then please either Swansont or Martin or Severian correct me.

Oh yeah it does. Especially if we are considering one that is not that big and moving at extreme velocities. Or much bigger objects (Although with bigger/more massive objects, what would happen is that the matter would warp around the black hole, thereby tearing it apart...)

That doesn't matter though. You are assuming that at black hole is some "hole" in space that just sucks everything up. A black hole is a solid object, like anything else. And like all objects in the universe, it has a speed, a mass, and momentum. Thus, it can carry and transfer energy to other objects, whether they are black holes or not. Just because it can "suck" in light doesn't mean that it can't collide like any other solid object. Any other action would be a violation of the laws of physics, and as far as I know, even black holes are bound by them. As well, black holes only have the gravitational pull that their mass allows for. A black hole with the mass of the sun, for example, will still only have the gravitational pull of that of the sun. It's just that you have to get a lot closer to it in order to cross the event horizon. Even smaller objects will have an even less gravitational influence... ------------------------------------------------------------ Of course, I'm just assuming that's its gravitational effects won't tear the Earth apart first before it even reaches it, which is what such an object would do to a planet under normal circumstances.

Why? A black hole is just like any other object, except really, really dense. Conservation of momentum still applies; if it crashes into some object, at least some of its kinetic energy will be transferred into the planet. It's the same as shooting an asteroid or a neutron star into a planet at relativistic speeds (except that a black hole is much more massive, and thus has a great deal more kinetic energy at those speeds). If black hole that sized collided with our planet at that speed, the Earth would probably be vaporized. Merged post follows: Consecutive posts merged I know of some claims of artificial black holes, but I have not heard of any ones that move at relativistic speeds w.r.t Earth.

If it was very small, then yes. But I think the OP was referring to any sized black hole, not just very small (i.e. subatomic sized) ones.

But if you make it impossible for intelligent AI's to turn against their creators, then I don't see what the problem is. Virtually every machine we have in existence has built in safety features to ensure that it is safe for humans, it follows that robots and super-intelligent AI's will have them too. For your fear to be not unfounded, you would first have to show that 1) The safety features can be overridden 2) That, if truly independent, that they would even want to turn against us ala Skynet or Cylons.

It will depend on how big the black hole is. If it is moving at 99999999999c with respect to Earth, I wouldn't want to be in the way. Such an object would have an enormous kinetic energy, and if it crashed into our planet, even a small one would turn the crust into slag. A bigger one would just blow it apart (and probably ruin the entire solar system with it...), and a supermassive black hole would just gobble our planet up. I don't think we would have time to perceive it if such a black hole was headed our way. The only thing we would see is planets being flung right out of their orbits, if it was large enough. And if it was so small as to be of negligible importance, we would probably never detect it. Also, look at Relativistic Kill Vehicle: http://en.wikipedia.org/wiki/Relativistic_kill_vehicle

Well, I'm actually a bit skeptical about intergalactic travel, simply because of the enormous distance between galaxies (the Andromeda galaxy, one of the closest galaxies to us, is more than 2 million light years away). Even if we just send unmanned probes or even Von-Neumann probes, I doubt they would remain functional for very long. To put it in perspective, we've already built probes that can last for decades. We could probably make space-craft that can remain functional for hundreds of years. It's pretty unlikely that we could design anything that can last more that a few thousand years (although it is not strictly impossible I suppose). But millions of years at sublight speeds? Forget it. Most human made things and structures don't even make it to 1000 years, let alone hundreds of thousands to millions of years... No, I think if we do find any sort of extraterrestrial intelligence, it will most likely have originated from this galaxy.

Nope, I'm afraid Issac Asimov would disagree with you: Source: "Caves of Steel", Introduction, pg. viii-x They were designed precisely to guard against some sort of Terminator scenario. Of course, he went further in later novels to talk about their implications and various loopholes. But in no instance did the robots ever waged a full scale genocidal war against all of humanity, nor did they kill human beings out of malice or rage; the robots did not have any such desires, and such actions were just simply impossible in any case. Issac Asimov reasoned that since intelligent machines would be tools, they would have built in safety features, such as the Three Laws. Hence, their existence. Given that he made these laws in the 1950's in a science fiction novel, it would be foolish of us to make robots that followed the three laws exactly. But that doesn't mean that future machines won't have something similar to them. Indeed, in various academic circles there has been much debate on what laws (and modifications thereof) should be put in to ensure their safety.

Speaking of interstellar travel, there is an article out there that claims that it may be possible develop the ability to manufacture sufficient amounts of antimatter in a couple of decades: http://www.engr.psu.edu/antimatter/Papers/NASA_anti.pdf There is not too much math in it, other than basic algebra and simple formulas. And a couple of graphs. So, if you want to read it, then go ahead and enjoy. One thing I found interesting is that antimatter production does seem to be expanding exponentially, so who knows, maybe late in the 21st century we might be able to build a relativistic space-craft.

It doesn't. This guy is just a spammer. He posts threads like these, where he plagiarizes some book or article, and then doesn't really discuss the topic at hand. This post from another forum speculates on what, exactly, coberst is: http://www.military-quotes.com/forum/poll-what-coberst-t76295.html

Have you never heard of the Three Laws of Robotics? The whole point of those laws is that even if they have "super-human" intelligence, it would be extraordinarily unlikely that a Terminator scenario would come about, simply because at least some of their behavior would be programmed by us. And even if they prove to be independent, why would they behave like us humans, complete with our prejudices and whatnot. Why would they care if we exist or not. How many humans go around trying to kill off monkeys because of their inferior intelligence?

We will see one of these through a telescope on 2012:

The distances between galaxies are gigantic. If they are traveling at 1/6c to go between galaxies, it would take tens of millions of years minimum. Unless you can create a craft capable of functioning that long in the vacuum of intergalactic space, I don't think it would be possible for them to spread out over the volume that you proposed earlier. Besides which, I have not yet heard of one good reason for why every star in a galaxy has be colonized, should there exist a civilization capable of venturing away from their home star system. Just because they can travel between stars doesn't mean that they will colonize all of them. Indeed, humanity's current plans involve us colonizing only systems with Earth-like planets once we gain the capability.

You're in space! You don't need to maintain it. Don't tell me that you guys actually thought friction would be significant factor in space travel... All you need is enough fuel to speed up and slow down. And maybe a little extra to change direction.

Actually, there is not. We know of at least one way of traveling at a significant fraction of the speed of light: http://en.wikipedia.org/wiki/Project_Orion_%28nuclear_propulsion%29 While we humans as of yet haven't worked out the political difficulties of allowing this technology to become commonplace, there is no reason to believe that other civilizations would be as restrictive. Certainly, if there are other advanced civilizations out there, sooner or later it will develop the same capabilities and technologies that are currently available to us.

Well, for one, it seems to strawman the Rare-Earth argument, on page 19 where it compares it to "special creationism", when in reality it's almost nothing like that at all. And I saw one part where it tried to refute the idea that there could be large volumes of space uncolonized without really giving a convincing reason for why every habitable world in the galaxy has to be colonized in the first place. Other then that, I think my feeling, now that I think of it, was directed at the theories themselves rather than the paper. The paper itself does a good job presenting the different viewpoints. My personal preference is for the Rare Earth Hypothesis, even though there is scant empirical evidence for it to date. In particular, I think it is far more likely that intelligent life is much more rare than any other form of life, and that can be verified through the fossil record here on Earth. Some sci-fi novels, such as Asimov's Foundation series, does touch upon this somewhat. I don't find it that bizarre. I just think its a consequence of the fact that we don't really have any idea of what we are looking for. Sure, we might easily be able to find tons of ET biospheres, since the criteria for their existence is already well established. On the other hand, the criteria for what constitutes an extra-terrestrial civilization is not. The fact that there are a bunch of theories trying to answer the Fermi Paradox testifies to that. After all, we have such a hard time trying to agree on one with our own civilizations, let alone an alien one. In all the arguments I've seen, they all seem to agree that Type II or Type III level civilizations are easily detectable, although they don't give any rational for it at all. If all of those kinds of civilizations are like the ones we see in Star Trek, for example, then we would have almost no hope of detecting them simply due to the fact that they don't use conventional radio waves, and their engineering feats would simply be undetectable even if they aren't trying to hide it. I would imagine that even the ones that are capable of large interstellar projects would be extraordinarily difficult to detect, since it has yet to be addressed on how they could be distinguished from ordinary natural phenomenon. Also, there is the problem of trying to outguess what a Gyr civilizations would be like. We are talking about a civilization that has outlived entire geological epochs and eons, and quite possibly entire stars. It certainly has had more than enough time to survey and colonize our galaxy. The fact that there is no evidence whatsoever that they have visited Earth at anytime in the past 4.5 billion years means that either: 1)Faster than light travel is impossible 2)It's impossible to colonize the entire galaxy this large, even given an infinite amount of time. 3)They don't exist in our galaxy. Or 4) All of the above.

Alright, so I have this new concept for building a new computer, which is not only put multiple processors, but also multiple motherboards. I'm saving up for the parts of a new computer right now, so I am wondering if it is possible to synchronize two motherboards together. I want to do this to see if it will help improve performance (like faster speed, etc.). If it was possible, would it yield any significant advantage over having one motherboard?

Yeah, I would say that it depends on what, exactly, you are working on as a scientist. Big projects like Mars Exploration or finding a cure for cancer are certainly seen as prestigious, while topics like Google Earth Physics are not likely to get you noticed.

I just read the paper now, and it seems to me that the paper is either jumping to conclusions, or not really considering all possible arguments. For example, those who argue that most nearly every "habitable" planet must have been colonized seem to forget that despite our so-called technological might, more than 70% of the Earth remains uninhabited. And even though modern nation-states claim to own vast swaths of land, most of that is either uninhabited, or populated by various tribes that do not acknowledge the legitimacy of whatever government is in place (take, for example, the Amazon tribes of Brazil). It is interesting that the paper does note that because most Earth-like planets out there are billions of years older than our own planet, then there is a strong possibility that any civilizations that have evolved on those planets would have gone out and colonized the galaxy long ago. Of course, one has to remember that our current biosphere has only existed for 350 million years or so, and complex life in general for only 500 million years tops. If a civilization had visited Earth prior to that time (which would seem very likely), they would have found nothing of interest. If we assume that they are also oxygen breathing, then it would be very likely that they could have perceived Earth as a hostile planet at the time, and just simply not bothered with it. This and other factors could very well lead, I think, to a scenario in which even an aggressive type II or type III civilizations leave vast areas of the galaxy just simply out of touch. Also, I think it severely overestimates how easy it would be to detect extraterrestrial civilizations. Our own civilization is not visible even if we were as close as the Moon, and I read somewhere that even just past one light year our radio signals would be much too weak to detect. Certainly any alien probes standing on, say, Saturn wouldn't know that any intelligent life existed in our solar system (if you ever watched Pale Blue Dot, Sagan himself notes this). For us to be anywhere near visible on a galactic scale, our energy output would have to rival that of the sun. By contrast, we are trying to detect civilizations that are, at minimum, in the next few light years around. Also, if they did engage on mega projects on an interstellar scale, how would we tell the difference? Assuming a Ringworld like structure is possible (never mind a dyson sphere), that data could just as easily be interpreted as a dense asteroid field. Any large number of orbital space stations could just as easily be dismissed as asteroids, or even small moons. Any "star mining" could just as well be just solar flares; I feel that the argument that large Type II or Type III scale civilizations should be easily detectable to be a massively flawed argument and demonstratively false. Barring that, the only argument that I find to be defensible in that paper is the Rare Earth argument. While we may find loads of worlds with either simple or complex life, planetary space-faring species could be rare. Indeed, the fossil record suggests that evolution does not go in any particular direction, and there is no reason to believe that intelligence is inevitable. It certainly wasn't the case for us, and it sure as hell won't be the case for any ET biospheres we find in the universe.