Jump to content


Popular Content

Showing content with the highest reputation since 04/27/20 in Posts

  1. 7 points
    I am unsure why you would think that - you have never upset me in the slightest with anything you have said, so no apology is necessary at all. But just to set the record straight anyway: it is highly unlikely that I know more about GR than you do I am merely an interested amateur, and everything I post here - without exception - is entirely self-taught. Unlike Mordred, I have no academic credentials in any area of science; truth be told, I never even went to university at all. My understanding of GR and physics in general is cobbled together from a variety of textbooks over the years. I am on the autism spectrum, and one of the defining characteristics of people on the spectrum is that we tend to get totally absorbed by narrow areas of interest (this is called monotropism) - for me that just happened to be physics, specifically GR, at least in the beginning; so I did a lot of reading and self-study in that area. In recent years my interests have diversified somewhat, and I also got involved with certain areas of philosophy and spirituality. Also, understanding GR is natural and intuitive to me, in a way that does not seem to be the case for most neurotypical people; perhaps people on the spectrum find it easier to step outside established paradigms (in this case Newtonian physics) and look at things from a different angle. We tend to have difficulties with other aspects of life, though. I can only speak for myself here. I have no interest whatsoever in anything to do with politics; I stay as far away from it as I can. Anytime in the past when I needed to get involved in politics (workplace, family, etc) it ended badly for me in some way or another. The main reason would be that, as being on the autism spectrum, I am unable to read social cues and guess at peoples’ social intentions. Social interactions between neurotypical people are a complete mystery to me, I cannot understand them. I function reasonably well in daily life, but that is only because I have learned to mask a lot; it’s not the same thing. To me, politics is a bunch of people with strong opinions, who do not recognise them as being opinions, and mistake them for some kind of reality. So they get terribly agitated when others don’t share them; there is a lot of suffering it it, really, and no one seems to even see that. I have plenty of views and opinions as well, but I tend to be able to recognise them as such (or so I hope), and see how they are changing with time, so I don’t try to push them on other people. They are just constructs of my mind, so ultimately they say more about my mind than they do about the world at large. As for religion and ethics, they are areas of interest to me - but I personally don’t see them as something to be debated or discussed on social media, which is why I don’t participate in those threads. Religion - or rather: spirituality - in particular is something you do, not just some passive view on the world. I see lots of people who call themselves “Christian” or “Muslim” or “Buddhist”, but these are just labels - those same people may speak and act in ways that reveal complete ignorance of the nature of human suffering. And conversely, some of those people I have met who were most at peace with themselves and the world did not label themselves in any way; they just lived a truth that existed within them on a visceral, intuitive level. So religion and spirituality are never external things, they come from the inside; they are lived, not debated. That’s all I can really share with regards to this. Ethics, to me, is the art of finding the path of least suffering, for myself and everyone else who is involved, in any given situation. There is no such thing as “right” or “wrong”, there is only cause and effect. One can write down general principles for this that may hold true in most cultural backgrounds, but ultimately it is again something intuitive and visceral, something that happens inside. Intention has a lot to do with it - if we act from a place that understands the suffering inherent in all sentient life, and consciously choose to act in ways that minimises it to the best of our limited abilities, then the seeds of our actions will generally be wholesome ones. Again, I think it has a lot to do with one’s reasons for being here. I am on this forum for two reasons only - to expand my own knowledge and understanding, and to help others do the same; and very often, these two things are mutually co-dependent, and happen simultaneously. It is no longer about getting anyone else to adopt my own views on things. Ultimately you cannot force someone to understand something; you can only offer them the tools that might enable them to put the causes and conditions in place for such understanding to arise eventually. But different people come from different backgrounds, and they are at different stages of their own journeys when they arrive here on this forum; it does happen that someone just isn’t ready to listen, and then it won’t matter what you say to them, regardless of how rational and scientific it is. They will be unable to see the merit in it. It’s not even their “fault” really, it’s just that the conditions are not right yet for understanding to arise. Getting upset or offended will never help in these situations - most often it is best to simply disengage and walk away. After all, it is their journey, so I don’t need to loose my own balance over it.
  2. 4 points
    Why is it apparent that small things determine how big things work and not vice versa? Why is cause and effect noncommutative with respect to "size". In the sense that CAUSE is due to some physical laws: Quantum fluctuations CAUSE real and virtual particles. Real particles cause leptons, quarks, bosons. Leptons and quarks cause protons, neutrons and electrons. Protons neutrons electrons cause hydrogen helium and carbon atoms. Hydrogen, iron and oxygen cause stars, planets, and water. Stars, planets and water cause galaxies, solar systems, and oceans. Galaxies do not cause stars. Stars do not cause hydrogen. Hydrogen does not cause protons. Protons do not cause quarks. Quarks do not cause real particles. Real particles do not cause quantum fluctuations. The direction of time is forwards? The direction of cause is bigwards?
  3. 4 points
    A question about a sign convention that leads to a lot of confusion. This is not the only instance multiple sign conventions in Science. In this case it is a result of History. Thermodynamics was originally developed by physical scientists and engineers. They were concerned with making machines (steam engines) for the industrial revolution. Steam engines are heat engines. That is they thought in terms of input (heat in the form of fuel) and output (work). Both of these were thought of as 'naturally being' positive quantities. So they wrote their version of the Law of Conservation of Energy (The First Law of Thermodynamics) as ΔU = q - w. Chemists came to the scene from a different point of view. They wanted all forms of energy to have the same sign, whichever side of the conservation appearance they appeared so they could present the equation as a sum on both sides of the equation. So they wrote their equation as ΔU = q + w. By then it was also realised that, although all the terms are energies, there is a difference between ΔU , which is a state variable of the system, and q and w which are exchange variables of the energies crossing the system boundary. So they tidied up by stating that all energies crossing the boundary from the system to the surroundings are negative and all energies passing from the surroundings to the system are positive. Now they could add them up, move them about in equations and between equations in other parts of Science in a consistent manner. It is an improved system But it shows the importance of knowing the sign convention in use and the equations that go with it. This last remark also applies to other such instances of multiple conventions such as those in Electricity, Elasticity and elsewhere.
  4. 4 points
    Citation needed. Maybe it is just compensation for the Flynn effect. I would guess the lack of a good definition of IQ and the corresponding arbitrariness of the tests accounts for a large part of it. Maybe modern communication technology and social media means that cultural change is happening faster and the tests can no longer be fudged quickly enough to compensate.
  5. 3 points
    What makes you think that? Was it a hanging slinky that was dropped?
  6. 3 points
    This is awesome. A picture of the dust cloud around a star 520 light years away. But better than that, there are signs that a planet is forming. Full story here: https://www.eso.org/public/news/eso2008/ Note that this is a real image, not a simulation or "artists impression"
  7. 3 points
    Because - as I have attempted to explain - time dilation is a relationship between distant clocks, whereas a field assigns a particular object (a tensor of spinor of any rank) to each local event in spacetime. You cannot point to an event in spacetime and say “I am going to assign time dilation factor X to this event”, without any further qualification - this does not make any physical sense. The most fundamental entity in GR (and the solution to the Einstein field equations) is the metric tensor field - it assigns a metric tensor to each event in spacetime. To put it in the simplest possible terms, the metric tensor field allows you to quantify how each event in spacetime is related to all other events - both in spatial terms, and in terms of time. It does so by defining a mathematically precise relationship between neighbouring events, so that, by integrating along curves, you can calculate relationships between more distant events, e.g. the length of a world line connecting them. Time dilation in GR is a geometric property of world lines, in that it is the ratio between the lengths of world lines between the same events - the total time a clock accumulates between two given events is equivalent to the geometric length of the world line traced out by that clock. And how long that world line will be depends on the geometry of the spacetime it is in, and what kind of world line it is. Take for example a rotating spherical body, such as a planet. If you let a test clock orbit the planet once in its direction of rotation, starting and finishing at some point P, then that orbit will take a total time T1. If you now start at the same spot P, but orbit in the opposite direction (counter the planet’s direction of rotation, but along the same orbit, with all other initial and boundary conditions remaining equal), you will get some orbital time T2, which will be ever so slightly different. That’s because, even though you start at the same point P, and traverse the same spatial distance along the same orbit, the geometry of spacetime is such that the lengths of the two world lines will differ. The ratio between these two geometric lengths is one example of gravitational time dilation - the value of that ratio depends on where the point P is, the initial and boundary conditions of the clock kinematics, and the global geometry of the underlying spacetime. How would you capture all this by assigning a single value to point P, as you seem to want to do with your “time dilation field” idea? Again, on closer consideration, in order to capture all relevant degrees of freedom so that all aspects of gravity can be correctly modelled, independently of the precise circumstances, at least a rank-2 tensor field is necessary. That’s what GR does.
  8. 3 points
    There is a lot of false information there. -Without testing you do not know what you had. Making medical assumption based on gut feeling is really bad idea. -Influenza is not 100% symptomatic. Estimates are difficult (for obvious reasons). Longitudinal tests based on serological studies tend to estimate above 75% of asymptomatic cases (e.g. Hayward et al. Lancet 2014) . Note that influenza is much better investigated than COVID-19 and there are still a lot of unknowns and with influenza there are widely divergent estimates. The only thing we know with certainty is that your assertion is entirely unfounded. - Asserting that your feeling trumps actual data via testing is utterly ridiculous. Of course MDs should order tests. One might call it evidence-based medicine or just common sense. Acting on anything else is basically endangering oneself and others. - The unknown regarding immunity is actually correct. We only have limited data suggesting that there may be immunity, but we need to collect more. Also serological testing (but not, say gut feeling) can provide additional evidence of duration of immunity.
  9. 3 points
    A dream is nothing more, than a sea filled with life, full with the broken hearts of those before, experiencing pain and strife, wishing upon a star of light in which send theirhearts a soar, upon their gaze and flying wings, they jump in the sky searching for something more, in their flight they see the lands in which they never knew, and on catching the light in which they had dreamed, they discover something new, That the world in which they once inhabit was nothing but a dream, and that the knowledge in which they had captured is not quite exactly what it seemed, they had not flown into the sky, but through a looking glass. And upon reaching the end they realize something finally at last, They had not been flying but simply seeing through their own eyes, peering through a telescope, viewing their own demise. And upon viewing of the world they see others fall, those who are all still looking to the sky, hoping to hear the sirens call. So it is the dream in which I hope, to escape this land of mine, to understand the stars above, before running out of time, to finally touch the edge of the universe, before it is to late, to inspire those who dream of the impossible as well, before the world is consumed with hate, p.s. not sure how you wanted me to respond so I wrote my own poem! p.p.s. not good at poem structure soooo it might be a little bad. I do not know If this is guided towards me or not, but I don't know, build a boat I guess. Power only exists for those who believe in power, I just wanna make cool things and fly around because its fun!
  10. 3 points
    There are a number of elements that are used to fully describe a planet's orbit.: The semi-major axis of the orbit (average orbital radius) The eccentricity ( how elliptical the orbit is) The orbital inclination The longitude of perihelion The longitude of the ascending node. The last three are measured with respect to the Earth's orbit around the Sun. The imaginary plane which passes through the Earth's orbit is the ecliptic. The orbital inclination is how much the planet's orbit is tilted relative to this plane.* The longitude of perihelion is measured relative to the Vernal equinox. (draw a line from the Sun that passes through the Earth's orbit where the Earth would be on the date of the spring equinox.) If you draw a line between planet and Sun when the planet is at perihelion ( the closest point of its orbit around the Sun, the angle between this line and the line above will give you the longitude of perhelion. (which also gives you how the major axis of the orbit is aligned). The longitude of the ascending node gives you where the plane of the planet's orbit and the ecliptic cross each other. *Because the Earth is subject to various gravitational disturbance from other planets, this plane can change. To keep things simple, the ecliptic is defined as the plane of the Earth orbit on the starting date of the epoch we are presently in. That way, we aren't always adjusting the inclinations of the other orbits due to the Earth own orbital changes.) All of these elements are subject to change over time due to being perturbed by other bodies in the solar system. The Horizons web site can give the these values and the position of a planet for any date: https://ssd.jpl.nasa.gov/horizons.cgi#top
  11. 3 points
    Here is an example of a elliptical orbit where we can see the other focus more clearly than your drawings: (From: https://www.schoolsobservatory.org/learn/astro/esm/orbits/orb_ell) If we take the line between the Sun and the other focus, I think you are asking: "what is the angle of that line?" (Here it is aligned with the X-axis, but it could be rotated at any angle) Is that correct? If there is only a single planet (as in that diagram) then it doesn't really matter what orientation you choose because there is nothing to compare it to. If you have several planets, then their ellipses will all be aligned differently. The only way you can know the actual alignments is by making measurements of the planetary orbits. Here is a more realistic diagram of several orbits in the solar system: From: https://courses.lumenlearning.com/astronomy/chapter/orbits-in-the-solar-system/ - that looks like a good page that might answer a lot of your questions. As you can see, the planetary orbits are pretty close to circular. Also, the relative alignment of the ellipses will change over time as the interaction of the bodies will cause the orbits to deviate from perfect ellipses. Like this: From: https://en.wikipedia.org/wiki/Apsidal_precession Note that if you are simulating the orbits by calculating the positions after shot time intervals, you need to be sure your simulation converges. For example, if your time steps are too large, then the simulation will be inaccurate and the orbit will become unstable and you will fling the Earth off into space. Not easy, because the eccentricity the orbit is so small.
  12. 3 points
  13. 3 points
    In the equation, r is measured from the center of the Earth. It seems that you just plugged 424 in for r. The answer you got would have been the GPE for the spaceship if it were sitting on the surface of a world with the mass of the Earth, and just 424 m in radius. For one, you have to convert km to meters, and for the other, you are looking for the difference in GPE between sitting at the surface of the Earth and being 424 km above it, not just the GPE for some point.
  14. 3 points
    Why does scientific inquiry have to have a quantifiable benefit to society, beyond the new knowledge itself? A benefit that you can't know until you've made the discovery? To quote from The West Wing Senator Enlow: If we could only say what benefit this thing has. No one's been able to do that... Professor Milgate:That's because great achievement has no road map. Well, the X-ray's pretty good. So is penicillin. Neither were discovered with a practical objective in mind. I mean, when the electron was discovered in 1897, it was useless. Now we have an entire world run by electronics. Haydn and Mozart never studied the classics. They couldn't - they invented them.
  15. 3 points
    I understand how you can say that. But it's not that clear to me. First, dinosaurs, like any other megafauna, are almost anecdotal in terms of primary production, carbon cycle, etc. To give you an example, there are about ten trillion tons of methane stored in the oceanic bottoms that can't get out thanks to methane-metabolizing microscopic archaeas that are keeping it at bay. And, mind you, methane is 25 times more greenhouse-effect inducing than CO2 is. If you want to understand ecosystems you must look at microorganisms. They don't look as pretty in a theme park, but are far more important for the global chemistry. Another question is the rate at which this is happening. Back in the time of the dinosaurs the conditions were quite stable, and many big animals (quite a big bunch of them in terms of animal biomass) may have been slow-metabolism. As to the dinosaurs, we don't really know if they were or how many there were. We do know that all the plants were C3, because C4 plants did not exist. How did that affect the carbon cycle? Be aware, e.g. that RubisCO, the carbon-fixating molecule, is the most abundant organic molecule on Earth by far. In fact, C4 plants, which are more efficient at sucking up CO2 from the atmosphere, precisely evolved to adapt to the new, slowly-changing, low-CO2 atmospheric conditions. And that's the observation that leads me back to the question of rate. Organisms need time to adapt, measured in tens of millions of years, not decades, for those paradises that you picture in your mind to establish themselves. We are now pumping into the atmosphere an estimated billion tons of CO2 per year. The Earth is 100 years within a Milankovitch cycle of glaciation, and yet the glaciers are clearly melting, and fast. We are really fortunate that the Himalayas are still pushing up, because this geological process sucks CO2 from the atmosphere at an incredible rate, and sends it back to the sea. The really big question now is what will happen when the ice sheet on Greenland sloshes down to the North Atlantic, as it is sure that the salinity will go down significantly and the conveyor belt that equilibrates the water temperature will eventually stop. It is estimated that that will happen by 100 years' time. Have you thought in any depth about these and other factors?
  16. 2 points
    Just to echo what others have said, and to add my thoughts as I have some (limited) experience of garden-shed inventing. First, your experiences are not new. This is the process that most (all?) inventions and new products have to go through - a sort of rites of passage for want of a better phrase. Apparently WD40 is so called because it was the 40th formula for a water displacement product, after 39 failed attempts to come up with something viable. Successful inventors need to be customer, not product, focussed by identifying thier (the customer's) need and wants, gaps, and ambitions. This is achieved best by targetted market research. If your unsolicited emails are not working then as others have said you need to put in some legwork and invest time, energy and most definitely money. ie speculate to accumulate. Once you have a foot in the door, not only do you need to sell your ideas and concepts you need also to sell yourself - build up your CV to give yourself credibility and added value. You should also consider that those you approach may have contractual obligations or strict procurement processes that may prevent them from direct engagement. And most importantly: learn from your "failures" then try, try and try again. Good luck
  17. 2 points
    @Theredbarron here is an idea how I think you could have formulated the initial question with lower risk of being dragged in an (unwanted) detailed discussion about the specific experiments. Hopefully this post helps OP in future topics and increase the odds for fruitful discussions*. I have an idea about doing some experiments in vacuum. Not just low pressure as on a mountain top or high up in the atmosphere, but vacuum. More specifically I wish to create, or get as close as possible, to the vacuum of space. Right now I have a meter. The best I manage to get to using my current equipment is a reading of 29 inch hg on the meter. How does my current meter reading compare to the vacuum of space? What difference would it make if I could reach a reading of 30; how much closer to the vacuum of space would a reading of 30 be? The above question is not intended to be the perfect vacuum question from engineering or scientific point of view, it’s just a variant on the initial question intended to help the formulation of future questions. The question intentionally still contains issues from OP regarding units, measurement relative to local atmospheric pressure etc, written from OPs point of view with the information available at that point. From this point there would still be lots of questions about the meter, units, issues with equipment and others but maybe less focus on the actual experiments. *) I've learnt some new things about vacuum measurements and units from this thread.
  18. 2 points
    I'l try: The upward normal force from the table and the downward force due to gravity are two different forces acting on the same object. Action/reaction pair is the same force seen from two points of view. In the above case action/reaction could be seen as two separate action/reaction pairs: 1: Gravitational interaction Book-Earth and Earth-book 2: The books force pushing down on the table and the tables push on the book If everything is at rest then the forces will balance so numerical values of force due to gravity (1) and normal force (2) are same. Now try a case where 1 and 2 are not balaning each other: Accelerate the table upwards (for instance in an accelerating elevator). Then the normal force would change but gravity remains the same. (1) is still action/reaction pair and (2) is still action/reaction pair but (1) and (2) does not balance out.
  19. 2 points
    On the example of Hydrogen-1 atom: free proton, and free electron have higher mass-energy than bound together proton and electron. Similarly free nucleus (multiple protons and eventually neutrons bound together) and many free electrons have higher mass-energy than when they are bound together. If they join together, energy is released. Usually in the form of multiple lower energy photons. This process can be reversed. When energy is delivered to atom, molecule, electron is ejected. Usually energy is delivered by particles in the form of kinetic energy. Photons with enough energy, electrons with enough kinetic energy, or other particles or molecules with enough kinetic energy. It is what scientists call ionization energy. https://en.wikipedia.org/wiki/Ionization_energy Different particles, different elements, different isotopes, have different ionization energies. e.g. if you have Helium-4 element with 2 electrons it is electric neutral atom. After 1st ionization it changes to positively charged He+ nucleus and free e-. After 2nd ionization it changes to He2+ and two free electrons e-. He2+ is also called alpha particle. https://en.wikipedia.org/wiki/Alpha_particle 2nd and further ionizations require significantly more and more energy. Outermost (valence) electrons are the easiest to be ejected. Innermost (the closest to nucleus) are the hardest to be ejected. The example gave by joigus, Lithium has small energy of 1st ionization. As you can read in this table it requires 5.39172 eV energy. For instance ionization energy of Hydrogen is 13.6 eV. Two and half more energy needed to eject electron. https://en.wikipedia.org/wiki/Ionization_energies_of_the_elements_(data_page) If Lithium has contact with element (let's call it "X") which has not fully filled orbitals, Lithium valence electron is intercepted, and Li+ positive ion and X- negative ions are created. They are still bound by electrostatic forces, ionic bonding https://en.wikipedia.org/wiki/Ionic_bonding Similarly, stable isotopes made of multiple nucleons (i.e. protons and neutrons), https://en.wikipedia.org/wiki/Nucleon , bound together are at lower energy state than when they are free. Energy needed to disintegrate their nuclei is called nuclear binding energy https://en.wikipedia.org/wiki/Nuclear_binding_energy Unstable isotopes have enough mass-energy by themselves, therefore they decay to lower energy state isotopes and various 3rd party particles, in various radioactive decay paths https://en.wikipedia.org/wiki/Decay_chain I hope so this will help a bit for a while. Read carefully the all articles in links that I gave.
  20. 2 points
    @william1952 In the meantime, here is a paper that could be a starting point for further reading: "On the dimensionality of spacetime". https://space.mit.edu/home/tegmark/dimensions.pdf The paper explains how there are issues with any idea that requires another number of dimensions than 3+1. The paper also provides references for further reading.
  21. 2 points
    I'm kind of a stickler for language. I would say entropy is not experienced by systems. Entropy is a property of some systems about other systems they are measuring, observing or describing (if they are thinking systems.) So it's a correlative property (system A watches or describes system B.) Or a property of the description (system A describes system B.) In order to describe a system, you (another physical system) must produce in your brain an ordering, a structure that, as closely as possible, reproduces features of, or resembles, the described system. In order to do that, you unavoidably must ignore some variables of described system and probably own variables too. Thereby the necessity of an entropy. In the universe chances are that things won't repeat themselves because the universe is describing a sequence of more ordered states to less ordered states (IOW, the initial state was far more ordered than the later ones.) Also, the accelerated expansion may render complete thermalization impossible. Poincaré's recurrence theorem only works for closed systems after they completely thermalize, so that thermal fluctuations, given enough time, get you as close as you want to a previous condition or, AAMOF, to any particularly bizarre condition (Boltzmann's brains.) So, on second thought, the OP may be right in that "anything that may happen will happen" for thermal systems, given enough time. An example would be a thermally isolated gas in a box. Given enough time, some bizarre dynamical configurations might appear as a result of thermal fluctuations. They would last a gazillionth of a second, I surmise. The universe is not like that.
  22. 2 points
    Besides the people who died merely by following his shit advice directly (drink Clorox?), there’s also the issue of all the weeks he spent downplaying things and trying to spin information so he wouldn’t look bad... every second he was unclear and was prevaricating could’ve instead been used manufacturing tests and PPE and generating support for a collective “we’re all in this together, let’s wear masks” response. Even today, wearing masks has become political, he forces his people to take them off in meetings, and he’s contradicting the advise of his own experts. Tens of thousand of deaths could’ve been avoided, but he was too busy blaming Obama like a fucking toddler
  23. 2 points
    Well unfortunately for me, I have tried to "truly" learn some physics previously, but I came across unscalable walls and bottomless pits. The biggest obstacle for me was the mathematics. I simply don't understand them. I can follow instructions. I can find the area bounded by two hyperbolic functions. I can follow matrix calculus operations. But I can't understand them. They have no "meaning". There are mathematical techniques and tricks that are used that I can accept are true, but I cannot logically comprehend them and cannot apply logical proof to the equations once they are added. In addition I have questions about the legitimate use of some mathematics. There are some assumptions that are taken for granted, or at least rarely mentioned, but these assumptions underlay ALL the conclusions that are drawn from the results the mathematics give. Just for example, off the top of my head, integration relies on a coordinate system that is "uniform", that is the gap between integers are consistent, but what if it isnt? That throws integration out of the window. Any integration with respect to Time from zero to infinity, assumes that it is uniform and consistent from the beginning and forever What evidence do we have this is so? Sure you can calculate the area under a curve...but only if you assume your axes are consistent and uniform. What if the gap between 2 and 3 was larger than the gap between 1 and 2, such that 1 +2 =/= 3? We already know space expands, that is, the axes are stretched. Are they stretched evenly everywhere at the same time? Do two volumes of space mutually exclusive from each other's observable universe and future universe stretch at the same rate? How does space expansion reconcile with an isotropic universe? The second biggest obstacle for me was the scope. If you want to "truly" know one thing, you have to know ten other things first, the rabbit hole never ends. I am truly awestruck by how vast the scope of physics is. It is like running up a mountain of infinite size, and everytime you summit a local maxima, there's ten more summits behind. The third problem was time and attention. I don't have the time or the attention or even the ability to learn all the things I need to know to answer my own questions. The bottom line is, I am resigned to forever never truly understanding anything, and forever asking questions like a child.
  24. 2 points
    So if I publish a paper on Invisible Pink Unicorns in my back garden, and no one responds to it, then that means my unicorns must be real? What a ridiculous argument.
  25. 2 points
    I can't say I do, I'm sorry. I'm thinking of taking a back sit on this one. I'm not ready for this discussion... just yet. I want to read more arguments. Yes, I did. I had nothing to add to that one. Yes and no just doesn't do it for me. It's just that I want to take a break from fundamentals of QM for a while. I've had so much arguing for years with my friends from university... There's been so much nonsense said and written about it through decades that I feel overwhelmed. It is entirely possible that I misinterpreted. Occasionally I need to take a step back and let everything sink in.
  26. 2 points
    I don't see how one follows on the other. Why would their respiratory requirements affect whether or not we think they exist in the first place? The real issue is more about complexity. The lifeforms we know of that "breathe" other elements (sulphur, hydrogen) are pretty simple organisms, and not the kind of species you'd expect to develop space travel. The more complex organisms we know of use oxygen in some way. Also, aliens don't need to be exactly like us in order to manipulate oxygen. Many creatures on Earth use oxygen in different ways to get what they need.
  27. 2 points
    I consider science and religion (the general concept, not any particular religion) to be different and distinct domains of enquiry, that ask different questions about the world and the human condition. As such, there is no reason why the two can’t coexist harmoniously, in fact it is natural for them to do so. Problems only arise when people start conflating the two - making religious claims about the empirical world, or conversely making “scientific” claims about what is not readily amenable to the scientific method, quickly leads to unnecessary disharmony and arguments (and potentially worse). You don’t use a torque wrench to hammer in a nail - one must pick the right tool for the job at hand. I think both science and religion are equally of value when it comes to understanding what it means to be born human, but they shouldn’t be conflated and confused, because they relate to different aspects of our experience.
  28. 2 points
    Why? Change doctor It is easy.. If you have decimal e.g. 1111 factors will be 101 and 11. If it is e.g. 111111 factors will be 1001 and 111. And so on. You just have to answer question if number of decimal ones is dividable and has factors by itself. 91 is not prime. It is dividable by 7 and 13. 1111111 1111111 1111111 1111111 1111111 1111111 1111111 1111111 1111111 1111111 1111111 1111111 1111111 is dividable by 1111111.
  29. 2 points
    ..but OP nowhere said it is sequence of binary ones..
  30. 2 points
    Two very important concepts you don't seem to grasp. The universe, in the Big Bang model, evolves from a smaller version of itself, where separation between non-gravitationally bound objects decreases, as you go further backwards in time. The logical end result of this backward trip in time, is a singularity, but there are many reasons to discount the singular universal beginning, so we conjecture a hot dense initial state. Once expansion ( and/or inflation ) starts, we have an era that is dominated by radiation, as electrons cannot sick to protons to form atoms. The ambient 'energy' ( temperature ) is like in the Sun, a plasma, and only when the temperature drops below 3000 deg C , will electrons bond to protons without ionizing. If we consider this temperature, and factor in the approximate expansion of the universe since the end of the radiation era ( slightly more than 1000 times, we get the temperature of the CMB ( I believe G Gamow first did this calculation in the 40s ) of 2.7 deg C. And sure enough, Penzias and Wilson found the CMB in the 50s, at just that temperature. You cannot be 'outside' the universe. Saying that 'if you cannot visualize it it doesn't exist', is a cop-out for that reason. Where is the center of a doughnut shape, if you are INSIDE ? And since anytime you are looking into a distance, you are in effect, looking back in time ( finite speed of light ), it makes no sense to consider only 3dimensional volumes. You need to consider 4dimensional space-time. Can you visualize that ??? Both of these concepts also explain why the CMB has not passed by you. The CMB is the relic radiation of EVERY POINT in the universe, not a specific location, so it can never pass you by on its way to somewhere else. One final point... You ask us to discuss your conjecture based solely on 'logic' ( not mathematically defined logic, but personal subjective 'logic' ), yet you demonstrate that you lack the basic knowledge of even some of the things you are trying to explain, such as Dark Matter. ( I would hate to hear what your take on Dark Energy is ) You are basically asking people to waste their time discussing your conjecture, as all indications are that any mathematical model will be similarly flawed. You wan't to build a skyscraper, yet you lack the foundations to build it on; why not ask questions where you lack knowledge, and build a foundation. Then you'll have some idea as to what kind of building you can build on those foundations
  31. 2 points
    Start by realizing that most behavior is classified along multiple spectrums. By arbitrarily picking one aspect where you think someone else has more natural talent than you do, you're ignoring all the other aspects of existence where you may keep pace or even excel. Since we're far beyond the point where any single person could know everything about just one scientific subject, your focus should be learning everything we know about something that really interests you. Don't worry about adding to that knowledge; I think that happens naturally as you learn more about the subject. Don't force insight to come; it grows out of necessity. Perhaps your jealousy is more about feeling a need to catch up rather than feeling others are smarter. We often look at those we think of as "naturally talented" and assume everything comes easier for them, that they got some kind of head start. But learning isn't really a race. You need to know what you need to know, without knowing what for, or how much time you'll have. All you can do is find trustworthy information and learn what you can at your own pace.
  32. 2 points
    Enough is enough. I'm not sending INow any more photos.
  33. 2 points
    Relying on friction probably isn't good enough to ensure a safe and controlled speed of descent. You have to take the cart back up to the top, which would require a source of energy. Also, there is probably limited number of people who only ever want to go downhill so, at some point, you are going to have get the people back up to the top as well. Now, here's an Idea: why not have two of your carts tied to each other with a cable that goes round a pulley at the top of the hill. The cable is just long enough that when one cart is at the top, the other one is at the bottom, When you have passengers in both carts, you let the one at the top go down and pull the other one up. You may need to use some power to overcome different loads and control the speed, but less than without the counterbalancing cart. https://en.wikipedia.org/wiki/Funicular
  34. 2 points
    Surely this belongs in the enginnering section, you even asked for an electrical engineer. It is not rocket science after all. However asking for an engineer is a good idea since there is much engineering commonsense and experience involved. 'Line of sight' is funny thing because it begs the question "who can see what ?" Height is important, but not all important. It depends what is in the way. You can (sometimes) achieve the same result moving two feet to the right or left to avoid a nearby chimney stack as 20 feet or more vertical elevation to look over the top of it. I agree with the underlined words of this extract from StringJunky's link But Amazon as a first class engineering supplier ?? The linked site seems only to shop at old smiley. Some advice if you are doing this yourself. Only a vey small part of the antenna is actually the receiving or pickup device. Most of the antenna is either focusing/directing/filtering metalwork. So dimensional and alignment accuracy and stability are vital in assembly. (Most DTV antenna come as self assembly flat packs). Small errors of twisted or displaced parts can ruin the performance of the best antenna. To answer your two questions directly, The range depends mostly upon the height of the transmitter, not the receiver. Which is why these are placed on mountains where possible. And yes if the transmitter can place a signal 200 miles away, that signal can be received. As an example, my antenna is about 75 miles form the Bristol Transmitter, which is placed on top of the Mendip range of hills. It is installed in my attic (roofspace) simply hanging by two cords. I get a better signal inside the roof than on top of it because of nearby chimneys. I get almost zero signal at ground and first floor level, even in the trees in the garden away from the house. The antenna picks up a better signal from the Mendip transmitter than the nearer Blackdown Hills transmitter, which is only 20 miles away.
  35. 2 points
    It would be "aren't" because we require grammatical agreement. In the same that we say "you are" and not "you is" even when talking to a single person because "you" is a plural pronoun (we lost the singular form, "ye", a long time ago although it is still used in some dialects).
  36. 2 points
    Then this is probably the best advise given this thread. Well, I thought I was, but I will try to make my terms equate to the terms in Griffith's. I'm on it. I'll post something relatively soon.
  37. 2 points
    I suppose the real problem is not knowing in advance if the research is utilitarian. e.g. what practical use could anyone around 1900 expect from investigating black body radiation? My favourite example is Faraday's apocryphal responses to Gladstone's question "What use is electricity?" "What use is a new born baby?" or "I don't know, but some day you will tax it."
  38. 2 points
    Hi everyone ! In shops, one remaining Covid contamination path is money. An answer is to allege that money doesn't host the virus, I read that. Or we can try to tackle the problem. UV light is known to destroy virusses, including Sars-Cov2. UV LED are available for near-ultraviolet Hg wavelengths, compact, reliable, efficient. This could irradiate the money between the cashier's and the customer's hands, in both directions. The rest is mechanical design, still imprecise. The apparatus must stop the UV from exiting but irradiate both sides of banknotes and coins. Both users could introduce the money at the top, say between a pair motorised soft rolls, and grasp it at the bottom, after an other pair of rolls. UV between the pairs of rolls would be blocked by the rolls. Nice for banknotes, but the coins would fall at once. It also needs a soft material that survives UV. This shape has the smallest footprint. Or a platter would tun slowly. The customer has a sector to introduce and extract money, the cashier has an other sector, and the two sectors in between irradiate the money under a cover. Silica and variants make the platter transparent to UV. Maybe banknotes and coins should have different paths. Possibly the soft rolls for banknotes and the platter for coins. The apparatus must be easy to open, and opening must halt the UV emission. Fluorescent surroundings would reveal any UV leak. Marc Schaefer, aka Enthalpy
  39. 2 points
    Perhaps a just a minor aspect but how the heck are life forms in hydrovents separate from all other lifeforms on Earth?
  40. 2 points
    Some thoughts,frequently speculative, in no special order, on the thread OP and some of the points made by other members: The OP contains the inherent assumption that IQ has a strong correlation with "success" of the individual and of society. I think it is generally understood that "success" is much more complex than that. Thus Nelson Mandela was undoutedly of above average intelligence, but it was his grit, determination and compassion that enabled his achievements. That raises the question, why would a decline in IQ (unless it were off a precipice) be of much concern? I would be more troubled by a fall in commitment and caring. I suspect that declining average IQ is unlikely to have a major impact on the value of the outliers. There should still be Newtons and Einsteins and lesser luminaries to do the heavy mental lifting for society. Most of us are drones compared with the 'top level thinkers'. The development of AI is likely to eliminate a large scale need for those with above above average IQs but that fall short of genius level. The increasing reliance on AI over the next century may be the real challenge we face in relation to societal intelligence. I keep getting flashes of the Eloi and Morlock of H.G. Wells' Time Machine, in which the decadent and now dumb elite are preyed upon by the subterranean worker Morlocks. (The novel was, at its heart, about the nature of society and its possible trajectory. The SF element was a device to enable that exploration.) I have long thought the main value of the IQ test was to determine how people would do on an IQ test. I benefited from a University education funded by the government, fees paid and sufficient money to live on, so that aspect (for undergraduates) of Moreno's proposals resonates positively with me. However, that was at a time when university education was, in the UK, for 5% of the population, not closer to 45%. I hope that this expansion of student population has not been achieved at the expense of standards, but I remain nervous on that point. Of all the points raised in the thread so far the drop in attention span is the one I find most concerning. Intelligence is only of value when it is employed effectively. That takes time and practice and application. In other words, it requires one's attention be focused on a problem until it is solved. On an upbeat note, perhaps we are developing aspects of intelligence that are appropriate to the environment we are now living in and that are not well discerned by the current tests.
  41. 2 points
    Yeah, but I can't keep up with 'modern' usage. It changes way too quick . Apparently I'm out of bed, showered, shaved and dressed, but I'm not 'woke' yet.
  42. 2 points
    It's also a fact that attention span is declining in most technologically advanced countries. Since a large part of IQ testing involves pattern recognition, maybe we don't have the attention span to recognize patterns as quickly. Anyway, when you find an IQ test that challenges differing cultures/economic status equitably, then maybe you can draw some conclusions.
  43. 2 points
    This is purely anecdotal, but I will present it anyway... During the 1950s ( after the war ) most Italian small towns and villages south of Rome were 'agrarian'. Very few businesses and even less industry ( mostly in larger cities ) and any paying job was extremely difficult to come by. My dad emigrated to Argentina for work in the early 50s, and returned to Italy in '55. He married my mom in '57 and I was born a few years later. He went to work in Switzerland for several years, and I only saw him during summer vacation and Christmas time. Finally, we came to Canada in '68, so the whole family could be together. My dad worked two jobs, and my mother also worked, but we purchased a home ( where I still live ), and both my brother and I were able to attend University ( we both studied physics ). I consider myself to be a productive member of society, even though I come from what you've labelled an 'agrarian' background. Where people come from doesn't matter; what matters is what they make of themselves.
  44. 2 points
    'Imagine there's no heaven It's easy if you try No hell below us Above us only sky Imagine all the people Living for today. Imagine there's no countries It isn't hard to do Nothing to kill or die for And no religion, too Imagine all the people Living life in peace. Imagine no possessions I wonder if you can No need for greed or hunger A brotherhood of man Imagine all the people Sharing all the world. You may say I'm a dreamer But I'm not the only one I hope someday you'll join us And the world will live as one." John Lennon 1971 Imagining is easy. Realization is the hard part.
  45. 2 points
    How can a continuum be a constant? Could you elaborate on that? Maybe you're on to something. Can a stone be unhappy? See my point? If there is **one** feature of gravity that singles it out from every other force in the universe is the fact that you can always locally achieve absence of gravity (equivalence principle, EP). The only limit to this is second-order effects, AKA tidal forces. Jump off a window and you'll find out about EP. Get close to a relatively small black hole and you'll find out about tidal forces. Read a good book and you'll find out about how this all adds up. Oh, and mass is not concerned at all in GTR, as it plays no role in the theory. It's all about energy. It's energy that provides the source of the field. What you call mass is just rest energy, and this is no battle of words. Photons of course have no mass because they have no rest energy; and they have no rest energy because... well, they have no rest. Incorrect: Special Relativity (SR) says nothing (massless or not) can travel faster than the speed of light. Because GTR says geometry of space-time must locally reduce to SR, things moving locally can't exceed c. In other words: things moving past you can't do so at faster than c. People here have been quite eloquent so I won't belabor the point. I don't want to be completely negative. My advice is: Read some books, with a keen eye on experimental results; then do some thinking; then read some more books; then some more thinking, and so on. Always keep an eye on common sense too. Listen to people who seem to know what they're talking about, ask nicely for inconsistencies and more information, data. Always be skeptic, but don't just be skeptic. It doesn't lead anywhere.
  46. 2 points
    You should watch them. The rise they cause in blood pressure and vigorous exercise, thumping the wall with ones fists and kicking the furniture to pieces, obviate the need for regular exercise.
  47. 2 points
    There is also the quite simple aspect that many restriction enzymes bind as dimers, and each half recognizes the sequence on the opposite strand resulting in a palindromic recognition site. There are thermodynamic aspects to it, too, in terms how the enzyme bends the strand but that has a bit more to do with how the enzymes bend the DNA while nicking (I am hazy on details though).
  48. 2 points
    There is no difference between the mathematician's definition of 'compact' and the physicist's. Indeed this is explicitly stated at the beginning of your link. note the sentence which begins "the methods of compactification are various....." Here you are talking about compactifying a group. Nothing wrong with that , not all sets are groups though mathematically the meaning is the same. But mathematically 'compact' and 'compactification' is about sets. We like compact because it allows us to use general theorems like the Heine-Borel theorem as justification for the mathematics of our functions and operations on them eg calculus. We like compact surfaces and manifolds as they keep sets and their coverings under control. The same ideas are also used by Engineers, as this extract from "Introduction to Differential Geometry for Engineers by Doolin and Martin" shows. Note their comment about research papers!
  49. 2 points
    What I am saying is that once we establish a manufacturing base in space that uses in situ materials the economics of space flight will change. Right now everything has to be dragged out of the Earth's gravity well, the economics of that is truly staggering but building a brobdingnagian object in space using materials already there will cut costs considerably. Perhaps I dumbed down the concept a bit, I am trying to avoid as much typing as possible since I almost sliced off my thumb a few days ago. Yet trying to type fast to avoid the boss, my wife my wife hits me in the head with a ball bat, plastic thank god, when she catches me... Actually, if you on a slow boat fuel requirements are smaller and a solar sail could be used to slow down at the end. I am honestly unaware of where I made any claims about speed, please let me where and I'll either defend to admit i was wrong. See above... An actual dyson sphere consisting of a solid sphere covering the sun violates all known and hypothetical physics... https://www.space.com/38031-how-to-build-a-dyson-swarm.html Sending small objects in orbit to build larger structures is currently being done, the international space station is an example. ???? I was answering the idea that physics prevent star travel when in fact it does not.We currently have two space craft on the way to doing it. Time and energy are what it's all about, which do you have the most of? "To say anything is impossible you must point out something about it that supports that idea. Neither space travel, dyson swarms, O'Neil cylinders, or star travel has any impossible or even yet to be invented aspects but controlled fusion would be a nice touch for star travel.... If you did not say these things were impossible I apologize Please show me were I am tap dancing around anything? Building things in microgravity redefine scale... I cannot find where I claimed much of the stuff you are asking about,sadly there appears to no way to tell what number post I said these things, I feel overwhelmed swansonT but I will say,and please take note of this I am hear to learn not to convince people of things not true but answering this post makes me feel like you have mistaken I said either out of context or attributed to me something someone else said. I need help here, please show where I claimed these things. I have labeled them with question marks for your benifit...
  50. 2 points
    Several valid points regarding Sweden have been made in posts above. My experiences so far: -There is not enough data available to state anything conclusive regarding the current approach here in Sweden. It's too early. -Most decisions so far seem to be based on scientific evidence. -As far as I can tell there are good models, adjusted to local conditions but maybe not adjusted to Corona yet My guess* is that the lack of data makes it hard to run the models with a valid set of parameters, models have been proven to work in other situations may or may not produce good predictions. The models' predictions are open for various interpretations. Data in this early stage can support both a lockdown and an open strategy; there is an overlap. Both may be sound scientific interpretations, there are scientists (and others) on both sides in the discussion. I can't guess if this policy will have a good or bad outcome. But I can see the logic behind the attempt to balance for instance: -Base decisions on local conditions, not so much on what others have done. -Try to close down enough to allow for health care to cope and adjust. But do not close down more than that. -Try to make recommendations that people will choose to follow over an extended period of time, it is not a three weeks sprint run for a vaccin. There are lots of other observations to add but that would turn this into blog post. If there is interest in some specific aspect I'll try to answer or find sources. *) I do not have studied the numbers and methods enough claim any insight (yet).
  • Create New...

Important Information

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