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  1. 4 points
  2. 4 points
    Ok, I get you now. This is not a trivial question, and the short truth is that we do not really know the answer, based on currently known physics. The trouble is this - the established model currently available to describe gravity (General Relativity, or GR for short) is purely classical, meaning it does not and cannot account for quantum effects. When we describe the process of gravitational collapse, then in the beginning stages of that process quantum effects can be neglected, so up to a certain point GR does a really good job in describing things. We can even cheat a bit, and extend the range for which our description is valid by considering already known quantum effects simply as classical pressures that counteract gravity. For suitable initial conditions, this may yield an equilibrium state such as a dwarf star, or a neutron star, or something more exotic like quark stars. However, once the total mass of the collapsing object exceeds a certain limit, there is no known mechanism by which the collapse could be stopped - in these cases the object keeps collapsing under its own gravity, and eventually becomes so dense that quantum gravitational effects can no longer be ignored. At that point General Relativity quite simply stops being a valid model. And this is where we get stuck, because we do not yet have a model of quantum gravity, so we simply do not know what happens in the final stages of such a collapse, and what happens to the mass of the original object. There are a few speculations, hypotheses and candidate models, but none of them is sufficiently well understood, or tested in any way. If we naively consider GR on its own, the end result of this collapse is a singularity - all the mass of the collapsing object becomes concentrated in a single point of infinite density, and infinite spacetime curvature. The ‘size’ of that infinity is always zero, regardless of how much mass you start out with, and regardless of how much mass falls into it later on. However, this is not to be understood as a physical prediction - in physics, when a model becomes singular and infinite, then that simply means that we have wrongly extended that model beyond its domain of applicability. In this particular case, we have attempted to apply a purely classical model to a physical situation that is decidedly not classical, so obviously the answer we get is not physically meaningful. Note that the singularity itself, for mathematical reasons, wouldn’t be part of the spacetime manifold, so counterintuitively the entire spacetime in and around a black hole of this kind would be completely empty. The mass of such a black hole is actually a global property of the entire spacetime, and cannot be localised anywhere. The volume of a singularity - in so far as that concept makes sense (it doesn’t, really) is zero. This is true for both point singularities, and ring singularities. Yes, in the purely classical picture of GR it would be matter compressed to infinite density. But we know (see above) that this is not a physical meaningful concept, since it cannot happen in the real universe. Even the already known laws of quantum physics prohibit such a state (ref e.g. the Pauli exclusion principle). Again, in the classical picture of GR the answer is no - the singularity remains point-like or ring-like. What does change though is the radius of the event horizon. When we look at current attempts to write out a model of quantum gravity (a very difficult problem!), then three main themes emerge, depending on which model is used: 1. Below a certain length scale, a new symmetry emerges that turns the collapse into a rebound - so the collapsing matter will never become singular, but instead begins to ‘bounce’ back out while the event horizon shrinks. However, due to the extreme time dilation in that region, this process would take a very long time (~100s of billions of years) as seen by an outside observer, which is why it has never been observed. 2. You end up with some sort of exotic degeneracy state below the horizon, such as a fuzzball. 3. Spacetime itself becomes quantised below a certain length scale, so the question as to what happens to the matter or where it goes becomes meaningless There is no telling at present if any of these possibilities describes what actually happens in the real world. Yes, but at the same time it will also continue to evaporate via Hawking radiation.
  3. 4 points
    Attitudes such as these have led to over 800 thousand deaths and counting. It also the reason why folks do not vaccinate against influenza and thereby needlessly increasing death rates. It would only be sad, if folks who adhere to these beliefs were also the victims. Unfortunately dealing with diseases is a community effort.
  4. 3 points
    Always I see the same pattern. Brush aside explanations and equations as if you didn't even read them, but always latch on to any idea that justifies a failure to understand relativity as if that's just another equally valid viewpoint. I think Asimov's "my ignorance is just as good as your knowledge" quote applies. You say your view is "simpler" but it's just a misunderstanding. It makes me think that people who put effort into trying to explain things to you over and over are just wasting their time. You ask questions as if you want to understand, and then reply to answers as if your questions were only meant to demonstrate what you see as "problems with Relativity" and you had no interest in understanding how they're resolved. If you were interested in understanding it, you'd spend more time talking about what relativity says that doesn't make sense to you, and less about how much sense an alternative makes.
  5. 3 points
    Wait, a youtube video was inaccurate? Noooooooo!
  6. 3 points
    Decades of gerrymandered districts, voter suppression, power concentrated in the hands of only 2 parties, tribal us/them indoctrination where people vote party over person or policy, plus massive, unlimited, anonymous inflows of money into politics has allowed the craziest and most extreme candidates to “represent” us. The Republican Party saw a wave of extreme representatives come to power after the Great Recession with the anger of the Tea Party movement, has spent years denying basic facts on topics like evolution and climate change and tax cuts paying for themselves and all of that fertilized the ground for conspiracy thinking and treating their opinions as if they are equivalent to other people’s facts. This led then to an opening where the entire party experienced a hostile takeover in the 2016 election where Republicans were too afraid follow their conscience, to speak out against Trump, or to vote in favor of his impeachment. They put personal power over health of the nation and correctly calculated that their own voters liked Trump more than they liked them so they needed to fall in line or leave. Now it’s mostly just a cult who thinks people on the left are subhuman garbage in need of a bullet to the face and these divisions are being actively stoked by state actors like Russia, China, and Iran and are being further amplified by US citizens themselves who have plugged into QAnon and other actual fake news sources.
  7. 3 points
    So another sort of analogy then: This thread of yours seems like saying "given a banana could ride a bicycle, I claim it would compete in the tour de France" ... and then trying to say "I don't want to talk about how a banana rides a bike, just the impact on the cycle race". After someone dies, what is retaining their last thought or feeling?
  8. 3 points
    You can publicly express support for any theory you want. But others can publicly express their displeasure, and ridicule you for it. Free speech is for all. Even on this forum, you are allowed to present alternate theories of human evolution. But you had better do it in good faith, and back it with evidence.
  9. 3 points
    The reddening we see with the setting Sun is due to the blue end of the spectrum being scattered. Thus the light coming from the direction of the Sun has less Blue light and looks redder. The red-shft we see from distant galaxies cannot be due to a like effect. We measure red-shift by looking at the light's spectrum. In it are patterns of lines that are like "fingerprints" for elements. Each pattern isn't only unique, but it is produced in a certain point of the spectrum. If the red-shift was due to a scattering out of blue light, all you would see would be a dimming in the blue end of the spectrum. The spectral lines would still be there and in the same place. This is not what we see. Instead we see a shift of the whole spectrum towards the red. Spectral lines have moved further to the red end of the spectrum. The wavelength of the light itself has been changed, rather than just certain frequencies filtered out leaving redder light behind. (in fact, red-shifting will shift non-visible frequency ultraviolet into the visible light range.)
  10. 3 points
    ! Moderator Note We have certain requirements for discussion of speculative ideas, and your posts fall well short. This is a science discussion site, meaning there needs to be some scientific basis for the discussion. Your ideas seem to have been pulled out of...an alternate dimension. Don't bring this topic up again.
  11. 3 points
    Exciting update! IDoNotCare had now been permanently banned for similar offences.
  12. 3 points
    GR certainly does predict the mass of supermassive BHs. There is no upper limit on BH size/mass. We don't yet understand the localization of large amounts of mass/energy in the early universe to account for them. But again, that is a problem with galaxy formation; you have it backwards. Pray tell. How does your model cope with the information paradox ? How does it preserve information once behind the event horizon ? Why can you easily 'see' problems with BHs as defined by GR, or as defined by Ghideon in his demonstrative thought experiment, but you are totally oblivious to the problems in your conjecture ? Take off the blinders !!
  13. 3 points
    All of them; but by proxy.
  14. 2 points
    I have to advise caution in the interpretation of food-borne disease illnesses. Countries have different ways to identify and quantify outbreaks and one cannot easily just look at the raw data. There is also a difference between severity which makes it even trickier. One way to normalize the data is to calculate disability adjusted life years (DALY), which basically is an estimate of years lost to ill-health or death. From there and using WHO data there is not a vast difference between the North American region (USA, Canada, Cuba, 35 DALY per 100,000 ) vs Western Europe (40-50 DALY per 100,000; I do not have finer grained data on hand). While there are significant differences in the type of diseases. there is not a huge difference when it comes to Salmonella infections. In fact, it is slightly lower in the NA region (9 vs 12), though it is difficult to disentangle the effects of animal handling, food production, impact of chlorination and the health care system. However, the point is that it the calculated health burden are the totality of all these measures. I.e. it is possible that without chlorination the DALY might increase in the US, which would indicate that Europe is doing something better without the need for it. Or it may not make a difference, indicating that the practice is useless. But the tricky bit is really finding which elements in the whole chain are really protective, especially as certain elements may rely on other part of the whole thing. So as a whole it is not trivial to state whether the whole food chain is safer in Europe vs North America (or even US specifically). Each regulations seem to keep the burden of food-borne diseases somewhat similarly in check, but there are also other benefits when it comes to different approaches in regulating the food chain. But again, I think direct comparisons are difficult, not least because rules and regulations in each region are not necessarily based on best science, but rather a quagmire of heavily politicized historic rules, regulation and practices. With increasing globalization the food supply chain has become even more complex and I have severe doubt that regulations are keeping up.
  15. 2 points
    The EU is big enough to tell the US to stick their chlorinated chicken where the Sun doesn't shine. Post Brexit, the UK will be over a barrel and will have to accept pretty much any offer that the US makes. Anyway; Biden wants the Irish American vote (or, at least, doesn't want to upset them) so it's perfectly sensible US politics for presidential candidates to have a clear view on ensuring the future of the GFA. Since Borris' plan to break international law puts that agreement at risk, it's sensible for any other country to have a view on it. Most countries would prefer to maintain the GFA. If you are Mr Putin- or one of his supporters- you might want to sow discord at the boundary of Europe in order to make Russia look good by comparison. In that case you would want Boris' plan to go ahead. The same would be true for other rogue states with an interest in undermining international law and cooperation.
  16. 2 points
  17. 2 points
    Have you seen such a label in a restaurant? "Figures suggest that the percentage of people who fall ill with food poisoning annually is up to ten times higher in the US than the UK." from https://www.sustainweb.org/news/feb18_US_foodpoisoning/ And, not to put too fine a point on it; I'm not very concerned about chlorinated chicken; I'm concerned about chlorinated chicken sh1t.
  18. 2 points
    I don't think that's true. I don't see a single reply here from michel123456 that relates to trying to understand any of the answers and explanations given. No asking for further details. No working through a solution. Every reply is a justification of not making an effort to learn, an argument of why the explanations can be ignored. Literally 10 years ago he was asking about the same "problems" he had with relativity. 10 years from now, he'll have a similar list of "problems", after thousands of attempts by people to explain it to him, after 0 attempts to work through it. What he's good at, is asking questions that makes one think he's interested in learning about relativity. But look at the replies. The only interest is in what doesn't make sense to him. Anything making sense of it is ignored. That's the only answer he's interested in: that it doesn't make sense. All his questions are phrased as if the answer he expects is that it can't make sense, never a question about how the resolution to the problems work out correctly. So I think he's soapboxing, getting much better responses by stating "relativity is nonsense" as a question. Edit: To be fair, page 1 of this thread is full of counter examples to what I said, including asking about specific examples and numbers and their explanations. I don't know how we got from that on page 1 to page 2 with:
  19. 2 points
    Actually, it is based on the principle that the spacetime interval between two events is invariant (as others here have already pointed out). The invariance of SOL is a consequence of that. Because the spacetime interval is an invariant. Because the spacetime interval is invariant. All observers agree on the same reality - being the invariant spacetime interval. I don’t know what number five was meant to be, but it’s almost certainly addressed by the fact that - you guessed it - the spacetime interval is invariant. One twin is inertial, the other one isn’t, so obviously there is no symmetry, because the frames aren’t related by a Lorentz transformation, but by something a little more complicated. The one who physically measures a non-zero value on his accelerometer at some point on his journey. So you would accept a model that precludes elementary particles from having the property of spin, and where the strong, weak, and EM interactions do not exist? Because all of these things are intrinsically relativistic phenomena. I presume you hold this view because you are not aware of the crucial role relativity plays for the dynamics - and even mere existence - of the particles we observe, never even mind how those particles move under the influence of gravity. There is no ‘space being created’, not sure where you got that from. Apart from that, intelligent people use relativity because they are intelligent enough to realise that it works very well within its domain of applicability. But intelligence isn’t the problem, because you are evidently very intelligent as well, in your own way. The problem is that you equate it (the model) not making sense to you with it having to be wrong. But that’s just a common logical fallacy. Relativity is very much “true”, in the sense that it is a model that works extremely well; whether it makes “sense” (what does that even mean?) to you as an individual person or not is entirely irrelevant to this. Quantum field theory (e.g.) makes little sense to me, it feels like an odd jumble of ad-hoc made-up bits, which are made to fit using even more ad-hoc made-up bits. Nonetheless, I acknowledge that it works really well within its domain, and right now it is the best description of the microscopic world that we have, so I choose to accept it for what it is and study it to the best of my ability. But let’s just say you won’t see me loosing any sleep should it one day be augmented/replaced by something different. This is why we have the scientific method - to minimise subjective measures such as “making sense”. “It doesn’t make sense to me” is simply not a scientific argument. The other problem I see on this thread is that you are rejecting something that you evidently don’t understand very well, judging by some of the statements you have made here. That would be like me fighting tooth and nail against some particular design for a building, even though I know absolutely nothing about design principles, very little about structural mechanics, and even less about how it all fits into the surrounding cityscape. My arguments would thus just be personal opinions without any objective basis, and thus pretty much meaningless to any architect worth their salt. Long story short - if your opinion about relativity is not based on thorough and intensive study of the model itself (which it isn’t - no offence intended at all), and how it fits into the overall framework of physics, then it is scientifically unreliable and you need to question it. This is the core issue that you haven’t grasped in all this - relativistic effects are relationships between frames/observers in spacetime, not things that happen “to” or “in” a single frame. So there is no force contracting anything, and nothing slowing down any clocks. It is only when you take two clocks or two rulers from different frames, and compare them in some suitable manner, that you find that the relationship between them is such that one is dilated/contracted with respect to the other. So for example, when we collide heavy gold ions in the RHIC, then the resulting shower of particles after the collision as seen in the lab frame is consistent only with the gold ions having the shape of flattened disks (due to length contraction in the direction of motion only), not with them being spherical - we can easily tell, because the transition amplitudes of the various scattering and decay processes seen in the lab frame explicitly depend on the spatial distribution of the original ensemble (the ion). The necessary calculations are complicated, but the result is not only consistent with, but mandated by relativity. The same is true in the ion frame (in the sense that the exact same outcome is predicted) - now the ion itself is seen as spherical, but distances in the accelerator are length-contracted, and the oncoming ion is more heavily time-dilated and contracted. But the eventual outcome is the same, so there is perfect symmetry (at the time of collision, i.e. after the acceleration phase). This is a real-world experiment, so we know experimentally that it all checks out.
  20. 2 points
    I think it is wrong to narrowly focus on the Trump administration. It is merely the result of at least decades of anti-science sentiments. One of the main topics used to be creationism which got a strong push into the open in the 2000s (incidentally one of the reasons why I joined this forum). The movement started well before that, though and was an alliance of industrial interests, conservative leadership and media. In essence it was a broader effort to undermine the very concept of scientific validity and thereby allowing politicians to act without the constraints of reality. Key efforts were obviously put on areas with monetary interest, such as climate change denial and over time it morphed into a weird form of conservative identity. Originally a bit fringy, over time it it became the mainstream we see today. This is not exclusive to the US, even in other Western countries, such as Canada, and Australia similar political efforts were made to silence scientists involved in climate change research. However, the cultural identification with denial seems to be an US export.
  21. 2 points
    I don't believe it for one minute ! Not the part about the steel bar of soap, but a Polish guy making Bolognese sauce.
  22. 2 points
    Yeah, I make Phosphine ( see my profile ). I won't go into specifics, but it involves the continuous conversion of white Phosphorus to 20-25% red Phosphorus ( with heat ), and then reacting the slurry in very high strength Phos acid at temps of 300 degrees with superheated steam sparging, according to this patent https://patents.google.com/patent/US3371994A/en None of the required conditions seem unlikely to be found on Venus, so I would suspect a geological process, rather than bio-decay, as the cause ,IF it does turn out to actually be Phosphine.
  23. 2 points
    Where is the overstatement? (I don't intend that as a belligerent observation, but a genuine query as to what you think was overstated.) They do not 'headline' the possible evidence for life - the title speaks of the detection of phosphine They refer in the abstract to the apparent presence of phosphine. They detaill the abiotic routes to phosphine they have eliminated and note that a biotic source is suggested through analogy with its terrestrial production, not via any demonstrable pathway. They searched carefully all current databases for other possible chemical species that might have been responsible for the transition signature. They discuss at some length within the paper and the supplementary material what abiotic processes they have considered and why they have rejected them. They caution that other phosphene transitions should be sought in order to solidfy or disprove their belief that phosphene is responsible They note that "Even if confirmed, we emphasize that the detection of PH3 is not robust evidence for life, only for anomalous and unexplained chemistry." Where is the overstatement in all that? i genuinely don't see it.
  24. 2 points
    That simply isn't true. Some kids have parents that don't give a damn, they drink or have problems with drugs or money. Some schools have outdated textbooks, broken laptops and no or limited access to the internet. https://www.nytimes.com/2018/04/16/reader-center/us-public-schools-conditions.html Some students don't have the internet at home or have very bad internet and only reference books. Some families need help at home and take kids out of school to help out on the family farm or are forced to help out on the farm after school. https://www.dailymail.co.uk/news/article-6728209/Children-skipping-education-help-family-farm-drought.html Some kids don't have access to extra curricular activities like sports or music. https://www.theatlantic.com/education/archive/2015/01/the-activity-gap/384961/ Some kids don't have access to tools and equipment required to study certain activities. One example could be a student in my school built a wooden boat as a school project from wood and tools his family had just lying around and got an A1 in the woodworking class. I had little to no tools at home and barely got a C. But it gets worse. Some kids have access to tools like Unreal Engine because their parents can easily afford computers capable of running. For a long time I didn't have a computer that could run unreal engine at all. Then there is the university places gimmick. Access to university is controlled by a points system. The number of places puts people in their boxes. Poor people do the low paid courses and rich people do the better courses. There is some allowed movement between rich and poor but really the government doesn't want too much change. If poor people start to do better then the points increase. https://www.theguardian.com/education/2020/aug/13/almost-40-of-english-students-have-a-level-results-downgraded
  25. 2 points
    It isn't as simple as that, because intelligence (which I assume is the 'observable' you are quantifying here) isn't a linear thing, it is multi-dimensional. What I mean by that is that most people are differently abled in different areas of life. For example, I have a friend who is absolutely useless in maths and most other academic subjects, but a brilliant artist, and earns a decent living by producing art. I myself am very intellectual-minded, and thus perform well in academic subjects such as maths and physics, but I am useless when it comes to social skills, so I'd be a miserable failure if I were to go into (say e.g.) politics. So what does it mean for someone to be 'stupid' or 'intelligent'? These terms are meaningful only in a specific context. You don't need to have book smarts to be successful in life, and conversely plenty of book-smart people never do particularly well in the competitive world of business. So no, we shouldn't give money to people purely for lack of intelligence, unless of we are dealing with a recognised intellectual disability. What would be a far better thing to do is provide an unconditional universal basic income for everyone, because that would give people a better chance to develop their full potential in life without having to worry about their basic survival, even if that potential cannot be immediately quantified in terms of monetary value.
  26. 2 points
    If the universe were not expanding, we would not see any red shift with distance. Thus the increasing red-shift we see with increasing distance is evidence that the universe is expanding over time, and was smaller in the past than it is now. If we extrapolate back in time, we get the very dense, very hot state of the Big Bang. The acceleration of the the expansion over time is evidenced by the exact relationship between red-shift and distance. There are three possible scenarios for an expanding universe. All of them will show a red-shift: Case 1: expansion slows over time Case 2: expansion remains constant over time. Case 3: expansion speeds up over time. Only in case 2 will there be a perfect direct relationship between distance and red-shift, where doubling the distance exactly doubles the red-shift. In the other two cases, doubling the distance results in a red-shift that is not an exact doubling. Whether it is less than double or more than double distinguishes between the two cases. We have found that the red-shift distance ratio indicates that the universe's expansion rate has been increasing over time, and thus the rate of the expansion is accelerating.
  27. 2 points
    Not sure what the focus of this thread is (and the two replies so far certainly don't help me to identify a focus). So I'll just throw in a few random comments: - You do explicitly mention "hiring recently-unemployed people". I am not sure how different that is to "hiring people" to you. For hiring people to do X, there are the obvious questions who hires/pays and often also how X competes to other things that could be done with the (monetary) resources. I think there is no shortage of good ideas that someone could do if they were just given the resources. Restricting your hiring to recently-unemployed people would be considered inefficient from a free-market perspective (note: I explicitly do not mean that the free market perspective is the one you need to take - but it is a major voice in economic decisions in most countries). Maybe it is more efficient to re-assign a trained lumberjack and have the unemployed history teacher help in a children daycare, for example. - If you do not re-grow the trees, burning wood is not much different from burning fossils fuels with respect to the climate impact. It is the re-growing that makes wood count as a renewable energy source. (Of course, burning the wood to replace some fossils is better than just burning the wood in forest fires - greetings to Brazil ...). - To burn wood instead of fossil fuels you have to change the energy-generating technology, for example replace oil burners with wood burners for heating houses. This is not a problem in principle. But you need to make sure in practice that this pays off. I would actually not be too surprised if the current wood market in the US could simply absorb some extra wood you cut, and that you would not need to "make room" in the fossil energy sector. - For educational purposes, I strongly suggest you try to do some estimate calculations about how much fossil fuel usage you could reduce by having extra wood. In my experience, most people do not understand how extreme a replacement of fossil fuels is in terms of scale / the numbers. The US national oil consumption should be easy to find, a kg of wood has roughly the same energy content as a kg of oil => just have a look at how much of an impact that replacement would have. Spoiler: I am not aware of any future energy scenario that assumes that we can simply replace fossils with wood and forget about all these annoying issues with solar and wind.
  28. 2 points
    To rhyme with rubles I presume... There's a reason why rubble has a double B. It's absurd; they are all bad attempts to reinvent this wheel;. ˈtrʌb(ə)l On the other hand, I gather that spelling contests are only national TV in anglophone countries... It's quite entertaining to get anyone- particularly a well educated native English speaker- to read this out loud. "I take it you already know Of tough and bough and cough and dough Others may stumble, but not you On hiccough, thorough, laugh, and through. And cork and work and card and ward And font and front and word and sword Well done! And now you wish, perhaps To learn of less familiar traps, Beware of heard, a dreadful word That looks like beard and sounds like bird. And dead: it’s said like bed, not bead– For goodness sakes don’t call it deed. Watch out for meat and great and threat, They rhyme with suite and straight and debt. A moth is not a moth in mother, Nor both in bother, broth in brother. And here is not a match for there, And dear and fear for bear and pear. And then there’s dose and rose and lose– Just look them up–and goose and choose, And do and go, then thwart and cart. Come, come, I’ve hardly made a start! A dreadful language? Man alive! I’d mastered it when I was five." We also have route pronounced the way Americans pronounce route and the two bits of equipment, a router and a router with different pronunciations. It depends if it's a modem like thingy where it's pronounced like roux; or a woodworking tool where it's pronounced like row.
  29. 2 points
    "We have two lives, the second begins when we realize we only have one." - Confucius.
  30. 2 points
    Sure. There are 22 different numbers on the sheet (ignore the arrows). So there is only one that begins with a zero - 0.668 near the top right. Further down on the right there are three numbers that begin with a 4, one above the other. 447 ; 423298 ; 487643 and so on for the rest. Moths table has two columns. The left hand table lists the digits 0 through 9, though why he has put 0 at the end I don't know. The right hand column shows the number of occurences of these digits in the 22 numbers on the sheet. It is called a frequency table and the numbers in the right hand column are the frequencies of occurence of each specific digit.
  31. 2 points
    The rotation isn’t in 3D Euclidean space, but in the 4D Minkowski spacetime of Special Relativity. The geometry of that spacetime is hyperbolic, so the situation is more complex than what can be easily visualised. Note also - and that is important - that spin is not a function of spacetime coordinates, so visualising it as some kind of rotation about itself is highly misleading. Rather, the rotation involved is one of the wavefunction about a hyperbolic angle in spacetime - in other words, a Lorentz transformation between inertial frames. I think a better way to understand spin is to take it to signify what kind of mathematical object the quantum mechanical wavefunction of the entity in question needs to be, in order for it to be compatible with both the laws of quantum mechanics and Special Relativity. Spin-0 means we are dealing with a scalar, spin-½ means it is a Dirac spinor (bispinor), spin-1 means it is a vector, and spin-2 means it is a rank-2 tensor. Of course all these object types are closely related, in that they are all representations of the Lorentz group - that group which captures the symmetries of spacetime. So spin is at its heart a relativistic phenomenon, and an expression of symmetry.
  32. 2 points
    I had this thought which bugs me: "If absolutely nothing existed, reality wouldn't exist either. Therefore, absolute nothingness cannot be real. And thus, something has to exist." Thoughts? Can it stand as a logical statement? Why do you think there might be something instead of nothing?
  33. 2 points
    1) A taylor series, like any converging series (do you understand converging) may be used to estimate in numeric calculation or stand in for algebraically in formula an expression that is difficult to handle. If the series convderges quickly enough (it often does) we can ignore all terms after the first n, for some small n. There are criteria for deciding how many terms to use. The process of discarding the rest is called truncation. Wolfram has a good explanation https://mathworld.wolfram.com/TaylorSeries.html 2) An aperture is an opening, which is used to describe the 'size' of something or the size of something being measured or that can pass through. So this term is widely used in geosciences. Polyzoa (Fenestrilina) colonies form a basket like weave with apertures in the basket to filter and trap particles washing through. Acidic groundwater percolating through susceptible rocks (eg limestone) solution weather apertures in the solid rock. In photogeology the aperture is the camera opening that controls the amount of light entering. Similary magnetic sensor arrays and seismic arrays have an aperture sensitivity. These control the amplitude and frequency that can be accepted by the arrays. Other wave phenomena (eg ultrasonic) have similar use of the term. https://en.wikipedia.org/wiki/Seismic_array
  34. 2 points
    Because any conceivable clock - even an ideal one - must be massive, and therefore it cannot be comoving with a photon. Mathematically speaking, you can't parametrise the length of a photon's world line using proper time (because ds=0); however, that doesn't mean that their world lines don't have a well defined length in spacetime. They do, you just need to use a different affine parameter.
  35. 2 points
    A scalar is something that can be represented by a number (and usually units) Mass, for example. A rock with a mass of 2 kg. A vector has a direction. It has a value, but also tells which way. Velocity, for example. “moving 10 m/s in the x-direction” The magnitude of a vector is a scalar “I am 100m north of you” represents a vector. “I am 100m away” represents a scalar.
  36. 2 points
    Well, his 2nd marriage was to his cousin.
  37. 2 points
    Everything we can detect is within the observable universe. Beyond the last scattering surface, the universe is opaque to radiation and we can't see anything, except maybe with gravitational waves; and beyond that, not even with gravitational waves. I agree that local objects bend space, but on average the universe looks very (spatially) flat. Around black holes and very massive objects you can detect local curvature, like e.g. Einstein rings, but the sphere of the sky looks pretty flat overall. What the paper that @iNow has linked to seems to imply is that within the observable universe the telescopes have detected large-scale lensing that must have to do with curvature within the horizon. That's what's very surprising to me. I'd like to follow up on that.
  38. 2 points
    One way to approach a difficult problems is to break it down into small steps ie substitute a series of lesser questions in this case. So we have How many ways can something exist ? I suggest a great many. How many ways can nothing exist ? I suggest at most one. So the substutute question becomes Statistically why are we suprised that something exists ?
  39. 2 points
  40. 2 points
    Hi. Welcome. Very old question, but very difficult to answer nonetheless. So I'm going to get hold of some visual aids found on the web. Nothingness is quite easy to picture in your mind. Maybe we get that picture from our hours of sleeping without dreams. I don't know. But, The picture of the closest thing to nothingness that we can build from physics is not a featureless scenario. It's more like this: Or, more diagramatically, like this: A perpetual struggle of opposites annihilating each other. It just isn't just nothing. What it suggests is that what we call "nothing" is more like this ephemeral tug of war between ephemeral somethingnesses (virtual particle-antiparticle pairs). Nothing (in a poetic picture derived from serious physics) is a struggle between opposites in which nobody wins. At some point in the past, somebody won (why that was so is still an enigma; I don't like the word "mystery".) The status of the theory so far is that something like this sea of opposites annihilating each other must have fell downhill some kind of modulating field (inflaton field) 13 point something billion years ago, generating real particles and filling the universe with structure. That's called inflationary model of the universe. I hope that helps, but it's been a long time since Leibniz set that question to nowadays. So the story has become more involved.
  41. 2 points
    Come on guy's, time to stop feeding it... 🤒
  42. 2 points
    Today I learned about Vavilovian mimicry. Nikolai Ivanovich Vavilov was a biologist who studied the evolution of domesticated plants, in particular rye. He proposed that rye was "accidentally" domesticated. Originally it was a weed in fields of wheat and so early farmer would pick it out to ensure their wheat could grow. But they were more efficient at picking out the immature rye plants that looked most different from wheat. So they inadvertently selected for rye plants that looked more wheat-like. Eventually rye became so similar to wheat that it was a useful grain in its own right. This is generally accepted today, even though Vavilov is largely forgotten. Vavilov was killed by Stalin, who only liked science that fitted his political beliefs (e.g. Lysenkoism).
  43. 2 points
    I understand how therapeutic it can sometimes feel to vent, but there sin't really anything to discuss here and it's mostly a rant
  44. 2 points
    Fewest. (Well, it's a discussion about words..)
  45. 2 points
    While scanning for more information I found a paper with several similarities to your opening post and the concepts introduced. Emphasis mine: Source: http://www.m-hikari.com/astp/astp2020/astp1-4-2020/p/uruenaASTP1-4-2020.pdf * (On Energy Condition Violation for Shifting Negative Mass Black Holes) @muruep00 is the paper worth reading to get more details about your idea? To me at least, it looks like something very similar has been published? Spotted an error, meant to say: I do not see how a solution using just GR can use quantum effects for support. *) I have no opinion regarding the reputation of the publisher or the quality of the paper or if any peer review was performed.
  46. 2 points
    Thank you very much, although you cut short @MigL's answer only to show what you want (he telling you that you're right about something). And now I quote Wikipedia: https://en.wikipedia.org/wiki/Black_hole_information_paradox I would have to go in more detail into what @MigL was trying to tell you. Maybe he misunderstood you. I may have also misunderstood you, as it's very difficult to be sure what you're talking about (you never seem to get around to defining mathematically what you're saying). But further below he told you: Anyway... The information paradox has nothing to do with macroscopic entropy, which is the item you seemed to be referring to. It has to do with microscopic entropy, which is just volume of phase space. There are two versions for it; one classical (Liouville's theorem), and another quantum mechanical (unitarity, although I don't like that term; it's clearer if you say "pure states into strict mixtures"). Microscopic entropy (phase space volume) is strictly conserved in physics. Volume in phase space has two parts: One you can see by coarse graining (macroscopic) and another you can't see (total minus coarse-grained). The total is the one that concerns the paradox. Of course BHs create lots of macroscopic entropy, but that's not the problem, nor is it a paradox. It's actually the common pattern in Nature. What is a paradox is that BHs seem to require the violation of conservation of phase-space volume, which Leonard Susskind, e.g., calls "distinctions", because he is very careful about the concepts. Violation of the number of distinctions is not the same as irreversibility. Hossenfelder is also very careful to distinguish between what she calls "irreversibility" (it's actually non-conservation of distinctions) and violation of time-translation invariance. I think Hossenfelder (in what clearly is a popular video, not a lecture) does a very good job of explaining a difficult concept, but unfortunately she uses the word "irreversibility" which has a long tradition in thermodynamics, and is to do with macroscopic entropy. Nevertheless, she superimposes a movie explaining what she means, and it becomes very clear she means conservation of distinctions: Liouville's theorem. This "irreversibility" (it should never be called that way, and I stick to Susskind's term "conservation of distinctions") is what seems to be violated in Hawking's argument. If that's what your theory solves, well congratulations. I haven't seen a single formula yet proving that your "model" transforms pure states into pure states. Your insistence on time reversal only suggests to me that you keep confusing both (different) concepts, as explained by Hossenfelder. In the classical version, this would imply that two different initial states: \[q_{1},p_{1}\] \[q_{2},p_{2}\] merging into the same outgoing state: \[q,p\] Or the opposite (one trajectory splitting into two). That would also result in violation of Liouville's theorem. So "irreversibility" is an outstanding misnomer. It would be non-injective character in the evolution mapping, in either direction. I don't think that name will stick though. In the QM version of such violation, a pure incoming state: \[\rho_{\textrm{in}}=\frac{1}{2}\left(\left|\psi_{1}\right\rangle +\left|\psi_{2}\right\rangle \right)\left(\left\langle \psi_{1}\right|+\left\langle \psi_{2}\right|\right)=\left|\varphi\right\rangle \left\langle \varphi\right|\] comes out as a strict mixture: \[\rho_{\textrm{out}}=\frac{1}{2}\left(\left|\psi_{1}\right\rangle \left\langle \psi_{1}\right|+\left|\psi_{2}\right\rangle \left\langle \psi_{2}\right|\right)\] Now, it's not a matter of thermality, really. Thermality is not the crux of the matter. It can be added to the picture, it's probably there, but it only confuses things. It's rather a matter of one trajectory splitting into two, as Leonard Susskind very clearly explains in several lectures, available online. That's probably why Hossenfelder doesn't like to characterize it in terms of information. "Information" seems to imply an observer. In this case it's Nature itself that's erasing its distinctions. You see? Susskind's word "distinctions" is what conceptually cuts it. And even better is using some maths, they leave little or no doubt about what you mean. Edit: x-posted with MigL
  47. 2 points
    Difficulty with reading comprehension might be a result of the virus.
  48. 2 points
    Today I learned, after a seagull knocked some off my roof, that the humble Lichen is a composite organism. It is a symbiotic relationship between cyanobacteria and fungi. Nearly 6% of the Earth is covered in Lichen, which is testament to, if you get along, you'll be successful. https://en.wikipedia.org/wiki/Lichen
  49. 2 points
    Ok, since getting a straight answer seems not possible at this point I'll illustrate the issue with an example*. Let’s identify the rules as I understand them from your earlier posts: -What lays beyond the event horizon of a black hole can’t be directly observed (I agree on that) -Beyond the event horizon we are free to assume the existence of things that according to current consensus may be considered unphysical in space outside the event horizon. For instance negative gravity or negative energy. -The mathematics model running the simulation does not have to agree with consensus of relativity experts; Markus objections have not had an effect on your stance so far. Singularity: Make a simulation that cuts off the compression of matter inside the black hole at some very high density. That avoids a singularity and will, from the outside, result in a black hole matching observations. Markus, Mordred and other experts would object against my mathematics and my lack of compatibility with GR (and QM). I say they can’t observe what’s inside the black hole and I have no singularity, similar to your argumentation. As for the growing event horizon, inflation of the black hole or apparent increase of mass: I could modify the model of the vacuum inside the event horizon. Allowing regular matter to be created in some circumstances, adding mass to the black hole. Don’t worry about conservation of energy, we are inside the event horizon and I may propose such quantum fluctuations as per your argumentation. Result: By using your approach towards observations and falsifying I have pulled some examples out of thin air and ended up with something that seems to match your model’s predictions and current observations. My example ideas do not rely on negative mass, negative energy so they are simpler and more plausible. I have, as you did, ignored input from experts regarding flaws in my application of mathematics. Do you get the point? Can you show how we could tell that your idea is correct? Not just against my illustrations, but against such ideas in general. There must be something that makes your idea to stand out, allowing it to be confirmed or falsified. My point is that the level of explanations you have provided so far is not enough to support the claims you make. Please don't put too much energy into pointing out that my idea is an invalid approach. I know that and that is the intention. I want the details, how to tell that your idea is not just as invalid as my example is. * (Disclaimer: the example is not intended to be in line with mainstream consensus. The purpose of this example is to highlight the issues with the approach and arguments from OP up to this point. Again I choose to neglect Markus objections; trying to drive a fruitful discussion from an experimental point of view. )
  50. 2 points
    ! Moderator Note I would also suggest you make an effort to put your threads in the appropriate place. Moved to Suggestions, Comments and Support. There was no discussion of that. It barely got a mention in your opening post. Feel free to open a serious thread on the topic. But you might want to read up on some of the hundreds of projects doing this already, before posting. Call me old fashioned, but I just think the combination of immature humour and ignorance is not the best possible start to a discussion of the science and technology involved.
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