They don't. If you get distortion in the exact direction of the perpendicular then it is hard to detect. The key to detection is that if it comes in at even a little angle then the two lasers will be distorted relative to each other.
There is a part of the feminist community that does downplay male rape and male victims of domestic violence, and this is a serious problem. But some of the people doing the best work for raising awareness about these issues are feminists. Aliraza Javaid for example is a vocal feminist who has wrote a lot on the subject of male rape and how the victims are mocked or ignored. Gillian Mezey is not as vocally feminist but has also wrote about it. And one of the recurring points is how sex and gender expectations and biases make it difficult for these victims to get attention or to get psychological or legal support. See for example http://www.internetjournalofcriminology.com/javaid_male_rape_the_invisible_male_ijc_jan_2014.pdf.
Basically, it mostly matters to the theoretical-physicists-based economy. To all these people for whom the validity of the Relativity is required (together with all what follows to it, like Quantum Mechanics), because in case of being proven wrong (and/or useless), lots of big projects/reputations/money-generations might be lost.
It is true that we don't have a direct application of this at the moment, but most things don't have direct applications when they are initially discovered. Electricity didn't, nor did radioactivity, nor did relativity (which is actually applied in GPS systems). But there are a lot of people who care about this who aren't theoretical physics people (I'm a mathematician for example.) Moreover, there would actually be more likely be money and new big projects if the gravity waves didn't meet the theoretical expectations. It is much easier to get money for research when a field is in a state of complete confusion.
Finally, please note that quantum mechanics doesn't follow relativity, but is essentially orthogonal. One can do quantum mechanics in a completely classical space-time (and in fact that's much easier). Special relativity can be made consistent with QM, but we cannot at this point reconcile quantum mechanics and GR.
Essentially a flexing of space, but it isn't easy to visualize. Imagine a circle as a gravity wave goes through it then the horizontal direction will get flattened and the vertical (direction of the wave) will get stretched out, and then the reverse. The actual equations for what it does to an object though are non-trivial.
This matters for a bunch of reasons. First, it helps close confirm predictions of general relativity. We had a lot of evidence already but more is good. Second, if we get more data we might be able to rule out or narrow down our search space for any eventual quantum gravity theory since they have predictions about how gravity waves should behave (although this would require massively upgrading LIGO). Third, this gives us insight into stellar objects that we normally lack the ability to examine. For example, we don't know much about what the cores of neutron stars are like, but different ideas about them give different predictions about what sort of gravity waves two merging neutron stars will create. So this may give us more data about what exotic objects are actually doing. Fourth, this gives us for the first time a way of getting data from very far away sources that isn't in the electromagnetic spectrum. Right now, we can detect neutrino bursts if they come from a few million light years away but pretty much everything from outside our little galactic neighborhood has to come either from electromagnetic radiation or detecting cosmic rays. But LIGO can already detect gravity waves from events that are a billion light years away. So this gives us a whole new long type of data.
You're absolutely right. The fact 50% of domestic violence victims have 0% of federal funding and shelters, and 50% of rape victims aren't even legally recognized, is a real and serious problem.
I'm not sure what your point is. Yes, there are massive problems with how male victims of domestic violence and rape are treated. Problems exist in how we treat men and problems exist how we treat women. We shouldn't ignore either class.
Gender issues are a real and serious problem. And you don't need to be a "SJW" to get that. Inefficiencies introduced by biases are bad because they make less good code get written or accepted. This harms *everyone*. And understanding exactly how much of a bias there is and where there is bias or isn't bias is important. If there's no problem in a given area, then we should know about that so we can focus resources elsewhere. We don't lose by getting more good data about the situation.
In the first case, not that serious aside from processing power.
In the second case, so many technical problems that it took in inflation adjusted dollars more than 20 billion dollars and http://www.brookings.edu/about/projects/archive/nucweapons/manhattan and even after that most countries still can't do.
In the third case, lack of understanding of aerodynamics and lack of efficient combustion engines.
In the last case, they were actually moving in that direction. The real problems that slowed it down were metallurgy and quality control.
For a site supposedly for nerds the nerds sure are short sighted when it comes to technology
I think you are missing the point here. My comment was to not say that this is impossible, but exactly what I said: the technical problems are immense. If he can get over them, that's great, but it is worth appreciating how difficult this is likely to be.
Is he? I didn't get the impression of that from TFA that it would switch over. TFA talks about both electric and VTOL but not about using conventional power during flight. If that's what he meant, that's much more potentially reasonable but given his long-term goals of dealing with global warming and fossil fuel dependence (which is why he's so in favor of electric cars) that doesn't seem like that's what he means. Do you have a citation or source that he means that?
Good points which do make my concerns less severe, especially in regards to efficiency. And yes, you are right that we can synthesize fuel directly although it seems like that would be economically very expensive. I like the idea though of capturing carbon from the water.
You can recharge/refuel more frequently with an electric car. A bit hard to land and recharge in the middle of the Atlantic ocean. So the reduced range of an electric car (around 200 miles for an electric car as opposed to 300-400 miles for a gas car) doesn't matter as much. Also, cars are less dependent on fuel in some sense than planes since planes need to go fast. So you need a lot more fuel proportionally, so its efficiency matters more for planes.
Batteries do not have the energy density of jet fuel. The primary thing that matters here is energy density, which has two forms, energy per mass and energy per volume. https://en.wikipedia.org/wiki/Energy_density Both need to be much better than they are today for electric airplanes to have any chance (lifespan and and number of cycle uses also need to improve but that's in some ways less of a barrier.) Energy density of batteries by both metrics batteries has increased by 5%-10% a year depending on the exact metric and choice of examples https://www.quora.com/Is-it-true-that-battery-energy-density-improves-5-8-per-year which is exponential growth ( but with a much slower doubling time than something like Moore's Law. One has a doubling about once every 8 or 10 years.) Jet fuel has an energy density of around 45 MJ/kg, The most efficient batteries have a little under 1 MJ/kg. So one needs at least about 5 doublings before batteries can reasonably compete which will start to occur if they have an energy density of around 32/ MJ/kg. Similar remarks apply to energy density measured by joules per volume. However, there are technical reasons to think that batteries will stop doubling before that (see theabove quora link for details which argues that we can't make batteries much than four times as efficient before we start running into serious theoretical limits). At around 20 MJ/kg, one maybe could run planes practically but they would be much less convenient and practical than today's jets and that would be at the very upper end of the plausible limits just from a straight energy density estimate.
However, the situation is even worse than that. When you use jet fuel, you use it up. Depending on the type of airplane, at take off fuel is generally 25% to 50% of the mass of the plane. So one gets serious savings that one doesn't have to move all the used fuel the entire way. That doesn't work with batteries: they are the same mass and volume whether or not they are charged, and dumping them would defeat most of the point. It might be possible to do some sort of staging approach where one uses some set of batteries to nearly empty and then have them break off in a modular plane that returns to the ground site. But that itself would lead to all sorts of additional problems.
So it is likely that we will still see fossil fuels used for jets for the next 40 or 50 years. Indeed, it is likely that they will be the very last use of fossil fuels.
Followup: acording to this thread https://news.ycombinator.com/item?id=11014175 the number in question fails at even being a pseudoprime for small bases, which means that even the most simple checks were not done. That thread also mentions the individual responsible for giving the "prime"- I'm not sure why he's not being grilled pretty heavily right now.
This cannot happen accidentally. We have for example versions of the Miller-Rabin test https://en.wikipedia.org/wiki/Miller%E2%80%93Rabin_primality_test which easily test primality if you believe the Riemann Hypothesis and other versions which unconditionally give such a high probability that one is more likely to have had a cosmic ray wreck your computing results than for the test to be erroneous. You can use for example this Javascript http://www.javascripter.net/math/primes/millerrabinprimalitytest.htm. There's no obvious way one would come up with a composite number unless one was deliberately trying. Hopefully there's enough of a record to note when this fake prime was put in.
That sounds like you estimate a very high chance that Clinton will either not be the Democratic nominee or that she will if she is the nominee lose the general election. Can you estimate your probabilities for those events?
The Fermi Paradox is really pseudoscience. There are many big problems with it.
I'm not sure what you mean by this and your following statements. Your primary point seems to be that intelligent life might be less likely than we think. But that's not a criticism of the Fermi paradox but a possible resolution of it. Your point about signal detection is certainly correct if that were our only way of detecting civilizations. In particular, we see no ring worlds, or Dyson spheres or other large scale constructions despite systematic searches http://home.fnal.gov/~carrigan/infrared_astronomy/Fermilab_search.htm. We don't in general see any signs of large scale energy use. We've looked at around 100,000 galaxies and found zero full-scale galactic civilizations. See http://phys.org/news/2015-04-advanced-civilizations-earth-obvious-galaxies.html. The universe looks natural. And yes, there are many possible explanations for this, but we need to ask how likely they are. If there is a Great Filter https://en.wikipedia.org/wiki/Great_Filter then it doesn't go away simply because we've found a semiplausible alternate explanation.
However, science is generally logical enough to recognize that such uses of technology are counterproductive.
How long did it take to recognize that lead in gasoline was a bad idea? More seriously for existential risks like the sort under discussion, it doesn't take science collectively as a whole to do something stupid, just a handful of people might engineer a bad virus. Or a pollution problem could arise that is a collective action problem like climate change. The Fermi Paradox is a real problem https://en.wikipedia.org/wiki/Fermi_paradox and one of the easiest explanations for it is that civilizations wipe themselves out with technology.
Sure, I'm a mathematician and wouldn't accept it. All this is is a plausibility argument. In fact, from a standard mathematical perspective this is a trivially decidable issue in Peano Arithmetic.
Yes, certainly current knowledge levels are very far from actually proving hard limits on this sort of thing. It is possible that very advanced circuit lower bound techniques could prove something like this in a reasonable model but we are nowhere near that, And even then, you'll always have doubt how accurate the model is.
Under the presumption that you are the same AC as earlier, I will note that you haven't responded to anything I said, but have made your position more hardline. You are arguing now not just that we might one day find this out but that it is "certainly... not unknowable." I'd comment more but I doubt it would be productive, and I just broke my hand so typing is tough.
Yes, you can partially factor 2^n+1 if you write n= 2^(a (2k+1)), but it only gets you too big factors which are about the size of 2^(2k+1) and the other being the rest. That helps only a tiny bit, and is part of why I choose an example that had an n with a very large even factor.
A small continuous population, that doesn't give them the right to a self-governing state in that territory any more than it does small minorities in other states.
Land claims from well over 1000+ years ago notwithstanding.
Essentially in agreement here. We cannot in general let ancient land claims determine legitimacy of nations and national borders. That sort of thing leads to complete chaos and many dead.
Of course the Palestinian Arabs disagreed. A different ethnic group declares they're going to start colonizing your territory to create their own state, they then proceed to do so while you're under foreign occupation by states who generally side with the other ethnic group.
The foreign occupiers then propose to give the other group a state with most of the land even though you still have a bigger population. Is this a proposal you're going to agree to?
This is an oversimplification, although I think it does do a pretty good job of summarizing the Palestinian Arab perspective on things. One of the difficulties here is that every group has a narrative that emphasizes some aspects and details to make them sound like the aggrieved good guys. Note that while there was no native government to control immigration, the Jews going to Mandate Palestine were buying and settling land completely legally. It is also worth noting that the Partition Plan like all good compromises left essentially no group happy, and while the partition plan did give the majority of the lane of "Palestine" to the Jewish state, much of that land was land that was legitimately bought by Jews, and parts of the partitioned land would have likely then joined up as parts of Jordan and Egypt, so a simple percentage accounting doesn't quite summarize things. As always, the history is complicated. Unfortunately, both pro-Israel and pro-Palestinian groups often focus on the details that make their own story sound good rather than actually realize that everyone has a legitimate right, and that moreover, when anyone has been somewhere for multiple generations, getting a satisfactory result that doesn't result in everyone killing each other may be more important than trying to decide who is cosmically right as satisfying as that may be.
Slashdot Mirror
They don't. If you get distortion in the exact direction of the perpendicular then it is hard to detect. The key to detection is that if it comes in at even a little angle then the two lasers will be distorted relative to each other.
There is a part of the feminist community that does downplay male rape and male victims of domestic violence, and this is a serious problem. But some of the people doing the best work for raising awareness about these issues are feminists. Aliraza Javaid for example is a vocal feminist who has wrote a lot on the subject of male rape and how the victims are mocked or ignored. Gillian Mezey is not as vocally feminist but has also wrote about it. And one of the recurring points is how sex and gender expectations and biases make it difficult for these victims to get attention or to get psychological or legal support. See for example http://www.internetjournalofcriminology.com/javaid_male_rape_the_invisible_male_ijc_jan_2014.pdf.
Basically, it mostly matters to the theoretical-physicists-based economy. To all these people for whom the validity of the Relativity is required (together with all what follows to it, like Quantum Mechanics), because in case of being proven wrong (and/or useless), lots of big projects/reputations/money-generations might be lost.
It is true that we don't have a direct application of this at the moment, but most things don't have direct applications when they are initially discovered. Electricity didn't, nor did radioactivity, nor did relativity (which is actually applied in GPS systems). But there are a lot of people who care about this who aren't theoretical physics people (I'm a mathematician for example.) Moreover, there would actually be more likely be money and new big projects if the gravity waves didn't meet the theoretical expectations. It is much easier to get money for research when a field is in a state of complete confusion.
Finally, please note that quantum mechanics doesn't follow relativity, but is essentially orthogonal. One can do quantum mechanics in a completely classical space-time (and in fact that's much easier). Special relativity can be made consistent with QM, but we cannot at this point reconcile quantum mechanics and GR.
Essentially a flexing of space, but it isn't easy to visualize. Imagine a circle as a gravity wave goes through it then the horizontal direction will get flattened and the vertical (direction of the wave) will get stretched out, and then the reverse. The actual equations for what it does to an object though are non-trivial.
This matters for a bunch of reasons. First, it helps close confirm predictions of general relativity. We had a lot of evidence already but more is good. Second, if we get more data we might be able to rule out or narrow down our search space for any eventual quantum gravity theory since they have predictions about how gravity waves should behave (although this would require massively upgrading LIGO). Third, this gives us insight into stellar objects that we normally lack the ability to examine. For example, we don't know much about what the cores of neutron stars are like, but different ideas about them give different predictions about what sort of gravity waves two merging neutron stars will create. So this may give us more data about what exotic objects are actually doing. Fourth, this gives us for the first time a way of getting data from very far away sources that isn't in the electromagnetic spectrum. Right now, we can detect neutrino bursts if they come from a few million light years away but pretty much everything from outside our little galactic neighborhood has to come either from electromagnetic radiation or detecting cosmic rays. But LIGO can already detect gravity waves from events that are a billion light years away. So this gives us a whole new long type of data.
You're absolutely right. The fact 50% of domestic violence victims have 0% of federal funding and shelters, and 50% of rape victims aren't even legally recognized, is a real and serious problem.
I'm not sure what your point is. Yes, there are massive problems with how male victims of domestic violence and rape are treated. Problems exist in how we treat men and problems exist how we treat women. We shouldn't ignore either class.
Gender issues are a real and serious problem. And you don't need to be a "SJW" to get that. Inefficiencies introduced by biases are bad because they make less good code get written or accepted. This harms *everyone*. And understanding exactly how much of a bias there is and where there is bias or isn't bias is important. If there's no problem in a given area, then we should know about that so we can focus resources elsewhere. We don't lose by getting more good data about the situation.
For a site supposedly for nerds the nerds sure are short sighted when it comes to technology
I think you are missing the point here. My comment was to not say that this is impossible, but exactly what I said: the technical problems are immense. If he can get over them, that's great, but it is worth appreciating how difficult this is likely to be.
Sure, that could certainly be a use and it would avoid many of the associated problems.
Is he? I didn't get the impression of that from TFA that it would switch over. TFA talks about both electric and VTOL but not about using conventional power during flight. If that's what he meant, that's much more potentially reasonable but given his long-term goals of dealing with global warming and fossil fuel dependence (which is why he's so in favor of electric cars) that doesn't seem like that's what he means. Do you have a citation or source that he means that?
Good points which do make my concerns less severe, especially in regards to efficiency. And yes, you are right that we can synthesize fuel directly although it seems like that would be economically very expensive. I like the idea though of capturing carbon from the water.
This is a really good point, and it might be that planes are one of the few contexts where hydrogen really is the way to go.
You can recharge/refuel more frequently with an electric car. A bit hard to land and recharge in the middle of the Atlantic ocean. So the reduced range of an electric car (around 200 miles for an electric car as opposed to 300-400 miles for a gas car) doesn't matter as much. Also, cars are less dependent on fuel in some sense than planes since planes need to go fast. So you need a lot more fuel proportionally, so its efficiency matters more for planes.
Batteries do not have the energy density of jet fuel. The primary thing that matters here is energy density, which has two forms, energy per mass and energy per volume. https://en.wikipedia.org/wiki/Energy_density Both need to be much better than they are today for electric airplanes to have any chance (lifespan and and number of cycle uses also need to improve but that's in some ways less of a barrier.) Energy density of batteries by both metrics batteries has increased by 5%-10% a year depending on the exact metric and choice of examples https://www.quora.com/Is-it-true-that-battery-energy-density-improves-5-8-per-year which is exponential growth ( but with a much slower doubling time than something like Moore's Law. One has a doubling about once every 8 or 10 years.) Jet fuel has an energy density of around 45 MJ/kg, The most efficient batteries have a little under 1 MJ/kg. So one needs at least about 5 doublings before batteries can reasonably compete which will start to occur if they have an energy density of around 32/ MJ/kg. Similar remarks apply to energy density measured by joules per volume. However, there are technical reasons to think that batteries will stop doubling before that (see theabove quora link for details which argues that we can't make batteries much than four times as efficient before we start running into serious theoretical limits). At around 20 MJ/kg, one maybe could run planes practically but they would be much less convenient and practical than today's jets and that would be at the very upper end of the plausible limits just from a straight energy density estimate.
However, the situation is even worse than that. When you use jet fuel, you use it up. Depending on the type of airplane, at take off fuel is generally 25% to 50% of the mass of the plane. So one gets serious savings that one doesn't have to move all the used fuel the entire way. That doesn't work with batteries: they are the same mass and volume whether or not they are charged, and dumping them would defeat most of the point. It might be possible to do some sort of staging approach where one uses some set of batteries to nearly empty and then have them break off in a modular plane that returns to the ground site. But that itself would lead to all sorts of additional problems.
So it is likely that we will still see fossil fuels used for jets for the next 40 or 50 years. Indeed, it is likely that they will be the very last use of fossil fuels.
The really sad thing here is that it is likely that all of the original Apollo astronauts will be dead before anyone else goes to any non-Earth body.
Followup: acording to this thread https://news.ycombinator.com/item?id=11014175 the number in question fails at even being a pseudoprime for small bases, which means that even the most simple checks were not done. That thread also mentions the individual responsible for giving the "prime"- I'm not sure why he's not being grilled pretty heavily right now.
This cannot happen accidentally. We have for example versions of the Miller-Rabin test https://en.wikipedia.org/wiki/Miller%E2%80%93Rabin_primality_test which easily test primality if you believe the Riemann Hypothesis and other versions which unconditionally give such a high probability that one is more likely to have had a cosmic ray wreck your computing results than for the test to be erroneous. You can use for example this Javascript http://www.javascripter.net/math/primes/millerrabinprimalitytest.htm. There's no obvious way one would come up with a composite number unless one was deliberately trying. Hopefully there's enough of a record to note when this fake prime was put in.
That sounds like you estimate a very high chance that Clinton will either not be the Democratic nominee or that she will if she is the nominee lose the general election. Can you estimate your probabilities for those events?
The Fermi Paradox is really pseudoscience. There are many big problems with it.
I'm not sure what you mean by this and your following statements. Your primary point seems to be that intelligent life might be less likely than we think. But that's not a criticism of the Fermi paradox but a possible resolution of it. Your point about signal detection is certainly correct if that were our only way of detecting civilizations. In particular, we see no ring worlds, or Dyson spheres or other large scale constructions despite systematic searches http://home.fnal.gov/~carrigan/infrared_astronomy/Fermilab_search.htm. We don't in general see any signs of large scale energy use. We've looked at around 100,000 galaxies and found zero full-scale galactic civilizations. See http://phys.org/news/2015-04-advanced-civilizations-earth-obvious-galaxies.html. The universe looks natural. And yes, there are many possible explanations for this, but we need to ask how likely they are. If there is a Great Filter https://en.wikipedia.org/wiki/Great_Filter then it doesn't go away simply because we've found a semiplausible alternate explanation.
However, science is generally logical enough to recognize that such uses of technology are counterproductive.
How long did it take to recognize that lead in gasoline was a bad idea? More seriously for existential risks like the sort under discussion, it doesn't take science collectively as a whole to do something stupid, just a handful of people might engineer a bad virus. Or a pollution problem could arise that is a collective action problem like climate change. The Fermi Paradox is a real problem https://en.wikipedia.org/wiki/Fermi_paradox and one of the easiest explanations for it is that civilizations wipe themselves out with technology.
Sure, I'm a mathematician and wouldn't accept it. All this is is a plausibility argument. In fact, from a standard mathematical perspective this is a trivially decidable issue in Peano Arithmetic.
Yes, certainly current knowledge levels are very far from actually proving hard limits on this sort of thing. It is possible that very advanced circuit lower bound techniques could prove something like this in a reasonable model but we are nowhere near that, And even then, you'll always have doubt how accurate the model is.
Under the presumption that you are the same AC as earlier, I will note that you haven't responded to anything I said, but have made your position more hardline. You are arguing now not just that we might one day find this out but that it is "certainly... not unknowable." I'd comment more but I doubt it would be productive, and I just broke my hand so typing is tough.
Yes, you can partially factor 2^n+1 if you write n= 2^(a (2k+1)), but it only gets you too big factors which are about the size of 2^(2k+1) and the other being the rest. That helps only a tiny bit, and is part of why I choose an example that had an n with a very large even factor.
A small continuous population, that doesn't give them the right to a self-governing state in that territory any more than it does small minorities in other states. Land claims from well over 1000+ years ago notwithstanding.
Essentially in agreement here. We cannot in general let ancient land claims determine legitimacy of nations and national borders. That sort of thing leads to complete chaos and many dead.
Of course the Palestinian Arabs disagreed. A different ethnic group declares they're going to start colonizing your territory to create their own state, they then proceed to do so while you're under foreign occupation by states who generally side with the other ethnic group. The foreign occupiers then propose to give the other group a state with most of the land even though you still have a bigger population. Is this a proposal you're going to agree to?
This is an oversimplification, although I think it does do a pretty good job of summarizing the Palestinian Arab perspective on things. One of the difficulties here is that every group has a narrative that emphasizes some aspects and details to make them sound like the aggrieved good guys. Note that while there was no native government to control immigration, the Jews going to Mandate Palestine were buying and settling land completely legally. It is also worth noting that the Partition Plan like all good compromises left essentially no group happy, and while the partition plan did give the majority of the lane of "Palestine" to the Jewish state, much of that land was land that was legitimately bought by Jews, and parts of the partitioned land would have likely then joined up as parts of Jordan and Egypt, so a simple percentage accounting doesn't quite summarize things. As always, the history is complicated. Unfortunately, both pro-Israel and pro-Palestinian groups often focus on the details that make their own story sound good rather than actually realize that everyone has a legitimate right, and that moreover, when anyone has been somewhere for multiple generations, getting a satisfactory result that doesn't result in everyone killing each other may be more important than trying to decide who is cosmically right as satisfying as that may be.