# A question on General Relativity.

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#### jbachmurski

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<font size="2"><p>I can see how Einstein&rsquo;s General Relativity&nbsp;can be used to explain Gravity as it applies to objects and orbits in space, but how does his space-time continuum explain the force that holds me on the planet?</p></font>

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#### derekmcd

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I can see how Einstein&rsquo;s General Relativity&nbsp;can be used to explain Gravity as it applies to objects and orbits in space, but how does his space-time continuum explain the force that holds me on the planet? <br /> Posted by jbachmurski</DIV></p><p>General Relativity describes space in term of geometry.&nbsp; Objects follow a geodesic path (straight line in curved space) towards a more massive object's center of mass.&nbsp; The same concept applies to you standing on the earth as it does to satellites in space.&nbsp; The&nbsp; only difference between you and a satellite is velocity.&nbsp; </p><p>If the electromagnetic forces between your feet and ground were removed, you would freefall towards the center of mass along a geodesic path because you don't have enough forward velocity to maintain an orbit.&nbsp; Satellites in space are also in freefall towards the center of mass, but they have enough speed to maintain a continuous geodesic path around the earth.</p><p>Think of rolling a marble around in a bowl... without enough speed, that marble falls to the center of the bowl.&nbsp; If there was a sphere in the center of the bowl, the marble would hit it and stay there and the force of the marble against the sphere could be measure as weight similar to your weight laying against the earth. </p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

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#### jbachmurski

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Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>General Relativity describes space in term of geometry.&nbsp; Objects follow a geodesic path (straight line in curved space) towards a more massive object's center of mass.&nbsp; The same concept applies to you standing on the earth as it does to satellites in space.&nbsp; The&nbsp; only difference between you and a satellite is velocity.&nbsp; If the electromagnetic forces between your feet and ground were removed, you would freefall towards the center of mass along a geodesic path because you don't have enough forward velocity to maintain an orbit.&nbsp; Satellites in space are also in freefall towards the center of mass, but they have enough speed to maintain a continuous geodesic path around the earth.Think of rolling a marble around in a bowl... without enough speed, that marble falls to the center of the bowl.&nbsp; If there was a sphere in the center of the bowl, the marble would hit it and stay there and the force of the marble against the sphere could be measure as weight similar to your weight laying against the earth. <br />Posted by derekmcd</DIV><br /><br /><p>The way I see it, its not that simple. For example the fabric of space-time must be an elastic construct for General Relativity to work. But the elasticity of space-time will cause resistance, thus causing all orbiting objects to slow down and fall into the primary mass, hence the need for an expanding or contracting fabric, which seems to solve the problem in space&hellip; But when I try to apply these concepts to objects setting on, or moving independently on a surface, problems begin to arise. </p>

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#### DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The way I see it, its not that simple. For example the fabric of space-time must be an elastic construct for General Relativity to work. But the elasticity of space-time will cause resistance, thus causing all orbiting objects to slow down and fall into the primary mass, hence the need for an expanding or contracting fabric, which seems to solve the problem in space&hellip; But when I try to apply these concepts to objects setting on, or moving independently on a surface, problems begin to arise. <br />Posted by jbachmurski</DIV></p><p>I think maybe you need to learn a little about general relativity before making such pronouncements.&nbsp; The book <em>Gravitation</em> by Charles Misner, Kip Thorne, and John Archibald Wheeler is a classic in the discipline.<br /></p> <div class="Discussion_UserSignature"> </div>

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#### derekmcd

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The way I see it, its not that simple. For example the fabric of space-time must be an elastic construct for General Relativity to work. But the elasticity of space-time will cause resistance, thus causing all orbiting objects to slow down and fall into the primary mass, hence the need for an expanding or contracting fabric, which seems to solve the problem in space&hellip; But when I try to apply these concepts to objects setting on, or moving independently on a surface, problems begin to arise. <br /> Posted by jbachmurski</DIV></p><p>It certainly isn't that simple... I agree.&nbsp; The analogy I used or the rubber sheet model are simply visual aides.&nbsp; I'm not quite sure I understand what your dilema is unless you elaborate a bit further.&nbsp; Might you be taking the rubber sheet analogy to literally?&nbsp; The 'fabric' of space is really a misnomer brought about by the rubber sheet analogy.</p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

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#### jbachmurski

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Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I think maybe you need to learn a little about general relativity before making such pronouncements.&nbsp; The book Gravitation by Charles Misner, Kip Thorne, and John Archibald Wheeler is a classic in the discipline. <br />Posted by DrRocket</DIV><br /><br /><p>Sorry I wasn&rsquo;t aware that I made any &ldquo;pronouncements&rdquo; think of it as a question. I&rsquo;m missing something&hellip; and I can&rsquo;t find it in the books I&rsquo;ve already studied. I&rsquo;ve heard of Kip Thorne, but I don&rsquo;t have that one. Is it new, or old? Most of my books were acquired between 96 and 05. </p>

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#### jbachmurski

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Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>It certainly isn't that simple... I agree.&nbsp; The analogy I used or the rubber sheet model are simply visual aides.&nbsp; I'm not quite sure I understand what your dilema is unless you elaborate a bit further.&nbsp; Might you be taking the rubber sheet analogy to literally?&nbsp; The 'fabric' of space is really a misnomer brought about by the rubber sheet analogy. <br />Posted by derekmcd</DIV><br /><br /><em><p>&ldquo;Might you be taking the rubber sheet analogy to literally?&rdquo; </p></em><p>Sort of &hellip;but not exactly, three dimensional, much more elastic, much more complicated, not easy to describe.</p>

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#### derekmcd

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&ldquo;Might you be taking the rubber sheet analogy to literally?&rdquo; Sort of &hellip;but not exactly, three dimensional, much more elastic, much more complicated, not easy to describe. <br /> Posted by jbachmurski</DIV></p><p>I'm not sure where your confusion lies...</p><p>The only two ways I can think of off the top of my head to cause orbital degradation are due to tidal mechanisms or atmospheric drag.&nbsp;</p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

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#### emperor_of_localgroup

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I can see how Einstein&rsquo;s General Relativity&nbsp;can be used to explain Gravity as it applies to objects and orbits in space, but how does his space-time continuum explain the force that holds me on the planet? <br /> Posted by jbachmurski</DIV></p><p>This is really an interesting and important question even though the answer to this question is known to physicists for centuries ( correct or not). The reason most physicists shrug off this type of questions as 'a question asked by someone who doesn't know basic physics'&nbsp; is this property of the earth(or any huge mass) is taken for granted becuase we have been experiencing&nbsp; this for centuries.</p><p>According to basic physics, this is known as&nbsp; 'Inertia', Newton's first law.&nbsp; Inertia is a very interesting phenomena associated with motion which has not been investigated enough, IMHO. Inertia is&nbsp; the reason&nbsp; why the earth doesn't leave you floating in space when you try to make a jump shot in a basketball court. And then gravity pulls you down on the ground after the throw.</p><p>I'm not a general relativity expert, I do not know how general relativity explains inertia. But inertia is still puzzling to me.</p><p>&nbsp;</p> <div class="Discussion_UserSignature"> <font size="2" color="#ff0000"><strong>Earth is Boring</strong></font> </div>

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#### DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>This is really an interesting and important question even though the answer to this question is known to physicists for centuries ( correct or not). The reason most physicists shrug off this type of questions as 'a question asked by someone who doesn't know basic physics'&nbsp; is this property of the earth(or any huge mass) is taken for granted becuase we have been experiencing&nbsp; this for centuries.According to basic physics, this is known as&nbsp; 'Inertia', Newton's first law.&nbsp; Inertia is a very interesting phenomena associated with motion which has not been investigated enough, IMHO. Inertia is&nbsp; the reason&nbsp; why the earth doesn't leave you floating in space when you try to make a jump shot in a basketball court. And then gravity pulls you down on the ground after the throw.I'm not a general relativity expert, I do not know how general relativity explains inertia. But inertia is still puzzling to me.&nbsp; <br />Posted by emperor_of_localgroup</DIV></p><p>In principle inertia and gravity need not be related.&nbsp; It does appear, however, that they are closely related.&nbsp; If you step outside general relativity and go back to classical physics you can see mass appear in two places.&nbsp; One is in Newton's mechanics,&nbsp; F&nbsp;= ma.&nbsp; The "m" in this equation is called inertial mass.&nbsp; Mass also occurs in Newton's law of universal gravitation.&nbsp; F = mu*m1*m2/ r^2 .&nbsp; The m1 and m2 in this equation are called gravitational mass.&nbsp; Experiments have been performed to attempt to detect a difference between inertial mass and gravitational mass.&nbsp; No difference has ever been found.&nbsp; General relativity treats mass and energy as equivalent.&nbsp; It also replaces the notion of gravitational "force" with an effect realized through the curvature of space-time.</p><p>As for how general relativity handles inertia, we need to return to Newton's equation first.&nbsp; What Newton actually proposed was F = dp/dt where p is momentum.&nbsp; For the case of constant mass this reduces to F = ma.&nbsp; General relativity keeps the equation F= dp/dt, but requires that one use the momentum&nbsp; 4-dimensional space-time.&nbsp; That vector has as one component a quantity that is classically called energy while the remaining 3 somponents correspond to the classical notion of mass times velocity.&nbsp; <br /></p> <div class="Discussion_UserSignature"> </div>

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#### jbachmurski

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<br /><p>I just think that General Relativity&rsquo;s concept of space-time is incomplete. </p>

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#### DrRocket

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Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I just think that General Relativity&rsquo;s concept of space-time is incomplete. <br />Posted by jbachmurski</DIV><br />&nbsp;In what way ? <div class="Discussion_UserSignature"> </div>

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#### SpeedFreek

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I just think that General Relativity&rsquo;s concept of space-time is incomplete. <br /> Posted by jbachmurski</DIV></p><p>If you say you understand <font><font size="2">how Einstein&rsquo;s General Relativity&nbsp;can be used to explain Gravity as it applies to objects and orbits in space, you must also understand that it explains how two bodies in space can come into contact with each other. Asteroids can collide, comets can hit Jupiter, meteorites can fall onto Antarctica etc.</font></font></p><p>But what if an object, instead of "falling" towards another and hitting it, is simply created on the surface of the other object? </p> <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

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#### jbachmurski

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Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;In what way ? <br />Posted by DrRocket</DIV><br /><br /><p>For example does General Relativity explain why mass produces these curvatures in space-time? </p>

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#### DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>For example does General Relativity explain why mass produces these curvatures in space-time? <br />Posted by jbachmurski</DIV></p><p>No scientific theory explains "why", that is for theology.&nbsp; General relativity does explain how mass produces curvature.&nbsp; In fact that is essentially what the theory is about.&nbsp; The&nbsp;equations directly relate mass and energy distribution to curvature.&nbsp; <br /></p> <div class="Discussion_UserSignature"> </div>

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#### jbachmurski

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Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>No scientific theory explains "why", that is for theology.&nbsp; General relativity does explain how mass produces curvature.&nbsp; In fact that is essentially what the theory is about.&nbsp; The&nbsp;equations directly relate mass and energy distribution to curvature.&nbsp; <br />Posted by DrRocket</DIV><br /><br /><p>That is for theology?</p><p>I would like to make the hypothesis that General Relativity would work better if it treated matter as though it were absorbing small amounts of space-time. This alone would create the affect of a curvature where mass is involved.</p>

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#### emperor_of_localgroup

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>No scientific theory explains "why", that is for theology.&nbsp;&nbsp;&nbsp; <br /> Posted by DrRocket</DIV></p><p>Sorry, but I also disagree with that sentence. But I think you didn't mean the way it sounds like.&nbsp; Some of us may be willing to leave many 'whys' and 'universal constants' to theology, but some of us are not very comfortable with that idea.</p><p>&nbsp;Absorption of&nbsp; space-time by mass&nbsp; to produce curvature is not a bad starting point.&nbsp; A somewhat similar argument&nbsp; floating around in science world is 'a mass in space-time is like a solid object submerged in a liquid'. But note that there is a substantial amount of empty space-time in all masses, considering the distance between electrons and the nucleus and interatomic and intermolecular distances. Another way to look at it is the continuity of space-time is broken by the mass. We may even say space-time is displaced by the mass just as liquid gets displaced by a submerged solid. One difference is liquid can't flow thorugh most solids but space-time can.</p><p>Does spacetime exert, unlike liquid pressure, some mysterious type of pressure on mass causing curvature (or similar effects) in spacetime???</p><p>&nbsp;</p><p>&nbsp;&nbsp;</p> <div class="Discussion_UserSignature"> <font size="2" color="#ff0000"><strong>Earth is Boring</strong></font> </div>

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#### DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Sorry, but I also disagree with that sentence. But I think you didn't mean the way it sounds like.&nbsp; Some of us may be willing to leave many 'whys' and 'universal constants' to theology, ...Posted by emperor_of_localgroup</DIV></p><p>I distinguish between "why", province of theology, and "how", the province of science.&nbsp; <br /></p> <div class="Discussion_UserSignature"> </div>

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#### DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>That is for theology?I would like to make the hypothesis that General Relativity would work better if it treated matter as though it were absorbing small amounts of space-time. This alone would create the affect of a curvature where mass is involved. <br />Posted by jbachmurski</DIV></p><p>Science can only explain "how" things work,</p><p>If you want to make a hypothesis you need to frame that hypothesis with sufficient precision that it can, at least in principle, be tested.&nbsp; What do you mean when suggest that matter absorbs space-time?&nbsp; Precisely what is meant by abosorption, since matter and space-time do not appear to be comparable concepts.&nbsp; And, once you have made that notion precise explain how that absorption will cause a change in the curvature tensor for space-time.</p> <div class="Discussion_UserSignature"> </div>

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#### Tissa_Perera

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<p>jbachmurski,</p><p>Your question is perfectly valid.</p><font size="1" color="#0000ff">I can see how Einstein&rsquo;s General Relativity&nbsp;can be used to explain Gravity as it applies to objects and orbits in space, but how does his space-time continuum explain the force that holds me on the planet?</font><p> And unlike some of the answers from the others, I too&nbsp; say that GR&nbsp; does not have an answer to the what I call </p><p>"Weight problem" and also the "inertia problem". At least Newton states that there is a force GMm/r2, but does not qualify how.</p><p>I have thought of these for a long time and came up with a very plausible solution backed up by simple derivations</p><p>to the Weight and inertia problems and more. I can only hint of these at this time. See cosmicdarkmatter.com&nbsp;</p>

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#### DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>jbachmurski,Your question is perfectly valid.I can see how Einstein&rsquo;s General Relativity&nbsp;can be used to explain Gravity as it applies to objects and orbits in space, but how does his space-time continuum explain the force that holds me on the planet? And unlike some of the answers from the others, I too&nbsp; say that GR&nbsp; does not have an answer to the what I call "Weight problem" and also the "inertia problem". At least Newton states that there is a force GMm/r2, but does not qualify how.I have thought of these for a long time and came up with a very plausible solution backed up by simple derivationsto the Weight and inertia problems and more. I can only hint of these at this time. See cosmicdarkmatter.com&nbsp; <br />Posted by Tissa_Perera</DIV></p><p>If you think that you have a valid theory, present it.&nbsp; <br /></p> <div class="Discussion_UserSignature"> </div>

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#### jbachmurski

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<p>I predict that within 10 years time, Einstein&rsquo;s theories of Special and General Relativity will both be replaced by a single new and better theory. And that based upon that new theory, we will have tested a interstellar engine capable of moving hundreds if not thousands of times the speed of light! </p><p>And I will be responsible for these new discoveries!</p><p>The ability to move between the stars easily and rapidly will be the defining technology of the twenty-first century!</p><p>John A. Bachmurski</p>

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#### DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I predict that within 10 years time, Einstein&rsquo;s theories of Special and General Relativity will both be replaced by a single new and better theory. And that based upon that new theory, we will have tested a interstellar engine capable of moving hundreds if not thousands of times the speed of light! And I will be responsible for these new discoveries!The ability to move between the stars easily and rapidly will be the defining technology of the twenty-first century!John A. Bachmurski <br />Posted by jbachmurski</DIV></p><p>General relativity already subsumes special relativity so all you need is something that is better than general relativity.&nbsp; If this new theory is valid and if it permits what you say it will, then it not only will replace general relativity it will show it to be completely and utterly wrong.&nbsp; I would not bet a lot that this will happen.</p><p>Any such ability, if real, would almost certainly be the defining technology of the twnety-first or even thirty-first century.</p><p>So, what is the basis for your theory ?&nbsp; Do you smoke it, drink it, inhale it, or inject it ?<br /></p> <div class="Discussion_UserSignature"> </div>

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#### derekmcd

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I predict that within 10 years time, Einstein&rsquo;s theories of Special and General Relativity will both be replaced by a single new and better theory. And that based upon that new theory, we will have tested a interstellar engine capable of moving hundreds if not thousands of times the speed of light! And I will be responsible for these new discoveries!The ability to move between the stars easily and rapidly will be the defining technology of the twenty-first century!John A. Bachmurski <br /> Posted by jbachmurski</DIV></p><p>Good luck!!!&nbsp; Seriously, I'm rooting for ya.</p><p>Not likely it can be replaced unless we've really screwed the pooch on some very rudimentary fundamentals.&nbsp; About the best you can do with General Relativity is incorporate it into a new, more complete theory.&nbsp; Something many of the brightest minds of the last 100 years have been trying to do.</p><p>&nbsp;</p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

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#### jbachmurski

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Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Any such ability, if real, would almost certainly be the defining technology of the twnety-first or even thirty-first century.<br />Posted by DrRocket</DIV><br /><br /><p>Actually I first made the foundational discovery in 96, so it should have been the defining discovery and technology of the twentieth century. The primary problem so far is the lack of financing for my research. </p>

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