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.