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Showing content with the highest reputation since 08/26/21 in all areas

1. What taxes a billionaire?

There are several parallel issues here. One is that wealth acquired by the ultra wealthy tends to get put into tax shelters and nebulous investments so it grows (but remains outside the system), whereas that same money in the hands of the less fortunate goes IMMEDIATELY into the community around them. They spend it on groceries and vehicle repairs and school clothes for kids and paying the electricity bill so it’s not dark in their apartment anymore at night and their kids can read. The providers of those goods and services in that community where this money is being spent ALSO spend the money once received for THEIR groceries and THEIR service needs and on THEIR kids. Dollar for dollar / unit for unit… the money in the hands of the less fortunate does more net good than money in the hands of the already fortunate. Yes, spending from the wealthy also creates jobs and injects money back into the system, but very little relative to money used in “trickle up” stimulation packages. Also, a bit of extra money in the hands of someone who already has a bunch of it doesn’t tend to change their behavior or encourage extra spending. Getting $1,000 tax break when you’re sitting on$50M isn’t going to suddenly result in them finally making a call to a plumber or the purchasing a new dishwasher… but for the person living paycheck to paycheck that money literally changes lives, gets spent and injected back into the system quickly, and results in lasting reductions in poverty and suffering. When you’re living at the margins, every dollar counts. It also costs a lot to be poor. When the washing machine breaks, you can’t afford a new one but you can afford to pump quarters into the machine at the laundromat… but that ends up being more expensive on net. When the car breaks down, you don’t get to work on time and you get fired. The rich, however, have tax protected ways of growing their wealth and can afford tax attorneys to hide it. Paying more tax has more impact on their ego than on their lived experience. The anger at the rich is out of hand, though. We need better policies and enforcement mechanisms, not more hate and vitriol directed at those doing better than us. Sadly, the anger is probably in large part intentionally being amplified by the very people on the receiving end. If they can keep everyone mad and focused on the wrong things, then the status quo remains stable and no progress or change gets made. Like most issues in economics, we make a huge mistake by treating it as a moral failure when at its core it’s a policy failure. Fixing the policy is just super hard because the people with the power to change the laws tend to be the same ones benefiting the most from them… and also because focusing on wonky policy details is hard for a public who’s often just trying to survive through to tomorrow and who’d much prefer throwing stones and being distracted with us/them tribalism. Perhaps this thread could try focusing on wonky policy details instead of distractions like yachts and steel boats… or not.
5 points
2. Is Gravity a Force?

Yes @joigus, I lurk in the shadows and follow proceedings here whenever I get the opportunity At present I live in the jungles of Thailand, having recently been ordained as a monk, and do not have access to anything other than an old mobile phone with spotty and slow internet access, so I’m not really in a position to participate in discussions. It’s just too slow and painful to type this way. I will return once I get access to better infrastructure - perhaps some time next year. Satellites in orbit are in free fall - place an accelerometer into them, and it will show exactly zero at all times. No proper acceleration -> no force acting on them. And yet they don’t fly off into space, but remain gravitationally bound into their elliptical orbits. Clocks in them are also dilated wrt to far-away reference clocks, which is also a gravitational effect. Thus, no force, but still gravity. Newtonian forces are simply bookkeeping devices, and as such they often work well - but only in the right context. Their nature is descriptive, but not ontological. They are not very physical either, given that they are assumed to act instantaneously across arbitrary distances. The strong, weak, and EM interactions aren’t ‘forces’ in that sense at all, since they work in very different ways. They are only sometimes called ‘forces’ by convention, for historical reasons. They ultimately arise through the breaking of symmetries, with the particles involved being irreducible representations of symmetry groups. Finally, it should be noted that physics makes models, that’s what it sets out to do - and as such it is always descriptive rather than ontologically irreducible. So, asking whether gravity “really is” A or B, or whether A or B are “true” is fairly meaningless, since both A and B are descriptions of reality, but not reality itself. Like maps of a territory. The correct question is thus whether models A and/or B are useful in describing gravity, and in what ways and under what circumstances they are useful. So - Newtonian gravity is sometimes useful, but GR is more generally useful, as it gives more accurate predictions for a larger domain. So for now the best answer to “what is gravity” that we have is a purely descriptive one: it’s geodesic deviation, and thus a geometric property of space time. To put it flippantly, it’s the failure of events to be causally related in a trivial manner. Future advancements may upend this picture in the high-energy domain, perhaps radically. We’ll see. I’m sorry I can’t contribute much at the moment, but I’ll leave you with the above thoughts. I could have written much more, but it’s too much of a pain on a small mobile phone screen.
5 points
3. The UK as an American State or States

Oh sure, you say that now, you gorgeous bastard! Then we let you move in, you force us to clean chicken without bleach, make us give up our cookies for biscuits, and before you know it we're all sleeping together on the wrong side of the road! OTOH, if we get British television series standards, I vote LEAVE. It's the rare US show I like, while it's rare for me to find a British show I don't like. You seem to look for actors who can act rather than actors with no physical flaws, and your writers write the way people talk.
4 points
4. What keeps the universe going and will it stop or go on forever?

If by 'keep on going' you mean do things, like work, then it is energy that keeps it 'going'. Energy has some funny properties. If you have a box divided by a partition, where one side has a more energetic gas than the other side, the partition will be accelerated, and move. That is an example of doing work ( much like the pistons moving in your car's engine let you travel down the road ) When the gas on both sides of the partition has equal energy, obviously the partition will stop moving, and no more work can be done. Notice that the total gas still has energy, but it is the difference in energy that allows work, and processes to happen. So, we have useable energy, which can do work, and un-useable energy which cannot. We call this process, of converting useable energy into un-useable, entropy. Entropy can also be a measure of the 'order' of a system, which means that, although it can be reversed locally ( life is proof of that ), it must always increase globally. That is where the idea for the 'heat death' of the universe comes from. Once entropy of the universe is maximized, and there are no more energy differences, all work and processes will cease, and the universe will essentially be dead. This is a rather simple explanation, which is, hopefully, suitable for your level of understanding. If you should need elaboration, don't be afraid to ask.
4 points
5. Frank Sinatra is not a poached egg

Whoa! Remind me to visit your house some day, sounds like the place to be... I must admit I am baffled by this - you are a philosopher yourself, so surely you must see the issue with this? When you probe a sample of matter on atomic scales, what are you really going to find? Will you find ‘atoms’? Of course not. What you will find are ensembles of electrons, protons and neutrons, in various configurations, plus an abundance of vacuum. That is all. What we call ‘atom’ is a convenient convention to give a short name to such quantum mechanical ensembles, largely for historical - not scientific - reasons. They are real, but only in a conventional sense; ontologically there is no such thing. No experiment will ever detect the ‘atom-ness’ of an atom, because the only thing there is on that scale are electrons and nuclei. But it gets worse. If we decide to crank up the energy and probe said protons and neutrons, we find that they themselves are also ensembles of more fundamental particles, being quarks and gluons. So on subatomic scales, there’s no such thing as protons and neutrons either, they are convenient conventions too, but don’t exist as independent entities in and of themselves. So what about quarks and electrons? Surely they are ‘real’? When you try and take a closer look at them, they turn out to be pretty slippery bastards - try to confine them into smaller and smaller areas, and they move about more and more wildly. Try to measure their momenta, and suddenly you can’t pin them down any more. Send them through a double slit, and they behave like waves; try to measure their spin vector, and each time you laboriously determine one component, the other two get erased! It’s like trying to nail jelly to the wall. So to our dismay, even the very notion of ‘particle’ turns out to be just a convenient tool. Even such a seemingly innocuous concept as ‘number of particles in a given volume’ turns out to depend on who’s counting them! There’s not really such a thing in reality - there might be something there, but it’s nothing like our intuitive notion of a particle, unless you zoom out far enough so that quantum effects become negligible. So what are we left with? The most basic elements of reality we currently know of - and this is almost certainly not the deepest level - are quantum fields. So we don’t have a universe with 10^120 particles with independent existence - all we have is one spacetime with 37 (depending on how exactly you count) quantum fields. That is all. You don’t have any more independent existence than does that flock of birds, since both are just complicated ensembles of the same 37 quantum fields (according to current knowledge). On those scales you are not different from those birds, and on other scales you are not the same. There’s no contradiction - both are correct. You take what is found on human scales to be absolutely real only because that happens to be the scale your sensory apparatus is able to probe. And that’s my central point - if you probe reality on human scales, then you and me and the birds are ‘real’. If you probe it on molecular scales, then atoms are ‘real’. If you probe it on atomic scales, then ‘subatomic particles’ are real...and at the bottom, what is real are quantum fields, according to current knowledge. Hence, there is no one reality - what is real depends on the scale of the instrument that probes reality. It is scale-dependent. This is called contextuality. You will never find a ‘bird’ if you use the LHC to look - even if you look in the same region of spacetime. And when you look at subatomic constituents, then sometimes you’ll find waves, sometimes various quantum objects, depending on how you set up the probe. Mostly, you’ll find nothing at all. I will for now forgo any mention of counterfactual definiteness and the empirical violation of Bell’s Theorem, which puts further nails into the coffin of ‘reality’. Or what might happen if you look still deeper, beyond quantum fields. Or you could go the other way - what happens if a hypothetical very large organism (~10 billions of light years in size) tries to build a machine to observe my cat? Because the speed of light is so slow on such scales, metric expansion would rip this life form apart long before he could become conscious of the outcome of that measurement. My cat could never become part of his reality. So what is real depends on how you probe! That is why both ‘bird’ and ‘37 quantum fields’ are equally valid realities, but in different contexts and on different scales. Neither one is more ‘wrong’ or ‘right’ than the other, but both are contextual and scale-dependent conventions. They are both real enough and useful, but only in their own contexts. I will leave it at this for now. Personally I think the rabbit hole is much deeper than this still - I happen to think that reality doesn’t just depend on how you look, but also on who’s looking. But I won’t get into this here.
4 points
6. Is Gravity a Force?

OK...this is Don Lincoln here. My name was invoked and a little bird came and suggested I pop in. I have not read all of the chat above. Regarding gravity and belief. First, belief is a non-scientific word....or at least it has lots of really ridiculous connotations. When a scientist says that they believe in a theory, they're just being sloppy. (And I include me in that. But language is language and we do the best we can.) "Belief" to a scientist simply means in this context, that the theory is consistent with all relevant known data and we can take it as an approximation of the truth. Now, on gravity. It's very clear that Einstein's formulation is more accurate than Newton's or, for that matter, any other suggested theory of gravity. It's also eminently clear that general relativity fails at small sizes and very high gravitational fields. For that, we will need a theory of quantum gravity. Some ideas have been put forward, but none have been validated in any way, meaning to all intents and purposes, we have no believable theory of quantum gravity. However, given the established validity of general relativity, it follows that that when quantum gravity is evaluated for gravitational fields not strong enough to manifest their quantum behavior, that the predictions will be effectively identical to general relativity. From that, we can infer that the bending of spacetime will be valid in quantum formulations as well, although there may be additional explanatory insights. Accordingly, I feel quite comfortable in saying that I believe in general relativity in the realm in which it is applicable. Similarly, I believe in Newtonian gravity in the realm in which it is applicable. After all, we shot the New Horizon probe to Pluto - traveling billions of miles, passing by several planets, and NASA hit a target 10 km in size. Newton works. Einstein works. Well, until they don't. That's all of science. Theories work as long as they work. One other piddly point. Our current understanding of gravity is qualitatively different from the other known forces. Sure. Some of you have been discussing the meaning of the word force. Classically, it means something that has the potential to cause an object's velocity to change according to some reference frame. At the quantum level, it has a somewhat different meaning. There it means that the phenomenon can effect some sort of change, be it changing velocity or causing particle decay. The fact that the word has a nuanced meaning depending on the size scale at which it is being evaluated implies that the word is fuzzy and anybody trying to nail it down, will fail. This brings up a more important point is that the mapping of words onto scientific concepts is a dangerous endeavor. It is highly unlikely that any word can be mapped into a concept so well that it is impossible to find an exception. There will aways likely be a qualification of some sort. Accordingly, don't hold onto words very hard. They will fail you. Instead, understand the more nuanced scientific principle for which the word is nothing more than an imperfect and ultimately inaccurate placeholder. For the person who complained about the videos being at a commercial site. Well, I've worked for over three decades learning this stuff. I spent half a year writing the lectures, which comprise 12 hours of clearly-explained advanced science. I spent a week filming the project and many hours ensuring that the quality of the video and audio product was high. And someone has the temerity to suggest that I and the production company shouldn't be compensated for that effort? It's like whining that someone won't come and paint your house. Go ahead - enroll in the streaming service - you will have access to an astonishing amount of knowledge and expertise, translated in such a way that non-experts can understand a portion of the more complex ideas. BTW I was a solid presence at SPCF for a long time, but I will not be a regular here. I have just contracted my 5th or 6th book and that will take enough time that active involvement here is simply not in the cards. Cheers....
4 points
7. What makes the bulb glow?

I'm really sorry to you all, I only watched half the video. Here is the link: In the end he tells that all this is fake and he has been hiding his tesla coil under the table. Really sorry for wasting your time. Sorry @studiot @Intoscience and @iNow
4 points
8. Sign rule for multiplication

It's good that you asked in Linear Algebra And Group Theory, because we're going to need some algebra you likely have never seen (unless you went to college) to answer it. Multiplication isn't one thing. What multiplication is depends on what you're multiplying. Algebra is how we define this. In Algebra, there are a handful of different kinds of structures. Here, we're interested in Groups, Rings, and Fields. Rings and Fields are kind of made of Groups, so we'll start there. Say we have a set (the lay concept of set will work fine for our purposes), and we'll call it S. On this set, we need to define a rule called a "binary relation" that takes any two things in the set and gives some output. We want this set to be closed under this relation, so the relation can only give us things that are already in the set. For this combination of set and relation (for now, we'll use ? to denote the relation) to be a Group, they need to have the following properties: 1) Associativity: for any three things a, b, and c in the set, the relation doesn't care about where the parentheses go. a?(b?c)=(a?b)?c 2) Identity: there is a special thing in the set (traditionally denoted by e when talking abstractly) where, for any other thing a in the set, a?e=e?a=a 3) Invertability: for any thing a in the set, there is another thing in the set a* where a?a*=e=a* That's enough to be a Group. But we want a special kind of Group, called an Abelian Group. That's just a regular Group that has an extra property: 4) Commutativity: for any two things a and b in the set, a?b=b?a Tradition dictates that for Abelian Groups, + is used in place of ? and 0 is used in place of e and -a in place of a*. If a Group is not Abelian, we often use × (or nothing at all) in place of ? and 1 in place of e and 1/a in place of a*. If S is the set, we write (S, +) or (S, ×) for the group, but we often just write S if it is clear from the context that we're talking about a group. This is enough to let us build a Ring. With Rings, we still have a set S, but we have two relations. (S, +) is an Abelian Group, but × is a bit more lax. × only has to satisfy two properties: 1) Identity, and 2) Distributivity: for any three things a, b, and c in S, a×(b+c)=(a×b)+(a×c) Like how (S, ?) is a Group, (S, +, ×) is a Ring. If a Ring is commutative and has inverses for each relation, then the Ring is called a Field. There are four particularly important facts mentioned above that are important to why a negative times a negative is a positive: 1) a+(-a)=0, 2) a+0=a, 3) a×0=0 (not mentioned above, but still important), and 4) a×(b+c)=(a×b)+(a×c) Proof -a×-b = a×b: Let a and b be positive numbers in our field (S, +, ×). 0=b+(-b)=a(b+(-b)) -a×-b = (-a×-b) + a(b+(-b)) = -a×-b + a×b + a×-b = -a×-b + a×-b + a×b = -b×a + -b×-a +a×b = -b(a+(-a)) + a×b = a×b TL;DR: It's because Fields are commutative, have identities, and are distributive
3 points
9. Why is there a growing movement to deny reality in America?

I think the biggest change is the internet. 20 years ago if you said the earth was flat your friends and family would laugh and say, "no that's not right" and you would find no one to agree with you. Now you can go on the internet and find hundreds or thousands of people who will agree with whatever batshit crazy idea you have.
3 points
10. Frank Sinatra is not a poached egg

Unless I'm misreading things, and adding in my own thoughts, I suspect it is not Davy that is missed but the conversations he generated among the other members. I'm thrilled he is gone as I hate his type of approach to discussion. I find it very rude and disingenuous. On the other hand, like with the many trolls who occasionally roam our halls, I learned a lot as people made honest attempts to educate him. It wasn't Davy who provided any insights, it was everyone else. I've never enjoyed burst water pipes, losing a job, or a serious illness in the family, but I am always better educated once it is over.
3 points
11. Frank Sinatra is not a poached egg

! Moderator Note These arguments seemed eerily familiar, and after some digging the staff has determined that Davy_Jones is Reg Prescott, a previously banned user. The feeling of deja vu was because we had, in fact, done this before. Right down to the citing of Frank Sinatra in a thread title. If you find merit in the discussion please continue, but Davy/Reg will not be participating
3 points
12. Frank Sinatra is not a poached egg

I know I'm not first, but you continue to be obtuse. Bullshit. By providing one example after another of what you believe to be real you are defining for us what you think reality is. For example, In your second post in this thread: "I think the cannonball is real -- really real -- real even if no one is looking, its motion is real, and that physics describes this reality for us". Your position seems to be that the physics describing the cannon ball "describes this reality". So now you are obfuscating by claiming "well, I never actually said the words "The definition of reality is..."" Your little tap dance is fooling no one.
3 points
13. What is the real difference between science and philosophy?

Not that Swansont needs me to answer for him ... You must realize, Davy_Jones, that Physics treats the trajectory of a cannonball by considering forces acting on its center of mass, or center of gravity. That is, as a point mass. Is that your 'true reality' ??? We may not know much concerning Philosophy, but you have no clue about Physics ( nor reality, for that matter ). Maybe we ( actually you ) should start over, and, instead of being antagonistic and telling us what is wrong with our world view, try to learn from each other.
3 points
14. What is the real difference between science and philosophy?

Really? I know a little philosophy and physics. Enough to recognise crackpots in both disciplines. And where Krauss surely is a good physicist (cosmologist?) at the terrain of philosophy he is a crackpot. Of course I stumbled over the few lines where he talks pejoratively about philosophy. But by the quality of the arguments, one recognises the value of these remarks: none. If you do not like semantics, then philosophy is definitely not your thing. So it once was true that sun orbited earth? But when it was true, i.e. a perfect fitting model of reality, then once the sun really orbited the earth. And it stopped at the day Copernicus came with his heliocentric model? Davy (and I) are not confused. We see how complicated it is to give a correct account what happens in science. And as said earlier, I believe that the problem is grounded in the difficulty to account for the relation between language and 'reality', i.e. what is talked about. I am not 100% sure if I can also speak for Davy, but it is not about the praxis of science, the value of its insights, or its undeniable value for developing new technologies. Science works, that should be clear. It is about the selfunderstanding of science. Do you know the true nature of anything? (I am afraid I don't). I think a better criterion for'approaching the truth' is the increasing domain of theories: Ptolemy was OK for predicting celestial observations (but we would never have been able to send New Horizons to Pluto...), with Kepler the picture was greatly simplified, with Newton a connection with earthly phenomena was made (same explanation for falling objects and orbiting celestial bodies), and Einstein, making gravity Lorentz invariant (if this is a good description of GR) was even able to predict new phenomena. What we see is continuing extension of the domain of application theories. One could say, the more encompassing a theory is, the better it is. But if that means that we are 'closer to the truth' would suppose that we know there is some truth out there (how would we know that) and we are closing in. Another kind of example: we have a very extended theory of the electron. We know how it behaves in all kind of situations. It might be that there is nothing more to add to it. Suppose this is the case, do we then know the true nature of the electron? I would translate that, conform my musings above, that we know we do not have a complete theory of gravity: GR fails for the centre of black holes and the big bang. But when we have one (empirically validated), would we then know the true nature of gravity? Or are we a bit more humble, and say we have a pretty good understanding of gravity, because we can calculate through every possible situation we know of in which gravity is essentially involved?
3 points
15. Is Gravity a Force?

I think this is a matter of internal consistency. We know from experiment and observation that nature obeys certain fundamental symmetries - for example, from observing and playing around with a large number of particle interactions, and even before making any specific models, we will eventually notice that all these interactions are subject to what’s called CPT symmetry. Any model of particle physics we now develop must therefore reflect this symmetry (the current Standard Model does this). As it turns out, CPT symmetry implies that space time must have a certain local symmetry as well, called Lorentz invariance (this can be formally proven, and has been experimentally shown to high accuracy). This symmetry is not compatible with a Euclidean geometry - you need something that has different signs in the time and space parts of the metric, making it non-Euclidean. So you need non-Euclidean space time for internal consistency, or else there would be a conflict between particle physics and macroscopic physics. Poincare could not have known this, since the necessary observational data was not yet available to him. The other thing is that the strong and weak interactions are not invariant under rescaling, so shrinking and expanding rulers are not even an option. However, it should be noted that, given non-Euclidean space-time, you can describe gravity in ways that don’t use curvature - notably with a concept called torsion. Einstein himself tried this, but failed for technical reasons. Only in the 1960s was a functioning model along these lines developed; it’s called Møller gravity. Spacetime here is completely flat, and gravity is due to torsion alone. The physical predictions are the same as in standard GR, because they obey the same symmetries. Which, of course, further underlines my earlier point that the behind the scenes machinery of GR - such as curvature tensors - does not necessarily map into any element of reality. You can do away with curvature completely, and yet still obtain the same gravitational physics through other geometrical means. What both models share are again the underlying symmetries.
3 points
16. Is Gravity a Force?

I think the word we're all fumbling for here when we say 'reality' is in fact 'ontology'. One of the most important lessons of 20th-century physics is, I think, Nature doesn't care a great deal about our entities. I think @swansont, @MigL, @beecee, and myself; and perhaps most eloquently @DrDon have drawn arguments along these lines. Nature is probably connected all the way down to the most fundamental level. That's why such a thing as unification of physical laws is possible in the first place. But distinctions emerge. It is the business of physics to elucidate what connections/distinctions appear/disappear, and when (at what scale) they are relevant. Entities don't present themselves as 'solid' immovable categories; rather, as useful instruments for the scale of description given. Terms as bosonization (a fermion can be seen as a pair of bosons with a 'twist' between them), dualities (a strongly-coupled interaction in one region of space can be seen as a weakly-coupled one on the boundary of that region) etc., strongly suggest that any entities that we may propose are simply instrumental, and what emerges as really robust are physical principles, patterns, rather than 'things'. Lorentz invariance, locality, unitarity, symmetries and conservation laws. Those are the main characters in this play. Weinberg was a master at bringing out how they interplay. Einstein was one of the most brilliant theorists of all time, but this revolution caught him at a point in his life when he was already too set in his --ontological?-- ways. Weinberg was able to take home the lesson much more efficiently for what the 2nd half of the 20th century physics needed. Maybe nothing is, and everything emerges, in some kind of bootstrap mechanism of substantiation of entities in a grand cosmic scheme of which the building blocks are actually patterns and principles, and not things. --I'm getting blah, blah. I'm also glad that professor Lincoln has spent some time among us, be it ever so briefly.
3 points
17. Anti-abortion law in the USA

I always found that that to be bit of a a convenient excuse. See, folks do not have abhorrent believes, but it is because someone made them so. There are a few issues with that statement. The first is the use of political correctness of a pejorative of the right to criticize the left. In reality, there has always been an Overton window that determined what is palatable. The phrase PC has been weaponized by the right to shut down every criticism (justified or not) that stem from progressive ideas. In all honesty neither side is doing well with fostering dialogue, however it seems to me that the right has created a whole ecosystem to systematically shut them off from discourse, which is now exemplified by the presence of an alternative right-wing reality in which things like, say global warming or COVID-19 simply does not exist and antifa has taken over the government. If you want to follow this route and where the origins are, you won't find those in the opposite camp. There is a large body of research now which discusses this in more detail, but in short, it is not a reactionary or even new phenomenon. It follows a long tradition of right-wing patterns which elements of authoritarianism and xenophobia which are rolled into a zero-sum worldview. The only new thing is really the amplification of signals from all sides via the internet which allowed folks in fringe to create and maintain their own alternative universe. It should also be noted that one of the hallmark of these fringes is the duality of a) being heroes of their narratives but b) at the same time being downtrodden and forced to action by the enemy. The narrative that the left forces them to believe in crazy stuff because they have taken over mainstream media and science, is just another element to it.
3 points
18. Gravity

Magnetic fields have polarity. You have a North and South pole. Like poles repel each other and unlike poles attract. The poles always occur in pairs (a magnet will always have both North and South poles) Because of this, it is possible to arrange the poles in such a way that all the poles cancel each other out and you get no net attraction or repulsion. Gravitational fields have no polarity. They are purely attractive; mass attracts mass. The more mass, the greater the attraction. There is no way to arrange things to get a repulsion or cancellation. But, compared to magnetic fields, gravity is very weak, and it take a considerable amount of mass for this attraction to be easily measured. But, as swansont has already noted, we have measured gravitational attraction between relatively small masses. The earliest such measurement was done by Henry Cavendish in 1797. He took two brass* spheres which were placed on the ends of a long rod which, in turn, was hung from a piano wire at its midpoint. Two more larger Brass spheres were placed near the suspended spheres so that any attraction between them would rotate the rod and twist the piano wire. Then, by measuring how much rod rotated, and knowing how much torque it would take to twist the wire by that amount, he could work out just how much force was attracting the spheres to each other. And since he also knew the mass of the spheres, he was able to derive the constant of proportionality for gravity. This, in turn allowed him to work out the mass of the Earth. Up until then, while we could measure how much gravitational force there was between the Earth and an object of a known mass, and we knew how far the object was from the center of the Earth, we were still left with two unknowns: the mass of the Earth, and the gravitational constant of proportionality. Knowing either one would allow us to work out the other. Cavendish's experiment gave us the value of the gravitational constant, which meant he could now calculate the Earth's mass. Because of this, Cavendish has been referred to as "The man who weighed the Earth". *he used brass as it had no magnetic properties that could have skewed the results.
3 points
19. Is Gravity a Force?

Would it help if we thhrew out the concept of a 'force' in this context, and said that there are four fundamental interactions ? We don't know the exact nature of these nteactions, but we have various ways of modelling them. None of the models tell us what they are, but they make good predictions where they are applicable.
3 points
20. Can an A.I. System Be Considered An Inventor?

True, but it's not unreasonable to ask. How unsatisfactory would it be to a end a discussion about whether, or at what age, abortion should be legal, or the legal status of various drugs with 'whatever a court says'. AGI is irrelevant to this particular discussion. DABUS is far from AGI yet its legal personhood is still being discussed, and apparently granted, in some courts. With the development of narrow AI like AlphaFold, which vastly improves previous attempts to model protein folding with implications in drug discovery, these legal discussions will likely (and rightly in my opinion) become more frequent regardless of AGI development. Given the glacial speed of politics and law, starting the discussion before it becomes a pressing matter seems prudent. Regarding AGI, that blog was a bit vague. Here, about 350 ML researchers were surveyed regarding the estimated timeline of human level machine intelligence development. Granted, it might be something like fusion power (another 20 years right?), but it's the most thorough guess i've seen kicking around. I found it incredibly hard to find out anything about the actual architecture of this model. This is the closest i could find - short on detail. I very much doubt it's anywhere near GPT-3, AlphaFold or Tesla's self-driving architecture. Sounds more like a gimmick to start a discussion.
3 points
21. What makes the bulb glow?

If you learned something it's not a waste.
3 points
22. Vaccinating the site

With all the conspiracy, misinformation, and unevidenced claims going around, we're trying to achieve "heard" immunity. If you "heard" it somewhere, check it out before you spread it out.
3 points
23. Could the real size of the universe be infinite?

Inflation and expansion are not the same thing. Inflation is an accelerated expansion (i.e. it's a particular form of expansion) Having no central point is associated with expansion in general, not just with inflation. No, not so much. As above, changing scales is a feature of expansion, not just inflation. A meter isn't worth any less owing to expansion. Remember that expansion is only apparent where systems are not gravitationally bound to each other.
3 points

2 points

Currantly
2 points
26. What taxes a billionaire?

...and many more find that creating the illusion of it instead...is better for the bottom line
2 points
27. Strange rocky material fell from the sky with odd surface features and microbiology inside it

I don't think this object can have fallen from space. The chem analysis shows an amazing % carbon so it did not travel very fast through the atmousphere or it would have burned up. Sorry about the ? mark, I chose a sigma from the character set but it seems to have come out as ? mark. The other interesting thing about this analysis is the absence of hydrogen. However at 45% carbon I would guess some industrial chimney (there are plenty of these around Birmingham) or other was being cleaned out that night. If you have seen industrial chimneys at night you can often see the sparks and or material be ejected.
2 points
28. Political Humor

Meanwhile, in the USA
2 points
29. Game-changer for clean hydrogen production:

Just asking. Isn't Au (gold) a precious metal? It is good to see progress on better electrolyzers and I hope it flows through to renewable Hydrogen production. It won't become widely used without better electrolyzers. I see iron smelting and chemical feedstocks as the uses of most significance. I am less optimistic for H2 as transport fuel and as transportable fuel; iron production and chemical feedstocks can operate with on-site production and storage at low(er) pressure and therefore cheaper than bringing it from somewhere else. Battery electric looks better for vehicles - overall much higher energy efficiencies and piggy backs onto existing energy distribution networks. Hydrogen as transport fuel needs economy wide infrastructure built from zero. One more halving of battery costs will make existing type EV's unstoppable. One more doubling of energy density will make EV's unstoppable - and open up aviation to battery electric. Achieve both and it is game over for fossil fuels. Hydrogen won't be in that game. I'm cynical and think that, important as clean iron smelting and fertiliser production is too much is being made of Hydrogen - and the reason it has such widespread political support is that it can't do much any time soon. Those looking for empty gestures to follow up their empty gestures on zero emission targets like renewable Hydrogen sometime in the future, but so does the fossil fuel industry, that currently make most Hydrogen like it; it uses empty gestures on Carbon Capture and Storage to justify competing (with aid of subsidies from sympathetic politicians) against emerging clean Hydrogen and other clean energy.
2 points
30. Velocity and acceeration [ Vector calculus with applications ]

https://en.wikipedia.org/wiki/Whewell_equation Homework. No linear algebra or group theory here.
2 points
31. Frank Sinatra is not a poached egg

If I may, and with authentic respect… It’s likely bc you’re living now in a world where patience with bullshit and dissemblance leads to needless death and avoidable suffering… and you’re one of the good ones who desires neither
2 points
32. Examples of Awesome, Unexpected Beauty in Nature

I agree, the tepui does not seem to be attached. And there seems to be no room for a large enough lake. Edit: here is a link to discussion about the water: Note that the picture is posted in the art section.
2 points
33. Could the real size of the universe be infinite?

Don't go away Airbrush. The Big Bang theory is based on certain observations, like galactic recession increasing linearly with increasing distance and the CMBR. It is also predicated by GR, and the assumption that the universe is homogeneous and isotropic. So yes, you are right, it is an assumption.; and at large enough distances, a fairly accurate assumption, for the observable universe. Similarly GR does not allow for preferred frames, and a center of expansion certanly implies a preferred frame ( never mind the fact that the expansion with a center would look totally different unless we are the center; and what that implies for Religion ). So, unless drastic changes were made to GR, it would cease to be a viable theory. You are then left with the problem of having to explain the observational evidence for isotropic universal expansion, and the homogenous/isotropic CMBR. These are actual physical observations, and cannot be assumed away; they require an explanation. How would you do that ? B
2 points
34. What is the real difference between science and philosophy?

I love those questions and I don't think they are hard to answer (when you are as thick as me it is easier ) The first man or lady might have been escaping a wild beast of some description and instinctively appreciated the protection it gave. This appreciation may have been reinforced by repetition. So he was a proto scientist(statistician?) But trying to rationalize it in his free time he may have waxed philosophical (esp if he was trying to impress the lady)
2 points
35. Frank Sinatra is not a poached egg

Yes, the many worlds interpretation is an attempt to give QM a realist account. Can we ever prove it? I don't see how. The fact remains, however, he is trying to describe unobservable reality. "Are we to infer that there are an infinite number of realities which grow in number with every interaction capable of multiple outcomes ?" That's what the man is saying. Do I believe it? No. Is he trying to describe reality? Yes. Edit: MigL, try "Quantum Theory and the Flight from Realism" by Christopher Norris, if you're interested in these things. You'll love it!
2 points
36. Is Gravity a Force?

They follow paths in space-time, not just space. That’s a crucial difference. When in free fall, they will follow precisely that path which maximises proper time; so they tend to follow the longest possible path through space-time (‘geodesic’), which is also that path for which acceleration vanishes everywhere (hence free fall). This is called the principle of extremal ageing. Writing this mathematically gives an equation the solution to which is precisely the path followed by the falling body. Very simply put, the mathematical description for simple cases like the Earth (but not in more complicated cases!) ultimately depends on just two terms - one for time, and one for the radial coordinate. The former carries an additional factor of c^2, so it is much larger than any spatial effects. In that sense, time is the crucial thing here. Note that this is not necessarily true in more complicated spacetimes - just for some simple cases.
2 points
37. Frank Sinatra is not a poached egg

You seem to quote a lot of people. Philosophers you obviously admire, and whose thinking you respect. You also tend to put groups of people into different camps, like ( anti ) realists, ( contra ) idealists, etc. I was wondering, do you you ever post what YOU think about these subjects ? A scientist ( Physicist, as I like to pretend I am ), when asked will give you their opinion. Sometimes those opinions even differ, or are totally opposite, other scientists. But I assume you're human, just like the rest of us; surely you must have your own opinion without appealing to the authority of your (philosophical ) masters ? Tell us what YOU think that cannonball 'really' and 'truly' is ... edit And welcome back I thought you might have gotten upset and left us.
2 points
38. Fencing around Capitol for Sept. 18 ?

Ahh… of course. Thanks. I sort of stopped watching Lucy pull the football away from this particular Charlie Brown. First, Trump was to retake office on Inauguration Day, January 20. Then that came and went and he was to retake office on March 4. Then that came and went and he was to retake office on August 13. Now that’s come and gone so the date has slipped to September 13. PT Barnum was right. There’s a sucker born every minute.
2 points

2 points
40. What is the real difference between science and philosophy?

You did not say history, you said philosophy. Those are different disciplines. So please, don't move the goalposts. You're basically telling the ballplayer they don't understand baseball well enough, And you, as someone without any baseball creds. They might retort "Don't tell me about baseball" or even "WTH does philosophy have to do with baseball?" (something, as with the laser alignment issue, I would be interested in finding out) You should learn about renormalization. Well that would go back to Nobel and the invention of dynamite. What philosophy, specifically?
2 points
41. What is the real difference between science and philosophy?

The topic, of course. When it is no offense, what is it? I always wonder how physicists could say philosophy is useless, during them making philosophical remarks or ponderings. Take the famous Feynman video about 'what is magnetism'. He nearly does not talk physics: instead he is pondering what such 'what is ...' questions factually mean, and what physics can say about it (not what physics says about it). In another video he explains the role of experiment in science. But that is not physics either. So what is it? To give a hint: it starts with 'ph' but ends with 'y'... To repeat my disclaimer: Maybe it is a bit too harsh: I think the great minds examine this philosophical baggage, can explain it, maybe even justify it. Feynman is a fine example, even where he ridicules philosophy. It must haven been the quality of the philosophy lectures he visited.
2 points
42. Gravity

One other thing - magnetic dipole fields drop off as 1/r^3, while gravity drops off as 1/r^2, so even if you could get a solar system to work (you can't have everything attract, as Janus pointed out), it doesn't follow the pattern we see — the planets and moons etc. follow a 1/r^2 attraction.
2 points
43. Is Gravity a Force?

No, that's way off base. I never said we shouldn't believe what physicists say. I never came close to it. I'm saying that there is no basis to say that these discoveries show the underlying reality of the world. (Are you familiar with Plato's allegory of the cave?). Physics tells us how nature behaves, not how it is. Many of the parts of physics are calculational tools that let us more easily describe this behavior. quarks, bosons, etc. aren't "unobservable reality" We observe them, just not with the naked eye. And we are describing behavior. How they interact, and the rules of interaction . The interactions in QCD, for example - do you really think the physicists are claiming quarks and gluons are actually blue, green and red? That's reality? Can you explain how color has a meaning at that scale? Or perhaps, as I'm claiming, it's a convenience, used because of the details of the interaction, i.e. the behavior. We make models that make some kind of sense to us, and use them if they work.
2 points
44. COVID-19 antivirals and vaccines (Megathread)

This is utter nonsense. If that was the case why did developed countries fund several studies to look into efficacy of ivermectin? The big issue is that the performance was ultimately disappointing. The dewormer comment is also because people are actually buying formulation for deworming cattle for self-medication. In other words, it is not a knee jerk response but a very accurate description of what folks are doing. In your own link you can read why the study is problematic, and it is not because of censorship. It is because we need ideally controlled setups in order to look at efficacy. Yes people are taking it out of desperation but what is the evidence that it actually works? As I mentioned, controlled trials found no effects, some studies were retracted because the data sets were faulty. Employing a new drug should generally be a high bar to pass, at best you are wasting everyone's time, at worst you could make the situation worse. Even taken the small cohort data into account right now the evidence for a beneficial effect of ivermectin is at best moderate and if the ongoing trials see no increase in effectiveness, it is unlikely to see more traction. In other words, the hype around it is not supported by data. Just because many folks are taking it tells us nothing about its effectiveness. Has anyone for example seen that active case numbers in Peru are inversely correlated with use of the drug? If not that is not evidence. Even if it is not dangerous a drug has to perform. Otherwise you can peddle vitamin C, hydroxychloroquine and so on. Especially in the US folks are not taking it because they cannot get the vaccine. They take it because folks peddle it as something instead of vaccine. And that is where the danger is. I can understand desperate folks trying everything, even if it does not work. But in a community where the drug is actually plenty, this is just plain stupid. Moreover, if folks take an ineffective drug and believe that they are protected and therefore engage in risky behaviour, well that is going to drive cases upward. The whole thing is just a stupid endeavour in conspiracies. The ever present desire to be pertaining to some exotic knowledge where only few enlightened folks have access to (but not invest any work in even trying to understand how clinical trials are set up and how to evaluate the evidence). Any lack of evidence is then explained by the evil mainstream (also called science) who is just somehow suppress research groups... somehow (but apparently not before giving them money to research it in the first place). We all know by now that this is just a convenient way to brush away evidence and jus supplant evidence with narratives. It would be funny if it wasn't driving needless deaths and making the life of health care workers a living hell.
2 points
45. Is Gravity a Force?

To put it in layman's terms this is my understanding: Newton (Newtonian gravity) - gravity is a force that causes objects of mass to attract each other. Einstein (General relativity) - gravity is not a force but the curvature of space time caused by the presence of mass (also energy but lets keep it simple in this context) where objects follow this curvature resulting the appearance of attraction. Quantum Mechanics (Quantum gravity) - gravity is a force/field where gravitons are exchanged between masses resulting in interaction causing mutual attraction. The Newtonian model works very well for general predictions and suitable for most applications. The GR gravity model has been confirmed to produce more accurate predictions than the Newtonian gravity model, therefore supersedes as the best model of gravity we have. The GR gravity model predicts absurd results when used at the quantum level, predicting things like singularities... The quantum gravity models (hypothesis) solve this issue, however do not (as yet) consolidate with GR which has been verified as the best model of gravity we have. Maybe we are looking at this from the wrong perspective? Maybe focussing on "what gravity is" is not the answer to solving this dilemma. I think learning the nature of "what space-time is" will reveal what gravity is. Please jump in and correct my understanding! this subject is one that is most intriguing to me, and one I want to learn much more about.
2 points
46. Question about length contraction and motion

I'm assuming flat spacetime (no mass, SR only), and inertial motion unless specified. Generally yes. Also "when are you talking about?" matters and is more complicated than a Newtonian description. The positions of things on a map are coordinates within a coordinate system, and those are different for different observers. You could have a map where the Milky Way is at a fixed location and Andromeda is moving, or one where Andromeda is fixed and the Milky Way is moving. Those correspond to the coordinate systems of 2 observers at rest in the respective galaxies. Yes, the distance to the star is different in the different frames of reference. There are invariant measures of distance, eg. the "proper length" of a 1 m stick at rest is always 1 m and everyone will agree on that, even if the stick is moving relative to some observer and is length-contracted ie. has a coordinate length less than a meter in that observer's coordinates. We can say that. We can measure the distances to both galaxies using one frame of reference (eg. the one in which we're at rest), and you can measure the motion of objects using the coordinates of that frame. Consider the map analogy. The spatial coordinates can be represented by a grid drawn on the map. The same grid coordinates can be shown by putting a lattice of rulers throughout space. In our own frame of reference, our rulers are not moving and so they don't length-contract. An object light years away can wobble at speeds near c, but yet stay near one place in the grid of rulers. Meanwhile, that distant wobbling object is moving relative to our lattice of rulers, and our rulers do length-contract, in its frame of reference. For simplicity consider two different inertial frames of reference F1 and F2 that the wobbling object switches between. Each of those frames has its own set of rulers making up a lattice throughout space, each at rest and not length-contracted in its own rest frame. Say I'm at 1 LY from Earth, as measured by Earth, and I'm wobbling relative to Earth. I stay near the 1 LY mark on Earth's set of rulers, but those rulers are contracted by different amounts in F1 vs F2. For example, in F1 Earth might be 0.8 LY away from me and the 1 LY mark, and only 0.6 LY away in F2's frame. The reason that the distance as measured by Earth isn't changing much, and the distance measured by me is changing drastically, is that I'm switching between different frames of reference. The distance between Earth and the 1 LY mark, which has a proper distance of 1 LY, is length-contracted by different amounts to different observers, depending on their relative speed.
2 points
47. Existence is...the Absolute Singularity.

It seems you and I don't use the same definition of intelligence... Chance, chaos, they don't exist? I really am unsure why or how you get these ideas. I don't think these ideas hold up to scrutiniy, but I also realise that this is the extent to which you answer, so it might not be a very fruitful discussion. Things like 'be absurd' are... well your opinion. You like to state the way things are, but don't provide evidence or even follow sound logic that makes sure there are no other possibilities. It might be a good idea to focus on explaining your concepts in more steps, explain why things are like this and not in other ways. Thus far you did not seem to answer my question, or those of other people. I asked "Why does intelligence have to have always existed, what evidence is there for this. What evidence can you provide that goes agains the claim 'intelligence has not always existed' or 'there was no intelligence on Earth before life'. " One can only find several extra statements from which to understand that your definition of intelligence is different from that of other peoples. It might be good to give a proper definition of the words you use. Are they different from what some dictionaries propose, if so, you should note this down so we can understand.
2 points
48. Is Gravity a Force?

Re-reading myself I realise I didn't explain at least a couple of technical terms, so I'm sorry. Horizons: Surfaces in space-time that separate regions of space-time that are inaccessible to observers on one side of those surfaces Renormalization: Treatment of a physical problem taking into account how it depends on the scale at which you study it Entropy: A variable that measures lost information; physical information that gets scrambled Gravity is peculiar on all of these accounts. Other 'forces' don't have horizons associated with them. They're not scale-dependent, like gravity is. This is the meaning of 'bad-behaved'. Other forces don't have an "intrinsic" entropy. Gravity is not so much a weak force as it is a scale-dependent force. That is, whether it's weak or strong depends a lot on the scale at which you look at it. It's actually the dominant force at scales that approach a Planck's length worth of distance. At stellar distances gravity becomes relevant again, but not because of scale-dependence. Rather, because gravity cannot be screened. Gravity also has a cosmologically-relevant component, which is the vacuum energy. Gravity is peculiar in many senses. So, whatever a force is --I'm with other users here that whether it really is this or that verges on metaphysical--, gravity is very different to the other bunch. It's the odd one out. I really hope that was helpful, but it's a difficult topic. Other users express themselves more eloquently than me. And welcome to the forums.
2 points
49. Is Gravity a Force?

This is a very interesting question and much like you Davy-Jones the nature of what gravity is, rather than how it is modelled, is one that I often ponder. Interestingly in QM gravity is modelled as a force; "In theories of quantum gravity, the graviton is the hypothetical quantum of gravity, an elementary particle that mediates the force of gravitational interaction. There is no complete quantum field theory of gravitons due to an outstanding mathematical problem with renormalization in general relativity" So which is it, the curvature of space time or the exchange of particles between masses, or a field in which mass interacts?
2 points
50. Is Gravity a Force?

What is gravity? As @MigL and @beecee said, ultimately we don't know. You can model it as force at a distance, à la Newton, but that doesn't work for rapidly changing or relatively strong (stellar) fields. There comes general relativity to the rescue. You can model it as geometry of space-time, but that leads to a couple of problems: 1) Horizons are entropic (they hide information) 2) Gravity is non-renormalisable at arbitrarily strong fields (ultraviolet limit, high-energy collisions), because it's dimensionally bad-behaved. Problem 1) is both conceptual: What is this geometry with an entropy/temperature; what are the hidden degrees of freedom? And it is also wanting in mathematical/logical consistency: Since Hawking we know that black holes must evaporate if gravity is a quantum field, so microscopic information disappears ==> Distinctions between trajectories disappear ==> Predictability vanishes at too fundamental a level. Black holes are so interesting because they are quantum objects and they are general-relativistic objects; so many people hope they will show us eventually what's wrong with the present picture. A very interesting change in the mind frame of physicists took place in the 20th Century: Renormalisation. What is renormalisation? In very general terms, it's the realisation that physical problems look one way or another depending on the scale and the range of phenomena at which you wish to describe things. Consider a wooden stick. What is it? Newtonian mechanics considers it as a rigid body, which is described by 6 real variables --typically the position of its centre of mass and three orientation angles. But what if you want to consider situations like shooting at it, deforming it, breaking it into pieces? (higher energies, changes at small spatial scale). Then your parametrisation is no longer useful, and you need to take into account interatomic interactions. The motto for this loss of innocence is: My parametrisation of the physical system is not the physical system; it's just my parametrisation of the physical system.
2 points
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