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Edgard Neuman

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Posts posted by Edgard Neuman

  1. Sorry but I have no more time for this.
    Does anybody have a valid reason to believe negative rest energy/mass (if you think it's not the same thing, that's not my problem) particle can't exist ?

    18 hours ago, exchemist said:

    * If I crash my car into another one, I may end up with 2 crumpled cars, 2 hub caps, a headlight, a wing mirror and some fragments of windscreen. So the number of objects is not conserved, but some properties (energy, momentum) will be.  

    So "being an object" isn't a real thing, just like "being a particle". The metal of you cars "change its shapes", just like the energy of your particle "change its shapes".
    And the quantity of object that depend of kinetic energy of the cars, isn't frame dependent. Think about that.
    (I would have no problem explaining to you how it is possible, it's one of the thought experiment you have to understand to really understand the beauty of special relativity.. you would need to think about "inner" kinetic energy (frame independant; that can be generalized as thermal energy as long as you accept it can be macroscopical as in your cars) and "outer" kinetic energy (frame dependant, that is indeed the kinetic energy of the center of mass)... and then when you understand the "hierarchy" of systems, you would naturally conclude that obviously "inert mass" IS most certainly the inner kinetic energy of particles 🤷‍♂️)

  2. 13 minutes ago, exchemist said:

    Einstein said nothing of the kind.  Let's go through it. I quote the text of the link below:

    When Albert Einstein posits that energy and matter are one and the same, and one can be converted into the other, most people could not wrap their heads around the idea. They can imagine burning a piece of wood (matter) to get heat and light (energy), but the workings of chemical reactions (in this case oxidization) is well-established. But the idea that the stuff of matter itself (neutrons, electrons, protons) is made of this ethereal, barely-understood thing called energy, flies in the face of conventional wisdom and reasoning.

    We've come a long way since then... 

    - Einstein never posited that energy and matter are one and the same. What E=mc² says is that mass is associated with energy and vice versa. Not matter, mass. And not that they are the same, as quite clearly they are not, having completely different units. There is an "equivalence" between the two: when you multiply mass by the square of the speed of light, you find the associated energy.  

    - It is rubbish to say one is "converted into" the other and Einstein never suggested that. Both are present together. When you charge a battery its mass increases, although not enough to measure. That is what E=mc² means: the chemical potential energy added to the battery when you charge it increases its mass. Just as the mass of an atomic nucleus depends on the potential energy of its constituent sub-particles, as revealed in the "mass defect" when you split a heavy nucleus into two parts in fission.

    - The fundamental particles of matter are not "made of energy". They have energy.   

    Whoever wrote that passage on the website is incompetent. Why did you use it, when there are competently written sources all over the internet? 

     

    So I repeat once again, because you don't seem to think. I've written this 3 times now. SO PLEASE, READ AND THINK.

    Your model  : particle = "matter" with properties " mass"  and "energy". 

    I understand that. Thank you. That's how you see things. And you have a lot of people that write books that think the same. OK.
    So you think there is something called "matter" that exists. and IT CAN have mass and energy. 
    NOW. 

    I have 2 proton. SO that's "2 proton matter" what ever that means (and "rest mass" property ). 
    I accelerate them. SO That "2 proton matter" that have "a lot kinetic energy" as properties,
    (like their position, speed, that are also properties. I know what a property is thank you, I have 25 years of software development)

    THEY MEET. 
    Now you have 1000 particles. That's " 1000 particle matter" and "some mass and energy" (that is according to the conservation of mass energy).
    IF "particle matter" is something that "EXISTS", where does the "1000 particle matter" comes from ? 
    Was it in the two proton ?
    Does "2 proton matter"/ 1000  = 1000 heavy particles ? 
    I'm sorry, you're saying that "something" exists by itself, but that thing doesn't obey a conservation law. So maybe you're just wrong. 

    (By the way, if you knew logic, you would now that if something is "constant" it's usually indicate that it's not a "true" property, but the result of a law. Like PI isn't a property of circle of radius 1...  that's too meta.. in that case, we can agree that a property is an aspect of the way something exists and interacts with the rest of the universe)


     

  3. 10 minutes ago, exchemist said:

    What that link states is garbage. 

    You know that it's originally Einstein's idea ? That's "mass energy equivalence" .

    There was, once a "law of conservation of mass". And then a "law of conservation of energy". AND THEN, in 1905, Einstein discovered the TRUE LAW :
    the conservation of mass/energy.  
    Maybe you don't read enough of what I write. You suppose there is "something" else than energy, that go into particles. OK.

    I take 2 protons. I accelerate them. They have rest mass of two protons and a lot of kinetic energy, but in opposite direction. They interact. A thousand of various particle are created. What are the new particles made of ? Is there something else we had to add to the system to make those particles ? You may talk to me about "particle / anti particles" pair from the void. The particle / antiparticle annihilation is giving energy. So the opposite reaction need energy. (Virtual pair may exist a short time but can't last (I don't believe it, but it's how your physic model works).. )
    Particles physics doesn't work if you don't accept mass/energy equivalence. Sorry for your "caterogy". 

    26 minutes ago, studiot said:

    If that is the case are talking about inertial mass or gravitational mass ?

    Does one of them creates problem ? I read about the problem of negative inertia. There's good articles about the trouble with negative mass, and I know there's various analysis with different results. 
    https://en.wikipedia.org/wiki/Negative_mass

     

  4. 8 minutes ago, studiot said:

    If that is the case are talking about inertial mass or gravitational mass ?

    That's a trap. You answering my original question doesn't require me to dive into this question. (I know there are studies and as far as we know it's the same.). I have no reason to doubt that the thing that provoke both effects and measurements (the gravitationnal field and the resistance to forces)  is one unique thing. 

    8 minutes ago, exchemist said:

    If you can't respect the meaning of established terms, you are not going to get very far. Here is a definition of energy: https://physics.info/energy/

    A property of a system.  

    It is thus meaningless to speak of the property as if it were able to exist on its own. That would be like trying to talk about a bottle of momentum, or a jug of the colour blue.  

    I know what energy is. I know what mass is. I'm explaining to you that it's the same stuff that make both. Have you heard of nuclear reactions and particle accelerators ? Do you even understand relativity ? That a particle gain apparent mass when accelerating ? 

  5. 20 minutes ago, studiot said:

    Is there any need to shout ?

    I note that you have degraded my 'isolated single particle' to any old single particle.

    Single particles undoubtedly do exist, lots of them, as far as anything can be said to exist.

    Some have them have zero rest mass.

     

     

    What is the kinetic energy of an isolated single particle ?

    What is its potential energy ?

    When there is nothing whatsoever around that particle in any direction all the way to infinity.

    Both questions are meaningless.

    By the way I did not say that an isolated particle does not exist, I said its energy is meaningless.

    I accept that English is not your first language, so try to make sure you actually understand what is said to you beofre you start shouting the odds.

     

     

    Ok as I suspect, you are not understanding me. 
    ALL OF YOU. 

    READ THIS MASS IS ENERGY. I'm talking about negative rest energy that is negative mass. 
    You talking to me about RELATIVE FORM OF ENERGY is meaningless. 
    Talking about "negative mass" IS talking about "negative energy". 
    You may not "understand" that, but that's a very known fact. Energy you get from the sun, that make you leave.. comes from mass of hydrogen.. 

    I already said that about 10 times. 

    21 minutes ago, exchemist said:

    Terms in physics have quite precise meanings. Energy is one such term. If you decide you want to ignore the meaning of that term, you will not be able to talk to anybody about your ideas, because nobody will be able to understand what you mean.

    This article explains what a category mistake is: https://en.wikipedia.org/wiki/Category_mistake 

    If you think energy is "stuff" you are making a category mistake, confusing a property of entities with an entity. It's like thinking you can have a jug of blue, or a bottle of angular momentum. Both are nonsensical.   

    Evoking a "category mistake", that is about logic, that is the representation of things and not the things itself..  is .. a category mistake.
    I'm not even trying to be funny. You're talking to me about the name you give things and how you categorize them. That's not physics, that's philosophy.
    Energy is the name you give to a quantity that can change form in many process. Mass is a property of object that is observable by how they bend space time. It appear that rest particle have rest mass. NOW. You can convert mass into energy and energy into mass. EVEN THE REST MASS. So the law of conservation is the law of conservation of "MASS/ENERGY". If you could split a atom, you have part of the mass of the atom (that was really strong force energy) converted into OTHER FORMS of energy. 
    I don't make a category mistake : your categories are wrong. 

  6. 11 minutes ago, exchemist said:

    No that's wrong. You have fallen into the "Star Trek trap". Energy is a property, an attribute not an entity. You are making a category mistake. This will lead you into nonsense if you are not careful. I fear it is already doing so.  

    It is nonsense to talk of energy having a shape. A physical system that has energy may also have a shape. That is different. A physical system may consist of  particles and/or fields. Those are the entities that physically exist. They can have energy as one of their properties.

    But if you start talking about energy on its own, as if it has some kind of independent existence, you are not doing science any more but talking nonsense.  It's like talking about the shape of the colour blue. 

     

    "This will lead you into nonsense if you are not careful. I fear it is already doing so.  "

    OK. HOW ? WHY ? I'm sorry I need arguments. I'm not buying your "vision of things".. 
    " a category mistake" ? What does that even mean ? There is a "category law" in the universe? 

    ". A physical system that has energy may also have a shape." 
    Uh thank you. I wasn't talking about the "shape" of a solid object, I was talking about differents forms mass/energy can take. 

    I am really really astonished. You know about how quantum physics works. RIGHT ? 
    You throw 2 protons against each other. AND BY CHANGING THE ENERGY YOU PUT INTO, YOU GET MORE AND MORE PARTICLE OF VARIOUS NATURE. 
    Supposing that "something more" is needed to make a particle than energy, would physically  imply particle accelerators don't work.. 

    You had "energy" and now you have "various particles". How does that even work according to you ? In that scenario, how can you not agree that mass is energy and that there is no additional charge that are conserved that the one that are opposite to each other.  

    "Everything is made of energy" is a Einstein quote. You understand it when you understand the meaning of e=mc². I assumed every physist know that mass is a form of energy. There's tons of video explaining to everybody that a majority of the mass of a proton is the potential energy of strong force. Don't you know about that ?

  7. 1 hour ago, swansont said:

    Physics works, and it’s all intertwined. For me to explain why it works one way and not another would require you to meet me partway and have an understanding of physics; I don’t know what that level is, but I’m not prepared to teach you several semesters’ worth of it. Absent that, you just have to defer to folks who give you the big picture: Energy isn’t a substance. That’s been tried and it failed (e.g. caloric theory)

    “I have no understanding and I reject your science with no basis” isn’t an argument, either.

    BTW, convertibles and roofless cars exist. We could discuss how roofs keep rain out, because I presume you have an understanding of rain. 

    "BTW, convertibles and roofless cars exist."

    You don't seem to get my metaphor. Convertibles exist, therefor, in that metaphor, your model (your "car with roof") isn't the law because it works. 
    You're telling me I don't undertand things, by not giving me the detail of the argument, I supposedly don't understand ? You didn't give me any science by saying "that's how the model is build". If anything, if it's a choice of the model, it ain't a proven fact. 
    Why does the model require energy to be "a property" and what does that even mean is my question. I don't understand that rule. That's why, because you pretend to do, you can answer me. Right ? 
    Science I believe, but you're not science until you have arguments. Science is proven by experiments, not model.
    I don't have to "trust" you.

    28 minutes ago, studiot said:

    I am going to start by giving you +1 for understanding that an anti particle does not have negative energy, it has the same kind of energy as a particle.

    Unfortunately after that good start, your understanding has failed you.

    exchemist (+1) has explained that is energy not a particle, but a properties of particles.

    But here's the thing.

    The energy of a single isolated particle is meaningless.

    Energy is a property of a system of particles (and perhaps other things as well).

    Here's another thing.

    The terms positive and negative have more than one meaning.

    They are often used to indicate direction.

    Chemists have no problem with negative energy, when used in this manner.

    So if a system evolves (gives off) energy (to another system), that energy is classed as negative.

    And if energy receives energy from another system, that energy is classed as positive.

    But there is no such thing as a 'particle of energy', negative or positive.

    "The energy of a single isolated particle is meaningless"

    OK,  WHY DO YOU EVEN BELIEVE THAT ? 
    A single particle doesn't exist, does not a rest mass ?
    Maybe you don't understand me, because you don't understand that mass IS energy. 
    A rest mass isn't convertible into energy ?
    Is that "science" of yours written somewhere  ? 
    Give me the article of Wikipedia, or the link, that demonstrate that a single particle with its rest mass (that is SIMPLY CONVERTIBLE INTO ENERGY.. "massless" particles, using it's antiparticle) isn't measurable..

    Let's take a time to think about it. How many photons does a particle and a antiparticle annihilation. One ? Two ? Three ? Do you believe there is a "photon" charge that is conserved and we don't know about ?  Saying that energy has to be in forms of Particles.. OK. but saying more than that, imply particle are more than there charge and that something more exists IMPLY a conservation law.. and so some type of charges.. so no, I'm definitely NOT buying your apparent "property" thing. 

    I read books, scientific revues on a daily basis, and nowhere I have ever somebody write that energy (Not kinetic energy of course.  I speak about MASS/ENERGY) is relative. Matter EXISTS.  In opposite you can read ANYWHERE that matter is a form of energy. Have you heard of particle accelerator ? Are the particle emitted not real ? What are they made of ? What did we use to make them ? 
    So I'm really curious to understand why you are all convinced of that. 

    The fact that I apparently have to explain MASS/ENERGY equivalence is really weird. 

  8. 5 minutes ago, Genady said:

    Exactly. We start with the neg-mass-electron at rest, with kinetic energy 0. It emits a photon and starts moving, in the same reference frame, getting the negative kinetic energy, and the total energy is conserved.

    Sorry, I understand but then :  a none particle would probably emit "none-photons" (not ANTI photon which I KNOW are the same as photon) with negative energy (leaving positive kinetic energy)

    I wonder, is there a symmetry that "reverse" energy ? 

  9. 48 minutes ago, Edgard Neuman said:

    I understand I go a step further than what's is known.
    But whatever a particle is made of seems entirely convertible into "radiations", and opposite charges seems to be able to "cancel" themselves into nothing. So whatever the substance is, it's all convertible into the lowest form of it that is radiation. 
    AND if you understand relativity, you know that relativistic mass is mass. Energy has the same effect than mass. That's the point of "e=mc²". So for instance the "thing" that is kinetic energy of a fast particle, has the same effect of the "thing" that is rest mass of a resting particle.
    You know that two "light" particles with high kinetic energy can effectively transform into "2 heavy rest mass" particle (that's how particle accelerator).
    A particle accelerator take energy and transform it into matter (real rest matter of heavy particles). 
    Since "energy" in the energy form (like real relative kinetic energy) can transform into "mass" in the rest form, I can assume it's made of the same thing in different forms. (For some reason I thought it was common knowledge)

    But OK. I suppose it's only my interpretation. 

     

    So why would a "none-electron" do ? Why "energy conservation" (which is not energy loss) wouldn't apply to negative energy ? 

     

    24 minutes ago, swansont said:

    What is says is that we have a model - a very successful one - where energy is a property. If you want to hypothesize that things are made of energy, feel free to come up with such a model. 

    Thank you, I let you handle the semantics and the philosophy. I'm free to believe any idea, let it be any part of any model. As often, you seem to have "philosophical" reactions of pain and taboos when I present my "naive understanding of thing"

    If you know the real solid argument that justify why your model is that way and not another, feel free to explain it to me. Otherwise, you may as well be speaking about religion and dogma to me.   
    It's like saying : "we don't remove the roof of cars. We have cars with roof, they are very successful". That's not an argument.  

    I often ask question here that OBVIOUSLY I can't find in 2 seconds in Wikipedia using Google. I've been asking question a long time, so of course, the ones that still aunt me are not trivial. But for some reason, when I come here, the reaction is "Da ! equation ". Or "read this !" (I read, and it's something else.. like the sea of Feynman) or "let my proove to you that you're a idiot", or "it's like that, because that's the model". And I NEVER HAVE THE ANSWER TO MY QUESTION
     

    20 minutes ago, Genady said:

    Energy is conserved if a negative-mass-electron emits a photon. The photon gets energy E and the negative-mass-electron gets kinetic energy -E. This is unlike the ordinary electron which cannot get a negative kinetic energy.

    But here we are talking about REST energy. REST mass. A none particle would probably emit "none-photons" with negative energy (leaving positive kinetic energy)

  10. 8 minutes ago, exchemist said:

    Just be careful not to equate energy with some kind of substance. You can't have a jug of energy. "Pure energy" is Star Trek, not science. There's always a system, whether it is a particle of matter or a system of fields of some kind, like radiation.

    The same goes for electric charge. That too is a property of a system. It makes no sense to say that when charges cancel you are left with "nothing". What you are left with is an uncharged system of some sort. That is not nothing. 

    But this is a state of modesty saying "we don't know if there is something else", not saying "we know there is something else".
    Energy is conserved, so the fact that energy must take a form (of particles), doesn't imply that everything isn't made of energy.
    It's like saying "A rock always have a shape so there's something else than just rock"..
    Let's agree by saying that "information" imply energy must have some shape (that you call system) withing constrained form that are particles. 
    But then that's why I ask the question : can there be "true" negative system, that would completely cancel positive ones 

  11. 21 minutes ago, exchemist said:

    Steady on. Particles are not "made of" energy. Both mass and energy are properties of physical systems. Particles have energy and mass, but they are not made of them, any more than they are made of spin, momentum or electric charge.

    You can say mass is energy at rest, if you like, but you have always to be aware that these are just properties of some system. Particles do not annihilate into energy. They annihilate into radiation - which has energy, along with other properties (frequency, amplitude, angular momentum....).

    I understand I go a step further than what's is known.
    But whatever a particle is made of seems entirely convertible into "radiations", and opposite charges seems to be able to "cancel" themselves into nothing. So whatever the substance is, it's all convertible into the lowest form of it that is radiation. 
    AND if you understand relativity, you know that relativistic mass is mass. Energy has the same effect than mass. That's the point of "e=mc²". So for instance the "thing" that is kinetic energy of a fast particle, has the same effect of the "thing" that is rest mass of a resting particle.
    You know that two "light" particles with high kinetic energy can effectively transform into "2 heavy rest mass" particle (that's how particle accelerator).
    A particle accelerator take energy and transform it into matter (real rest matter of heavy particles). 
    Since "energy" in the energy form (like real relative kinetic energy) can transform into "mass" in the rest form, I can assume it's made of the same thing in different forms. (For some reason I thought it was common knowledge)

    But OK. I suppose it's only my interpretation. 

     

    17 minutes ago, Genady said:

    An 'ordinary' electron at rest would not emit a photon because of the energy conservation.

    So why would a "none-electron" do ? Why "energy conservation" (which is not energy loss) wouldn't apply to negative energy ? 




    To be honnest, I'm fearly sure there is a reason why there can't be none-particles.. (like for instance all the problems with negative inertia etc)

  12. 10 minutes ago, Genady said:

    Because this would bring them to a lower energy level.

    Why an electron doesn't go into a lower energy level, lower than its REST mass ? 
    (Are you talking about negative kinetic energy ?)

    10 minutes ago, Genady said:

    Because this would bring them to a lower energy level.


    I think I know what you're talking about. You are thinking about an electron in an ATOM. An electron in a atom emit a photon and goes into a lower orbit. So I'm going to write it again : 

    Matter lose energy via radiations because the relative motion of their charges (the structure they form, the orbital energies etc, their relative thermal motion)  comes to equilibrium by emitting photons (basically emitting momentum).  It's the thermal radiation, or electron losing "orbital" energy.  The energy you lose is never the rest energy. (rest energy of an electron is a constant)
    A single stable particle doesn't decay by losing energy.

  13. 5 minutes ago, Genady said:

    What would stop the 'regular' particles with negative mass from continuously losing energy while moving to lower and lower energy levels to negative infinity and at the same time infinitely heating the environment? 

    losing energy how ? You're talking about thermal radiation ?

    Matter lose energy via radiations because the relative motion of their charges comes to equilibrium by emitting photons.  It's the thermal radiation. 
    A single stable particle doesn't decay by losing energy, why would the none particle do the same ??

  14. On 5/16/2022 at 2:27 PM, Genady said:

    Dirac did, 90 years ago: Dirac sea - Wikipedia

    ("though they are mathematically compatible." . OK. THANK YOU. I've been promoting this for 20 years now. Void is made of none-particles and QM is only statistical but I digress)

    1) energy is mass. Mass is energy at rest. All particle are "made of" some energy. Particle and antiparticle anihilate into energy... it imply all particle are made of energy.
    2) rest mass isn't relative to the observer

    Just to be sure everybody correctly understand my question :
    Positron have positive mass. When you combine a rest electron and a rest positron, you get (at least) their rest mass in energy (according to e=mc²). 
    I'm talking about negative mass electron (with positive charge).. It's not a positron. A positron have positive energy. Here, I would invert rest mass. Let's call it "none-particle". (none-electron none-positron etc) 
    When you combine a rest electron and a rest none-electron, you would get 0, NONE energy (so it's not a positron).  The none-electron would have a negative rest mass.
    To be exact, it's not one of the CPT inversion. It's not a relativistic inversion. It concern the "rest" mass. (You should all know that a positron is an electron seen in reverse in time. Do you ?) Rest mass isn't frame dependent. It's not "time" dependent. Mass that is "dependant of the frame" is the relativistic mass


    Ok but why didn't Dirac assume there could be negative energy electrons AND ALSO negative energy protons or positrons (with the negative charges corresponding)  ? Since we invert rest mass.. we have to always invert electric charge, but we can invert mass and charge indepently in this scenario.. inverting one of CPT give antiparticles, but here i'm interested in only inverting mass. Since we want the particle to be the cancellation we have to invert charge, but you can do the same with other type of particle, and antiparticles as well.. Since a anti-electron has a positive mass, we can create none-anti-electron with negative mass and positive charge. 

  15. I made a graphic :

     

    dyson-pressure-cooker.thumb.png.f1eabb64cb84bca3e03de1e38ddda73b.png

    Apparently the correct formula for gas pressure in gravity field is the barometric formula. The pressure is proportional to exp(-h).. 
    So, ok, it will grow slower than gravity (when you get closer to the center).. and that's a problem for self stabilization. I do still believe that surface tension around the sphere would prevent it to bend into the gravity well.. because it would create more pressure in the other side.. (but then the sphere would need to be very strong in tension)
    The question of a hermetic balloon around some atmosphere isn't simple.

     

  16. I really don't understand what difficulties you have with the concept of a balloon filled with heated gas from the star. It's not a "free wind in space". It's a dense atmosphere  of several Pa heated by the star.. 
    The pressure has to build up. The mass loss from the wind is negligible for the star, but since it's hermetical, the matter stays inside the balloon and over time, the density gets higher (Does "hermetical" means something else in english ?). No matter comes out. Since the star is creating heat, the pressure will inevitably build up inside. 
    It is sealed. The title of my question is "CLOSED" dyson sphere. Sealed, Hermetical. I never said the opposite. I only said we should vent the sphere only because we don't want the pressure to get higher than necessary..At some point, since there a star inside, the pressure would get too high. 
    It's exactly like a pressure cooker, with the heat source in the center. It is first sealed, but then there's a vent so the pressure doesn't get to high and blow the cooker. The vents are there ONLY to control the pressure. It is not related to the positioning of the sphere, I never said that. 
    Gravity creates the gradient, and so the star keeps at the center.
    A gradient of pressure means that yes, AT EQUILIBRIUM there the same pressure at all point, BUT if you move the sphere, the pressure on the closest side is higher. Can't you understand what a radial gradient of pressure is ? 

    You say the pressure is "imaginary". So you put a star inside a hermetical container, a star the constantly emit energy, and the pressure wouldn't build up ? How does this work in you mind ? If it's not by means of matter, it's by mean of temperature. I talk about pressure. 
    I'm curious. 

    You don't even need the heat or the wind to keep the mass at the center.
    Suppose you put a hermetical balloon around a cold gas planet, and suppose of course the material of the balloon is strong enough to support tangential forces.. How could the balloon fall into the planet ?? The balloon will stay around. You can imagine that a part of the balloon starts to sink into the planet. But since we assume the sphere is strong enough, it won't happen because the balloon isn't extensible. Now, if the pressure inside is equal to the gravity of the balloon, the whole thing can be stabilized with minimal tensions, even if the balloon is a thick material like tons of metal.

    In the worst case, we can also simply control the position of the sphere by means of propulsion system around the sphere. 

    Listen I'm going to not answer anymore.  My explanation are very simple I don't like to repeat everything multiple times because you are allergic to "new ideas". Here I'm only discussing your inability to understand what I explain and you inability to picture something that is not a star with a free wind, but a closed pressurized sphere. 
    I come here very rarely because I always expect this kind of closed minds, and I'm never disappointed. 

     

  17. On 1/27/2022 at 3:02 PM, swansont said:

    What you are describing here is closer to a Dyson bubble.

    https://en.wikipedia.org/wiki/Dyson_sphere#Dyson_bubble

    uh.. no.. you would need the sphere to be hermetic for the gas inside to build up.
    Free solar wind or radiation pressure alone would never be able to counteract the mass of the sphere. We established that solar wind pressure is thousands of time too weak. 
    Here I suppose the gas inside the sphere exert pressure of several Pascals : the density of the gas inside is nothing close to density around a free star. The sphere would be filled with hydrogen / helium (i suppose). We can't tell the density since it depends of the temperature of the gas. 
    It can't be made of several parts or the gas would escape. So no, it's not what they call a "Dyson bubble".. (why do they call it a bubble if it isn't hermetical ?)
    The article doesn't seem to take into account that if you put the star inside a container, the space should start to fill up with atoms and gas.

    Do you agree that if you put the star inside a hermetical container, the pressure would build up ?

    Since we can (i suppose) build up the pressure this way, then a more massive sphere (not thin graphene, but any metal structure, thus more resistant to tensions) seems possible to maintains. The pressure inside have to be much greater than outside, greater that the normal distribution of gas around a free star. 
    We can even control the pressure inside (by venting the gas accordingly), so we can control the amount of tension. We would aim to exactly compensate gravity with gas pressure. I totally understand how impossible it would be to build, my question is more about the stability of the thing once pressurized.

     

    On 1/27/2022 at 3:02 PM, swansont said:

    It can at least be approximated by looking at the gravitational potential energy. The pressure should vary as pgh, where p is the density, g is the gravitational acceleration (which varies with r)

    I think it would be more complicated because of heat from the star.. I don't think the density of matter around a free star obey the pgh formula, because the star is emitting energy. It's not like a planet atmosphere. Honestly I think the only way to answer is to use simulations.

    And since the pressure at 1 AU (for my example, I put the sphere at 1 AU but i have no ideas how big the sphere should be to optimize it).. is 6 Pa, that imply the volume of gas inside the sphere is enormous and so the mass of the whole system depends on the density of gas ; the mass of "atmosphere" of the star isn't negligible relative to the mass of the star itself. 
     

  18. 1 hour ago, swansont said:

    But it's not from the sun (in direction), if the pressure is building up. Then it's just a gas contained inside a sphere. Solar wind gives a radial force that depends on distance from the origin. A gas in a container, by itself, does not give a force that depends on distance. 

    A gradient of pressure should be inside the sphere for the reasons I gave. 

    1 hour ago, swansont said:

    Then you need to calculate how big this will be. It's the gradient that gives you a restoring force, not the pressure itself. There needs to be a different pressure on one side vs the other to give this force. 

    I know, but i don't know how.. the result should be a combination of gas diffusion, gravity and solar wind..
     

    1 hour ago, swansont said:

    I was responding to your first post. But why does the sphere need to be supported? That's a different effect than keeping it centered on the sun. 

     

    The mass of the sphere of course. Since I suppose the sphere is 1 ton / m² (the interior surface of the sphere),
    The pressure inside needs to prevent the sphere to simply break and fall to the sun (the sphere doesn't need to be a rigid object).

    I though about it, I suppose it's a more general question : what would happen if we could put a planet atmosphere (like Jupiter) into a giant balloon...Could the balloon be in a stable state ? Will the balloon fall ? For the balloon to fall, the atmosphere would need to change shape and not be spherical anymore, for the balloon to bend. I think it would be stable. 
    For instance, some planets have a layer of liquid water : what prevent the inner core to move inside the water then ? You could say that the upper layer floats.. but then, in my case since the pressure inside the balloon should equal gravity of the material, it should be "as if" the sphere floats on the gas. 

  19. Ok you both seems to not understand my question. Please read carefully. 
    This is not a ordinary Dyson Sphere : no, it's not a structure orbiting the star.  In that case, the sphere isn't even rotating (since rotation would break symmetry and create tension in the sphere). The star and the sphere would be perfectly symmetrical : nothing rotates. We don't use centrifugal force in any way here. 

    In that case, we want the pressure of the gas, coming from the star to build up, until it's enough to thwart the gravity of the sphere, keeping it from falling or breaking. The sphere needs to be closed (that's the reason I put the word "Closed" right in the title. If it's not closed, the pressure wont build up, and in that case, of course it wouldn't work.. I understand what Dyson spheres are thank you.. and please don't quote this writing "no you don't" .. that would be very idiotic. The fact that people come here not to really think but to spew cheap rhetoric is really annoying. ). 
    It means inside the sphere, there's a high pressure of hot gas. There is a gradient of pressure inside the sphere, for 2 reason : 

    - gravity (by itself, the gas wouldn't distribute equally since the star gravity is strong at the center). It would be some sort of dense hot gas atmosphere around the star.

    - The continuous emission of gas from the star : there would still be a radial movement of matter. The sphere would need to vent some of the gas outside, because we want just the right pressure, so we want the gas to build up until the right pressure and then maintain this pressure.
    And since it's still a radial movement of matter, the surface that each sphere of gas progressing from the center to the the outer is proportional to R², and the pressure proportional to 1/R² . So yes, definitively a gradient of pressure (just like there is for the solar wind, and everything that goes away from a sphere : gravity is 1 /D² .. every wave.. ).

    Since there is a gradient of pressure, yes there is stabilization : if you move the sphere (let's say a length of x) , the pressure at the closest side would be 1/(R-x)² and the other side 1/(R+x)².
    You can check that in every case (for d << R) :  
    1/(R-x)² > 1/(R+x)²
    So yes, if the star isn't at the center, there is a force appearing to correct that.  And yes I understand that gravity would work in the opposite way. So both forces would have to be precisely adjusted.

    Now I understand, given the size of the thing, the real problem is how the forces would propagate through the sphere, and yes the sphere would have to support very large tensions (not necessarily be solid, but only tangential tensions to hold together enough)

  20. 11 hours ago, swansont said:

    How do you arrive at this number?

    If the pressure is due to this, you lose the restorative force. There is no differential pressure from translation. It’s like balloon, which does not maintain a position from its internal pressure.

    For the number, I used the simple formula that I explained.. can you read all my messages ? (I compute gravity force (Newtonian) for 1m² of sphere where I assume 1 ton by m²), and then the pressure necessary for this force is trivial (since it's for 1m²)

    The sun is inside the sphere.. it's not like a balloon movement, since the force from the sun come from inside.. 
    Now I see that as always on this forum, you don't really think and don't bring me thoughtful answers. 
    Bye.

     

  21. 2 hours ago, swansont said:

    Solar wind is fairly weak in terrestrial terms (1 ATM being ~10^5 Pa)

    "The wind exerts a pressure at AU typically in the range of 1–6 nPa ((1–6)×10−9 N/m2)"

    https://en.wikipedia.org/wiki/Solar_wind

    The differential pressure for a slightly off-center sphere would be much smaller. Not much "correction" would be happening

    I totally understand that the solar wind is 1–6 nPa ((1–6)×10−9 N/m2) at 1 AU
    For a 1 UA sphere, the pressure necessary to support 1 ton / m² is 5.9641110164 Pa  
    (since the solar wind pressure is also proportional to 1/D², the factor is always the same)

    BUT : if we prevent the solar wind from escaping, the pressure should increase rapidly inside the sphere. 
    All we have to do is to put vents that only open when the pressure gets dangerously high (here that would be >6 Pa at 1 AU).. 

    It's a "closed" sphere : the wind can't escape : it's a balloon, a sort of pressure cooker.

    The sphere would be filled with gas from the star at least at the necessary pressure
    (it would be incredibly difficult to construct before the pressure gets high enough) 

    And the pressure gets greater when the surface get closer to the star : the correction is totally happening.  Also I suppose the scale would make it extremely hard to manage the constraints provoked by any variation of the pressure around the sphere, and solar storm would break everything.. it would need a very calm star, with highly symmetrical wind and pressure. 
     

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