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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
    Evolution of a Physics problem through the ages... WHY DID THE CHICKEN CROSS THE ROAD ? Aristotle: It is the nature of chickens to cross roads. Isaac Newton: Chickens at rest tend to stay at rest, chickens in motion tend to cross roads. Albert Einstein: Whether the chicken crossed the road or the road moved beneath the chicken depends on your frame of reference. Werner Heisenberg: We are not sure which side of the road the chicken was on, but it was moving very fast. Wolfgang Pauli: There already was a chicken on this side of the road.
  5. 3 points
    That's a very big positive. The way I see it, academia advances in small steps. It is of course necessary, and immensely valuable. But perhaps the most significant big leaps are taken by people who are carefree, driven by an honest need to understand. They connect many more dots. They have time on their side. That's what I believe.
  6. 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.
  7. 3 points
    Wait, a youtube video was inaccurate? Noooooooo!
  8. 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.
  9. 3 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
  10. 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?
  11. 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.
  12. 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.)
  13. 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.
  14. 3 points
    Exciting update! IDoNotCare had now been permanently banned for similar offences.
  15. 2 points
    No, this is a common misunderstanding. Spacetime in a uniformly accelerated reference frame in otherwise empty space is perfectly flat - acceleration is not a source of spacetime curvature. Only distributions of energy-momentum (like planets, stars,...) are. Physically speaking, the defining characteristic of a curved spacetime is the presence of tidal gravity - however, if the reference frame in question is small enough, these tidal effects become negligibly small, which is why in a small local area only uniform acceleration looks like a uniform gravitational field. This is just the equivalence principle, and this is somewhat akin to the surface of Earth looking flat so long as you only look at a small enough section of it. Anyway, the upshot is that a uniformly accelerated frame in otherwise empty space has no spacetime curvature (the Riemann tensor vanishes).
  16. 2 points
    Well, this is just blatantly wrong. As a whole the European standards have raised the norms in the UK. Despite all the shortfalls, the EU norms as a whole are some (if not the) most developed in the world (and incidentally, the UK was heavily involved in developing these standards). The overall fear is that after Brexit the UK may result in less safe food. The issue is that as I mentioned, there are no fixed regulatory measures to create safe food pipelines. Rather they have been developed following EU directives in what is considered safe food. If now other pipelines are admitted, it may create a mix of procedures that as a whole become less safe. Another issue is that now UK has to develop new internal regulatory structures, for which it used to rely on EU systems. Likely it will stabilize at some point. But there is likely to be a state of uncertainty for some length of time at which issues such as food safety will remain unresolved. With regard to chlorination, I should add that I think I saw a paper somewhere indicating that chlorination is actually not a great measure as it does not sufficiently reduce the pathogen load, rather it seems that it just makes it harder to detect them. I feel that you are quite misinformed when it comes to UK EU relations. First, the Galileo signal services are free for everyone to use (outside the specialized defence applications). However, what has been said is that UK-based companies will not be able to tender for the production of new satellite components (and also are not allowed to participate in the development of the secure services). This is because the project is and remains an EU initiative. Also when it comes to the budget, the UK has invested about 12% of the budget but won about 17-19% of the budget back for industrial and research contracts. I.e. the UK was a net beneficiary of the project (https://www.nature.com/articles/d41586-018-07734-x). I mean, we could go through each of these claims, but I think at some point it is time to step back and revisit some basic assumption regarding the benefit-cost situation between EU and UK.
  17. 2 points
    I don't see what the problem is. D Trump was right. Large portions of the American population HAVE developed 'herd mentality'.
  18. 2 points
    Fate is a strange dice that we do not control. We jump and try our best. I was born very poor. A family of survivors from the Second World War purge, not a Jew, nor a Kossac, not a Gipsy but part of them, só, no sides to shelter my grand parents. I was borm very poor and remeber starving. Brasil is not for amateurs! On the other side, the college is for free and you can get food and some clothes, só, I could attend the university amongst very rich kids. Do not know how but my grades very high enough to be there. It was a game, like jumping a circle of fire. Maybe I was able to jump but, after some jumps, there was nothing but stress, poverity and decepcion. I am not telling a personal history as if it were a glorious fight. I saw fights in my place. Native fight against miners, againt diseases. I saw poor girls fighting against misery and winning all the odds in an “male world”. I like Carlos Castañeda books. Once I was told he is totally fake but I like Don juan most of all and Don Juan says that a warrior must grab the 1mm³ of chances he/she got. I am very pragmatic. I do not mind my role in that teather. I am going to do my best and extract the fully joy of that act. I believe we are very talented and able to do the best face to the rules of the game we have to play I know people that cannot be that clever. I know people that complain the husband they choose (there is no arranged matrimonies im my place for 200 years!), they complain the age, no matter how old are they, the lack of courage or the lack opportunities, spite you spare them the best piece of that play. You are a warrior and I sense that. Just wanted to say that I know you did the best and grabbed all the chances. Best /\/ /\/
  19. 2 points
    Boiling point of compound is not constant and depends also on pressure. So you can try lowering pressure to boil excess of water. It is widely used method: https://en.wikipedia.org/wiki/Vacuum_drying ..with ready to use equipment: https://www.google.com/search?q=Vacuum+dryer (anyone serious about chemistry should have a vacuum pump anyway)
  20. 2 points
    One of the few things you've said I wholeheartedly agree with.
  21. 2 points
    Einstein didn't 'guess' In fact he was one of the founders of the quantum theory. (1905) This was of course long before a probabilistic explanation was suggested. In any event the probabilistic wave theory has since been found inadequate/incomplete, though still able to provide calculation and prediction for some phenomena. I have underlined the appropriate words. So he was actually correct. https://blogs.scientificamerican.com/observations/einstein-and-the-quantum/
  22. 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.
  23. 2 points
    Fresh vegatables and fruit do not have a shelf life of 2-4 weeks. You want me to eat chicken nuggets and canned beans? Uber's are exploitative. You want me to substitute a claimed immorality for a real immorality? Well no, if I actually were a peasant I would grow all my own vegetables and drive to town with a horse and cart. (And the local kids would run behind with a sack to collect the horse crap for the vegetable plot.)
  24. 2 points
    I find this to be true, and I find that both parties are responsible. Some people of science tend to forget how long it took them to get to where they are now. Understanding a concept or readily being able to discern science from pseudoscience is a skill that is developed over many years and with a lot of effort. It is easy to get frustrated with someone who seems oblivious to a concept that to a scientist is so obvious. It is often difficult to determine if someone is closing their ears to science or if they are just not experienced enough yet to process the information they are being given. I find that lay people often respond out of emotion instead of reason, and therefore find people of science to be arrogant. People generally do not like being told that they are wrong, sometimes spectacularly, and that they are often wrong because they were duped. That is tough on the ego. It is easier on the ego to get angry at the person correcting you, than to acknowledge that you were a fool.
  25. 2 points
    I think there is no clear answer to that. Studies basically are looking it from two perspectives. One mechanistically, which looks at virus survival in droplets and ejection and the other is epidemiological where folks look at likelihood at being infected outside. From the latter viewpoint, it appears that casual outdoor infections are very rare and mostly connected with folks being close to each other. Mechanistically, evidence suggests that e.g. in saliva it would take minutes for sun-inactivation of SARS-CoV-2 (~6 minutes for 90% inactivation), so at least theoretically if someone sneezes in the air and you run straight through it, you might get exposed to active particles (sneezing on the ground would arguably be safer). But again, most evidence suggests that overall infection chances are low under these conditions.
  26. 2 points
    The cleaning begins with a natural chemical reaction called oxidation-reduction discovered by a Dutch gardener. He used his steel planting tool to remove the stubborn leek odors from his hands. When in contact with water, the metal ions in stainless steel capture and penetrate the sulfur and nitrogen molecules responsible for the foul fumes. So, on first contact with steel, the smell of foods rich in sulfur disappears immediately. An oxidation-reduction (redox) reaction is a type of chemical reaction that involves a transfer of electrons between two species. An oxidation-reduction reaction is any chemical reaction in which the oxidation number of a molecule, atom, or ion changes by gaining or losing an electron.
  27. 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.
  28. 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.
  29. 2 points
    It assumes that you have both liquid water and air with water vapor. And it means that equilibrium has been reached and as much water is evaporating from the liquid phase as water from the air is condensating. So the air has as much water as it can have at that pressure and temperature. Thereby the "saturated" word. So the key is: above that pressure, water from the air would condense. I hope that helps and I didn't make any mistake --it's been a while and I'm a bit busy with other matters so I'm making mistakes lately.
  30. 2 points
    Stop putting houses in the middle of fire prone areas. No different than not putting houses in flood plains.
  31. 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.
  32. 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.
  33. 2 points
    "We have two lives, the second begins when we realize we only have one." - Confucius.
  34. 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.
  35. 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.
  36. 2 points
    Obviously in most modern societies we are free to express pretty much anything we want (with notable exceptions, and with the caveat that some forms of speech will certainly result in consequences of various kinds). But - and let me play the devil’s advocate here - where does this fit into a larger picture? Is unrestricted freedom always necessarily a good thing, no questions asked? I hear so many people keep going on about their “right to free speech”, but very few ever talk about their corresponding responsibility to engage in ethical speech. People like freedoms, but they don’t like the responsibility that comes with it. If I say or do something that is deeply hurtful to a lot of other people, and is not conducive to peace, prosperity and well-being of society as a whole, in what sense is such a freedom to be considered ‘good’? Much has been said about people’s freedom to engage in whatever speech they want - but what about people’s freedom from forms of malicious or otherwise hurtful speech that is simply not compatible with a civilised and peaceful society that values the well-being of all its citizens? Before anyone responds, I’d like to point out that I grew up under a communist regime in the former Eastern Bloc, so I know first hand what it is like to live in a society that does not grant freedom of speech (well, theoretically you could say anything you wanted of course...but some things you were only ever going to say once, so effectively the freedom was severely curtailed). It isn’t just an academic concept to me, I’ve experienced it, and it is not a good thing. On the other hand though, I am also on the autism spectrum, and as such I am simultaneously more sensitive and vastly more conflict-avoidant that most neurotypical people. Some forms of speech with malicious intend, directed towards me, will affect me very deeply, and at the same time I am entirely incapable of confronting the speaker about it. So for everyone like myself, who is affected in different ways by harsh and malicious speech (essentially everyone who does not fully conform to the accepted norms of society) - where is our freedom from such forms of speech? Why is this never really debated? Given the choice, I would personally be very happy to trade some of my ‘freedom to’ for a bit more ‘freedom from’, if that is conducive to my overall wellbeing. Of course I am aware of the difficulties - who makes these decisions, based on what, etc etc...but still. I don’t have a very specific point to make, I just wanted to put this ‘freedom to’ vs ‘freedom from’ thing out there.
  37. 2 points
    As with all conspiracy theories, people who 'THINK' they understand, ARE the problem. No evidence, just 'coincidences and a gut feeling' ??? I thought we didn't do conspiracy theories on SFN. And with crap like this, the more exposure they get, the worse it becomes. ( I'd actually consider shutting down the thread, but that would be censorship )
  38. 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.
  39. 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 ?
  40. 2 points
  41. 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.
  42. 2 points
    Sorry for the condescending tone. Terminology is vital if you want to get your idea understood. Here is a suggestion, pick one small piece of your ideas and take some time to write it out. If someone questions an idea like "energy has direction", let's discuss it and make sure we have the same definition of 'energy' and 'direction'.
  43. 2 points
    Thousands of hours thinking about a physical problem without taking much input from experts' and known facts normally end up being thousands of hours down the drain. It's actually a very bad symptom. You're trying to re-write hundreds of years of progress in science. Be careful with how much time you spend thinking on your own. The best physicists spend thousand upon thousands of hours studying (or using) physics they can claim no authorship of, and only tens of hours thinking of new ideas. Most physicists spend their lives skillfully using other people's theories. That's how it works. So it's the other way around. Thousands of hours of study culminate in tens of hours of inspiration at best. Something like that. Again, I'm trying to be helpful.
  44. 2 points
    That is nonsense. First, as background, animals cannot synthesize B12, only bacteria (and archaea) can do that. In fact a lot of bacteria, including free-living ones are able to synthesize it de novo, as they also need it. From there it follows that folks do not need to harvest animals at all. And in fact some of the first production strains were soil bacteria including Sinorhizobium meliloti and Pseudomonas denitrificans but there have been efforts to make E. coli a better production strain (I am not sure how far they got). Feel free to look up the species together with industrial B12 fermentation, it should give you plenty of publications. The second part that your friend does not get is that in industrial fermentation you want to have a pure culture whenever possible to ensure a clean product. So if you have a production strain isolated, you keep a stock of them from which you can create fresh cultures whenever needed. Isolating a pure strain from a mixed sample (such as isolated from an animal) is a ton of work and may end up not giving you a working culture so there is no reason to do so. From what you have written it is rather obvious that your friend has spent no time reading up on how industrial fermentation actually works. The use of animal microbiota is something done in traditional food production (e.g. using cow rennet). However the key enzyme (chymosin) can now be produced industrially, without killing cows (again by using bacteria produce them).
  45. 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).
  46. 2 points
    It is also an invented reason to be angry. Adding a word to make it sound bad (be THE best) and then complaining about it is really quite unfair. Surely there are enough things to complain about that really happened.
  47. 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
  48. 2 points
    I am not sure to what extent that is common knowledge: Using reflectors to focus on a point, generate steam and then run a turbine just as in fuel-based power plants is actually done. It's called Solar-Thermal Power (see e.g. https://www.eia.gov/energyexplained/solar/solar-thermal-power-plants.php) or Concentrated Solar Power. As far as I know, for electricity generation this method is more expensive than using Photovoltaic systems, and therefore often not considered. And for generating heat you usually do not reflect+focus but simply absorb (-> Solar Collector). The biggest advantage of Solar-Thermal over Photovoltaics is that Solar-Thermal power plants can store the thermal energy to some extent before using it, so they are somewhat controllable in their generation and can generate electricity at night. In some situations, this can make them the preferred choice (according to a former colleague of mine who did a lot of energy system design for northern Africa). For the system cost I would assume that on the side of steam system, turbine and electrical system it's pretty much the same as for any other coal, gas or nuclear power plant, except that those tend to be larger and therefore perhaps more cost efficient. The difference in cost hence is heater vs. collectors+storage. I have no intuitive feeling for it, except that I expect the hater to be relatively cheap (specifically: a simpler piece of technology than a turbine). From an old Irena publication (https://www.irena.org/documentdownloads/publications/re_technologies_cost_analysis-csp.pdf) it seems that collectors+storage make up roughly 50% of the project cost (Figure 4.2 - there's also lot's of tables with more details if you are interested in those). So my answer to "how expensive can it be" would be "roughly twice the cost of a coal power plant" in terms of construction cost. You obviously don't pay for fuel (coal). End-costs for generated electricity (levelized cost of electricity or LCOE) always depend a lot on local situations and calculation method. On the Wikipedia page https://en.wikipedia.org/wiki/Cost_of_electricity_by_source the listed figures suggest 6.1 ct/kWh for Australian Solar Thermal generation and anything from 3.3 - 15.2 ct/kWh for coal. On a final note: You seem to implicitly assume that main investments into new power infrastructure goes into coal and nuclear power plants. That is not the case. Globally, new installations in renewable technologies have overtaken the non-renewables a few years ago. Even in the US, the only country that left the Paris Climate Agreement, new power installations are either renewable or gas (mostly because energy infrastructure is built private companies, not the federal government): https://www.eia.gov/todayinenergy/detail.php?id=42495 .
  49. 2 points
    Fewest. (Well, it's a discussion about words..)
  50. 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.
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