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Thread: Zero Total Energy

  1. #1 Zero Total Energy 
    Forum Freshman Polednice's Avatar
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    I've recently been listening to some talks by Peter Atkins, who is a chemist and popular science writer, and I've heard him a couple of times talk about the beginning of the universe in terms of "nothing coming from nothing." This is because he says that current data in cosmology tentatively indicates that the universe might have a total energy of 0, and, therefore, the universe ought not be considered to be something coming from nothing, but nothing separating into its component, self-annihilating parts.

    Is there a name for this theory in physics? Does it have many proponents? Can anyone elaborate on it for me?


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    yes.

    The scientific name for it is 'mystical nonsense'.

    the universe may have begun from a single exotic particle but it could not have begun with nothing.

    something cannot come from nothing.


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    And I precisely said that the theory is not about something coming from nothing, and also asked for further clarification about a theory that nevertheless exists in the scientific community. I don't appreciate your useless response.
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    and how exactly does 'nothing separating into its components' differ from 'something coming from nothing'.

    the theory is mystical nonsense.
    that may not be what you want to hear but that does not make my response 'useless'
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    The fact that I'm obviously not a physicist and am asking for clarification means I can't answer that question. It is also abundantly clear that you're not a physicist either, and totally unqualified to answer the question. You've taken your stab at a contribution; I think I'll wait for someone more informed to come along.
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    in other words you are looking for a specific response to back up what you already believe.

    well good luck with your 'scientific' explorations.
    GuessWho likes this.
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    It is entirely possible that the universe has a zero net energy, and therefore might have originated as a quantum fluctuation. This was first proposed in the late 1960s by a physicist named Edward Tryon.
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    Ah, OK. I didn't realise that this was an off-shoot of the quantum fluctuation idea - so would this all play into Lawrence Krauss's recent book?
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    I realize this is a bit off topic, being more a philosophical observation, but you mention Lawrence Krauss and his new book. This is from an interview of Krauss:
    KRAUSS: Well, the title of the book, "A Universe from Nothing: Why There is Something Rather than Nothing" deals with this question. It's been around for as long as people have really started to ask questions about the universe and is really at the heart of a lot of the world's religions. Why is there something rather than nothing?
    If we live in a universe full of stuff, how did it get here? And many people think that very question implies the need for a creator. But what's truly been amazing, and what the book's about is the revolutionary developments in both cosmology and particle physics over the past 30 or 40 years that have not only changed completely the way we think about the universe but made it clear that there's a plausible case for understanding precisely how a universe full of stuff, like the universe we live in, could result literally from nothing by natural processes.
    It seems that a lot of atheists are latching onto the quantum fluctuation idea as an alternative to the religious explanation of creation. No alternative is needed because the religious explanation merely gives it a name,"God," without telling us anything about God, or where God came from. If calling it "quantum fluctuations" makes you feel better, then more power to you. But it doesn't really explain anything more than the religious explanation. The next logical question becomes, where did the quantum mechanical theory that explains quantum fluctuations come from, and why does it apply to the universe we live in?
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    Agreed. High priests of religion will tell you "God did it" . But it's a non-answer pretending to be an answer. So is "the universe was born of a quantum fluctuation".

    Thenet energy of the universe isn't zero by the way. That's a myth. Something like a star is a massive concentration of positive energy, and the gravitational field energy is positive too. That's why "the energy of a gravitational field shall act gravitatively in the same way as any other kind of energy". The same applies to a galaxy, and to an ensemble of galaxies.
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    Quote Originally Posted by Harold14370 View Post
    It seems that a lot of atheists are latching onto the quantum fluctuation idea as an alternative to the religious explanation of creation. No alternative is needed because the religious explanation merely gives it a name,"God," without telling us anything about God, or where God came from. If calling it "quantum fluctuations" makes you feel better, then more power to you. But it doesn't really explain anything more than the religious explanation. The next logical question becomes, where did the quantum mechanical theory that explains quantum fluctuations come from, and why does it apply to the universe we live in?
    Yes, it would be silly for atheists to use it as an alternative Ultimate Answer, though, let's be clear, there is no religious "explanation", only fantasy. And I'm not looking for answers, I'm looking to learn more about physics.
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    Quote Originally Posted by Farsight View Post
    [/I]Thenet energy of the universe isn't zero by the way. That's a myth.
    Not really.

    There is an overview here, with references to further information: Zero-energy universe - Wikipedia, the free encyclopedia
    ei incumbit probatio qui dicit, non qui negat
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    Quote Originally Posted by Polednice View Post
    I've recently been listening to some talks by Peter Atkins, who is a chemist and popular science writer, and I've heard him a couple of times talk about the beginning of the universe in terms of "nothing coming from nothing." This is because he says that current data in cosmology tentatively indicates that the universe might have a total energy of 0, and, therefore, the universe ought not be considered to be something coming from nothing, but nothing separating into its component, self-annihilating parts.

    Is there a name for this theory in physics? Does it have many proponents? Can anyone elaborate on it for me?
    This comes up oin Alan Guth's book The Inflationary Universe in what he calls a "free Lunch" and contrary to what people might say, yes. Something can come from nothing. That's one reason of how the gross national product increases, money is created out of nothing. I was suprised to learn that but it made sense.
    ]
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    Quote Originally Posted by Strange View Post
    Quote Originally Posted by Farsight View Post
    [/I]Thenet energy of the universe isn't zero by the way. That's a myth.
    Not really.

    There is an overview here, with references to further information: Zero-energy universe - Wikipedia, the free encyclopedia
    I can't find in this thread where Farsight made that assertion. I'd like him to provide proof of his claim but I can'tproperly ask him if I can't find his original post.
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    he said it in post #11



    Quote Originally Posted by Farsight View Post
    Agreed. High priests of religion will tell you "God did it" . But it's a non-answer pretending to be an answer. So is "the universe was born of a quantum fluctuation".

    The net energy of the universe isn't zero by the way. That's a myth . Something like a star is a massive concentration of positive energy, and the gravitational field energy is positive too. That's why "the energy of a gravitational field shall act gravitatively in the same way as any other kind of energy". The same applies to a galaxy, and to an ensemble of galaxies.
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    It's a myth guys, really. There's no such thing as negative energy. There are no negative energy particles or fields. Binding energy is said to be negative and is given a minus sign, but a system comprised of say an electron and proton consists of positive energy. There's just 13.6 eV less positive energy than when the electron and the proton aren't bound. It's similar for positronium, where one binding energy is -6.8eV. The lifetime of positronium is short, and when annihilation occurs you're left with (usually) two 511keV photons, not nothing. Conservation of energy applies.

    It's similar for the Earth and a cannonball. A system comprised of the Earth and stone-cold cannonball sitting on the ground comprises less energy than a system comprised of the Earth and a stone-cold cannonball way out in space. When that cannonball falls to earth it hits the ground at circa 11km/s. That's a considerable amount of kinetic energy, which in a gedanken scenario is neatly dissipated as radiation, leaving you with a system comprised of the Earth and stone-cold cannonball sitting on the ground. Conservation of energy applies.

    The energy in a region of space where an electromagnetic field can be detected is positive. The energy in a region of space where a gravitational field can be detected is positive. Hence "the energy of a gravitational field shall act gravitatively in the same way as any other kind of energy". That's in The Foundation of the General Theory of Relativity. If anybody knows of any robust experimental physics where conservation of energy doesn't apply, I'll be glad to hear it. Until then I recommend you treat "something from nothing" hypotheses as hypotheses rather than taking them for granted because they've been popularised by celebrity endorsement. That's the size of it I'm afraid. High priests of religion pretend to know the answer when they say God did it. High priests of physics pretend to know the answer when they say a quantum fluctuation did it.

    Strange: I read the wiki article. A gravitational field has positive energy, not negative energy. Spontaneous creation is the stuff of worms and mud. We employ virtual particles in QED, but we do not see electrons appearing and disappearing in the lab.

    pmb: energy isn't like money. Money is just a tokenised agreement of value. It doesn't really exist. Take away the people, and all that money is reduced to bits of paper and metal and magnetised domains on computer storage. Energy does exist. It's the one thing you can neither create nor destroy, and matter is made of it.
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  19. #18  
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    Quote Originally Posted by Farsight View Post
    It's a myth guys, really. There's no such thing as negative energy.
    Sure there is. Where did you get that from? It comes up quite often in physics in fact. Negative energy comes up often in mechanics in fact. The zero level of potential energy is whatever you want it to be. For example; the zero point level of the gravitational potential of a point particle moving in the Earth's gravitational field is set to zero at infinity. If U is the potential energy of a particle in a field then

    U = -GMm/r

    which gives a negative value for any value of r. We could have changed the zero level to any other place but the potential energy would still be zero somewhere. Add on the kinetic energy then we get E = K + U where E = total energy, K = kinetic energy and U = potential energy. Let the particle be at rest. Then the total energy of the particle is zero.

    Notice how U is defined. The potential energy is defined as

    F = -grad U

    where grad is the gradient operator. This defines U. Notice how I can set U' = U + C where C is any constant that you like. Then U = U' - C.

    grad U = grad (U' - C) = grad U' - grad C


    Since grad of a constant is 0 we get

    F = - grad U'

    So our new U' is also a valid potential energy for the system. C can be any negative value that you choose.


    Quote Originally Posted by Farsight View Post
    There are no negative energy particles or fields.
    I'd still like to know where you got this idea from.

    Quote Originally Posted by Farsight View Post
    Binding energy is said to be negative ...
    See? You know of an example already. Just because the energy of the larger system is positive it doesn't negate the fact that the inding energy is negative.


    Quote Originally Posted by Farsight View Post
    The energy in a region of space where an electromagnetic field can be detected is positive.
    Yep. But we can always add a constant to make it negative.


    Quote Originally Posted by Farsight View Post
    pmb: energy isn't like money.
    Ah. Come onFarsight! It's like every time I use an analogy people mistake it for an identity. You do understand that the anaology between money and energy doesn't mean that the person using the analogy is using it to claim that the two things are entical.

    In the sense I used the term here the dictionary defines analogy as
    Analogy - Definition and More from the Free Merriam-Webster Dictionary
    resemblance in some particulars between things otherwise unlike
    See? Notice the term "otherwise unlike". It means that the anaogy is only applie to one aspect of money, its conservation. In fact Einstein used money in his book "Ideas and Opinions" to relate the euivalence between mass and energy.
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  20. #19  
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    Quote Originally Posted by Farsight View Post
    Strange: I read the wiki article. A gravitational field has positive energy, not negative energy.
    Gravitational potential energy, u = -GMm/r
    Gravitational Potential Energy

    We employ virtual particles in QED, but we do not see electrons appearing and disappearing in the lab.
    Well, we don't see them (they are virtual, after all) but we do see the effects, e.g:
    Lamb shift - Wikipedia, the free encyclopedia
    Casimir effect - Wikipedia, the free encyclopedia
    ei incumbit probatio qui dicit, non qui negat
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    Quote Originally Posted by pmb View Post
    Sure there is. Where did you get that from?
    E=mc. There isn't anything with a negative mass.

    Quote Originally Posted by pmb View Post
    It comes up quite often in physics in fact. Negative energy comes up often in mechanics in fact. The zero level of potential energy is whatever you want it to be. For example; the zero point level of the gravitational potential of a point particle moving in the Earth's gravitational field is set to zero at infinity...
    That's just a Newtonian convention. The particle doesn't consist of negative energy, nor does the Earth, and nor does its gravitational field.

    Quote Originally Posted by pmb View Post
    Quote Originally Posted by Farsight View Post
    There are no negative energy particles or fields.
    I'd still like to know where you got this idea from.
    Relativity. Do you know of anything that has a mass less than zero?

    Quote Originally Posted by pmb View Post
    See? You know of an example already. Just because the energy of the larger system is positive it doesn't negate the fact that the binding energy is negative.
    The energy of the system is positive, change the system and the energy is reduced by that binding energy, but the energy of the system is still positive.

    Quote Originally Posted by pmb View Post
    Yep. But we can always add a constant to make it negative.
    It doesn't work. The energy has a mass-equivalence and causes gravity. Adding a constant doesn't alter what that gravity does.

    Quote Originally Posted by pmb View Post
    Ah. Come on Farsight! It's like every time I use an analogy people mistake it for an identity...
    I use analogies a lot Pete, but this is one I don't like.
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    Quote Originally Posted by Strange View Post
    Gravitational potential energy, u = -GMm/r Gravitational Potential Energy
    It's just a Newtonian convention. A cold brick on the ground has less energy than the same brick up in space, but that energy is still positive.

    Quote Originally Posted by Strange View Post
    Well, we don't see them (they are virtual, after all) but we do see the effects, e.g:
    Lamb shift - Wikipedia, the free encyclopedia
    Casimir effect - Wikipedia, the free encyclopedia
    They're both virtual-photon effects related to the evanescent wave or near-field fluctuations. Think of them as something like the little random wavelets on the surface of the ocean. You don't think of them as being spontaneously created - you don't see a flat calm pool suddenly erupt into wavelets for nothing. In similar vein you shouldn't use them to justify a whole universe that's been spontaneously created. Ask the obvious question: if the universe was born of a quantum fluctuation, what fluctuated? You soon realise it's just another turtles all the way down non-answer.
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    Quote Originally Posted by Farsight View Post
    Quote Originally Posted by Strange View Post
    Gravitational potential energy, u = -GMm/r Gravitational Potential Energy
    It's just a Newtonian convention. A cold brick on the ground has less energy than the same brick up in space, but that energy is still positive.
    Nope. That's not it at all. In this comment you're confusing the thermal energy of a brick with it's gravitational potential energy. Temperature has nothing to do with this. We cold make that brick have any value we please. The gravitational energy using this convention is still negative.

    You still haven't tole me where you got this idea of energy not being negative.

    You have a different idea of energy than physicists do. If not then please prove your claim.
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    Quote Originally Posted by Farsight View Post
    Quote Originally Posted by pmb View Post
    Sure there is. Where did you get that from?
    E=mc. There isn't anything with a negative mass.
    You didn't answer my question Farsight. Where did you get that from?

    Before I get into all of this I'm goiing to stop here and get an answer to my question. Please prove that there is no such thing as negative energy. Before this let me show you what energy is.
    What is Energy?

    I'll tell you this. This is not someon's ignorant jabbering about energy. This is precisely how the term energy is defined in the wonderful world of physics. If you disagree definition then there is no reason to dicuss anything about energy. You can find a very similar definition in the Feynman lectures. Nothing personal my friend.
    Last edited by pmb; June 3rd, 2012 at 08:08 PM. Reason: I wanted to sound more polite that I did in the previous version
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    Quote Originally Posted by Farsight View Post
    Strange: I read the wiki article. A gravitational field has positive energy, not negative energy.
    You're confusing the energy density of the field with the energy of a particle in a gravitational field. This is basic physics 101 Farsight. Do you have a basic college level physics text or a text on classical mechanics?
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    positive energy works fine for electric fields.
    when a proton and antiproton attract each other together
    energy is released and the 2 particles annihilate each other

    all the energy in the field is converted to light and there is no field leftover.

    with gravity it doesnt work that way.
    when 2 masses attract each other energy is released
    but the net field of the 2 particles together is twice what it was for each particle separately
    this means the net field has 4 times the potential energy
    In order for energy to be conserved the gravitational potential energy must be negative.
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    Zero-energy_universe doesnt add up

    I would quote the post but I cant
    maybe someone else could do it
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    Farsight, there is really no problem with the notion of "negative energy". In the example discussed, i.e. the gravitational field, it simply means that the field is attractive rather than repulsive - pmb has explained it well in post 18, in that the gradient and thus the potential energy of such a vector field must always be negative, otherwise masses would move away from each other, which is obviously not the case.
    You are right in saying that the energy equivalent of a given mass will always be positive, assuming that there is no such thing as "negative mass"; this however is not the same as the potential energy within a gravitational field.
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    I think people are talking past each other. Negative energy (in terms of a zero-energy universe) is meant as that which is associated with the hypothetical concept of Negative Mass, which is not the same as the mathematical treatment of the behaviour of normal matter (or anti-matter as we think of it currently) as pmb has discussed. It does not satisfy the positive energy condition of General Relativity, but is still mathematically consistent within it.
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

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    not it isnt

    Zero-energy universe - Wikipedia, the free encyclopedia

    The zero-energy universe hypothesis states that the total amount of energy in the universe is exactly zero. When the energy of the universe is considered from a pseudo-tensor point of view, zero values are obtained in the resulting calculations.[1] The amount of positive energy in the form of matter is exactly canceled out by the negative energy in the form of gravity
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    Quote Originally Posted by KALSTER View Post
    I think people are talking past each other. Negative energy (in terms of a zero-energy universe) is meant as that which is associated with the hypothetical concept of Negative Mass, which is not the same as the mathematical treatment of the behaviour of normal matter (or anti-matter as we think of it currently) as pmb has discussed. It does not satisfy the positive energy condition of General Relativity, but is still mathematically consistent within it.
    I my opinion there can be positive energy but negative mass. The vacuum domain wall comes to mind. The active gravitational mass, which is mass that is the source of gravity, is negative in that it repels matter. In this case it is due to the contribution of negative pressure in the stress-energy-momentum tensor. This is the same idea of the cause of the acclerating rate of the universes expansion.
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    @ Granpa: Ah, I see. Then we will have to look at your contentions in post #25.

    Quote Originally Posted by pmb
    I my opinion there can be positive energy but negative mass.
    That does make sense.
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

    "Gullibility kills" - Carl Sagan
    "All people know the same truth. Our lives consist of how we chose to distort it." - Harry Block
    "It is the mark of an educated mind to be able to entertain a thought without accepting it." - Aristotle
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    Quote Originally Posted by Markus Hanke View Post
    Farsight, there is really no problem with the notion of "negative energy". In the example discussed, i.e. the gravitational field, it simply means that the field is attractive rather than repulsive - pmb has explained it well in post 18, in that the gradient and thus the potential energy of such a vector field must always be negative, otherwise masses would move away from each other, which is obviously not the case.
    The value of the magnitude of a potential does not imply that the field is attractive.

    Suppose we have a potential function which has a minium if -|b| and is concave up from -a to +a and concave down from -inf to -a and from +a to +inf and Phi(x) < 0 for all x. Here the potential energy is negative from -inf to a and from + a to inf. If a particle is placed at x > 0 the force on the particle will be is attractive towards the origin everywhere off the origin. Note that for x > +a and x < -a the potential P(x) > 0 and the force on a particle in those regions is also pointed towards the origin. The sign of total energy will be positive if the kinetic energy is always greater than the potential energy. The partcle can be trapped between -a and +a if the total energy is zero. If the kinetic energy is less than a certain value the particle will be bound in an even smaller domain and even then the total energy will be zero.

    Can you picture such a potential function in your mind or should I draw one out and post it?

    Farsight - You have chosen particular cases where the zero potential is adjusted such that the total energy is zero, e.g. binding energy.

    Let me make this simpler. You've chosen examples where the total energy is positive. That in no way implies that you have proved your case. Just because the examples you know of have a positive energy it doesn't prve your case. All a person has to do to prove you wrong is is to find one example where the total energy is negative and they've then proved you wrong. And that's what we've done here. We've given you well-known examples from classical mechanics where the total energy is negative. Physicists are trained to just look at a potential diagram and extract information from it such as whether the total energy is positive or negative. This can oten be changed by adding or subtrating a constant from the potential function.

    I should have created a web page to describe this. This will therefore be my goal for today. Yay! I get to draw pretty pictures! I so love creating diagrams in case you haven't figured that out by now.
    Last edited by pmb; June 4th, 2012 at 06:08 AM.
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    well in electrostatics it doest make sense to choose a potential that is non-zero when the fields are nonexistant.

    that limits your choices considerably
    Last edited by granpa; June 4th, 2012 at 07:50 AM.
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    Quote Originally Posted by granpa View Post
    well in electrostatics it doest make sense to choose a potential that is non-zero when the fields are nonexistant.

    that limits your choices considerably
    I don't understand the purpose of this post. Who was choosing a non-zero potential for a non-existant field? One can do it if they please. The absolute value of the magnitude of potential energy isn't meaningful. Only the difference in potential (e.g. gradient) is physically meaningful quantity. But there's no reason why one can't choose a non-zero value if they so please. It's important that people who want to understand the physics know this so they don't think that someone made an error when they see someone do it.

    Giving it anymore thought at this point would simply be a waste of our time.
    Last edited by pmb; June 4th, 2012 at 09:11 AM.
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    Quote Originally Posted by pmb View Post
    The value of the magnitude of a potential does not imply that the field is attractive.
    Not the magnitude, but the direction of its gradient. Why the minus sign in F = -grad U ? That's because the gradient is oriented towards the field's point of origin, thus all force vectors will point towards the point of origin. That makes the field attractive.
    ( I assume above that the field is conservative, i.e. curl F = 0 everywhere, otherwise it wouldn't be a good model for gravity )
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    Quote Originally Posted by pmb View Post
    Nope. That's not it at all. In this comment you're confusing the thermal energy of a brick with it's gravitational potential energy. Temperature has nothing to do with this. We cold make that brick have any value we please. The gravitational energy using this convention is still negative. You still haven't told me where you got this idea of energy not being negative. You have a different idea of energy than physicists do. If not then please prove your claim.
    I'm not confusing the thermal energy of the brick with its gravitational potential energy. I'm referring to the E=mc energy content of the brick that would be released if say you subjected it to matter-antimatter annihilation.

    Quote Originally Posted by pmb View Post
    Before I get into all of this I'm goiing to stop here and get an answer to my question. Please prove that there is no such thing as negative energy.
    I can't prove that there's no such thing as negative energy. I can't prove there's no such thing as fairies either. But can you point to anything that is comprised of negative energy? A gravitational field isn't.

    Quote Originally Posted by pmb View Post
    Before this let me show you what energy is. What is Energy? I'll tell you this. This is not someon's ignorant jabbering about energy. This is precisely how the term energy is defined in the wonderful world of physics. If you disagree definition then there is no reason to dicuss anything about energy. You can find a very similar definition in the Feynman lectures. Nothing personal my friend.
    That article emphasises conservation of energy and so supports my case. It also says "The most precise answer to the question What is energy? is Nobody knows!" It doesn't show us what energy is.

    Quote Originally Posted by pmb View Post
    You're confusing the energy density of the field with the energy of a particle in a gravitational field. This is basic physics 101 Farsight. Do you have a basic college level physics text or a text on classical mechanics?
    Yes, and I understand this stuff really well.
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    Quote Originally Posted by granpa View Post
    positive energy works fine for electric fields. when a proton and antiproton attract each other together energy is released and the 2 particles annihilate each other all the energy in the field is converted to light and there is no field leftover.
    No problem with that.

    Quote Originally Posted by granpa View Post
    with gravity it doesnt work that way. when 2 masses attract each other energy is released but the net field of the 2 particles together is twice what it was for each particle separately this means the net field has 4 times the potential energy. In order for energy to be conserved the gravitational potential energy must be negative.
    That's wrong I'm afraid. Conservation of energy applies. If we say the kinetic energy is dissipated as electromagnetic radiation we then have a "mass defect". The mass of the two bodies together is reduced, along with the net gravitational field.
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    Quote Originally Posted by Markus Hanke View Post
    Farsight, there is really no problem with the notion of "negative energy". In the example discussed, i.e. the gravitational field, it simply means that the field is attractive rather than repulsive - pmb has explained it well in post 18, in that the gradient and thus the potential energy of such a vector field must always be negative, otherwise masses would move away from each other, which is obviously not the case. You are right in saying that the energy equivalent of a given mass will always be positive, assuming that there is no such thing as "negative mass"; this however is not the same as the potential energy within a gravitational field.
    I'm sorry Markus, but this is wrong. Pmb talked about the Newtonian convention for gravitational potential energy which sets the zero level at an infinite distance from say the surface of the earth. The negative value at the surface of the earth is only relative to that. The brick I talked about is still comprised of positive energy. You have to add more positive energy to lift it, giving it gravitational potential energy. If you drop the brick this is converted into kinetic energy which is radiated away, and at all time conservation of energy applies. Take a look at The Foundation of the General Theory of Relativity and see page 185 which says "the energy of the gravitational field shall act gravitatively in the same way as any other kind of energy". That's positive energy too.
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    Quote Originally Posted by KALSTER View Post
    I think people are talking past each other.
    There's certainly an element of that, wherein I'm talking general relativity and conservation of energy whilst "a gravitational field is negative energy" is an assertion that emerges from setting the Newtonian zero level at infinity. The latter is merely a historical convention.

    Quote Originally Posted by KALSTER View Post
    Negative energy (in terms of a zero-energy universe) is meant as that which is associated with the hypothetical concept of Negative Mass, which is not the same as the mathematical treatment of the behaviour of normal matter (or anti-matter as we think of it currently) as pmb has discussed. It does not satisfy the positive energy condition of General Relativity, but is still mathematically consistent within it.
    Negative mass is speculative, it isn't something that is borne out by experimental physics. We shouldn't use that to support the "free lunch universe" speculation. See this bit from the wikipedia article: "Thus it can be seen that an object with negative inertial mass would be expected to accelerate in the opposite direction to that in which it was pushed". That's science fiction, not physics. Mass is a scalar, a negative mass makes as much sense as a negative distance. A negative displacement is OK because displacement is a vector quantity, but negative distance and negative mass aren't OK.
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    Quote Originally Posted by pmb View Post
    Farsight - You have chosen particular cases where the zero potential is adjusted such that the total energy is zero, e.g. binding energy.
    I'm talking about real-world situations. Binding energy is negative only because the positive energy of the bound system is less than the positive energy of the unbound system.

    Quote Originally Posted by pmb View Post
    Let me make this simpler. You've chosen examples where the total energy is positive. That in no way implies that you have proved your case. Just because the examples you know of have a positive energy it doesn't prove your case. All a person has to do to prove you wrong is is to find one example where the total energy is negative and they've then proved you wrong. And that's what we've done here. We've given you well-known examples from classical mechanics where the total energy is negative. Physicists are trained to just look at a potential diagram and extract information from it such as whether the total energy is positive or negative. This can oten be changed by adding or subtrating a constant from the potential function.
    I'm sorry Pete, but with respect, you haven't proven anything. The Earth and its gravitational field and the particle are all comprosed of positive energy. Setting the zero to wherever you want it to be doesn't change that at all.

    All: this is what internet discussions ought to be like. And let's face it, if we all agreed about everything there wouldn't be much to discuss.
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    Quote Originally Posted by Markus Hanke View Post
    Not the magnitude, but the direction of its gradient.
    Please recall what I was commenting on

    pmb has explained it well in post 18, in that the gradient [u]and thus the potential energy[/i] of such a vector field must always be negative, otherwise masses would move away from each other, which is obviously not the case.
    (Underline mine). This is what I was saying was wrong. Being negative does not tell us nothing about the direction of the force.

    Quote Originally Posted by Markus Hanke View Post
    Why the minus sign in F = -grad U ? That's because the gradient is oriented towards the field's point of origin, thus all force vectors will point towards the point of origin. That makes the field attractive.
    In the example I gave, yes, that's true. But that's just because I used a central force problem as an example. That doesn't hold in general. The potential function can be many things. The entire function could be negative and yet the force vector might point in any direction.

    Note: I'm stopping my contribution about force vectors nd its relationship with the potential right here. It could easily cause confusion. It's not the subject of this thread.

    ( I assume above that the field is conservative, i.e. curl F = 0 everywhere, otherwise it wouldn't be a good model for gravity )
    As I recall, the term "conservative" can mean two things. (1) work is not path independant or (2) the field is time dependant.
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    Farsight: Please don't take any of the following personally. None of it as intended as an insult. In my defense, I tried to avoid this by talking to you about this in PM. It seems that you don't want to talk about it there, you didn't read it or you read it but didn't have time to respond. However since it's about the subject matter at hand Ill have to make certain assumptions in what follows.

    I believe you already read my web page which explains everything about energy right? It's located at - http://home.comcast.net/~peter.m.brown/mech/what_is_energy.htm - You seemed to have interpreted that explanation to mean that you can give energy any meaning you wish since its not a defined quantity. That is far from the truth. We can't define energy. That in now way imlies that we don't know everything there is to know about energy. I should note that we can't define energy but we can precisely define total mechanical energy, potential energy, kinetic energy, proper mass energy and EM energy.

    Ive been trying to understand what you believe energy is. You dont seem to have a precise understand about its definition and use in classical mechanics. And regarding particle physics and nuclear physics, you seemt to take what you want and leave the rest. You acknowledge that E = mc2 is a positive quantity but you never even brought up the energy states of a hydrogen atom, which are negative. The energy levels of a hydrogen atom are

    En = - {Mee4/(2*hbar2) }/n2

    This too is a well known fact, i.e. that the energy levels of the hydrogen atom are negative (as are all atoms). This is basic quantum mechanics. If you studied QM you would have learned this.


    [QUOTE=Farsight;328345]
    Quote Originally Posted by pmb View Post
    I'm talking about real-world situations.
    Where in God's name did you get notion that I'm wasn't?? Never in my life have I ever not talked about real world situations when I was discussing physics. In fact that's all I think about.

    Quote Originally Posted by Farsight View Post
    Binding energy is negative only because the positive energy of the bound system is less than the positive energy of the unbound system.
    It's still negative energy Farsight. In any case you should know that providing examples of positive enegy in no way supports your unfounded belief that there is no such thing as negative energy. I think we're all waiting for you to provide a reason why what you say should be true.

    Quote Originally Posted by Farsight View Post
    I'm sorry Pete, but with respect, you haven't proven anything.

    And with all respect Farsight, I did. You just didnt understand it. Please uynderstand my position. This is my area of expertise. I've been studying it at the highest level for over a quarter of a century now. Had I not understand something so basic as this I would have noticed it a very long time ago. I recall a situation where a friend asked me about potential energy. I said that the potential energy of a ball on the ground was zero. He then asked me what would happen if he dut a hole and shoved the ball own the hole. What would be the energy then? This is when my understanding of potential energy increased by a quantum leap!

    I'm sorry Farsight, but will all due respect, I have proven everything I set out to prove. I beleive that you have some serious holes in your understanding of physics. Ive showed you a lot about what need to know about energy. Here is some more. Please follow the derivations. This is something you would have learned in a PHY 101 course (Introduction to Physics - Part I) --- http://home.comcast.net/~peter.m.brown/mech/basic_mechanics.htm

    The definition of the mechanical energy of a single particle moving in a force field is defined as Total Mechanical Energy (E) = Kinetic Energy (K) + Potential Energy (U) ==
    E = K + U

    The Kinetic energy of a particle is defined as K = (1/2) mv[sup]2[/sup. The potential energy of a particle moving in a field of force is defined implicitly as the U(r) in F = - grad U(r).

    This is where youre having problems. There are an infinite number of functions U which will satisfy this equation. They all differ only by a constant C. The value C is called a constant of integration. There is now way around it. It is impossible to define the mechanical energy of a particle without first choosing a value for C. Any value is just as good as any other value. You dont seem to know this part of mechanics. Every time we mention that constant you go start to make mistakes.

    Quote Originally Posted by Farsight View Post
    The Earth and its gravitational field and the particle are all comprosed of positive energy. Setting the zero to wherever you want it to be doesn't change that at all. The
    Here is a perfect example of your misderstanding. The value of the mechanical energy we are discussing is about a particle in a field. When we talk abut its energy we are not talking about the fields energy. Thats a separate problem. You seem to think that the value of the mechanical energy we are discussing in the field cannot have a negative value. In the case of the potential U = -GMm/r it is clearly a negative value. Here we are simply examining the case of a particle at rest (v = 0 so that K = 0). Physicists define the potential such that limit r
    inf U(r) = 0. In this case the constant of integration is zero!!!

    Again, please dont be insulted by anything I wrote. Im assaulting your knowledge of basic mechanics, not you.
    Last edited by pmb; June 4th, 2012 at 03:07 PM.
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    Quote Originally Posted by pmb View Post
    Farsight: Please don't take any of the following personally. None of it as intended as an insult. In my defense, I tried to avoid this by talking to you about this in PM. It seems that you don't want to talk about it. But since its about the subject matter at hand I’ll have to make certain assumptions.
    I do want to talk about it Pete. It's good to talk. Like I said we won't always agree on everything, and if we did there wouldn't be much point in discussion forums. When we discuss things and find we still can't agree, then we agree to differ in a civil fashion with mutual respect.

    Tsk, having said all that, the wife is hassling me. It's good to talk, but right now I've got to talk to her. I'll be back.
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    Quote Originally Posted by Farsight View Post

    Tsk, having said all that, the wife is hassling me. It's good to talk, but right now I've got to talk to her. I'll be back.
    I see that you responded to my PM. Thanks. I'm working on a visual aid right now. I'm also exhausted today. Gotta take a nap soon.
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    Quote Originally Posted by pmb View Post
    I believe you already read my web page which explains everything about energy right?
    Yes.

    Quote Originally Posted by pmb View Post
    It's located at - http://home.comcast.net/~peter.m.brown/mech/what_is_energy.htm - You seemed to have interpreted that explanation to mean that you can give energy any meaning you wish since it’s not a defined quantity. That is far from the truth. We can't define energy. That in now way implies that we don't know everything there is to know about energy. I should note that we can't define energy but we can precisely define total mechanical energy, potential energy, kinetic energy, proper mass energy and EM energy.
    No problem with mechanical energy, potential energy etc, but you can go further in defining energy whilst sticking to hard scientific fact and referring to Does the Inertia of a Body Depend Upon Its Energy Content? Maybe we should talk about that separately.


    Quote Originally Posted by pmb View Post
    I’ve been trying to understand what you believe energy is. You don’t seem to have a precise understand about its definition and use in classical mechanics. And regarding particle physics and nuclear physics, you seemt to take what you want and leave the rest. You acknowledge that E = mc is a positive quantity but you never even brought up the energy states of a hydrogen atom, which are negative. The energy levels of a hydrogen atom are

    En = - {Mee4/(2*hbar2) }/n2

    This too is a well known fact, i.e. that the energy levels of the hydrogen atom are negative (as are all atoms). This is basic quantum mechanics. If you studied QM you would have learned this.
    I know this Pete. The hydrogen atom is comprised of a proton and an electron, both of which consist of positive energy. Their bound state features a mass deficit such that the total positive energy is less, and the binding energy is said to be negative. But it isn't negative energy, it's just less positive energy. How can I explain it in simple terms? See the wiki article on atomic orbitals? In the introduction you can read "The electrons do not orbit the nucleus in the sense of a planet orbiting the sun, but instead exist as standing waves". Think of a standing wave in a box. If you reduce the size of the box the standing-wave wavelength has to be shorter and the frequency and energy have to be higher. But if you move the box around and around rapidly you can emulate a larger box and put a lower-frequency standing wave in it. This standing wave energy is less than for the motionless box, but it's still positive.

    Quote Originally Posted by pmb View Post
    I ever not talked about real world situations when I was discussing physics. In fact that's all I think about.
    Me too.

    Quote Originally Posted by pmb View Post
    Quote Originally Posted by Farsight View Post
    Binding energy is negative only because the positive energy of the bound system is less than the positive energy of the unbound system.
    It's still negative energy Farsight. In any case you should know that providing examples of positive energy in no way supports your unfounded belief that there is no such thing as negative energy. I think we're all waiting for you to provide a reason why what you say should be true.
    It's true because for any case you present I can show that what you think of as negative energy is merely less positive energy.

    Quote Originally Posted by pmb View Post
    And with all respect Farsight, I did. You just didn’t understand it. Please understand my position. This is my area of expertise. I've been studying it at the highest level for over a quarter of a century now. Had I not understand something so basic as this I would have noticed it a very long time ago. I recall a situation where a friend asked me about potential energy. I said that the potential energy of a ball on the ground was zero. He then asked me what would happen if he dut a hole and shoved the ball own the hole. What would be the energy then? This is when my understanding of potential energy increased by a quantum leap!
    I understand this, I really do, and I'm not making things up.

    Quote Originally Posted by pmb View Post
    I'm sorry Farsight, but will all due respect, I have proven everything I set out to prove. I believe that you have some serious holes in your understanding of physics.
    Not about this. And I'm sorry, but you haven't proved anything at all. All you've really done is say "that's how it's defined".

    Quote Originally Posted by pmb View Post
    I’ve showed you a lot about what need to know about energy. Here is some more. Please follow the derivations. This is something you would have learned in a PHY 101 course (Introduction to Physics - Part I) --- Basic Theorems for Mechanics
    With respect I'm past that level.

    Quote Originally Posted by pmb View Post
    The definition of the mechanical energy of a single particle moving in a force field is defined as Total Mechanical Energy (E) = Kinetic Energy (K) + Potential Energy (U)
    Let's start with a gedanken cannonball way up in space a long way from the Earth. Initially it isn't moving and we say E=mc. After a while we notice that it's starting to move towards the Earth. It's falling, and we can talk of E = K + U wherein U is being converted to K. It hits the ground and K is dissipated as radiation. Now we say E=mc again, and note that a radiating body loses mass. The cannonball is said to have negative potential energy on the ground, but it doesn't have any actual negative energy, it merely has less positive energy. At all times conservation of energy applies. When you lift the cannonball you do work on it and it gains potential energy. If you fire it upwards at 11km/s giving it enough kinetic energy to effectively escape the Earth's gravitational field, it ends up motionless in space. K has been converted to U, and this is in the cannonball.

    Quote Originally Posted by pmb View Post
    The Kinetic energy of a particle is defined as K = (1/2) mv2. The potential energy of a particle moving in a field of force is defined implicitly as the U(r) in F = - grad U(r).
    No problem. See gravitational potential on wiki and look at the plot on the right. The "force" of gravity on our cannonball is proportional to the slope. The potential energy is proportional to the height, only the convention is to say that potential energy is zero where the plot flattens out at the top.

    Quote Originally Posted by pmb View Post
    This is where you’re having problems. There are an infinite number of functions U which will satisfy this equation. They all differ only by a constant C. The value “C” is called a constant of integration. There is now way around it. It is impossible to define the mechanical energy of a particle without first choosing a value for C. Any value is just as good as any other value. You don’t seem to know this part of mechanics. Every time we mention that constant you go start to make mistakes.
    I'm sorry, but regardless of C and regardless of where the cannonball is located you can take it apart and annihilate its electrons and protons with antiparticles to yield energy. The yield varies, but it's always positive.

    Quote Originally Posted by pmb View Post
    Here is a perfect example of your misunderstanding. The value of the mechanical energy we are discussing is about a particle in a field. When we talk abut its energy we are not talking about the fields energy. That’s a separate problem. You seem to think that the value of the mechanical energy we are discussing in the field cannot have a negative value. In the case of the potential U = -GMm/r it is clearly a negative value. Here we are simply examining the case of a particle at rest (v = 0 so that K = 0). Physicists define the potential such that limit r -> inf U(r) = 0. In
    Quote Originally Posted by pmb View Post
    this case the constant of integration is zero!!!
    The definition is misleading. The cannonball sitting motionless on the surface of the Earth doesn't have any negative energy. It's just comprised of less positive E = mc energy than the same cannonball sitting motionless way up in space.

    Quote Originally Posted by pmb View Post
    Again, please don’t be insulted by anything I wrote. I’m assaulting your knowledge of basic mechanics, not you.
    I'm not insulted at all. Instead I'm a little concerned that you'll take umbrage at being challenged. Work it all through, put your relativity hat on, and balance that energy book.
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    Quote Originally Posted by Farsight View Post
    Quote Originally Posted by granpa View Post
    with gravity it doesnt work that way. when 2 masses attract each other energy is released but the net field of the 2 particles together is twice what it was for each particle separately this means the net field has 4 times the potential energy. In order for energy to be conserved the gravitational potential energy must be negative.
    That's wrong I'm afraid. Conservation of energy applies. If we say the kinetic energy is dissipated as electromagnetic radiation we then have a "mass defect". The mass of the two bodies together is reduced, along with the net gravitational field.
    LOL
    well sure there will be a tiny amount of mass radiated as light but that doesnt change the fact that the field will be bigger rather than smaller

    the full quote should have been

    Quote Originally Posted by granpa View Post
    positive energy works fine for electric fields.
    when a proton and antiproton attract each other together
    energy is released and the 2 particles annihilate each other

    all the energy in the field is converted to light and there is no field leftover.

    with gravity it doesnt work that way.
    when 2 masses attract each other energy is released
    but the net field of the 2 particles together is twice what it was for each particle separately
    this means the net field has 4 times the potential energy
    In order for energy to be conserved the gravitational potential energy must be negative.
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    Granpa: yes, gravity is different to electromagnetism. But as for 4 times the potential energy, consider the case where you have two planets close together going round one another. When you're a long way off in some orbit around them both, you can't easily distinguish the net gravitational field from that of a single planet twice as big. If their orbits around one another decay and they coalesce, the gravitational field you feel doesn't suddenly double. Instead if we say their kinetic energy is radiated away and remember that a radiating body loses mass, we'd reason that the gravitational field would reduce a little. You can't easily distinguish this difference, but if your instruments were really precise you'd find that you'd moved to a slightly higher orbit. This is just a little step towards the scenario where one planet is made of matter and the other is made of antimatter. When they coalesce they annihilate, and all their energy is radiated away. Then you're no longer in an orbit, you're moving in a straight line, because the gravitational field has reduced so totally that it's not there any more.
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    I wasnt talking about 2 planets orbiting one another.

    the case I was describing is 2 planets infinitely far away from each other being brought together

    the combined field is twice as great as for each planet alone and has 4 times the energy

    it is easy to see that in spite of the fact that energy was released the energy in the field has increased in magnitude
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    My two euro-cents on this,

    Altitude, to me, is a levelled coordinate plane. It doesn,t have a negative for altitude as height has a negative in depth.
    A positive depth is a negative height.

    Altitude is a coordinate and coordinates can be positive or negative. If altitudes where always positives this would assume an absolute zero for altitude. That makes depth impossible then ; every other altitude it,s higher. The whole universe and anything on and in it would be at a positive height to this zero coordinate then.
    That,s just too weird.
    In practice for zero coordinate a horizontal (thus curved) plane is chosen. Anything lower has a negative height to this altitude. The choice can be random or practically conveniant.
    -10 for altitude represents a depth or negative height but not a negative altitude. Only the number is negative not the altitude.

    Mathematical this is as - - = plus (neg depth => height) depth is negative (to height in words allready. Hence in a chosen system with an A=0 reference -10 D would be same as 10 h.

    But altitude this is impossible because for the word itself (or A) there is not a neg word to make such a wordpair. -10 negA would be pos A=10. All altitudes would be positive then.

    Zero altitude often used here in Holland is Dutch NAP. This funktions as referential altitude (A=0) for waterlevels everywhere.
    On Dutch wikipedia it wrongly says referential height.
    Referential altitude is what it is because a height zero would also be a depth zero. Height zero means no height so it,s impossible to refer to it as referential height then and using the word height is mistaken use of the word.
    The wordpair height-depth would have no meaning then.

    From or to this referential altitude (once this is taken as reference) water level can be higher or lower.

    When between two lakes the waterlevel is at Nap for both a windmill could make a difference of one meter. That,s half a meter difference to Nap for both lakes. delta A = 0,5 - (-0,5) = 1.

    When an architect builds a house with groundfloor at -3 meter (this is often the case) the architect will use groundfloor as zero altitude to build the house because this is more convenient. But when the house needs a drain to one of these lakes it,s better if the plummer uses Nap instead.
    Last edited by Ghrasp; June 5th, 2012 at 10:33 AM.
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    Quote Originally Posted by Ghrasp View Post
    My two euro-cents on this,
    Can I get a refund? Your post has nothing to do with the original topic.
    Strange likes this.
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    You want a refund on what was given and annihillate my two gifted cents ? I can pn my bankaccount for that.
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    Quote Originally Posted by granpa View Post
    I wasnt talking about 2 planets orbiting one another. The case I was describing is 2 planets infinitely far away from each other being brought together. The combined field is twice as great as for each planet alone and has 4 times the energy. It is easy to see that in spite of the fact that energy was released the energy in the field has increased in magnitude
    It hasn't increased fourfold. It's only doubled. Check out escape velocity wherein . If you fell towards a planet your impact speed v would be the same as escape velocity, which is proportional to the square root of the mass, not the mass. If the planet was twice the mass, your impact speed doesn't double, but kinetic energy does because KE=mv.
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    Quote Originally Posted by Farsight View Post
    ]I'm not insulted at all. Instead I'm a little concerned that you'll take umbrage at being challenged.
    Nope. I have no problem with being challenged. If that's what you've gleened from my posts then you did so incorrectly. What I'm concerned about is your not telling us what you think energy is anf what is tellingf you tjat it can' be negatie. Until then I can't contribute any more.
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    Since you insist: in deep fundamental terms energy is stressed space. Space has an innate stress-energy, a pressure rather than tension, and it doesn't have a negative volume. And there are no "hole in space" particles or fields that can swallow up the energy of a photon or electron or planet and make it disappear. A gravitational field doesn’t do anything like that. It merely converts potential energy into kinetic energy. Energy is conserved.
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    Quote Originally Posted by Farsight View Post
    Since you insist: ..
    [/i] Insist? Of course I insist. That's the topic of conversation and you have now demonstrated that you're right and everybody else is wrong. I now see the problem. You don't know what energy is. I.e. you are using the term energy differently than anybody else in the entire physcs community. So yes I inist. Of course I insist and I'd wager that everone else does too. Energy can't be negative when you use that term differently than anybody else in the world so when you choose tp change the meaning of it then you can make any claims that you're right. But you're not right according to physics.

    There is something you should know. Just because the term can't logically be defined in all generality, it doesn't mean that we don't know what it is. Example; the term set cannot be defined either. However if you were give me something that you think is a set then I can tell ou if your're right or wrong. The same thing in geometry. Even though the term straight line is undefined in Euclidea geometry it doesn't mean that you can claim that a cirlce is a straight line.


    The same holds true with energy. We don't know how to define it energy but we know what energy isn't

    And what you think it is, is wrong. Any physics text will explain that Farsight. Pleasse take me word for it and learn what is by picking up, say, any college level "physics" text and read it. I'll work with you on this if you want and show you where you've gone wrong and teach you about energy. Ony if you really want to learn about it. I can also show you the mechanism behind the relationsip E = mc2 (exept how it pertains to high energy paticle physics, i.e. I don't know what the Higgs mechanism is.


    Moving on: Here is a warm and fuzzy definition of what energy is

    The following terms are well defined in the physics community. For a single particle

    Kinetic Energy

    Potential Energy

    Mechanical Energy

    Mechanical Energy = Kinetic Energy + Potential Energy

    Energy = A constant of motion = total mechanical energy = total kinetic energy + total potential energy.

    In such a case the energy can be negative energy

    What I've explained to you is correct because I know how to define the total energy in each example. What you claim is just plain wrong. Long story short; I know energy when I see it and wat you claim just ain't it.

    At this point I've now said all that can be said so I won't be posting anything else, especially against your attempts to convince me that what you said is right. That's not what it means to be open-minded in case that's what you now had in mind. I.e. just because someone tells you that you're wrong and they won't accept it, it doesn't mean that they are being closed minded. Especc ially since you merely chose a different definition than physicists use. That may mae you think I'm contradicting myself, but I'm not. As I said, I know what energy is when I see it and that ain't it

    Later my friend. This is the point where bug out.

    Pete
    Last edited by pmb; June 5th, 2012 at 10:16 PM.
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  57. #56 Energy diagram 
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    Please recall the post made by Markus Hanke

    [quote = Markus Hanke]
    ... pmb has explained it well in post 18, in that the gradient and thus the potential energy of such a vector field must always be negative, otherwise masses would move away from each other, which is obviously not the case.
    You are right in saying that the energy equivalent of a given mass will always be positive, assuming that there is no such thing as "negative mass"; this however is not the same as the potential energy within a gravitational field.
    [/quote]

    I created a diagram to explain why this is wrong. I posted it for some odd reason it disappeared. Let me explain wha you see in the diagram this time.

    The potential function is V(x) = 3 - 8e-x2/9

    The line labeled E1 which passes through V(x) = 4 represents a particle moving with enough kinetic so as not to be bound by the system which has a total energy of 4 joules.

    The line labeled E2 which passes through V(x) = 1.5 represents a particle moving with a kinetic energy which is not enough for it to be free but is still positive having a total energy of 1.5 joules.

    The line labeled E3 which passes through V(x) = -2.5 represents a particle moving with a kinetic energy which is not enough for it to be free but has a total energy which is negative having a total energy of -2.5 joules.

    The constant of integration as chosen such that the potential was minimum at -5 joules and whose maximum was at 3 joules. We can always change the constant of integration such that the minimum was zero but then the energy at infinity was still positive at infinity. Notice that at infinity the force will be zero. Or we can choose the constant of integration such that the potential at infinity would be zero and the force on it will be zero at well. But the minimum potential will be negative leaving open the posibility that any bound particle would have a total energy which would be zero.
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  58. #57  
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    Quote Originally Posted by pmb View Post
    In the example I gave, yes, that's true. But that's just because I used a central force problem as an example. That doesn't hold in general. The potential function can be many things. The entire function could be negative and yet the force vector might point in any direction.
    I understand that, and agree with you. But aren't we talking about gravitational fields ? I take gravitational fields to be "central force problems", at least if you consider the field from a global perspective.
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  59. #58  
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    Quote Originally Posted by Markus Hanke View Post
    I understand that, and agree with you. But aren't we talking about gravitational fields ? I take gravitational fields to be "central force problems", at least if you consider the field from a global perspective.
    The first example I gave was for the potetial energy of a particle in a gravitational field of a point source. We already discussed that.

    The current diagram ismuch more general. It was simple generic potential diagram in one dimension. All it mean is that the force field it represents is given by F(x) = -dV/dx. Suppose we change it a bit to V(r) obtained by letting r = sqrt(x2 + z2). Now instead of being a function in one dimension its a function in three dimensions. It will represent the height of the surface from some given reference point. The surface will be curved and have the shape of an inverted Gaussian function. In case you didn't recognize it the potential had a Guassian shape! The potential will then have the physical meaning of having that gravitational potential a distance above the zero reference.

    Can you picture that?
    Last edited by pmb; June 9th, 2012 at 05:40 PM.
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    Quote Originally Posted by Farsight View Post
    Quote Originally Posted by granpa View Post
    I wasnt talking about 2 planets orbiting one another. The case I was describing is 2 planets infinitely far away from each other being brought together. The combined field is twice as great as for each planet alone and has 4 times the energy. It is easy to see that in spite of the fact that energy was released the energy in the field has increased in magnitude
    It hasn't increased fourfold. It's only doubled. Check out escape velocity wherein . If you fell towards a planet your impact speed v would be the same as escape velocity, which is proportional to the square root of the mass, not the mass. If the planet was twice the mass, your impact speed doesn't double, but kinetic energy does because KE=mv.
    yes but you also have to double the mass of the infalling object
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    The chinese and greek philosophers belive that pre-creation is a state of disorder and that creation is the capasity to change into somthing ordered, self aware or not it is irrelevant, that it is the motive that makes the universe have its energy. they call it yin and yan, order and chaos. That somehow creation is a fundamental part of order. No scientist would disregard the perception of just about anything remotely rational. To me it is very good to hear such logic that describes states of existance without being judgemental or bias. Many people base thier ideals around the oldest philosophers and the most hidden wisdom and look for thier own answer, I belive that is what your guy has done.
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    If youre frame is moving and semting is moving with it , youre energy can be zero and you can call youre univers the cycle univers and thing can be retern
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  63. #62  
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    Quote Originally Posted by Water Nosfim View Post
    If youre frame is moving and semting is moving with it , youre energy can be zero and you can call youre univers the cycle univers and thing can be retern
    There is nothing that can move a framje of reference. At best one can move the measuring devices which define a frame. But that does not mean that the frame is moving. It's a fine, but important, point.
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    fine, well I can see your using my awful grammer as a point of reference. Clearly if I want a nobel prize I may have to use a spell checker, or stop drinking. The greatest men who have influenced this world have based thier ideas on knowledge. All the greatest scientists use other scientists to back up thier theory, it gives it power and impact on the masses. A common point of reference to this would be to explain that so many of our greatest, make the most obvious mistakes in thier work, this draws attention to a seminally great person, ultimately destined for genius.

    I was narrating, the mans theory, as I saw it. To kick open the doors of perception.

    I am no mathematician. The Ideal that no energy can come from no energy is about opposites and necessity, Imaginary numbers like -1 squared, as we know impossible but yet is activly used in measuring resistance.

    All we really have is procrastination.

    Ive been thinking, for the universe to have anykind of energy it would have to be self aware. For egsample we, as life, would have to be less important than the universes existance and our existance would be a state that makes the universe exist. This would make life essential its universe, life must exist for existance to exist. That would prove there is such a thing as any universe with some kind of relative energy. But to say the universe just has a value of energy is a bit vauge much like my explination of a vampiric univrse that must have life in it so it exist.

    Proving the universe is self aware is hard, because where would we draw that line? Possibly when we have proved the universe could have relative force of measurement? I personally belive that the universe existed without life for unimaginable periods of distance and extended time with no life atall and at some points very little atall of anything, sort of like the thermodynamic nuclear cooling and warming of vast expanses of time and space, in a infinity.

    The big bang, which I really hate, does not exist. Its design is to inspire and make you self aware. I totally agree the universe has a total evergy of 0. A total enegy of anything else would be very confusing for our understanding of creation, life and existance as we know it (pre-creation, whatever that means to you).
    Last edited by Spgsamuel; June 16th, 2012 at 06:56 AM.
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