Oliver Thewalt

    Oliver Thewalt

    Theoretical Physics | Quantum Biology | Dark Matter Research Cluster

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    MIT Video Lecture by Prof Edmund Bertschinger about General Relativity and Astrophysics - Excerpt

    I have written this text (almost literally)  according to the words by Prof Edmund Bertschinger in this MIT Open Course Ware Lecture about "Exploring Black Holes - General Relativity & Astrophysics - Einstein's Field Equations". 

    Although I have checked this text many times, I cannot guarantee that this text and the words by Prof Bertschinger are EXACTLY identical, because some expressions were just turned from everyday language into a more formal way. But I am quite sure that the meaning and validity of this text can be confirmed. This is also related to the inner logic and thinking of Einstein and Prof Bertschinger.

    Hence, I will not comment this yet, but let me say that I, concering especially this excerpt, mostly agree to Prof Bertschinger.

    In view of the cause and effects of gravity, I would alter and/or extend Einstein's thinking due to Gravimetrics, a theory about the cause and effects of gravity.
    Link is here

    Space is not warped, there is no distortion of space-time. I do not agree to Wheeler's statement (Spacetime tells matter how to move, matter tells spacetime how to curve) this doesn't seem to be  correct. The cause of gravity is the disassociation of space fields by matter fields. Hence gravity is related to energy, yes, but also to symmetries (remember, why did Einstein discover this covariance of time (--> energy) in an inertial frame (Special Relativity) and why is there zero gravity during a parabolic flight? What happens to a(n) (matterwave-)object  when an inertial frame is transforming into a freely falling frame - and taking into account the  "quanta"  of motion? 

     (hint: an object (=matter(wave)) is a kind of "transformed" space vacuum! (this is why a mass induces  a  residuing non-commutative gauge field potential (hence, gravity is not a fundamental force of nature, not induced by a particle (boson, graviton))

    Well, I have written this for educational purposes. Think about this! :-) May be you will have a look here. http://hixgrid.de/pg/blog/read/37625/einstein039s-special-and-general-relativity-are-meeting-the-quanta


    Wording taken from the video lecture of Prof. Edmund Bertschinger, MIT.

    A  charge in motion is inducing an electromagnetic field - Einstein's field equations indicate that the source for gravity includes energy and pressure. Energy is not a Lorentz invariant. Gravitational fields can induce or modify gravitational fields. The gravitational field itself has energy. 


    Electricity is caused by electric charge - electric fields carried by a photon have NO electric charge. Gravity is fundamentally different from electricity. Gravity itself carries it's own source. The Field Equations must be consistent with energy momentum conservation. A possible negative pressure implies the existence of repulsive gravity.


    Einstein’s most famous equation indicates an equivalence of energy and mass (E = mC^2). Different forms of energy are interconvertible to each other and into mass: chemical energy, nuclear energy, kinetic energy … 


    How about gravitational energy? A source for gravity is mass … 


    Let’s ask about the inverse square law of electrical attraction! Is gravitational energy convertible? Let me look at an hydrogen atom:  I bring together proton and a neutron into a bound state: is the energy of that system the same as the energy of a proton and an electron that are separated widely?  No, because there is potential energy, in Newtonian terms on that  potential energy is negative – for an attractive potential (negative energy).


    What if you just replace that electrical attraction by gravitational attraction? The only thing it changes is the magnitude of attraction. Would the mass energy of that very weakly bound gravitational atom be the same as the mass energy of the separated particles?


    No, otherwise I could not conserve energy. I know that to pull apart two particles that are gravitationally bound to one another takes work. I can get that work by for example converting a little bit of rest mass into energy. Hence, the inner conversion of mass and energy implies that gravitational fields themselves must have energy.

    If energy through E equals mC squared is the source for gravity then gravitational fields themselves must be a source for their own existence. Gravitational fields can induce or modify gravitational fields  the field itself has energy. The equations (Einstein’s field equations) are non linear, the linear superposition does not work.


    In this way gravity is quite different from electricity. Electricity is caused by electric charge. Electric fields carried by photons have no electric charge. Gravity is fundamentally different from electricity. So let me ask the question, electricity is an inverse square law, so how come I cannot just take the Maxwell equations and then replace all the electric fields by gravity fields and I would get a theory of gravity?


    There are a lot of reason why this is not possible but one major reason is this fact: that gravity itself carries its own source – energy!


    Next point of Einstein’s thinking:

    The field equations or the theory must be consistent with energy momentum conservation.


    This excerpt was taken from this

    Video Lecture

    at almost between minute 45 and 50.