Jump to content

Leaderboard


Popular Content

Showing content with the highest reputation since 06/16/20 in all areas

  1. 5 points
    The 'bowling ball on a rubber sheet' is a two dimensional reduction of a 4 dimensional configuration. It has multiple problems, one of which is that you can observe it from an embedding third dimension. Space-time has no embedding dimension; both the bowling ball and you, the observer, would need to be intrinsic to the rubber sheet ( i.e. also two dimensional ). A three dimensional representation would already get rid of some problems, but not all. Picture a three dimensional grid, where x, y, and z axis divide up the space into cubic elements. A mass placed in this space would curve the x, y, and z lines such that the elements are moreskewed, and smaller, as you get closer to the mass. That is 'space' curvature, and one aspect of gravity, but already much harder to visualize than the two dimensional example of the bowling ball/rubber sheet. Actual gravity is four dimensional 'curvature' of space-time, and I can't help you visualize that as it is impossible. Some problems are just not suited to visualization, but understanding even just the basics of the math goes a long way to clarifying things.
  2. 5 points
    At which point, I have to post this: https://what-if.xkcd.com/1/ Spoiler: it doesn't end well
  3. 4 points
    My little bother just ate all the Scrabble tiles and his poop made more sense than you do.
  4. 3 points
    I will not attempt to answer that particular 'why', but I will offer you a plausible explanation as to why your thoughts have been generally dismissed by other forum members. In no particular order: You have failed to provide a concise and coherent explanation of your proposal. You have made many assertions, but have offered no meaningful support for those assertions. Your posts have seemed belligerent, discourteous and at times hysterical You have not been attentive to replies Your proposals may have much value and even be the correct way forward, however emotional rants will never be as effective as rational argument. I recommend organising your thoughts, presenting them in a simple, straightforward manner, and toning down on the patronising agression. Of course, if you don't really want to convince anyone, then keep doing what you are doing.
  5. 3 points
    @IDoNotCare Sorry if you're feeling attacked but you need to be able to summarize(and no I'm not a sock puppet). Nobody can read minds here. I might hazard a guess that you're talking about a post scarcity society and more specifically 'fully automated luxury communism', but you need to spell that out. Without a good reason to, nobody wants to sit through a bunch of YouTube videos or go offsite to a random link. In some cases there is just an initial investment hump that automation has to be pushed over. Admittedly communist countries also tend to nationalize simultaneously, which is a great way to kill outside investment. I think we'll at least see automated trucks. For long-hauls along a highway it would be simple enough. Even if legally they end up needing a truck tender, you could find someone cheaper than a full time driver. At it's heart most R&D boils down to an optimization problem, so algorithms can work for some things. We might still need either a person or possibly a well trained AI, to define problem constraints. I don't think work will be truly eliminated but it might be more of what people actually like or want to dedicate themselves to.
  6. 3 points
    Well, I'll be damned. One wave of the hand, and 5+ billion of us, who just happened to be born into non-Christian cultures, sentenced to burn in hell for all eternity. Makes me wonder just which of those two guys to blame, really.
  7. 3 points
    Just to add to what has already been said by other contributors here: 1. First and foremost, the notion of "gravitational potential" can only be defined in spacetimes that are stationary (more precisely: those which admit a time-like Killing vector field) and asymptotically flat. It cannot be generalised to more general spacetimes, which makes it useless so far as a general model for gravity is concerned 2. Gravitational potential itself is not an observable, only differences in potential can be observed and measured. This is because the potential has a gauge freedom, in that one can freely choose where the zero point is, without affecting the physics. The same is not true for the speed of light, hence the relation above is trivially and obviously wrong, since it equates two quantities that cannot physically and numerically be equal, on fundamental grounds. 3. A varying speed of light would constitute a violation of Lorentz invariance. This symmetry has been experimentally and extensively tested with modern equipment to extremely high precision, both here on Earth and in the vacuum of space - needless to say, no such violations have ever been found. Given the degree of precision of these tests, any variability in the speed of light can effectively be ruled out far beyond the usual 5 sigma threshold. 4. A variable speed of light would also break CPT symmetry, which underlies the Standard Model of Particle Physics. Since we continue to successfully use and test this model in particle accelerators on pretty much a daily basis, any variability in c can also effectively be ruled out on that ground. 5. Neither classical Maxwellian electrodynamics nor quantum electrodynamics allow for varying values of permittivity and permeability (in the same medium of course). Hence the notion of a varying speed of light is actually in direct contradiction to what we know about electrodynamics. 6. As has been pointed out on another recent thread, a scalar field theory such as this one is fundamentally incapable of capturing all required degrees of freedom of gravity; there is more to gravity than just time dilation! I could probably go on, but these are the points that immediately come to mind without thinking about the issue too much. I'll leave it at this.
  8. 3 points
    Disclaimer: Black hole not visible, southern hemisphere required. https://www.theregister.com/2020/05/06/nearest_black_hole_earth/
  9. 3 points
    You mean calling him a "racist"? That is no more "name calling" than referring to someone a "physicist" or a "plumber". Name calling implies an insult. "Racist" is a title he earned all by himself. I don't see what is to be gained by dancing around words to spare people's feelings. This place is not a quilting circle. So there is the "status quo" and there is "your way". Some people feel there are other means to change the status quo, and they don't involve allowing others a platform to share hatred and bigotry. I allow no room in my heart for showing understanding for racism. Hatred of others based on the color of their skin is never acceptable to me. I will not stand by while others spew hate without calling them out. There is a reason people lose sponsors, advertisers, and even jobs after making racist comments. It is not acceptable. I don't see why we should be an exception.
  10. 3 points
    ! Moderator Note No, you're racist because you espouse racist beliefs, the expression of which on this forum (besides being wrong) is also against the rules. Consider yourself banned.
  11. 2 points
    https://medicalxpress.com/news/2020-07-rna-reversing-mutations-underlying-neurological.html?fbclid=IwAR38JE4SGPC-ODBqRzTmdpenmcsLHHiSbfUa63rZhH42UFk0Lfxg-qPd5vI This sounds to me like a piece of very interesting news. Possibilities of editing RNA is a topic that fascinates me, although I still have to learn a lot about it.
  12. 2 points
  13. 2 points
    Because physicist don't bother, as long a they have perfect operational definitions of time. The question 'What is time?' is, as already remarked, a philosophical question. Not a question about physics. I think even you have no problem to understand what the traffic sign '50 km/h' means. Really, physicists have no problem with their 'dx/dt', or whatever changes according to t. And there are already several threads about time, and I think most of them in the philosophy-forum, where it belongs.
  14. 2 points
    In his mind I suspect it was the "...idiotic thread. We don't care about you beliefs" part. Accurate or not (I looked at the thread) it could be interpreted as rude and intended to dehumanize him. Just sayin'.
  15. 2 points
    ! Moderator Note This is a difficult admission, but a sensible one. A couple of things, though. You didn't quit. Your idea was refuted through discussion, and that's the way this works. Discussion helps fill the gaps in our knowledge, and shows us where we need to study more. So the other thing is, you don't need to be sorry for posting your idea. You need to stay and join some other discussions, ask questions, and keep learning. It's obvious you're smart. Thanks for posting and taking the time to respond to critical examination. I'll close this thread and hope to see more.
  16. 2 points
    Can we please just agree that the risk from knives is not equivalent to the risk from firearms and move on from this silly tangent? Yes. Not perfect, but much better
  17. 2 points
    “We will automate everything” is a pipe dream. 1. For processes where it was cheaper to automate, it would have already happened. 2. Some things we are trying to automate and are finding that it’s very hard (see:self-driving cars) 3. Things like R&D will likely never be automated Also, if you want to propose communism, you need to not only draw a path of how to get there, but also how you will avoid the catastrophes observed in previous attempts
  18. 2 points
    I hesitate to say that you are confused, since you have not acquired sufficient knowledge of your subject to reach such a progressive state. Rather, you are wrong on just about everything you have said. Obviously you share an interest in evolution, as do those who have replied in this thread. I think that's a good thing, not least because I am your companion in such an interest. Unfortunately the only statement I can see that may be thought true is "Evolution is a slow process". If we look back ten generations we find that while the alleles (variants) of genes may be different in some cases, nearly all of those differences are due to mixing of existing alleles during fertilisation. In terms of evolution this will produce only short term differences that are easily reversed. Until you have taken this concept on board (then several more) there is no point in you wasting your time with wild, unfounded speculation. There are some very knowledgeable members on this board - I think some of them are professional biologists. You should take advantage of their presence by asking question that will help educate you on the subject, instead of proposing crazy ideas.
  19. 2 points
    He launched yet another weapon of mass distraction
  20. 2 points
    I agree that the OP definition is not quite right, but both your A and B examples have two errors. Yes a zero error is a systematic error but it is not due to a wrongly marked or non uniform graduation and yes it can result in an increased or decreased actual measurement. A simple example of a zero error would be dirt on the pan of an otherwise accurate weighing scale.
  21. 2 points
    Aren't you all glad that you found science as an interest/vocation? We could all easily be victims to this kind of BS if we didn't know the science basics.
  22. 2 points
    My very short answer: A value of a random variable. Let's say you receive a symbol "1". If this is the only possible symbol the fact that you received it does not give you information. But if this symbol is one of two possible, "0" and "1", then the reception of symbol "1" may contain information. So having more that one symbol is a requirement, but not sufficient. Lets say you receive the pattern "111111...". The probability of the symbol "1" is 1. Again there is no information. But if random sequences are allowed, for example "00", "01", "10", "11" then we may use these sequences to represent information. So conceptually information can be seen as a value form of a random variable. The above is an attempt at an extremely short introduction to information theory, which is tied to discrete probability theory. Most important early contributor was Claude E. Shannon and his paper “A Mathematical Theory of Communication”, dealing quantitatively with the concept of “information”. Shannons concepts and the mathematics he used to describe information and to measure information content is a remarkable contribution. I believe it's tricky to find any areas of IT where his work does not contribute. Wikipedia* has links to some concepts related to your question. Feel free to ask additional questions. *) https://en.wikipedia.org/wiki/A_Mathematical_Theory_of_Communication For an early predecessor of Shannon, working on sinus signals and frequencies, see Hartley: https://en.wikipedia.org/wiki/Ralph_Hartley
  23. 2 points
    No. They are purely about the "completeness" of formal systems. In other words, can a formal system (e.g. mathematics) prove that anything that can be written down using that formal system is either true of false. And the answer to that is no. You can write something using mathematics that you cannot use the same mathematics to prove or disprove. You can extend your formal system to make it more complete and allow you to prove that statement. But then there will be other statements that this extended system cannot prove. And so ad infinitum. Physics uses mathematics but it is not limited by that mathematics in the same way. (And some mathematicians complain that physicists are a bit "ad hoc" and don't really stick to absolutely formal derivations.)
  24. 2 points
    That is out of my knowledge. The only thing I can say is that trying to change the elements (river, sea, land) in a specific way most of the times drive to unexpected results. I have the experience where a hotel constructed a small dock in the sea for his single inflated boat sportcraft had the result to erase completely its sandy beach.
  25. 2 points
    Since this is the lounge I'll do some less rigorous analysis showing why science is of no use. Observations in the movie clip. 1: Zoro does not seem to follow the trajectory of a massive object; heigh above ground seems maintained. 2: Zoro does not seem affected by air resistance; speed is not reduced during the flight 3: There is atmosphere on the world where the fight takes place. 1: means that (a) Zoro is either massless* and hence unaffected by gravity or (b) neutrally buoyant in the atmosphere, like as a hot air balloon. 2&3: means Zoro could be (c) extremely dense, having extreme momentum. But (c) can't be compatible with 1, massive object fall down. And (b) is not compatible with 2, balloons stop quickly when thrown in air. (a) is pointless, a massless Zoro, swords included, would have zero effect on a stone golem; there is no kinetic energy or momentum that can affect the golem. That means Zoro travels through air by magic because the described airstrip is physically impossible. I do not know how magic affects drag and Bernouilli's principle, so again: Side note: That fact the manga story is failing to describe physically probable action does not mean I can't see it as entertaining. I enjoy entertaining stories, if the canon of the universe where the events take place allow magic, faster than light travel etc I don't care how impossible that might be according to mainstream science. I just chose to not mix my interest in science and engineering into the events of fiction and fantasy in the story. *) I know that would mean a photon speed of c in vacuum and massless bodies of macroscopic size does not exist AFAIK; creating one would require magic. But this is the lounge after all, and we will get to the point anyway.
  26. 2 points
    Just to add to that, it's not like in SR where each observer also has a different notion of simultaneity, but each of those is physically meaningful. Eg. in flat spacetime, any two events that can be considered simultaneous by someone will have intersecting future light cones, where different future observers can agree or disagree on whether the events were simultaneous. In GR you must make a choice of how to define the surfaces of a foliation, that's not just based on a physically meaningful connection between its events. You'd choose it to make a useful tool, not a 'real' representation of simultaneity throughout the universe for a given observer.
  27. 2 points
    If you have scientific evidence for a non-mainstream topic, and you think you can defend it reasonably, put it in Speculations. If it pertains to a field of personality studies you can defend using science, post in Psychiatry/Psychology. If it's something you feel might pertain to a specific philosophy or ethical approach, post in Philosophy. If it's just New Age mysticism that works because you say so and wave your hands a LOT, please don't post anything at all.
  28. 2 points
    There are things the Bible doesn't say and almost everybody believes it does. There was no apple. It could have been a quince, or maybe a fig, as there were no apples back then in the Middle East. The Bible doesn't say it was an apple, actually. The Bible doesn't say Jonah was eaten by a whale either. The Bible doesn't say there was an angel at the Garden of Eden, but a cherub, which was a mythical animal represented very frequently in the gardens of palaces throughout the Middle East. The Hebrew Bible doesn't say that Mary was a virgin, but a "young woman." ------------------------------------------------ There are things the Bible says and few people know it does. The Bible talks about a pantheon of gods that are subservient to Yahweh. And names God both as Yahweh and El. Is it the same god? I'm not sure. Asherah, the wife of Yahweh, is also mentioned, but the interpretation was presumably changed, as it's mentioned as a synonym for "a stick" in very obscure passages, when she is known to have been a goddess, as archaeology has shown. The stick was one of the symbols of the goddess. Back to Adam and Eve: There's at least one thing the Bible says twice in different (incompatible) ways: Ezechiel 28. Two prophecies, one of them against the king of Tyre. There you can see that the king of Tyre is expelled from the Garden of Eden, on account of his sins. The cherub also appears. Very similar legend; two different narrative uses. Who was expelled from the Garden of Eden, Adam and Eve or the king of Tyre? I'm not so sure. The authors of the Bible seem not to be either. Some scholars believe the Oracles against the king in Ezechiel 28 predate the Adam and Eve story in Genesis. ------------------------------------------------ There are things the Bible says that are taken from somewhere else: The Bible takes the story of Noah from The Epic of Gilgamesh, Utnapishtim , and adapts it to its own narrative needs. ------------------------------------------------ There are blatantly obvious things the Bible is silent about: Omri, big king of Samaria, was a very relevant character of the Assyrian domination period, but the Bible only mentions him in passing, as a baddie. The Bible also plays down the role of many other kings, like Manasseh, although he made Israel into an important olive oil factory and brought a period of peace, contrary to what Hezekiah, his father, did. ------------------------------------------------ And lastly, there are many things the Bible says that cannot be true. Josuah didn't conquer Jericho, as Kathleen Kenyon has proved. Jericho was uninhabited at the time. Plus the Egyptians were in control of Canaan and had the country strongly policed from Beit She'an. I don't believe God gave the law of gravity a suspension for some hours for the benefit of his people to the detriment of the Canaanites either. Plus the Canaanites and the Israelites were the same people: No difference in material culture or belief system, as Israel Finkelstein has shown. Abraham could not have possibly used camels. Camels were domesticated about 1000 years later.
  29. 2 points
    One of the best little pieces of comic theatre of all time was based on this. Here is wikipedia, you may be able to find a ytube of it. https://en.wikipedia.org/wiki/Class_sketch Yes indeed it is quite long, so I do not find it suprising there are some contentious points. The author is rather dismissive of the use of auxiliary verbs in general and the verb to be in particular. He claims that the verb to be is unneccessary and has almost withered away. Not so. Consider the travels of Marco Polo to China, a jourrney that took several years. Had he been English, Marco might have said, "I'm going to go to China next week." As he left Italy he might have said "I'm going to China". Two years later he was still "going to China", he had not by then arrived. One thing he would not have said would be "I go to China". The action was "imperfect" as it occupied an extended length of time and was still in progress during other events that might be spoken about. Imperfect here means that it is not complete at the time of utterance. A perfect action is complete from start to finish. An imperfect one may never be completed for some reason. Two other gripes with the article. Firstly no mention is made of the difference between spoken and written language when comparing English to other languages. It is my belief that this difference is one of the key factors as most languages are largely phonetic, English being the glaring exception. So it is emminently possible to learn and know many words and the associated grammar in English but not to be able to say or recognise them when spoken. Even English speakers sometimes have this trouble. Take the letter a as in car or cat. The big difference in the pronunciation of the 'a' leads to two difference pronunciations of the word castle, which confuses many. Secondly the thesis that it was the influence of the Vikings who did away with the manyfold word endings. One wonders why they did also do this with old French. Or why the endings were still there in middle English a couple of centuries after the end of the Viking era.
  30. 2 points
    Hi Ahmet, just some thoughts... Very (extremely) few people achieve to live from music. Even less as a composer. You better make software: easier, well paid, many jobs. Violin professors have hundreds of students in their career, one is more talented and trains seriously, and becomes her or himself a professor. Sometimes, this exceptional student is even more exceptional and earns his living by playing music rather than teaching it. These are the orchestra musicians. Soloists are even much rarer, composers too. How many composers does a concert need? Presently, Covid-19 is an absolute disaster for all performing arts. No concerts, or concerts without public, meaning less incomes for the orchestra. Most musicians are not on the permanent payroll, so they get no engagement at all. Playing on the street is presently no-no in many countries. Youtube brings zilch to standard musicians. Romania is a fantastic place to hear music. But to play it? People from Romania and Moldova go to Germany and Austria to live from music. What kind of music? A few people manage to live from folkloric / cigani / klezmer / etc music. That could work better than classical music. It's often not a first choice. Illenyi Katica, Rusanda Panfili... are all excellent classical musicians who jumped into folkloric music to make a living. Or do you mean songs for the TV?
  31. 2 points
    We can already invalidate Yanchilans theory as we have already tested different gravitational potentials for time dilation at different elevations. With precision atomic clocks. Even testing it a distance of one foot. The results agree with GRT. https://www.nist.gov/news-events/news/2010/09/nist-clock-experiment-demonstrates-your-head-older-your-feet This isn't the only experiment done at different elevations. I assisted at a University that also conducted similar experiments as part of the course curriculum. Though we used the coastal mountains of BC coast. It was pointless publishing the results. Nothing newsworthy or unexpected.
  32. 2 points
    When people say "Well, the dictionary says..." they obviously don't realize that a modern dictionary is a contemporary record of usage and not an authority. The people at large determine the usage in any given period.
  33. 2 points
    That is a really good question, because I still don't know what your position actually is. You seem to be saying that the concept of an evaporating Schwarzschild black hole is self-contradictory - which is trivially true, because Schwarzschild black holes are of course stationary by definition. But evaporating black holes aren't of the Schwarzschild kind, so where exactly is the issue? Then so you also seem to be saying that even ordinary Schwarzschild black holes are self-contradictory, because somehow event horizons can't exist? But I don't understand why you think this, because the reasons you give don't make any sense.
  34. 2 points
    I think it makes no sense to say that the vedas were twisted or not. They have grown organically. There are so many reasons for a text to change, especially when it originally was an oral tradition. Without having the 'original' how would you see that the texts changed? There are methods to find out which of the present versions we have are probably the oldest, but of course we can have no idea what the first written down version of the vedas were. And then there are many reasons why texts change over time, just to name a few: errors when copying the texts corrections of (language) errors authors putting in their ideas into the texts, in good or ill faith I only know a little about the history of Christian texts, which are of course not so old as the vedas, and also here already the problem exists that we do not know exactly what the original texts were. But we know copyists made errors, corrected errors, put in sentences or even complete stories, often because these copyists had a theological agenda to promote their version of Christianity. From some texts we know that there must have been more original texts, but they did not survive. With the vedas this will be worse, because they were orally passed to others for a much longer time. In Christianity, especially the new testament, there are at most only about 100 years between the oral tradition and the first written down versions we have (often less: the gospels were written till about 100 years, the earliest one probably only 30 years, after Jesus' death). With the vedas it is several millennia before they were written down.
  35. 2 points
    This is what I got from your posts: 1) A black hole and all the events in its interior can be described in the coordinates of an observer at infinity. 2) A Penrose diagram of an evaporating black hole shows that the formation and disappearance of a black hole have the same time coordinate. 3) If an event A has a coordinate time that is less than the coordinate time of an event B, then A happened before B (maybe even in B's past?). Problems with this: (1) The interior events do not have meaningful time coordinates for this observer. (2) If that's what the diagram really shows, then the coordinates used in that diagram can't be the same as for the observer in (1). (3) You're comparing coordinate times of events that have no causal connections, and their ordering is irrelevant, but you see "logic problems" by treating it as something physical.
  36. 2 points
    Really ? Cosmic rays enter the atmosphere billions of times, yet not a single micro BH has ever been detected. Maybe you can produce a citation of a detected micro BH. I can certainly post numerous citations of cosmic ray detections.
  37. 2 points
    Stu the cockatoo is new at the zoo...
  38. 2 points
    The issue that I see with this thread is that I'm proposing actual implementable changes. To the Police Unions and Hiring/training practices, for example. Then we start to work on the DAs who bring up unfair charges on minorities. Saying the problem is systemic ( your meaning CY ) means the whole justice system ( and more ) needs to change, from cops, all the way to the Supreme Court. And we both know that's not going to happen; so nothing will change. The higher up you go in the justice system, the more political it is. And with your polarized two party system, who would even propose such a change, and hope to get re-elected ? Myself, I don't see the point of self-flagellation, and saying "It's all whitey's or the system's fault, and not trying to do something about it. People are dying needlessly, and all I'm hearing is blaming, but no solutions.
  39. 2 points
    Where did this red herring come from? We’re not talking about all criminal activity, we’re talking about police, who are supposed to protect and serve the public, and who should be held to a higher standard. We’re also talking about violent behavior. That’s not an instance of excessive force. I was short of straw before but now I have a lifetime supply. Sure. But you had only proposed screening for white supremacy Yes. If they had not tolerated such behavior, you might say...
  40. 2 points
    I suspect it relates to the alleged instances of people time travelling without the benefit of physical mechanism. The example that comes to mind is of the two visitors to Versailles early in the 20th century who seemed to be transported back to an earlier period where the people they saw and the layout of the gardens matched (allegedly) the late 18th century. Wikipedia article. There is also a silent movie era newsreel (?) in which a member of the crowd appears to be using a mobile phone. All of the instances have simpler, more convincing, mundane explanations, but its a useful plot device for stories.
  41. 2 points
    They are NOT the exact same things. You are confusing the word "special" with the word "preferred". We don't laugh at the the idea of the Earth being in a special place, we laugh at the idea that the Earth might be in a preferred place. When you were but a wee child and your mother said you were "her special boy", she simply meant you held some significance for her. You were 'neat', or 'cool'. She wasn't implying that the universe was centered on you. Similarly, we live in a special time and place. We witnessed the first time humans detected gravity waves and the invention of the autostereogram. If we weren't at this location (on Earth) at this time, we could not have seen that with our own eyes. Unfortunately we did not exist at that special time when the four fundamental forces were combined, but we are lucky to live at the special time when all these superclusters can be detected. And that is really neat.
  42. 2 points
    Yes it helped and I got my answer.
  43. 2 points
    That's what I think. Art and/or symbolism certainly imply intelligence. But I would make the further qualification that first hints only too reasonably come later than the real thing. The excavations of Homo naledi (335,000–236,000 years ago) at the Rising Star cave in South Africa have shown that, very likely, a stray cousin of ours that looked very much like an upright ape and didn't use tools or made any kind of art, seemed to go to the trouble of carefully placing their dead in an almost inaccessible dead end of a cave where no other fossils of animals have been found. My suspicion is that some "human" attributes go farther back than we dare to postulate. Cautiousness is mandatory, of course.
  44. 2 points
    My earlier comments related specifically to Schwarzschild black holes - which are stationary, hence they don’t evaporate. Generalising this to the case of an evaporating black hole is not straightforward or trivial. Such black holes are called Vaidya black holes, and this represents an entirely different solution to the field equations, and thus a spacetime with a different geometry. While Schwarzschild is a vacuum solution, Vaidya is not, because now all of spacetime is filled with radiation, so we are no longer in a vacuum. Adding relative motion between observer and a Vaidya black hole does of course not yield the aforementioned Aichlburg-Sexl ultraboost, but some different metric, which I have not encountered in my studies. Like in the Schwarzschild case, that new metric would be related to the Vaidya metric by some coordinate transformation, but I suspect the transformation will be a lot more complex than in Schwarzschild spacetime, mostly due to the presence of off-diagonal terms in the metric tensor. I’m sure it can be done though, and probably has been, though a quick search does not immediately turn up anything. But the answer to your question will be “no” regardless, because in both cases we are in a curved spacetime, so you can’t naively use the transformation rules of SR. The total time dilation here has a kinetic component from relative motion, and a gravitational component from spacetime curvature. So the lifetime a specific observer calculates for the black hole will be subject not only to his relative speed, but also to the particulars of the geodesic he traces out (i.e. to the initial and boundary conditions of his motion), and where on this geodesic he is when he performs the calculation; so it will be some (probably quite complicated) function of his trajectory and the surface area of the horizon (which will itself be some complicated function, since the horizon is no longer spherical for such an observer). This is a common misunderstanding based on the fundamental error of using the wrong solution to the field equations for the scenario at hand. I know that countless papers have been published showing this calculation, but ultimately these results are not physically meaningful. If you naively go and consider free-fall observers in Schwarzschild spacetime, then yes, the maths will show you that they can’t detect Hawking radiation. However, evaporating black holes are by definition not Schwarzschild, so this point is moot. When done correctly using Vaidya spacetime, the free fall observer will definitely detect radiation (it is a non-vacuum spacetime after all!), just at a different temperature relative to other observers. The type of physical spacetime one is in is characterised by curvature invariants, which is something all observers always agree on, even if they use different coordinate charts to map that spacetime. Like I said, one must use the correct spacetime to model this scenario. How in-fall time is related to evaporation time of a black hole in Vaidya spacetime is a question I can’t answer off hand. It would likely depend on the initial mass of the black hole, its age (as calculated by the in-falling observer), and the in-fall geodesic. For solar-mass (at the time of in-fall) black holes though the lifetime of the black hole will be much longer than the length of most in-fall geodesics, by many orders of magnitude.
  45. 2 points
    Generally speaking, I am on your side. In this specific case, they made a comment where it is difficult to interpret it in any way that isn't racist: The first part of this comment implies that the people that Hitler deliberately committed genocide against don't get to count as "people". The second part is so facially false in its misrepresentation of basic history that it indicates the writer is either a troll or such a committed racist that they don't even care about the genocide itself. Either way, a forum setting is not going to convince them to change their ways. Part of the difference is that they did more than express distaste. They used that distaste to make derogatory claims about black culture as a whole, and to dismiss the protests without even engaging with the basic claims of the protests, with a strong implication that black people don't deserve to protest. On a side note: I strongly disagree with the implication that "disrespect for authority" is necessarily a problem. To a large extent, the protests are about the claim that that authority is being abused - and authority being abused should not be respected.
  46. 2 points
    There are two somewhat different issues here: one is discussing racism in general, and another is discussing it on this site. As for the latter, as iNow and Phi (and possibly others) have pointed out, we want arguments to be in good faith. Disagreement must maintain a certain amount of civility. So if someone shows up dropping N-bombs, or disparaging religions, they will be shown the door. We are not obligated to make people suffer written abuse in an effort to change a bigot's mind. If that's the price of participation, for us it's too high.
  47. 2 points
    Racism isn't about labels, it's about hate. Hate is an issue of emotion not intellect. As emotion, the afflicted may only be solved or remedied by therapy rather than by reasoned discussion as we may find in open forums like this. In this forum, we can intellectualize the causes and cures for hate but we can no more treat that condition via our online debates with racist than we can remotely remove a tumor. There's a reason why this science forum discourages visitors seeking medical advice. Similarly, there are reasons why hate filled sufferers are equally discouraged in this forum. They need help we can't render here.
  48. 2 points
    essereio has been permanently banned for repeated violations of rule 2.1.
  49. 2 points
    I assume you aren't making the final decision so don't take that responsibility. You should create a PowerPoint presentation referencing the various options that are available and present that to the other members of your team so an informed decision can be made. If you are uncomfortable doing so yourself I'm sure you can recruit a consultant on a temporary basis to do so.
  50. 2 points
    With the limited information available my answer will be very general. I would be cautious if someone provides detailed answers based on limited information. 10s of thousands can be a tiny or huge depending on the amount of data, how the traffic is clustered, response time requirements, processing required to create an answer, what standard services that are already available as services, API, micro services etc.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.